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Orogenic Gold Deposits of China
Abstract
China produces about 450 t Au per year and has government stated in-ground reserves of approximately 12,000 t Au. Orogenic gold, or gold deposits in metamorphic rocks, and associated placer deposits compose about 65 to 75% of this endowment, with lodes existing as structurally hosted vein and/or disseminated ore- bodies. The abundance of orogenic gold deposits reflects Paleozoic to Triassic closure of Paleo-Tethyan ocean basins between Precambrian blocks derived from Rodinia and Gondwana as well as late Mesozoic-Cenozoic cir- cum-Pacific events and Cenozoic Himalayan orogeny. The deposits range in age from middle Paleozoic to Pleis- tocene. The Jiaodong Peninsula contains about one-third of China’s overall endowment, and large resources also characterize East Qinling, West Qinling, and the Youjiang basin. Although gold ores in Jiaodong postdate formation and metamorphism of Precambrian host rocks by billions of years, they are nevertheless classified here as orogenic gold ores rather than as a unique Jiaodong-type or decratonic-type of gold deposit. Similarly, although many workers classify the gold lodes in the Youjiang basin and much of West Qinling as Carlin-type gold, they show significant differences from gold ores in Nevada, United States, and are better defined as epi- zonal orogenic gold deposits.
Although there are widespread exposures of Precambrian rocks in China, there are no significant Precam- brian gold deposits. If large ancient orogenic gold deposits formed in Archean and Paleoproterozoic rocks, then they have been eroded, because these deep crustal rocks that are now exposed in China’s cratonic blocks have been uplifted from levels too deep for orogenic gold formation. The oldest large gold deposits in China are perhaps those of the Qilian Shan that were formed in association with Silurian tectonism along the present-day southwestern margin of the North China block. Closure of ocean basins in the outer parts of the Central Asian orogenic belt led to late Carboniferous to Middle Triassic orogenic gold formation in the Tian Shan, Altay Shan, Beishan, and northwestern North China block. Deformation associated with amalgamation of the North China block, northern Tibet terranes, South China block, and Indochina, as well as initial Paleo-Pacific sub- duction, can be related to Late Triassic orogenic gold formation in West Qinling, East Kunlun, Youjiang basin, West Jiangnan (Xuefengshan belt), Hainan Island, and Yunkaidashan gold provinces. In the middle Mesozoic, continued subduction along the Paleo-Pacific margin was associated with gold ores forming in East and Cen- tral Jiangnan, whereas early to middle Mesozoic deformation along the northern North China block formed important orogenic lodes in Precambrian basement (e.g., Jiapigou, Zhangjiakou, and Yanshan districts). Contin- ued Yanshanian orogeny in the eastern half of the North China block led to extensive orogenic gold formation during the main period of decratonization and regional extension at ca. 135 to 120 Ma (e.g., Jiaodong, Liaodong, Chifeng-Chaoyang, Zhangbaling, Taihangshan, and East Qinling). At the same time, strike-slip events in central Transbaikal were associated with orogenic gold formation in both Russia and adjacent northeastern China and likely are the source for China’s most productive gold placers in the upper Heilongjiang basin. China’s youngest orogenic gold deposits formed in the Ailaoshan, Lanping basin, Ganzi-Litang belt, Daduhe district, and areas south of the Lhasa terrane in Tibet during the middle Cenozoic, as well as in the northern half of the Central Range of Taiwan during the Pliocene-Pleistocene.
... In comparison, the ore sulfides have Pb isotopes significantly different from those of Qinling, Erlangping, Kuanping, and Danfeng Groups exposed in the North Qinling Terrane. Notably, they are comparable with lead isotopes of the Cambrian-Devonian sedimentary rocks widespread in the Qinling Orogen (Fig. 13d) from which the fluids and metals were derived to form the early Mesozoic gold deposits in the western South Qinling Terrane (e.g., Chen and Santosh 2014;Chen et al. 2015;Liu et al. 2015a;Yang et al. 2016;Xue 2017;Goldfarb et al. 2019;Qiu et al. 2020;. ...
... Such similarities in formation ages, mineral assemblages, and isotopic compositions indicate that Yangxie deposit shares similar sources of hydrothermal fluids and metals and ore-forming processes with the varieties in the western South Qinling Terrane. Previous studies have shown that ore-forming fluids and metals responsible for the Triassic gold mineralization in the western South Qinling Terrane were mostly derived from devolatilization of the hosting and underlying Paleozoic sedimentary rocks during their greenschist-to amphibolite-facies metamorphism (e.g., Chen and Santosh 2014;Chen et al. 2015;Liu et al. 2015a;Yang et al. 2016;Xue 2017;Goldfarb et al. 2019;Qiu et al. 2020;, which thus further support a metamorphic devolatilization source of metals and fluids for the Yangxie gold deposit. Taken together, the Yangxie deposit in the North Qinling Terrane is better classified as an orogenic gold deposit (e.g., Goldfarb et al. 2019). ...
... Previous studies have shown that ore-forming fluids and metals responsible for the Triassic gold mineralization in the western South Qinling Terrane were mostly derived from devolatilization of the hosting and underlying Paleozoic sedimentary rocks during their greenschist-to amphibolite-facies metamorphism (e.g., Chen and Santosh 2014;Chen et al. 2015;Liu et al. 2015a;Yang et al. 2016;Xue 2017;Goldfarb et al. 2019;Qiu et al. 2020;, which thus further support a metamorphic devolatilization source of metals and fluids for the Yangxie gold deposit. Taken together, the Yangxie deposit in the North Qinling Terrane is better classified as an orogenic gold deposit (e.g., Goldfarb et al. 2019). The North Qinling Terrane hence could be another Triassic orogenic gold province thus far has not been well recognized. ...
... It has been well established that subduction is the most important process controlling the formation of diverse types of gold systems (Groves et al., 1998(Groves et al., , 2021Goldfarb et al., 2005Goldfarb et al., , 2021Wyman et al., 2008Wyman et al., , 2016Deng and Wang, 2016;Deng et al., 2015Deng et al., , 2017aDeng et al., , 2019Deng et al., , 2020aDeng et al., , 2020bDeng et al., , 2022Sillitoe, 2020;Wang et al., 2022a). These include: (1) formation of orogenic gold systems in convergent margins during syn-subduction accretion to late-subduction lithosphere thinning, or continental collision ( Fig. 1; Groves et al., 1998Groves et al., , 2020Groves et al., , 2021Kerrich et al., 2000;Groves and Bierlein, 2007;Deng et al., 2015Deng et al., , 2022Goldfarb and Groves, 2015;Deng and Wang, 2016;Goldfarb et al., 2019;Wang et al., 2022a); (2) formation of intrusion-related gold systems during post-collisional back-arc or intraplate extension (Lang and Baker, 2001;Sillitoe, 2020); and (3) formation of Carlin-type gold systems in an orogeny to orogenic collapse (Cline et al., 2005;Hofstra et al., 2005;Muntean et al., 2011;Pinet et al., 2022). However, the processes that define the intracontinental gold mineralization history in relation to evolving oceanic subduction have not been well constrained. ...
... There have been long-standing controversies about the genetic types of gold deposits in the SCB, especially in the Youjiang Basin (Su et al., 2018;Wang et al., 2020a). Previous workers used the term Carlin-like (Deng and Wang, 2016;Hou et al., 2016), Carlin-type or Carlin-style (Hu et al., 2002(Hu et al., , 2017aWang and Groves, 2018), intermediate between Carlin-type and orogenic (Su et al., 2018;Xie et al., 2018aXie et al., , 2018b, Carlin-style orogenic deposits (Tran et al., 2016), and epizonal orogenic gold deposits (Goldfarb et al., 2019) to describe the gold deposits in the Youjiang Basin. Based on detailed deposit geology, robust mineralization ages, and geochemical data, the Triassic sediment-hosted orogenic gold deposits that are widespread in the central-southern basin are distinguished from early Cretaceous (150-134 Ma) Carlin-type ones which selectively developed in the northern basin. ...
... The features of orogenic gold deposits include (1) compressional or transpressional ore-controlling structures (Figs. 5b-e, 6a, d, e); (2) sulfidation, silicification (quartz), sericitization, carbonation, and chloritization as typical alteration types (Fig. 6b, f, g;Li et al., 2022c); (3) pyrite-and arsenopyrite-dominated ore minerals (Fig. 6c, h); (4) lowsalinity and mid-low temperature H 2 O-CO 2 -NaCl(-CH 4 -N 2 ) fluids (Groves et al., 2003;Zhao et al., 2013;Goldfarb and Groves, 2015;Ni et al., 2015;Goldfarb et al., 2019). This deposit type includes the Precambrian-hosted Gezhen deposit in Hainan (Fig. 5d), Zhengchong in the central Jiangnan Orogen (Figs. 5c, 6a-c), and the Phanerozoic sediment-hosted Gaolong and Lannigou deposits in the Youjiang Basin ( Fig. 5b. ...
The diverse types of Mesozoic intracontinental gold mineralization in the South China Block (SCB) are genetically linked to prolonged oceanic plate subduction. These gold deposits, with estimated resources greater than 2000 tonnes, comprise four gold provinces: Hainan Island, Wuyi-Yunkai Belt, Jiangnan Orogen, and Youjiang Basin. In these provinces, Paleo-Pacific Plate subduction, crustal thickness and composition, structural reactivation, and fluid-wall rock reactions collectively controlled the distribution and diverse features of the Mesozoic intracontinental gold mineralization. Three stages can be identified in the metallogenic evolution of the SCB. (1) Formation of orogenic gold deposits gradually younging from the coast (Hainan) to the hinterland (Youjiang Basin and Jiangnan Orogen) related to flat-slab subduction of the Paleo-Pacific Plate and clockwise rotation of the SCB between 245 and 200 Ma. (2) Formation of intrusion-related Au-(Sb-W) deposits in the western Jiangnan Orogen in a continental extensional setting in the wake of flat-slab subduction between 210 and 195 Ma prior to the early to middle Jurassic hiatus (190–170 Ma) of high-angle subduction and stagnant slab. (3) Between 170 and 90 Ma, intermittent formation of intrusion-related gold deposits in the coastal region (∼160 Ma, ∼100 Ma) and hinterland (∼160 Ma, 140–130 Ma), and the formation of Carlin-type gold deposits in the Youjiang Basin (∼140 Ma) during episodic extension caused by slab foundering and changes in subduction angle. After 90 Ma, regional differential crustal thinning and denudation determined the extent of uplift and exposure of various types of ore deposits. In stage 1, the quartz vein-type and disseminated orogenic gold deposits hosted in Precambrian rocks, and with a subcrustal source, are related to the reactivation of crust-scale NE-trending faults. In contrast, disseminated orogenic gold deposits hosted in Phanerozoic rocks and influenced by fluid-rock reactions relate to landward propagation of a fold-thrust system. In stage 2, intrusion-related Au-(Sb-W) deposits only formed in intracontinental Precambrian rocks and were controlled mainly by shallow, brittle, and extensional NW-trending structures. Highly fractionated late-stage S-type granite (used sensu lato throughout) complexes controlled the distribution of intrusion-related gold-(polymetallic) deposits in stages 2 and 3. In stage 3, stratabound and disseminated Carlin-type gold deposits are restricted to platform facies carbonate sequences, and intrusion-related gold deposits are structurally related to the reactivation of NE-trending faults. Both are interpreted to have a magmatic-hydrothermal source. The crustal architecture of the four gold provinces exhibits marked differences in crustal thickness, contrasts in rheology, abundance of deep faults, and intensity of mantle-crust interaction. Those gold provinces in the central-southeastern SCB are the result of the reactivation of a paleo-orogen, in contrast to those hosted by deformation systems in shallow crust in the western SCB during the Mesozoic. The Carlin-type and intrusion-related gold deposits are located in regions with more mafic and felsic components, respectively, as indicated by seismic Vp/Vs ratios. However, the spatial distribution of orogenic gold deposits is poorly correlated with that of Vp/Vs ratios, suggesting a subcrustal source.
... Dimensions, which refer to the size and extent of a target, can influence the imaging result significantly. Because metamorphism and deformation can cause orebodies to become contorted and discontinuous and because even economic ore deposits can be small relative to seismic wavelengths [35,58,61], the effects of dimensions needed to be further Table 1. ...
... Dimensions, which refer to the size and extent of a target, can influence the imaging result significantly. Because metamorphism and deformation can cause orebodies to become contorted and discontinuous and because even economic ore deposits can be small relative to seismic wavelengths [35,58,61], the effects of dimensions needed to be further clarified for orogenic gold deposits. For exploration experiences in sedimentary basins, it is generally believed that the seismic reflection method has inherent limitations of resolution in both the vertical and horizontal directions. ...
... The giant Zaozigou orogenic Au-Sb deposit in central China is located in the northwesternmost part of the West Qinling Orogen ( Figure 6) [35,63,64]. It hosts 118 t of Au, averaging 3.42 g/t and >0.12 Mt Sb, averaging 0.99%, representing one of the largest active gold producers in the West Qinling Orogen [65,66]. ...
The demand for deep prospecting has led to an increase in the enthusiasm for seismic techniques in mineral exploration. Reflection seismology applications in the base metal industry have achieved success. For orogenic gold deposits, however, their applicable conditions remain to be investigated. This paper simulated seismic wave propagation based on a finite-difference algorithm with an accuracy of eighth order in space and second order in time to investigate the factors influencing the reflection seismic exploration results. Then, the paper assessed the algorithm’s feasibility for orogenic gold deposits, taking the giant Zaozigou deposit in central China as an example. The forward modeling showed that the petrophysical properties, dimensions, and dip of targets significantly affected the seismic exploration results. In the Zaozigou model, shallowly dipping orebodies were well imaged with precise extension and thickness. Steeply dipping orebodies were recognized but their thickness information was lost. Steeply dipping orebodies at depth were not detectable under a surface configuration. These problems could be effectively solved by increasing the array length and using vertical seismic profiling methods. For small orebodies, multiwave and multicomponent seismic techniques offered more valuable information in terms of mineral exploration. In conclusion, it was possible to locate orogenic gold deposits using the reflection seismology method.
... The lode Au and Au-Sb deposits of the district are mostly located along NW-striking faults and are hosted by late Paleozoic to early Mesozoic greenschist-facies slates and by Triassic intrusions. This is also the case for the largest deposits, which correspond to the Zaozigou (118 t Au) and Jiagantan (120 t Au) deposits (Goldfarb et al., 2019;Qiu et al., 2020). The strong spatial association between gold and shear zone, as well as geochronological and geochemical data, indicate that the lode Au and Au-Sb deposits of the Xiahe-Hezuo district are orogenic gold deposits formed during the Late Triassic and are related to the collision between the South Qinling Terrane and the South China Block (Goldfarb et al., 2019;Yu et al., 2020). ...
... This is also the case for the largest deposits, which correspond to the Zaozigou (118 t Au) and Jiagantan (120 t Au) deposits (Goldfarb et al., 2019;Qiu et al., 2020). The strong spatial association between gold and shear zone, as well as geochronological and geochemical data, indicate that the lode Au and Au-Sb deposits of the Xiahe-Hezuo district are orogenic gold deposits formed during the Late Triassic and are related to the collision between the South Qinling Terrane and the South China Block (Goldfarb et al., 2019;Yu et al., 2020). Other deposits in the district correspond to magmatic-hydrothermal systems, for example, Dewulu and Gangyi Cu skarn (Jin & Sui, 2020;Qiu & Deng, 2017;Sui et al., 2017), which are generally located next to Triassic plutons and are genetically associated with Early Triassic granitoids (J. ...
... The collision between the South China and North China blocks triggered widespread Triassic orogenic Au-Sb of mineralization in the Qinling Orogen (Figure 1; Goldfarb et al., 2019;Qiu et al., 2020). Integrating previously published thermochronological data and sedimentary record, it is suggested that the whole Qinling Orogen experienced rapid exhumation during the Late Triassic (e.g., Hu et al., 2006;Wang et al., 2014;Zeng et al., 2012). ...
Epizonal orogenic Au‐Sb deposits are generally Phanerozoic in age, possibly as a consequence of erosion that can entirely remove older mineral deposits in rapidly uplifting orogenic setting. Quantifying post‐mineralization thermotectonic processes is essential for documenting the exhumation and preservation of epizonal deposits, which in turn is critical for constraining regional deformation. This study focuses on the giant Zaozigou deposit, and documents cooling rates using amphibole and biotite Ar‐Ar, zircon U‐Th/He, and apatite fission track dating. Six cooling phases are identified, including Early to Middle Triassic very rapid cooling, Late Triassic rapid cooling, Early Jurassic slow cooling, Middle to Late Jurassic rapid cooling, Cretaceous to Oligocene slow cooling, and Miocene to present rapid cooling. Initial cooling corresponds to thermal exchange between magmatic rocks and wall rocks. Phases two through five are related to a sequence of post‐mineralization compressional, strike‐slip, compressional, and extensional events, pointing to multi‐phase tectonic evolution of the Qinling Orogen since the Late Triassic. Late exhumation is probably related to lateral growth of the Tibetan Plateau and/or to rapid erosion induced by intensification of the Asian monsoon. In total, ∼6.3 km of rock was removed post‐mineralization. We conclude that Cretaceous to Oligocene extension retarded the continuous erosion and thus played an important role in the preservation of Zaozigou. Combined with known orogenic processes, our results demonstrate that a long‐lived extension is a favorable tectonic environment for the preservation of epizonal orogenic Au‐Sb deposits in rapidly uplifting orogenic setting.
... Li et al., 2018;Dong et al., 2019). The geological features of Au mineralization at Zhaishang include: (1) orebodies controlled by regional shear zones (Fig. 1, 2), (2) disseminated and breccia-type ores with native gold (Fig. 4), (3) Au-related alteration dominated by silicification (Fig. 5c, 7j), (4) lack of lateral metal zoning, and (5) trace-element association of Au-As with low Ag, Cu, Zn, and Pb contents Goldfarb et al., 2019). Based on these characteristics, the Zhaishang gold deposit has been classified as a Carlin-type or an orogenic deposit (Deng and Wang, 2016;Goldfarb et al., 2019). ...
... The geological features of Au mineralization at Zhaishang include: (1) orebodies controlled by regional shear zones (Fig. 1, 2), (2) disseminated and breccia-type ores with native gold (Fig. 4), (3) Au-related alteration dominated by silicification (Fig. 5c, 7j), (4) lack of lateral metal zoning, and (5) trace-element association of Au-As with low Ag, Cu, Zn, and Pb contents Goldfarb et al., 2019). Based on these characteristics, the Zhaishang gold deposit has been classified as a Carlin-type or an orogenic deposit (Deng and Wang, 2016;Goldfarb et al., 2019). The Zhaishang gold deposit is compared to conventional Carlin-type and orogenic gold deposits in Table 1, but the additional deduction is beyond the scope of this study. ...
... Hainan Island is located in the southern margin of the South China Block, and is adjacent to the northern part of the Indochina Block [1,2] (Figure 1a). More than 50 gold deposits and occurrences have been discovered on this island, making Hainan Island a prospective region for gold exploration in South China [3][4][5][6][7]. The Gezhen gold belt, which consists of a series of similar gold deposits along the NE-trending Gezhen shear zone in the western Hainan Island, has become the most prospective gold exploration target within the island [4,5,8]. ...
... Xu et al. [5] summarized previous studies on deposit geology, ore-forming fluid characteristics and isotope compositions of the Gezhen gold deposits and concluded that these gold deposits were best classified as orogenic in genesis. Our new data on H-O-S isotopic compositions of the Tuwaishan gold deposit further support the orogenic gold classification not only because the H-O-S isotopic compositions of the Tuwaishan gold deposit are consistent with those of typical orogenic gold deposits worldwide [6,54,73,74] (Figures 6 and 7) but also because the comprehensive interpretations of our new H-O-S isotopic data with ore-forming fluid properties favor a metamorphic rather than a magmatic origin. ...
The Tuwaishan gold deposit is located at the northeastern end of the Gezhen shear zone in the western part of Hainan Island, South China. It is one of a series of similar gold deposits hosted in the Mesoproterozoic basement rocks and structurally controlled by the Gezhen shear zone. The hydrothermal ore-forming period can be divided into quartz-pyrite-arsenopyrite stage, quartz-pyrite-base metal sulfides stage and quartz-carbonate stage. Eleven gold-bearing quartz vein samples yield δDV-SMOW and δ18OV-SMOW values of −75.9‰ to −54.4‰ and +8.1‰ to +13.7‰, respectively, and the corresponding δ18Owater values range from +3.1‰ to +8.7‰. In addition, the pyrite separates from 14 ore samples yield δ34S values of +4.5‰ to +7.9‰. The H-O-S isotopic data, along with fluid properties of the Tuwaishan and other gold deposits along the Gezhen shear zone, suggest that the ore-forming fluid and materials are of metamorphic rather than magmatic origin. Hence, we propose that the Tuwaishan gold deposit is best classified as orogenic gold deposit that resulted from regional metamorphism. Considering that the Mesoproterozoic basement rocks have experienced amphibolite facies metamorphism prior to the gold mineralization, the metamorphic devolatilization of the Ordovician-Silurian rocks at depth would provide a realistic source of fluid, gold and sulfur for the Tuwaishan and other gold deposits of the Gezhen gold belt.
... Previous studies have shown that Au deposits in the NGXR can be classified mainly into orogenic, epithermal and porphyry types. Orogenic Au deposits are mainly formed during the Early Cretaceous, which were distributed mainly in the Upper Heilongjiang Basin (e.g., Shabaosi and Baoxinggou Au deposit; Li, 2015;Liu et al., 2015;Goldfarb et al., 2019). Minor orogenic Au deposits with Late Triassic ages are also located along the Nenjiang-Heihe tectonic complex zone (e.g., Mengdehe Au deposit; Li et al., 2021b). ...
... The ore bodies of the Early Cretaceous orogenic Au deposits are mainly hosted in the clastic sedimentary rocks Goldfarb et al., 2019) with mainly crustal contribution for the ore-forming metals . The Early Cretaceous epithermal Au deposits are distributed in the eastern NGXR (Lv et al., 2005;Shi et al., 2006;Liu et al., 2011;Che et al., 2016;Li et al., 2020). ...
The northern Great Xing'an Range (NGXR) gold (Au) metallogenic belt is characterized by the wide occurrence of the Early Cretaceous orogenic and arc-magma related epithermal Au deposits. Information of the newly discovered granite-hosted Walali Au deposits in this area could shed new light on the Early Cretaceous Au metallogenesis in NE China. The ore-hosting granite at Walali shows zircon U-Pb ages of 310.6 ± 2.2 Ma, which are significantly different from the ore-bearing pyrite Rb-Sr age (119.9 ± 1.7 Ma). The distinct ages indicate that the Au mineralization occurred at the Early Cretaceous and therefore preclude the genetic link between the Late Carboniferous magmatism and Au ore formation. The fluid inclusion studies show that the ore precitpitated from the hydrothermal fluids with a temperature range of 150-330 °C and a salinity range of 3.4-11.6 wt% equiv. H-O isotopic compositions indicate the involvement of both magmatic and meteoric water in the hydrothermal system. The pyrite and galena S (δ 34 S V-CDT values: 7.7-10.0‰) and Pb (206 Pb/ 204 Pb ratios of 18.177-18.217; 207 Pb/ 204 Pb ratios of 15.614-15.633) isotopic compositions suggest a crustal contribution for the ore-forming materials at Walali. By comparison, the Walali Au deposits are more comparable with the strata-hosted orogenic Au deposits in the north NGXR, but different from the epithermal-and porphyry-type Au deposits in this area. Combined with the Late Mesozoic tectonic evolution in NE China, we conclude that the Early Cretaceous extensional setting caused the large scale magmatism, which drove the remobilization of crustal materials and resulted in the formation of the granite-and strata-hosted Au deposits in the NGXR.
... Many types of deposits have been discovered in East Junggar , e.g., orogenic gold deposits (Goldfarb et al., 2019), epithermal gold deposits (Chen et al., 2012b), IOCG Fe-Cu-Au deposits (Liang et al., 2019), porphyry Cu -Mo deposits (Aibai et al., 2019;Hong et al., 2020), magmatic Cu-Ni deposits (Tang et al., 2020), and skarn Cu -Mo deposits et al. , owing to the presence of abundant accreted juvenile material and the influence of related fluids (Yakubchuk et al., 2005). ...
... Orogenic gold deposits, also known as epigenetic lode-to disseminated-style gold-only deposits in metamorphic rocks, generally form at convergent margins during syn-subduction accretion to latesubduction lithosphere thinning or even continental collision (Gebre-Mariam et al., 1995;Groves et al., 1998;Robert et al., 2007;Goldfarb et al., 2019;Wang et al., 2022;Safonova and Perfilova, 2023;Zeng et al., 2023). Gold deposits of this type are widely distributed throughout the world and account for a significant proportion of the world's gold resources and production (Goldfarb et al., 2005;Weatherley and Henley, 2013;Chinnasamy et al., 2015). ...
The Pianyanzi gold deposit is situated at the western margin of the Yangtze Craton, and represents a rare sellaite-bearing orogenic gold deposit. This deposit belongs to the Dauduhe gold belt of southwestern China and remains poorly documented. In this paper we present first petrographic and in-situ geochemistrical and sulfur isotope data from pyrite as well as results of multielement mapping. The deposit is dominated by native gold (average gold fineness = 980.8) filling fractures in minerals (e.g., pyrite, quartz, sellaite and hematite) or also emplaced along the contact interface between mineral grains. Pyrite is the most abundant sulfide mineral of this deposit. We identified five generations of pyrite: Py1, Py2a, Py2b, Py3, and Py4. Gold occurs in sellaite- and hematite-bearing mineral assemblages formed simultaneous with the formation of Py2a&b and Py4, respectively. Py1 formed in the Au-poor ore stage, while Py3 formed during the late galena-dominated sulfide stage. All generations of pyrite exhibit low concentrations of gold with an average value of less than 2 ppm. Py2a&b possess distinctive textures and chemical zonation, with trace elements displaying greater variations compared to Py1, Py3 and Py4. The δ34S values vary from -0.52‰ to 7.08‰, which is consistent with those of orogenic deposits of the Daduhe gold belt. The deep metasomatized mantle lithosphere acted as a potential source of ore fluids. We conclude that the co-precipitation of native gold and sellaite was triggered by the interaction between auriferous fluids and dolomite.
... since the 2020s China has been, with ~330 metric tons (t) of gold per year, the largest gold producer in the world (USGS, 2023), more than half of which comes from the North China Craton (NCC) (Fig. 1a; Goldfarb and Qiu, 2019). The NCC hosts several major gold districts, such as the Jiaodong, Xiaoqinling-Xiong'ershan, Liaodong, Chifeng-Chaoyang, Jinan, Jibei-Jidong, and Central Taihangshan gold districts Zhu et al., 2015). ...
... Carlin-type gold deposits in the Youjiang basin were sometimes classified as orogenic gold deposit associated with Indosinian orogeny (Goldfarb and Groves, 2015;Goldfarb et al., 2019;Yang et al., 2020). This interpretation was largely based on the occurrence of these deposits (e.g., Jinfeng and Jinya) within the compressional structures, e.g., tight anticline, thrust, and/or shear zone . ...
Selecting a robust chronometer is crucial to determine the primary mineralization age of the deposits that have
witnessed multiple hydrothermal events. The Youjiang basin of South China hosts the world’s second-largest
Carlin-type gold province. However, the age of the Carlin-type gold mineralization remains highly debated,
partly due to the presence of multiple hydrothermal events that may have disturbed the primary isotopic system
with low durability. Hydrothermal zircon is a robust chronometer that can survive multiple hydrothermal events.
To this end, in this study, we report in-situ secondary ion mass spectrometry (SIMS) and laser ablation inductively
coupled plasma-mass spectrometry (LA-ICP-MS) U–Pb dating results of hydrothermal zircon identified in carbonate–
sericite–sulfide–altered dolerite from the Badu Carlin-type gold deposit to constrain the timing of gold
mineralization.
The hydrothermal zircons exhibit subhedral to anhedral morphologies, sector cathodoluminescence zonings,
and contain gold-related mineral assemblages of arsenian pyrite, quartz, sericite, and carbonate. Primary twophase
fluid inclusions also commonly occur in the hydrothermal zircons. Compositionally, these zircons
feature relatively flat light rare-earth element (REE) patterns, high La contents, low (Sm/La)N values, and small
Eu and Ce anomalies, which are different from the magmatic counterparts of the Badu pluton but consistent with
those of hydrothermal zircons reported worldwide. These features indicate that the hydrothermal zircons are
probably paragenetically associated with the gold mineralization. Consequently, the U–Pb ages of ca. 140 Ma of
these zircons, which are much younger than those of the magmatic zircon in the fresh dolerite, can represent the
timing of primary gold mineralization of Badu. Our new data suggests that there truly was an episode of gold
mineralization during the Early Cretaceous in the Youjiang basin, which may have been driven by large-scale
lithospheric extension in the interior of South China. This study demonstrates that hydrothermal zircon could
be a robust clock for investigating the timing of magmatic rock-hosted Carlin-type gold deposits.
... The Xikuangshan deposit in Hunan Province, China, is the world's largest Sb deposit, which has supplied more than half of all globally mined Sb (Yang et al. 2006;Deng and Wang 2016;Hu et al. 2017;Goldfarb et al. 2019;Fu et al. 2020a;Luo et al. 2020). It provides a natural case to better understand the ore fluid evolution and stibnite precipitation mechanisms in hydrothermal S . ...
Society annually consumes 250% more Sb relative to the year 1960 and a sustainable supply of antimony depends critically on understanding the precipitation mechanism of stibnite (Sb2S3) that is the globally predominant source of this important technology metal. Previous solubility studies revealed that antimony is transported in mesothermal hydrothermal fluids mainly as the aqueous species thioantimonite (H2Sb2S4, HSb2S4−, Sb2S42−) and hydroxothioantimonite [Sb2S2(OH)2]. Thioantimonite can transform to hydroxothioantimonite with a decline of H2S concentration. However, whether this transition occurs in hydrothermal systems and its role in stibnite precipitation are unknown. In this work, bulk Sb isotope measurements for stibnite from the world’s largest Sb deposit in Xikuangshan China were conducted to address ore fluid evolution and stibnite precipitation mechanisms. The abundance of the stable antimony isotopes 121Sb and 123Sb were measured in stibnite from the Xikuangshan orebodies and reported as δ123Sb. The δ123Sb values show a trend of decreasing first and then increasing from proximal to distal parts of orebodies. This reveals that 123Sb had been preferentially partitioned from the ore fluid into stibnite first, then 123Sb remained preferentially dissolved in the ore fluid. These data indicate that the dominant Sb-complex transforms to Sb2S2(OH)2 from H2Sb2S4 with consumption of H2S. Speciation diagram considerations indicate that stibnite precipitation from the ore fluid was controlled by two telescoped processes: (1) boiling of the ore fluid induced a decrease in H2S that reduced the solubility of H2Sb2S4, and (2) subsequent cooling that induced a decrease in the solubility of Sb2S2(OH)2. This study highlights that understanding the controls of Sb isotope fractionation is critical to constrain fluid evolution and stibnite precipitation mechanisms in Sb-rich mineral systems. In particular, the stable Sb complex in the hydrothermal ore fluid may change during fluid evolution and affect the isotope fractionation mechanism.
... Some of these resources are bituminous, chromite deposits, Fe laterite, cobalt, manganese, and nickel laterite deposits (van Leeuwen and Pieters, 2012;Hadiwardoyo & Fikri 2013;Surono, 2013;Hasria 2021a) as well as orogenic gold deposits (Idrus el al., 2011;2012;Hasria et al., 2017;2019a;2019b;2019c;2021b). Orogenic gold deposits are the most important type of gold resource in the metamorphic belt containing more than half of the world's gold ore production (Goldfarb et al., 2019) and are formed in folded and orogenic belts that occur in active continental margin settings (Groves, 1993;Groves et al. al., 1998;Goldfarb & Groves, 2015;Awadh, 2019;Awadh et al., 2008). In addition, the worldwide orogenic gold deposit has a significant role because more than 75% of the gold discovered by humans belongs to this type of deposit (Philip, 2013). ...
This research aims to examine the relationship between hydrothermal alteration and mineralization (ore mineralogy) in the study area and geological structures in the deformation mechanism. The hydrothermal alteration was determined based on petrographic analysis, and ore mineralogy which was determined based on the ore microscopic analysis. The deformation mechanism is determined by paleo stress analysis using win-tensor, and the direction of principal stress on joints/veins and faults is calculated by the right-dihedron method. Hydrothermal alteration includes silicification, argillic, propylitic, and phyllic alterations; and ore mineralogy consists of stibnite, cinnabar, pyrite, chalcopyrite, sphalerite, covellite, hematite, and arsenopyrite at metamorphic rocks. The geological structure developed in the study area consists of shear fractures and Wumbubangka right Normal-slip Fault, which is accompanied by Wumbubangka right-slip lag fault and Wumbubangka reverse-slip fault formed in a simple shear mechanism. Crenulation, micro-folds, and porphyroblastic are also recognized in thin sections. The Wumbubangka right normal-slip fault, considered a syn-mineralization structure, formed the transpressional and transtensional geologic structures, forming the quartz vein parallel to and crosscutting the foliation. The correlation between surface geological structures and microstructures indicates that tectonic regimes have controlled the alteration and gold mineralization in the study area.
... However, a notable exception is the giant Jiaodong gold province of China, where the gold deposits formed in a reactivated and previously heated Precambrian basement along the Asian continental margin during the latter stages of Jurassic-Cretaceous orogenesis and are, therefore, distinguished from other Phanerozoic orogenic gold deposits (Goldfarb et al., 2021). Approximately 95 % of the gold resources in Jiaodong are hosted within Mesozoic granitoids that have intruded Archean and, to a lesser degree, Paleoproterozoic basement rocks (Goldfarb et al., 2019;Qiu et al., 2020). The Jiaodong deposits formed approximately-two billion years after the high-grade metamorphism of the Precambrian rocks, which depleted the restitic crust of the Precambrian basement in volatiles (Goldfarb and Santosh, 2014;Wang et al., 2021), thus negating the typical supracrustal devolatilization model. ...
Orogenic gold deposits account for more than 30 % of the global gold resources. To understand the genesis of orogenic gold deposits and ultimately target new orogenic gold deposits, it is important to determine the origin of gold. However, there has been a continuing debate surrounding gold source reservoirs. The Jiaodong gold province, comprising ore hosted within Mesozoic granitoids that intruded Archean metamorphic rocks, together with other gold occurrences in the North China block, collectively constitute the only Mesozoic world-class gold resource in a Precambrian basement. This geological setting, with young deposits in ancient rocks, offers a great opportunity to better determine the gold source because it allows us to fingerprint the isotopically distinct reservoirs. Specifically, it is possible to determine whether the mass-independent isotopic fractionation sulfur (MIF-S)-bearing Archean supracrustal rocks that form the lower crust are a permissive source. We present multiple sulfur isotope (δ34S and Δ33S) measurements of pyrite grains (n = 161) from 18 gold deposits in the six main districts of the Mesozoic Jiaodong gold province. Gold-associated pyrite grains yield non-MIF-S signatures (Δ33S = 0 ‰), indicating that Archean metasedimentary rocks are not a source reservoir of sulfur and gold. The isotopically heavy S (average δ34S = +9.0 ± 3.7 ‰, 2SD) demonstrates a sulfur contribution from a subducted oceanic slab and, in particular, its overlying sediments while excluding mantle and magmatic sources. The subduction-related metamorphism released appreciable gold and sulfur from the top of the downgoing slab into aqueous-carbonic fluids that ascended into the upper plate along crustal structures traversing a tectonically thinned crust. Here, we demonstrate that these giant Mesozoic orogenic gold deposits sourced gold and sulfur during subduction-related devolatilization reactions.
... In situ U-Pb isotope analysis of carbonate minerals has been recently developed and can provide temporal constraint on diagenesis, fluid flow, and tectonism (Hansman et al., 2018;Mottram et al., 2020). This method has potential to be applied to both carbonate-rich Carlin-type and sediment-hosted orogenic gold deposits (Cline et al., 2005;Goldfarb et al., 2005;Jin et al., 2021), particularly where there is controversy about their distinction, as in the Qinling-Dabie Orogen of eastern China (Goldfarb et al., 2019). ...
In situ U–Pb dating of carbonate minerals and Rb–Sr dating of illite was carried out on the Yata sediment-hosted disseminated-type gold deposit in the Youjiang basin, South China. The new study determines the timing of gold mineralization and clarifies the geological conditions required for the successful application of in situ U–Pb dating of alteration-related carbonate minerals. The results suggest that the Yata gold deposit likely formed during two metallogenic episodes. Illite Rb–Sr ages of 178.6 ± 5.8 Ma (MSWD = 1.2) for the 2–0.5 μm fraction and 171.3 ± 3.4 Ma (MSWD = 0.62) for the 0.5–0.2 μm fraction constrain an earlier episode of gold mineralization to >178.6 Ma. Hydrothermal carbonate minerals within the Yata gold deposit are associated with organic matter. In situ U–Pb dating of paragenetically early ankerite and later calcite veins yields ages of 149.0 ± 10.4 Ma (MSWD = 2.0) and 147.3 ± 32.6 Ma (MSWD = 1.8), respectively. These mineral ages and their petrographic relationships provide unequivocal evidence that another episode of gold mineralization occurred in the Early Cretaceous. Importantly, this study demonstrates in situ U–Pb dating is applicable to low-temperature deposits consisting of organic-rich hydrothermal carbonates characteristic of relatively high common Pb. Such deposits potentially include hydrothermal antimony, Carlin-type gold deposits, gold-uranium, and carbonate-hosted uranium deposits.
... Previous studies have examined the geology, fluid inclusions, trace element chemistry, and C-H-O-S-Pb isotope geochemistry of the Gaolong deposit, but the origin of the ore-forming fluids remains controversial, and many models of ore formation have been proposed: syn-sedimentary (Zhang et al., 2008); basinal fluids (i.e., brines; Hu, 2003); deeply circulating meteoric waters (Li, 1990;Guo et al., 1992;Hu, 2003); magmatic fluids Song et al., 2022); and metamorphic fluids (Lin et al., 2021). Yang et al. (2020) suggested that the Gaolong deposit is a shallow orogenic Au deposit (Goldfarb et al., 2020) based on the ore deposit geology (e.g., the structural geometries, mineralization, and alteration types), which is different from the Carlintype Au deposits in the northwest Youjiang Basin . In our earlier study of the Gaolong deposit (Lin et al., 2021), we identified Chen et al., 2015a, b). ...
Apatite can record the evolution of magmatic–hydrothermal ore systems, but it is unclear whether it is suitable for investigating low-temperature, sediment-hosted hydrothermal ore systems. To fill the knowledge gap. we investigated the Gaolong Carlin-type Au deposit in the Guangxi Zhuang Autonomous Region, southwestern China (Youjiang Basin). Results show that the hydrothermal apatite occurs in quartz–sulfide ores, has an intact crystal form and homogeneous texture, and is F-rich (2.77–3.67 wt%) and Cl-poor (<0.01 wt%). The apatite is enriched in rare earth elements (REEs; ΣREE = 739–2481 ppm) and has middle-REE-enriched chondrite-normalized REE patterns with positive Eu anomalies (δEu = 1.35–2.00). These REE features were inherited from a reducing hydrothermal system in which anion complexation was dominant. The apatite has high Sr contents (up to 0. 9 wt%) and relatively uniform initial 87Sr/86Sr ratios (0.709055–0.709208), suggesting that Sr was leached or derived from the deep continental crust. In situ U–Pb dating of 156.8 ± 8.3 Ma for apatite shows that the Late Jurassic–Early Cretaceous was an important time for the formation of Carlin-type Au deposits in the Youjiang Basin. The Au mineralization was associated with far-field tectonism and deeply sourced hydrothermal ore-forming fluids. Hydrothermal apatite can be used to fingerprint low-temperature, sediment-hosted hydrothermal ore systems.
... In contrast to those orogenic Au deposits that formed in an oceanic subduction setting, commonly during one single event, albeit with multiple fluid pulses (Goldfarb et al., 2019), there are several episodes of orogenic Au mineralization related to continental collision in Tibet (Wang et al., 2020c. Three episodes with different metallogenic features are distinguished: 1) 60-45 Ma mesozonal (in the sense of Gebre-Mariam et al., 1995) quartz-vein deposits controlled by the compressional regime that formed along the Yarlung-Tsangpo Suture Zone and along the western SCB (Yang et al., 2021a) (Fig. 4A); 2) 32-21 Ma mesozonal quartz-vein and epizonal disseminated Au deposits that developed along the Ailaoshan and Xiaojiang shear zones in the western SCB (Gao et al., 2018;Wang et al., 2022) (Fig. 4C); and 3) 19-15 Ma mesozonal to epizonal disseminated and veinlet Au mineralization, commonly associated with Sb mineralization, that are widespread in the Himalayan domal belt (Zhang et al., 2020b) (Figs. 3, 4B). ...
This paper reviews the spatial-temporal distribution, geological and geochemical features, and geophysical context of diverse types of Cenozoic ore deposits formed during India-Eurasia continental collision in Tibet, in order to shed new light on their genesis and their control by mantle lithosphere. The parental magmas for porphyry-skarn Cu (± Mo ± Au) deposits were derived from metal-rich pre-Cenozoic juvenile crust, and the high magma oxidation state was controlled by involved mantle-derived basic magmas and thickened crust condition; magma emplacement was controlled by structures related both to tears in the subducting continental slab to deep and to mantle-crust decoupling parts in the deep. Orogenic Au deposits mostly formed intermittently from hydrothermal fluids formed by devolatilization of earlier-fertilized mantle lithosphere that was triggered by asthenosphere upwelling; they were largely controlled by lithosphere-scale shear systems that reactivated earlier-formed suture zones. Giant MVT ZnPb deposits, hosted by ancient oil reservoirs, formed during salt diapirism and infiltration of metal-rich basinal brines related to crustal-scale channel flow. The diverse range of ore deposits was derived predominantly through release of metal and fluid components, introduced into the crust and mantle lithosphere that occurred in the earlier oceanic subduction during anomalous lithosphere-scale deformation. The metallogenic history of collisional orogens contrasts with those of accretionary orogens.
... It is situated in the western part of the Chifeng-Chaoyang metallogenic belt of the northern margin of North Chian Craton (NCC), which is an important gold mining district in China [45][46][47][48][49][50][51][52]. Metallic deposits in this area include Au-Cu, Mo-Cu, Pb-Zn, Cr and Fe [52][53][54][55][56]. [48,57]). ...
In recent years, the exploration of concealed deposits has become extremely urgent as the shortage of surface resources worsens. In this study, naturally formed nanoparticles in five media (deep-seated fault gouge, ascending gas flow, soil, shallow groundwater and deep groundwater) in Chaihulanzi Au deposit, China, were analyzed by transmission electron microscopy. The characteristics of category, shape, lattice parameters, chemical component and association were obtained. The results show that deep media can carry natural nanoparticles to the surface media, resulting in an increased proportion of O and metal chemical valence such as Pb and Cu in nanoparticles. The metal elements Au, Ag, Cu, Zn and As in nanoparticles correspond to those of orebody minerals. Au-Ag-Cu, Fe-As, Cu-Sn and Pb-Zn element associations in nanoparticles are similar to those of mineral composition or orebody paragenesis in Chaihulanzi deposit. Compared with nanoparticle characteristics in deposit and background areas, it can be deduced that natural ore-bearing nanoparticles come from concealed orebodies. With the characteristics of more oxide forms and the dislocation of the crystal lattice, these nanoparticles are formed by faulting and oxidation. Nanoparticles produced in concealed orebodies that migrate from the deep to the surface media could be used for prospecting.
... In order to ensure the accuracy of the test, the NIST SRM 610 and 612 reference material glasses were used as an external reference material for trace element determinations on apatite. The internal element standard isotope was 43 Ca for apatite trace element analyses. Concordia plots and age calculations were reported at the 2σ uncertainty level and were processed using the ICPMSDataCal 11.8 program [62]. ...
The northward subduction of the Paleo-Tethys oceanic crust in the Paleozoic to Mesozoic is critical for the tectonic evolution of the Qinling-Tongbai-Hong’an-Dabie-Sulu-Imjingang-Gyeonggi orogenic belt. However, the Paleozoic geological fingerprint of the Paleo-Tethys oceanic crust subduction in the Dabie-Sulu orogenic belt remains obscure. In the present study, apatite from the Muniushan monzogranite in the Houkuang area was analyzed to constrain the age of metamorphism in the Jiaobei Terrane and is regarded as the response to the Paleo-Tethys oceanic crust subduction in the Early Permian. Muniushan apatite with obvious negative Eu anomaly is enriched in LREE and depleted in HREE. The chondrite-normalized REE patterns of apatite correspond with I-type granitoids and mafic igneous rocks, implying a magmatic origin. Igneous apatite grains have reset compositional zonation in the cathodoluminescence image. Apatites plotted on a support vector machine apatite classification biplot and Eu/Y-Ce discrimination diagram shows a tendency from the region of “mafic igneous rocks and I-type granitoids” to “low and middle metamorphic”. This evidence consistently suggests that the Muniushan apatite suffered metamorphism at a later stage. The twenty-six apatite grains from the Muniushan monzogranite yield a metamorphic age of 297 ± 8 Ma (by LA-ICP-MS U-Pb), which is different from the Muniushan zircon SHRIMP U-Pb results of 2110 ± 4 Ma, indicating the metamorphism occurred in the Early Permian and reset the U-Pb system of apatite. The Early Permian metamorphism that occurred in the Jiaobei Terrane is synchronous to the subduction of the Paleo-Tethys oceanic crust and is the response to the Paleo-Tethys oceanic crust subduction.
... Many current discoveries of gold deposits with hosted metamorphic rocks such as Buru and Seram Islands orogenic gold deposits, in Mollucas (Idrus et al., 2014;Samalehu et al., 2021); LS-epithermal at Poboya, Central Sulawesi (Syafrizal et al., 2017); mesothermal at Awak Mas, South Sulawesi (Querubin and Walters, 2011) and orogenic gold deposits at Rumbia Mountains, Southeast Sulawesi (Idrus et al., 2012;Hasria et al., 2019). One of the most important types of gold resources in metamorphic belts that are formed by orogenic processes and contain more than half of the world's gold production ore is orogenic gold deposits (Goldfarb et al., 2019). Suitable geological environments for the formation of these deposits are the folded and orogenic belts and which occur on the active continental margins settings (Groves, 1993;Groves et al., 1998;2003;Goldfarb & Groves, 2015). ...
The research at Mendoke Mountains, Southeast Sulawesi Province, particularly for the study of gold deposits, becomes a new challenge because there is no previous detailed study. This study aims to analyze the characteristics of orogenic gold deposits, which include the type and texture of quartz veins, alteration and hydrothermal mineralization with hosted metamorphic rocks. The research methods used include fieldwork and laboratory analysis. The type and texture of quartz veins were identified based on the field observations. The hydrothermal alteration was analyzed using X-ray diffraction analysis, and hydrothermal mineralization which analyzed by ore microscopy. The results showed that there are three types of quartz veins parallel and crosscut to the direction of foliation, and laminated quartz veins. The quartz veins’ texture is deformed, segmented, brittle, sheared, laminated, sheeted, irregular veins, brecciated, massive and sigmoidal. The hydrothermal alteration consists of sericitization, argillic, propylitic and carbonization alterations. The hydrothermal mineralization consists of native gold, chalcopyrite, pyrite, stibnite, covellite, cinnabar, galena, arsenopyrite, chrysocolla, magnetite, hematite and goethite. The host rock of gold mineralization in the study area is classified into the greenschist facies. Based on these characteristics, it shows that gold deposits in the Mendoke Mountains are orogenic gold deposits.
... In addition, the 126 to 90 Ma intracontinental deformation phase thermotectonic evolution as inferred from the western and eastern Qinling Orogen is correlated using apatite fission-track data [41,84], which are similar to the deformation and sedimentation investigated in Qinling area [85]. Furthermore, voluminous mafic and felsic magmatism and large-scale Mo-Au-Ag polymetallic mineralization are extensively distributed in the Qinling Orogen [46,86,87]. Their geology and geochemistry suggest an intracontinental extensional setting during the Late Mesozoic [58,88]. ...
Determining absolute ages of orogenic faults is critical to understanding the deformation process in the upper crust, but obtaining age remains a problem due to the lack of readily available techniques. Carbonates occur as veins in faults in a range of geological settings, and thus it is a suitable mineral for U-Pb geochronology. Here, we apply the new approach of U-Pb dating on syn-tectonic dolomite veins from the Gelouang gold deposit in the western Qinling Orogen to unravel the absolute timing of the fault formation shedding new light on the regional upper crustal deformation archive. In situ LA-ICP-MS U-Pb dating of dolomite yielding a successful age of 115–112 Ma demonstrates that the dolomite precipitated coeval with tectonic events ascribed to the post-orogenic deformation phase in the Qinling Orogen. This event is possibly correlated with broader intracontinental processes and might be an inevitable response to the extensional deformation of the Qinling Orogen. The presented LA-ICP-MS dolomite U-Pb age successfully represents the age of a specific structure that encompasses the intracontinental process in the Qinling Orogen. Moreover, it demonstrates the utility of the method to decipher a response to complex deformation histories on a regional scale.
... However, because there are no significant Precambrian Au deposits in northeastern China , it is also possible that this poorly studied and undated deposit is Mesozoic in age. The world-class orogenic Au deposits of the Jiaodong and Liaodong Peninsulas, which are located in the JLJB ~500 km to the southwest of the Hunjiang basin, are Early Cretaceous and are thought to have formed as part of a complex episode of Izanagi slab subduction and regional extension (Goldfarb and Santosh, 2014;Goldfarb et al., 2019). Deposits of the Jiapigou Au belt ~100 km to the northeast of the Hunjiang basin have been dated as Triassic (Miao et al., 2005) to Cretaceous (Deng et al., 2014). ...
The Hunjiang basin in the northeastern North China block is host to a wide range of ore deposit types that are currently exploited by more than 100 past and producing mines. Extensive field and laboratory investigations were conducted to summarize the regional metallogeny, classify the different deposit types, and to place the deposits within a regional geologic and tectonic context. The Archean basement of the basin is host to magnetite deposits that have been affected by high-grade metamorphism. In addition, Proterozoic magmatic Cu-Ni deposit and orogenic Au deposits that are likely of Mesozoic age are located in the metamorphic basement rocks. Pol- ymetallic Co-Cu and Ni-Co-Cu deposits are located in Proterozoic schists within the basin and are of pre- to syn- metamorphic origin. However, most deposits in Hunjiang basin can be related to Mesozoic igneous activity. This includes porphyry Cu and Cu-Mo deposits as well as associated skarns and carbonate replacement deposits. Economically most significant are Au deposits hosted in Proterozoic limestone and dolomite that are located distal to the Mesozoic igneous intrusive centers. This includes the White Mountain deposit near Baishan City, which contains an endowment of more than 50 tonnes Au. There are no known high-sulfidation epithermal deposits within the Hunjiang basin, which is consistent with fluid inclusion evidence demonstrating that emplacement of the porphyry intrusions occurred at significant depth below the paleosurface. Geochronological constraints indicate that Mesozoic igneous activity and associated deposit formation in the Hunjiang basin occurred as a result of Jurassic subduction processes and subsequent extension after slab rollback and litho- spheric delamination under the Eastern North China Block in the Cretaceous. Future mineral exploration efforts in the Hunjiang basin should focus on the distal sedimentary rock-hosted Au deposits associated with Mesozoic intrusions, with special emphasis on the northern part of the basin where these deposits occur preferentially at the intersection of extensional faults with a vanished evaporite unit that is distinctly enriched in Fe oxides providing a chemical trap.
... Moreover, the H, O, He, and Ar isotopic data implied that the fluids of the deposit were formed by mixing meteoric and magmatic fluids. These FIs and stable data demonstrate a simple cooling trend and mixing with meteoric waters during the evolution of the fluid [120][121][122][123]. Meanwhile, the data of the FIs from the middle-stage and late-stage with relatively lower salinity and lower temperature fail to provide any evidence for boiling. ...
The Changkeng–Fuwan Au-Ag deposit is representative in South China, which is located in the southwest of the Qin–Hang metallogenic belt (QHMB). The Au and Ag orebodies are located in the same altered fracture zone, forming independent gold and silver orebodies respectively, with the characteristics of “upper gold and lower silver” in space. Three metallogenic stages have been identified: the pyrite–quartz–sericite stage, the polymetallic sulfide stage, and the quartz–calcite stage. The fluid inclusions (FIs) from the deposit are the two-phase liquid-rich (type I) and the pure liquid FIs (type II). The microthermometric measurements of type I FIs are characterized by temperatures of 158–282 °C and 146–289 °C and salinities of 0.35–9.88 wt.% NaCl equiv. and 0.18–11.70 wt.% NaCl equiv. The H, O, He, and Ar isotopic data show that the ore-forming fluids of the deposit were derived from a mixture of magmatic and meteoric fluids. The C and O isotopic data suggest that the carbon of the fluid may derive from a magmatic source. The S and Pb isotopic data indicate that the primary source of the metals in the Changkeng–Fuwan deposit may be a magma source. Based on the geological characteristics, FI microthermometry, and isotope data (C, H, O, He, Ar, S, and Pb), we propose that the Changkeng–Fuwan deposit should be classified as a far-source low-temperature magmatic–hydrothermal deposit.
Hydrothermal alteration is crucial in the formation of many ore deposits, with potassium (K) mobilization and cycling being prevalent. Potassic metasomatism of wall rocks generally forms K-bearing minerals, such as hydrothermal feldspar and mica. However, determining the source and redistribution of K (and other elements transported by the same fluid) in hydrothermal systems is challenging. K isotopes offer a potential solution to this problem. This study presents new K isotope data from two K-rich alteration assemblages — K-feldspar and sericite-quartz-pyrite — in the Jiaodong gold province of China. The data covers a compositional range from unaltered granites to syn-magmatic potassic alteration (formation of K-feldspar) and post-magmatic syn-mineralization phyllic alteration (formation of sericite). Potassic alteration in granite correlates with significant K addition, whereas phyllic alteration of earlier phases of magmatic and hydrothermal K-feldspar resulted in K loss. K-feldspar altered granites display similar δ41K values (−0.55 to −0.42 ‰ for whole-rocks and −0.56 to −0.48 ‰ for K-feldspar separates) as unaltered granite (−0.52 to −0.47 ‰). The narrow δ41K range suggests that magmatic fluid exsolution and magmatic-hydrothermal alteration have a minor effect on δ41K of the altered rock. Phyllic alteration of K-feldspar altered precursor rock leads to K loss and elevated δ41K values ranging from −0.36 to −0.19 ‰ for whole-rocks and −0.34 to −0.17 ‰ for sericite mineral separates. As sericite preferentially incorporates 41K, sericite will have higher δ41K values than the precursor K-feldspar, whereas the fluids will have lower δ41K values. Our study demonstrates that hydrothermal alteration may affect the K isotope composition of altered rocks in several ways, contingent on the nature of the involved phases, making K isotopes a promising tool for studying hydrothermal alteration and associated mineralization.
About 200 known coastal deposits of heavy mineral sands (HMS) occur in China, in which considerable mineral resources of titanium, zircon, rare earth elements, and thorium exist in the forms of ilmenite, rutile, zircon, and monazite. More than 20 of these HMS deposits are reported as having been or are actively being mined in China during the past three decades, of which 12 have been reported to have industrial resources. Commercially important deposits occur almost entirely in Cenozoic beach and sand dune deposits, principally along China’s eastern coast (e.g., Shandong Province) and southern coast (e.g., Guangxi, Guangdong, Hainan, and Fujian provinces), and particularly on Hainan island. There are also important deposits of HMS along coastal areas of Taiwan. China has the largest share of the world’s economic ilmenite resources in HMS deposits (31%).
A variety of igneous and associated metamorphic rocks along the coastal areas of China provided an abundant source of heavy minerals for the formation of the HMS occurrences. Studies of titanium-rich HMS deposits have shown that ilmenite is mostly sourced from igneous rocks. For example, 40% of the bedrock of Hainan island consists of Triassic and Cretaceous granites emplaced into rocks of the Cathyasia Block, and all of the HMS districts on the island lie no more than 15 km downstream from a Middle Triassic suite of syenite to granite intrusions. The southern coastal regions of Guangdong and Guangxi provinces are dominated by Jurassic granodiorite, biotite granite, two-mica granite, and A-type granite, with minor gabbro and syenite. Identified accessory minerals in the Jurassic alkaline granitoids include zircon, apatite, allanite, titanite, magnetite, ilmenite, monazite, and niobite. Thus, multiple plutons are in proximity to the Cenozoic coastal plain and are available as bedrock sources for the detrital titanium minerals, zircon, and monazite.
More than 100 HMS deposits and prospects have been identified in Shandong Province, consisting of more than 20 varieties of heavy minerals in quartz sand, which include zircon, ilmenite, rutile, monazite, magnetite, xenotime, and gold (in general order of abundance) derived from Precambrian metamorphic basement and Mesozoic intrusions. Of these minerals, zircon, magnetite, gold, and quartz sand have economic significance. The quartz sands are used by the glass and construction industries. The placers mainly occur in and adjacent to the littoral zones of the northern and southern coasts of the Jiaodong Peninsula in Shandong province. Seven beach placer, HMS prospective areas have been delineated in coastal areas of the peninsula.
Due to nearly exhausted placer reserves in the Chinese coastal zones, as well as increased environmental restrictions, future prospecting for heavy minerals will likely focus on ancient beach systems in China’s inland sedimentary basins. Also, offshore deposits of HMS in shallow coastal waters are other potential sources of heavy minerals, such as the Baoding Sea zircon-titanium, minerals-rich placer under development near Wanning on Hainan. Similarly, there is potential for offshore HMS deposits in shallow waters of the entire coastal area of southern Taiwan that remains to be fully evaluated. Reconnaissance sampling along Taiwan island’s coasts has revealed the potential for extensive, high-grade HMS accumulations nearshore.
The temporal-spatial distribution of metallic ore deposits in China, including magmatic Ni-Cu ± platinum group elements (PGE), porphyry, skarn, volcanogenic massive sulfide (VMS), epithermal, sedimentary rock-hosted Pb-Zn, Carlin-like Au, and orogenic Au deposits, reflects a diversity of tectonic settings. The ore deposits belong to 14 metallogenic provinces, contained within six age groups, which are classified based on geodynamic setting. Three of the provinces developed in the Precambrian (group I), nine developed in the Paleozoic and Mesozoic (groups II, III, IV, and V), and two developed in the Cenozoic (group VI). Except for the group I provinces, each of the other provinces is characterized by a major metallogenic age peak corresponding to a series of interrelated tectonic events or mantle plume activity. The Precambrian group can be subdivided into a Neoarchean metallogenic province in the North China craton that hosts several VMS deposits; a Proterozoic metallogenic province in the North China craton that hosts the 1505 Ma Bayan Obo carbonatite-related rare earth element (REE)-Nb-Fe deposit and the 832 Ma Jinchuan magmatic Ni-Cu-(PGE) deposit, and a Proterozoic metallogenic province in the South China block that hosts several iron oxide copper-gold deposits. Many of the deposits in these metallogenic provinces are related to continental rifting. The second group of metallogenic provinces occurs in the Chinese part of the Central Asian orogenic belt. It includes a Cambrian-Ordovician metallogenic province that developed during subduction of the Paleo-Asian oceanic plate, a Carboniferous-Triassic metallogenic province (Tianshan-Altay) that developed during final closure of the ocean, and a Permian-Triassic metallogenic province (NE China) that developed after arc-continent collision. Important ore deposits in these metallogenic provinces are, respectively, the 485 Ma Duobaoshan porphyry Cu-Mo deposit the 445 Ma Bainaimiao porphyry Cu-Mo-Au deposit; the 363 Ma Axi epithermal Au deposit, the 322 Ma Tuwu-Yangdong porphyry Cu deposit, the 284 Ma Huangshanxi magmatic Ni-Cu deposit; the 245 Ma Chehugou porphyry Mo-Cu deposit, the 223 Ma Jinchangyu orogenic Au deposit, and 220 Ma Hongqiling magmatic Ni-Cu deposit. The third group of metallogenic provinces occurs in the Tethyan metallogenic domain and can be further divided into a Cambrian-Ordovician Qilian-Kunlun-Sanjiang province that developed during subduction and closure of the Proto-Tethyan Ocean; a Carboniferous-Triassic province that developed during birth, subduction, and consumption of the Paleo-Tethyan Ocean; and a Jurassic-Cretaceous Tethys province that developed during subduction of the Meso-Tethys oceanic plate. Important ore deposits in these provinces include the 411 Ma Baiganhu W-Sn skarn deposit and the 412 Ma Xiarihamu magmatic Ni-Cu deposit that formed in a continental-arc setting; the Laochang Pb-Zn VMS deposit associated with ocean island basalt-like volcanism, the 220 Ma Pulang porphyry Cu deposit that formed in a continental-arc setting, and the 230 to 210 Ma Carlin-like Au deposits formed in a postcollisional environment in the western Qinling and the Youjiang basin; and the 119 Ma Tieyaoshan Sn skarn-greisen deposit, the 88 Ma Tongchanggou porphyry Mo deposit, and the 83 Ma Gejiu Sn skarn deposits. The fourth group of metallogenic provinces developed during subduction of the Pacific oceanic plate beneath southeastern China and comprises a Jurassic and a Cretaceous province. The former is represented by a cluster of ~160 Ma W-Sn skarn deposits in the Nanling region; the latter is known for many ~135 Ma skarn and porphyry Cu-Au deposits in the Tongling region and numerous ~125 Ma unusual orogenic Au deposits in the Jiaodong and Xiaoqinling regions. The fifth group is the Emeishan metallogenic province that is related to Permian mantle plume activity in southwestern China. Several world-class magmatic Fe-Ti-V oxide deposits, a few small magmatic Ni-Cu deposits, and a couple of small magmatic Pt-Pd deposits associated with mafic-ultramafic intrusions are present in this province. The sixth group of metallogenic provinces developed in the Cenozoic during continental collision in the Tibet and Sanjiang region. This group can be further divided into the Sanjiang province that is related to oblique collision, and the Tibet province that is related to orthogonal collision. Important ore deposits in these provinces are the ~41 Ma Yulong porphyry Cu-(Mo) deposit, the 37 Ma Beiya Au-Cu skarn deposit, the ~26 Ma Jinding sedimentary rock-hosted Zn-Pb deposit, the ~30 Ma Zhenyuan orogenic Au deposit, and the ~15 Ma Qulong and Jiama porphyry Cu deposits. The youngest metallogenic province in China occurs on the Taiwan Island. This province developed during the subduction of the Philippine Sea oceanic plate beneath the island in the Pliocene and the accretion of the Luzon volcanic arc to the island in the Pleistocene. This province contains numerous Pliocene orogenic gold deposits as well as the Pleistocene Chinkuashih epithermal gold deposit in northern Taiwan.
As the second largest economy in the world, China plays an important role in the global mineral resources sector. In this contribution, an overview of the minerals industry of China covers the evolution of policies, mineral rights, mineral royalties, and mineral taxation. The advantages and challenges of conducting exploration and mining in the country are discussed. With more and more international mergers and acquisitions, Chinese companies have begun to more consistently apply Western technologies and management to their domestic and overseas exploration and mining projects. Despite the controversial mineral royalty policy and increasingly strict environmental protection regulations, the government recently relaxed some other regulations to make it easier for the industry. The general trend of improving conditions for overseas investment in China’s exploration and mining industry is encouraging for international companies and investors in mineral exploration.
A- and I-type magmas are commonly associated with rare earth element (REE) and gold (Au) mineralization. However, the behavior and solubility of the REEs and gold within the A- and I-type magmas and their synchronous magmatism remain unclear. This study focused on the synchronous Early Cretaceous A- and I-type magmatism that formed alkaline and granodioritic complexes within the Luxi and Jiaobei terranes of the central-eastern North China Block, terranes that contain the third largest known REE deposit in China and the third largest gold province in the world. Our integrated whole-rock geochemical and Nd isotopic data and zircon Hf-O isotopic data provide new insights into the petrogenesis of these contemporaneous A- and I-type magmas and their role in the generation of the REE and gold mineralization in this area. The alkaline magmas that formed the intrusions in the Luxi terrane had A- and I-type affinities, were oxidized, were fluorine-, sulfur-, and copper-rich, were H2O-poor, and were generated by low-pressure partial melting of a source region containing enriched lithospheric mantle material and minor amounts of Paleoproterozoic A-type granitic crust. In comparison, the granodioritic magmas within the Jiaobei terrane had I-type affinities, were relatively reduced, were sulfur-rich, contained low concentrations of Cu, were hydrous, and were formed by high-pressure partial melting of a source region containing enriched mantle material and large volumes of Archean to Paleoproterozoic crustal material. The A- and I-type magmas within the Luxi terrane also have higher high field strength element (HFSE; e.g., Th, Nb, Ta) and total light rare earth element (ΣLREE) concentrations as well as higher ΣLREE/total heavy rare earth element (ΣHREE) ratios than the I-type magmas enriched in large ion lithophile elements (LILEs; e.g., Ba, Sr) in the Jiaobei terrane. These characteristics suggest that the diversity of REE and gold mineralization was the result of interaction between the lithospheric mantle and hybrid sediment-derived melts and aqueous fluids under rutile-bearing eclogite-facies (>2.0 GPa) conditions within the Luxi terrane and with aqueous fluids under amphibolite- to eclogite-facies (>1.5 GPa) conditions within the Jiaobei terrane. Our study strongly suggests that the interaction between the lithospheric mantle and sediment-derived melts, the presence of coexisting REE- and fluorine-rich magmas, and low-pressure partial melting were all crucial factors in the formation of A-type intrusion-related REE deposits, whereas high-pressure partial melting and contemporaneous sulfur and chalcophile element enrichment were critical processes in the formation of I-type intrusions prospective for gold mineralization.
Located along the southern part of the West Qinling, Yangshan gold deposit is one of the largest gold deposits in China. The major gold ores of the Yangshan are disseminated in metasedimentary host rocks with minor native golds amounts in stibnite‐gold quartz veins. Pyrite and arsenopyrite are the major Au‐bearing minerals. Hydrothermal muscovite from gold‐bearing quartz vein was dated by in situ Rb‐Sr method to determine the formation age of the Yangshan gold deposit. The Rb‐Sr isochron age of the muscovite yielded 210.1 ± 5.6 Ma (MSWD = 1.2). This age is near the lower end of the period of the mineralized granitic dykes (210.49–213.10Ma). Two stages of gold‐rich process are recognized in gold bearing pyrite. The first gold enrichment process is incorporated with the Co, Cu, As, Ni enrichment. And the second stage of gold enrichment is accompanied by Bi, Co, Ni, Pb, Cu, Sb concentration. The in‐situ sulfur isotopic values of pyrites show a restricted δ ³⁴ S range of ‐1.43 to 2.86 ‰ with a mean value of 0.43 ‰. Trace‐element mapping and in‐situ sulfur isotopic analysis of pyrite suggest that the sulfur sources are likely derived from magmatic source and likely assimilated by sulfur from the sedimentary bedrock. The magmatism plays a critical role in the formation of the Yangshan gold deposit.
The northern margin of the North China Craton (NNCC) hosts Mesozoic gold deposits of significant economic importance. The metal sources of these gold systems have long been debated with mainly magmatic‐hydrothermal versus metamorphic fluid models. Mercury (Hg) isotopes, which undergo unique mass‐independent fractionation, can provide important insights into the source of metals in gold deposits due to the close association between Hg and Au in such systems. Here, we investigated the Hg isotopic composition of six gold deposits of the Middle Jurassic to Early Cretaceous age and potential source rocks in the NNCC. Variable ∆¹⁹⁹Hg values were observed in bulk ore and pyrite samples (−0.28‰ to 0.34‰, n = 51) and coeval granites (−0.21‰ to 0.13‰; n = 25). The negative ∆¹⁹⁹Hg values of bulk ore and pyrite samples mostly agree with that observed for metamorphic basement rocks (−0.37‰ to 0.11‰; n = 32). The positive ∆¹⁹⁹Hg values of bulk ore and pyrite samples agree with those reported in marine sediments (0‰–0.3‰). So the data suggest binary mixing of ocean‐recycled Hg originated from the subducted oceanic slab, and terrestrial‐recycled Hg from the Precambrian basement in Mesozoic gold deposits. The contribution of Hg (and Au, by analogy) from both reservoirs varies depending on active continental arc versus intracontinental setting and is ultimately controlled by translithospheric heat flow driven by paleo‐Pacific plate subduction.
The process and mechanism of gold mineralization are frontier issues. The Dunbasitao deposit is the most important gold deposit discovered along the Armantai suture zone, East Junggar, NW China, which indicates the potential for future ore exploration in this area. Orebodies are mainly hosted in Lower Carboniferous Jiangbasitao Formation volcano-sedimentary rocks, and the ores are characterized by multistage pyrites. Based on microscopy and backscattered electron imaging studies, pyrites are classified into five types: the pre-ore framboidal/colloidal Py0; the early-stage coarse-grained, cubic, and homogeneous Py1; and the middle-stage fine-grained, cubic/pyritohedron Py2 that includes Py2a (core), Py2b (mantle), and Py2c (rim). The results of the EPMA and in situ LA-ICP-MS analyses show that trace elements of pyrite mainly occur in two forms: solid solutions and invisible or visible inclusions. Mn, Co, Ni, and As enter the pyrite lattice, whereas Ti occurs as mineral inclusions, and Au, Cu, Zn, Sb, and Pb can occur in both forms. Au and As show a positive linear relationship with r = 0.850. Py2b has much higher Au contents (20.1 to 201 ppm) than other pyrite types (Py0: 0.01 to 0.36 ppm; Py1: 0.01 to 0.02 ppm; Py2a: 0.31 to 2.48 ppm; and Py2c: 0.18 to 18.0 ppm). The Dunbasitao deposit is classified as an orogenic gold deposit using the two latest machine learning classifiers based on pyrite trace element data. Fluid immiscibility, sudden cooling, and the substitution of S1− with As1− might be crucial mechanisms leading to Au precipitation. Initial ore-forming fluids brought major amounts of As, Au, Co, Ni, Se, Zn, Ag, Cd, Sn, and other elements, and the Jiangbasitao Formation host rocks contributed a certain amount of As, Ni, Cu, Sb, Pb, and Bi, at least.
The Youjiang Basin in Southwest (SW) China is the second-largest Carlin-type goldfield in the world after Nevada, USA; however, the spatial, temporal, and genetic links between Carlin-type Au mineralization and magmatism in SW China remain controversial compared with those in Nevada. The Mingshan gold deposit is one of the few Carlin-type gold deposits that exhibits a close spatial relationship between gold orebodies and magmatic rocks in the Youjiang Basin. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) uranium-lead (U-Pb) dating of magmatic zircons from quartz porphyry dikes and hydrothermal apatite associated with gold yields the intrusive and gold mineralization ages of 96.34 ± 0.89 and 139.9 ± 4.8 Ma, respectively, indicating that the magmatism was much younger than the gold mineralization at Mingshan. Petrography and microthermometry of the fluid inclusions from ore-stage quartz and calcite suggest a low to moderate temperature (140–240 °C), low salinity (3–8 wt% NaCleqv), and moderate to low density fluid. The hydrogen and oxygen isotope compositions of the ore-stage quartz indicate a metamorphic fluid source of the ore fluid. Thus, we propose that the close spatial contact between the gold orebodies and igneous dikes could have resulted from the same NWW-trending fault space during the Early Cretaceous precipitation of ore fluid and the Late Cretaceous intrusion of the quartz porphyry dikes. However, the genetic link between the quartz porphyry and Carlin-type Au mineralization was not observed at Mingshan. The primary metamorphic fluid associated with Early Cretaceous gold mineralization in the Youjiang Basin was derived from syn-orogenic shortening deformation and metamorphism in the compressional tectonic setting caused by the subduction of the Paleo-Pacific Plate. Subsequent post-orogenic extension during the rollback of the subducted Pacific slab led to significant extensional faults and intrusions of Early Cretaceous concealed granites, which may have provided heat, materials, and energy for the transport of ore fluid. The ore fluid was transported through permeable extensional structures from the deep crust and reacted with the carbonaceous and Fe-rich host rocks in the shallow crust, resulting in the Early Cretaceous gold mineralization event in the Youjiang Basin.
The Jiaodong Peninsula is one of the most important Au ore provinces in China. There is an ongoing debate on the correlation between ore formation and magmatism in this province, because few intrusive rocks exhibit a clear association with ore deposits. A mineralized biotite monzodiorite (BM) stock, with disseminated ore, pervasive phyllic alteration, and no deformation, was found in a borehole in the footwall of the Zhaoping fault within the Luanjiahe Au deposit, which may shed light on this debate. The biotite monzodiorite contains explosion breccias, miarolitic cavities, skeletal and dendritic quartz, and late-stage evolved aplite dikes, and the in-situ δ34S values of the disseminated pyrite which is associated with Au mineralization are −1.7‰ to 7.3‰ (mean=3.5‰), indicative of a magmatic-hydrothermal system. These findings, combined with the reported age of 123 Ma, show that the intrusion has close spatial, temporal, and geochemical relationships with Au mineralization in the area. The biotite monzodiorite is metaluminous, high-K calc-alkaline and shoshonitic, with enrichment in light rare earth elements (REEs) and large-ion lithophile elements (LILEs), depletion in high-field-strength elements (HFSEs), and enriched Sr-Nd isotopic compositions. The intrusion may be the product of partial melting of enriched lithospheric mantle with a small lower crustal component. The hydrous, Au-bearing, enriched mantle source, and the strongly oxidized magma that was generated, created favorable conditions for Au mineralization.
The Bajiazi gold deposit, located in the northeast of the North China Craton, is a typical representative of the Jiapigou ore cluster in northeast China. The deposit is hosted within the Neoarchean–Paleoproterozoic supracrustal rocks (greenstone belts) and metamorphosed plutonic rocks. The orebodies occur along NE-trending ductile–brittle faults as auriferous quartz veins. The mineral assemblages reveal three stages of mineralization: quartz–pyrite (early), quartz–polymetallic sulfide (main), and quartz–carbonate (late). Three types of primary fluid inclusions (FIs), namely A-type (aqueous), C-type (aqueous–carbonic), and PC-type (pure carbonic) FIs, have been distinguished in different stages of quartz. The early- and main-stage quartz grains contain C-, A-, and a few PC-type FIs, while the late-stage quartz grains contain only A-type FIs. The early-, main-, and late-stage FIs homogenized at temperatures of 288–397 °C, 183–281 °C, and 120–190 °C, corresponding to salinities of 8.8–19.5, 3.9–18.8, and 3.2–11.3 wt% NaCl eqv., respectively. The ore fluid system evolved from H2O–NaCl–CO2 to H2O–NaCl during ore formation. The gold precipitation resulted from fluid immiscibility during the main mineralization stage. The HO isotope data reveal that the ore fluids originally came from magmatic water, and mixed with meteoric water during ore formation. The δ³⁴S values (−0.2 ‰ to 8.3 ‰) of ore-related sulfides suggest that the sulfur in the ores was originally magmatic-sourced, and mixed with the sulfur in wall rocks during fluid migration. The Pb isotope ratios (²⁰⁶Pb/²⁰⁴Pb = 15.890–16.794, ²⁰⁷Pb/²⁰⁴Pb = 15.188–15.530, and ²⁰⁸Pb/²⁰⁴Pb = 36.589–37.710) of ore-related sulfides indicate the metals in the ores originated primarily from the lower crust, with a minor mantle contribution, and most likely came from a deep magmatic system. The Late Triassic gold mineralization has a clear genetic link to a quartz syenite porphyry. Based on the geological, FI, and isotopic constraints, the Bajiazi deposit is classified as a mesothermal lode gold deposit, which formed in an extensional setting after the closure of the Paleo-Asian Ocean.
The Xinfang gold deposit is situated in the southwest of the Liaodong Peninsula, and represents the first large-scale gold deposit hosted by the Xinfang Metamorphic Core Complex. We conduct pyrite and galena Rb-Sr isotope dating, multiple isotope compositions (H-O-S-Pb-Sr), fluid inclusions (FIs), and pyrite laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) trace element analysis to constrain the genesis of the deposit. Our fluid inclusion analyses show that the ore-forming fluids belong to a medium-low-temperature and moderate-low salinity NaCl-H2O-CO2 fluid system. Fluid boiling is the key factor for Au precipitation in the Xinfang gold deposit. In-situ sulfide S-isotope data (δ³⁴S = −1.64‰ to 6.07‰) favor a magmatic source. The initial ⁸⁷Sr/⁸⁶Sr ratios of the sulfide samples range from 0.709556 to 0.710731, indicating that the ore-forming materials came from a mixture of the crust and mantle. The in-situ lead compositions of sulfides (²⁰⁶Pb/²⁰⁴Pb = 16.562–18.367, ²⁰⁷Pb/²⁰⁴Pb = 15.257–17.071, ²⁰⁸Pb/²⁰⁴Pb = 37.005–38.750) reveal that the ore-forming materials originated from the crustal source with a small amount from the mantle source. The δ¹⁸OH2O (−3.28‰ to 3.64‰) and δDH2O (−89.6‰ to −81.3‰) values suggest that the ore-forming fluids came from magmatic water with a contribution of meteoric water. LA-ICP-MS trace element analyses reveal that stage II was the main gold mineralization stage, and Archean gneiss may have contributed ore-forming materials. The Co/Ni ratios suggest that the pyrite may have formed from hydrothermal fluids. Pyrite and galena samples from the quartz-polymetallic sulfide-gold vein yielded a Rb-Sr isochron age of 122.6 ± 2.1 Ma (Initial ⁸⁷Sr/⁸⁶Sr = 0.710255 ± 0.000059, MSWD = 1.2), which is interpreted to be the ore-formation age. In combining all available data results, we propose a magmatic-hydrothermal source for the Xinfang gold deposit and that the ore formation is related to the subduction of the Paleo-Pacific Plate beneath Eurasia.
Gold deposits in the Xiaoqinling province, southern margin of the North China Craton, are hosted by Neoarchean amphibolite-facies rocks of a metamorphic core complex. Over 630 t of gold resource was concentrated in the narrow-uplifted basement, which was classified into three (northern, middle, and southern) major ore belts. Gold-related scheelite grains from the Qinnan and Qiaoshangzhai (northern belt), Tonggou (middle belt), and Yangzhaiyu (southern belt) deposits were analyzed using a combination of cathodoluminescence (CL) imaging and LA-ICP-MS trace element analysis to decipher their metallogenesis. Our new results indicate that: (1) the Xiaoqinling scheelites are characterized by high Sr content and varying internal texture, replicating fluid-rock reactions. Oscillatory zoning and inhomogeneous trace element compositions suggest a dynamic hydrothermal system with fluctuating chemical properties; (2) the REEs of Xiaoqinling scheelites were mainly controlled by the substitution mechanism 2Ca²⁺ = REE³⁺ + Na⁺. All scheelite grains yielded typical bell-shaped REEN patterns, with negative and positive Eu anomalies occurring in samples from the Qinnan-Qiaoshangzhai and Tonggou-Yangzhaiyu deposits, respectively. Meanwhile, the scheelite Mo concentration in the northern belt (>100 ppm) is much higher than that in the middle and southern belts (<20 ppm), suggestive of significant variations in the oxygen fugacity (fO2). The spatial association of the northern ore belt with the Taiyao detachment fault may imply an increase in the fluid fO2 by percolating meteoric waters; (3) the obtained scheelite ⁸⁷Sr/⁸⁶Sr ratios show a broadly increasing trend from north to south (are 0.71480 to 0.71626 for Qinnan, 0.72784 to 0.72920 for Qiaoshangzhai, 0.71864 to 0.76251 for Tonggou, and 0.72760 to 0.74781 for Yangzhaiyu). This trend may depict the ore-fluid flow direction, i.e., the Sr isotopic signature shifted towards a more radiogenic composition with increasing distance from north to south due to fluid reaction with the Taihua Group (amphibolite- to granulite-facies metamorphic rock pile).
The Xiaoqinling district, located in the southern margin of the North China Craton, is one of China’s most significant gold districts (resources of >630 t Au). A complex series of overprinting Mesozoic tectonic and related hydrothermal events associated with the metallogenic evolution in this region has led to controversial interpretations and models. Here we present new geological, mineralogical, ore texture, geochronological, and in-situ S isotope data from the Dahu Au-Mo, Qinnan Au-Mo, and Tonggou Au deposits from this region which indicate that the Mo and Au were introduced in two discrete mineralization events. The Mo-bearing mineral assemblage mainly comprises quartz, anhydrite, pyrite, molybdenite, and rutile that yielded an age of 216.1 ± 9.7 Ma at Dahu. In-situ LA-ICP-MS δ³⁴S values for the molybdenite and related pyrite cluster tightly at -10 to -9‰. On the other hand, the Au-bearing mineral assemblage mainly comprises quartz, pyrite, galena, sphalerite, chalcopyrite, native gold, and Te (±Bi) minerals. Hydrothermal rutile and monazite associated with auriferous pyrite yielded ages of 124.7 ± 3.9 Ma (Dahu), 121.5 ± 1.3 Ma (Qinnan), and 122.1 ± 2.0 Ma (Tonggou). The in-situ δ³⁴S values of gold-related sulfides fall within a range of -4 to +3‰. Although Mo and Au ores are both present in the same ore veins, their mineral assemblage, mineralization age, fluid properties and sources are different. Textural relationship shows that the earlier Mo-bearing quartz-anhydrite veins were overprinted by later auriferous fluids. Several lines of evidence support a multiphase mineralization process of Mo and Au, which are genetically linked to the post-collisional extension of the Qinling orogen and the Paleo-Pacific post-subduction tectonics, respectively. The episodic hydrothermal mineralization in Xiaoqinling represents a protracted and complex lode system.
The extreme fluctuations in pressure during earthquakes are widely regarded as responsible for gold mineralization in quartz-vein-hosted gold deposits. However, it is barely noticed that base metal sulfides can precipitate together with gold during these processes. Here we present the phenomenon and unravel the mechanism of the co-precipitation of Au and base metal sulfides during the fluid boiling via geological study and thermaldynamic modeling, respectively. The Bangbu deposit, a lode-type orogenic gold deposit in Tibet shows two mineralization substages of pyrite. The pyrite formed in the later substage is hosted in the wall rock selvages of laminated crack-seal quartz veins formed by the fault-valve processes. The pyrite grains are characterized by anhedral small crystals with a porous texture and abundant native gold, chalcopyrite, galena, and sphalerite inclusions. They also contain higher concentrations of Cu, Pb, Ag, Sb, and Au, and lower concentrations of Co and Ni, compared to the euhedral large-grained pyrite formed in the initial substage. The textural and trace element characteristics of the pyrite indicate that vigorous boiling occurred during fault-valve behavior, which decreased the solubilities of Au, Cu, Pb, and Zn in the ore fluid in Bangbu. The co-precipitation of Au and base metal sulfides triggered by fluid boiling have also been reported in other orogenic gold deposits worldwide.
Thermodynamic models are designed to acquire the predominant species and solubility of Au, Cu, Pb, and Zn in orogenic ore fluids under varied chemical conditions. The results show that Au, Cu, Pb, and Zn are dominantly transported as hydrosulfide complexes under lower mesozonal to epizonal deposit conditions. At temperatures of about above 350°C, Au hydrosulfide species still predominates, but the predominant Cu, Pb, and Zn species change from hydrosulfide to chloride complexes. A sudden decrease in the reduced sulfur concentration during fluid boiling may be the most important mechanism controlling the precipitation of Au, Cu, Pb, and Zn in lower mesozonal to epizonal deposits. The decrease of logfS2 during fluid boiling can increase the fluid pH, resulting in the decrease of solubilities of base metal chloride complexes and thus explain the co-precipitation of Au and base metal sulfides in hypozonal deposits.
The Mongol–Okhotsk and Paleo-Pacific tectonic regimes both have an influence in NE China during the late Mesozoic. The Sishanlinchang and several newly reported late Mesozoic porphyry Cu–Mo deposits in NE China are typical products of this interaction. A systematic study of these deposits provides new insights into the genesis of porphyry Cu–Mo systems in the region. Here we present petrological, geochronological, whole–rock geochemical and isotopic data from the ore-forming rocks in the Sishanlinchang deposit, together with a compilation of data from late Mesozoic porphyry Cu–Mo deposits in NE China, to reveal their magma source, and corresponding geodynamic settings. Zircon U–Pb dating shows that the studied granites were emplaced at 111 Ma, which contrasts with previously reported occurrences of late Jurassic porphyry Cu–Mo deposits in the northern NE China, indicating at least two episodes of porphyry Cu–Mo mineralization during the late Mesozoic. Whole-rock geochemical data show that all of the late Mesozoic ore-forming granites have low Y and Yb, high Sr contents, and high Sr/Y ratios (35.70-71.59), which exhibit an adakitic affinity. High Na2O, Cr, and Ni contents, and Mg# (47-58) values, a low proportion of garnet in the source, positive whole-rock εNd(t) values (1.21-2.27) and pronounced positive zircon εHf(t) values (6.85-9.37) indicate that the adakitic rocks were derived from partial melting of oceanic crust with assimilation of enriched mantle materials. Combined with our studies and previous studies, we conclude that the Early Cretaceous porphyry–epithermal Cu–Mo–Au deposits in the eastern NE China were controlled by the Paleo-Pacific tectonic regime, which is different from the Late Jurassic Cu–Mo deposits in the northern NE China controlled by the Mongol–Okhotsk tectonic regime.
The Xiangzhong (XZ) Basin and its neighboring Xuefengshan (XFS) Mountain in South China, as one of the world-class antimony (Sb) producers, have provided appropriately 67% of globally exploited Sb metal (0.46 million tons) in human history. The associated gold (Au) with Sb in this region is also of significant economic values. In previous studies, these Sb-Au deposits were debated as a diversity of genetic types such as epithermal, magmatic-hydrothermal, sedimentary exhalative (SEDEX) and orogenic Sb-Au deposits. To evaluate these genesis hypotheses, we select the representative Longwangjiang-Jiangdongwan (LWJ-JDW) orefield to reveal the Sb-Au accumulation process and metal-fluid sources of these deposits. Our orefield-scale structural analysis shows that the localization of principal Sb-Au orebodies is controlled by a NE-striking sinistral shearing system composed by an integrated set of NE-striking and SE-dipping fractures in the pre-ore folded Neoproterozoic Wuqiangxi slate. Two chief ore periods were identified, including the marine sedimentation (SI, pyrite nodular) and tectonic-metamorphic hydrothermal period (SⅡ−SⅣ, Sb-Au veins). The second period is further subdivided into three stages of SⅡ (pre-tectonic deformed pyrite-milky quartz veins), Siii (syn-tectonic pyrite-arsenopyrite-stibnite-quartz veins) and SⅣ (post-tectonic stibnite-calcite veinlets). It is notable that gold precipitation is significantly prior to Sb ores at LWJ-JDW. Three sericite samples throughout SⅡ−SⅣ yield a group of well-defined ⁴⁰Ar/³⁹Ar plateau ages (253 ± 4, 234 ± 3 and 206 ± 2 Ma, respectively). This indicates the multistage Sb-Au mineralization initiated from Early Triassic and terminated at Late Triassic time. Further trace elements analyses show the earliest nodular PyI is enriched in a list of As, Ni, Sb, Cu, Se, Co, Pb, Zn and Ti that can be analogy to the diagenetic pyrite in the organic-rich marine sedimentary rocks. Extremely high Sb (median, 1107 ppm) and mediate Au (0.07 ppm) are monitored in PyI, indicative of the initial Sb and Au involvement from the Neoproterozoic sedimentation. Comparably, sulfides of the later SⅡ−SⅣ possess a similar spectrum of trace elements but with highly variable concentrations. All the sulfide generations host the wide range of in-situ δ³⁴SV-CDT values (-23.9 to -3.7‰ for SⅠ, -7.6 to -2.9‰ for SⅡ−SⅣ, respectively), indicating sulfur originally sourced from bacterial sulfate reaction (BSR) of the Neoproterozoic seawater sulfates, and then gradually reduced by thermochemical sulfate reaction (TSR) during the subsequent Au-Sb-induced tectonic-metamorphic hydrothermal activity. The lead isotope compositions in accordance with the evolution lines of upper crust and orogen, implying that the Pb were chiefly sourced from host slate of the Wuqiangxi Formation and its underlying basement. Synthesis of these data, we proposed that the Sb-Au accumulation at LWJ-JDW was caused by the multistage mineralization from Neoproterozoic marine sedimentation to Triassic episodic deformation and metamorphic processes (253−206 Ma).
The Xinfang gold deposit (＞20 [email protected] 2.85g/t) is situated in the southwest of the Liaodong Peninsula. Ore bodies are hosted by the Archean gneiss in the footwall and Neoproterozoic metasandstone in the hangingwall of the Xinfang Metamorphic Core Complex. Here, we conduct pyrite Re-Os dating, C, O, Si, He-Ar, S, and Pb isotopes in order to constrain the ore-forming age and genesis of the deposit. Field observations show that three ore-forming processes are recognized: (1) quartz- coarse-grained pyrite stage (stage Ⅰ), (2) quartz-polymetallic sulfide-gold stage (stage Ⅱ), and (3) quartz - calcite ± pyrite stage (stage III). Pyrite from the quartz-polymetallic sulfide-gold vein yielded Re-Os isochron age of 121.1±1.2Ma (Initial ¹⁸⁷Os/¹⁸⁸Os=1.49±0.01, MSWD=1.2), which is interpreted to be the ore-formation age.Theδ¹³CV-PDB and ¹⁸Ov-SMO W values of calcite from stage III range from -5.1‰ to -4.9‰ and from 9.7‰ to 10.1‰, and the δ³⁰Si values of quartz from stage Ⅰto stage III range from -0.5‰ to -0.4‰, -0.1‰ to -0.3‰, and -0.2‰ to -0.1‰, respectively, indicating that ore-forming fluids were derived from a magmatic-hydrothermal source. Sulfur isotopic compositions of sulfides between -1.9 ‰ and 4.4 ‰ (mean=2.4 ‰), are consistent with that of magmatic sulfur. The galena yielded a wide range of lead isotopic composition (²⁰⁶Pb/²⁰⁴Pb = 16.995-17.252, ²⁰⁷Pb/²⁰⁴Pb = 15.335-16.343, ²⁰⁸Pb/²⁰⁴Pb = 37.461-37.580) suggesting an external lead source. The He and Ar isotope compositions of pyrite and galena (³He/⁴He = 0.14Ra-0.62Ra), indicate a crustal source with minor mantle contributions. Combining all available data results, we propose that a magmatic -hydrothermal source for the Xinfang gold deposit and the ore formation was related to the subduction of the Paleo-Pacific Plate beneath Eurasia.
Keywords: LA-ICP-MS Trace elements Pyrite Chang'an gold deposit Sanjiang Tethyan metallogenic domain The Chang'an gold deposit, Yunnan province is one of five large gold deposits in the Ailaoshan gold belt that is the most important ore belt of the Sanjiang Tethyan metallogenic domain. Geochemical study of pyrite in the deposit was conducted using laser ablation inductively coupled plasma mass spectroscopy. Three types of hydrothermal pyrite were identified in the ores and wall rocks, i.e., the coarse euhedral crystals in syenite (Py1), the coarse grains disseminated in altered sandstones or sandstone ores (Py2), and the fine-grained euhedral pyrite in sandstone ores (Py3). Their trace elements exhibit different concentrations, associations and rim-core zoning, implying different geneses and crystallization processes. The cores of Py1 were formed by magmatic fluids and have the lowest concentrations of Au, As, Cu and Zn. The cores of Py2 were formed by metamorphic fluids and have relatively high Au, Ag, Ni, Pb and Cu concentrations. The Py3 grains and the growth rims of Py1 and Py2 show consistently high contents of Au, As, Pb and Co, suggesting that all of them were rapidly deposited from a mixing fluid system that was probably composed of fluids of metamorphic and magmatic origins. This interpretation is supported by the observation that the high-grade ores generally contain lots of Py2 and Py3. Hence we consider that the deposit was formed during India-Asia collision, slightly postdate the 33-35 Ma tectono-magmatism.
The Triassic gold deposits of the Youjiang Basin, southern China, have been variously correlated to Carlin-style and orogenic gold deposits or classified as a new intermediate deposit type. However, in terms of a multi-scale mineral system approach, they show remarkable similarities to the Tertiary Carlin-type deposits of Nevada and distinct contrasts to orogenic gold deposits. Both the Nevada and Youjiang deposit groups formed in a continent-scale post-orogenic extension event on fragmented continental crust underlain by metasomatized lithosphere. Both form roughly orthogonal deposit trends that subparallel near-orthogonal margins of a continental crustal block, with deposits controlled by gentle anticlines, monoclines or half-horsts and extensional faults, not tight, “locked-up” anticlines, and shear zones. The mineralogy and ore geochemistry of the two groups are similar, with differences consistent with slightly deeper and higher temperature of formation of the older Chinese deposits, commensurate with deeper erosional levels. The Youjiang gold deposits should be classified as Carlin-type, rather than Carlin-like or other terminologies, with their lower gold endowment probably related to a more distal thermal and fluid source than the Nevada Carlin-type deposits.
The Caojiaba tungsten deposit (19.03 [email protected] 0.37 wt% WO3) is hosted by skarn along the contact between clastic and carbonate rocks in the Xiangzhong Metallogenic Province of southern China. The deposit is characterized by an early prograde skarn containing low andraditic garnet (Ad0.7–21.9) and hedenbergitic pyroxene (Hd52.9–77.3) overprinted by a retrograde biotite–chlorite assemblage and then by quartz–scheelite veins, similar to well-studied reduced tungsten skarns worldwide. Scheelite has low MoO3 (0.01–0.16 wt%), and ore commonly contains up to 1.5 ppm Au and up to 0.33 wt% Sb. Sensitive high-resolution ion microprobe (SHRIMP) U–Pb analyses of hydrothermal titanite coexisting with scheelite in three skarn ore samples provide ages between 206 ± 5 Ma and 196 ± 3 Ma (2σ). Our new ages demonstrate that the tungsten mineralization took place at Caojiaba between 206 and 196 Ma, overlapping the 228–201 Ma emplacement age of granitic rocks in the Xiangzhong Metallogenic Province. Mineralogical and geochronological evidence collectively indicates that Caojiaba is a distal reduced W skarn deposit. The 226–196 Ma granite-related W mineralization recognized throughout the province has a possible link with the widespread Sb–Au mineralization in the region.
The Yangjiashan scheelite-bearing deposit (38,663 metric tons of WO3 with an average ore grade of 0.70% WO3) is hosted in quartz veins in a biotite monzogranite intrusion and surrounding slate in the Xiangzhong Metallogenic Province of southern China. The monzogranite has a zircon SHRIMP U–Pb age of 406.6 ± 2.8 Ma (2σ, n = 20, MSWD = 1.4). Cassiterite coexisting with scheelite yields a weighted mean ²⁰⁶Pb/²³⁸U age of 409.8 ± 5.9 Ma (2σ, n = 30, MSWD = 0.20), and molybdenite intergrown with scheelite yields a weighted mean Re–Os age of 404.2 ± 3.2 Ma (2σ, n = 3, MSWD = 0.10). These results suggest that the Yangjiashan tungsten deposit is temporally related to the Devonian intrusion. The δD and calculated δ¹⁸OH2O values of quartz intergrown with scheelite range from − 87 to − 68‰, and − 1.2 to 3.4‰, respectively. Sulfides have a narrow range of δ³⁴S values of − 2.9 to − 0.7‰ with an average value of − 1.6‰ (n = 16). The integration of geological, stable isotope, and geochronological data, combined with the quartz–muscovite greisen style of ore, supports a magmatic–hydrothermal origin for the tungsten mineralization. Compared to the more common tungsten skarn, quartz–wolframite vein, and porphyry tungsten deposits, as well as orogenic gold deposits worldwide, the Yangjiashan tungsten deposit is an unusual example of a granite-related, gold-poor, scheelite-bearing quartz vein type of deposit. The calcium needed for the formation of scheelite is derived from the sericitization of calcic plagioclase in the monzogranite and Ca-bearing psammitic country rocks, and the relatively high pH, reduced and Ca-rich mineralizing fluid may be the main reasons for the formation of scheelite rather than wolframite at Yangjiashan.
The Gangcha gold deposit in Hezuo, Gansu, China, is a newly discovered medium-scale (19 tons) epithermal deposit occurring within the western Qinling orogenic belt. The Daguanshan Formation, represented by metamorphosed volcanic–clastic rock suite, is the main ore-bearing strata. Gold occurs mainly as submicroscopic inclusions in sulphides and quartz. The hydrothermal alteration is characterized by mid- to low-temperature mineral assemblages such as pyrite, arsenopyrite, and fluorspar. We report results from Rb–Sr isotopic dating of pyrites in the main orebody, which yield an isochron age of 225.3 ± 3.4 to 229.9 ± 4.7 Ma suggesting that the mineral deposit formed during the middle Triassic within a collisional orogenic setting. The initial 87Sr/86Sr value of pyrite (0.710326 to 0.710349) is lower than that of the continental crust and higher than that of the mantle. The S isotope data of pyrites from the deposit show a narrow range from 0.6‰ to 1.3‰ with an average of 0.975‰. Their Pb isotopes exhibit characteristics of a crust–mantle mixed source with a μ (238U/204Pb) of 9.39 to 9.53 and a ω (232Th/204Pb) of 36.81 to 38.14. The S and Pb isotopic composition indicates that ore-forming materials were derived from a magma sourced in the lower crust, which also incorporated mantle components.
The South Tianshan is located north of the Tarim block and defines the southern margin of the Paleozoic Central Asian orogenic belt. This study presents new structural, geochronological, and geochemical data for the Wuwamen ophiolite mélange in the Chinese segment of the South Tianshan. In the south, the Wuwamen ophiolite mélange shows typical block-in-matrix fabrics and occurs in the footwall of a south-dipping thrust fault, the hanging wall of which is composed of weakly metamorphosed and deformed Lower Paleozoic marine to deep-marine sequences from the South Tianshan. In the north, a south-dipping thrust fault juxtaposes the Wuwamen ophiolite mélange in its hanging wall against the high-grade and strongly deformed metasedimentary rocks from the Central Tianshan in its footwall. Three stages of ductile deformation are distinguished on the basis of structural and kinematic analyses on different lithotectonic units across the region. They are, from older to younger: (1) regional top-to-the-north ductile shearing linked with subduction and accretionary tectonics; (2) widespread refolding of the earlier foliation, which likely resulted from a subsequent collision (or amalgamation) event; and (3) localized ductile right-lateral strike-slip faulting attributed to late-orogenic extrusion tectonics. Geochemical data indicate that the igneous rocks in the Wuwamen ophiolite mélange include mid-ocean-ridge basalt- and oceanic-island basalt-type volcanic rocks with arc-like features. Sr and Nd isotopic data further indicate that these igneous rocks formed in a back-arc oceanic basin. Our zircon U-Pb ages combined with published data indicate that the igneous blocks in the mélange formed during 334-309 Ma. An undeformed granite dike crosscutting the ophiolite mélange yielded an age of ca. 300 Ma and provides a minimum age of mélange formation. Meta-sandstones, which were previously interpreted as Devonian or Proterozoic in age, were deposited during the late Carboniferous (ca. 325-310 Ma) and yielded U-Pb detrital zircon ages consistent with a single Central Tianshan provenance. We propose an updated geodynamic model for the Paleozoic tectonic and paleogeographic evolution of the South Tianshan. We suggest that the Central Tianshan was locally separated from the Tarim block by back-arc oceanic basins during the Devonian to Carboniferous. This study shows that the Paleozoic tectonic activity of the Central and South Tianshan was characterized by the opening and subsequent closing of back-arc basins prior to its final amalgamation to the Tarim block, similar to the Cenozoic tectonic evolution of the western Pacific region, and such processes may be major characteristics of orogenic belts during the transition from accretionary to collisional systems.
Tectonic process involving amalgamations of microblocks along zones of ocean closure represented by granite-greenstone belts (GGB) were fundamental in building the Earth’s early continents. The crustal growth and cratonization of the North China Craton (NCC) are correlated to the amalgamation of microblocks welded by 2.75–2.6 Ga and ∼2.5 Ga GGBs. The lithological assemblages in the GGBs are broadly represented by volcano-sedimentary sequences, subduction-collision related granitoids and bimodal volcanic rocks (basalt and dacite) interlayered with minor komatiites and calc-alkalic volcanic rocks (basalt, andesite and felsic rock). The geochemical features of meta-basalts in the major GGBs of the NCC display affinity with N-MORB, E-MORB, OIB and calc-alkaline basalt, suggesting that the microblocks were separated by oceanic realm. The granitoid rocks display arc signature with enrichment of LILE (K, Rb, Sr, Ba) and LREE, and depletion of HFSE (Nb, Ta, Th, U, Ti) and HREE, and fall in the VAG field. The major mineralization include Neoarchean BIF-type iron and VMS-type Cu-Zb deposits and these, together with the associated supracrustal rocks possibly formed in back-arc basins or arc-related oceanic slab subduction setting with or without input from mantle plumes. The 2.75–2.60 Ga TTG rocks, komatiites, meta-basalts and metasedimentary rocks in the Yanlingguan GGB are correlated to the upwelling mantle plume with eruption close to the continental margin within an ocean basin. The volcano-sedimentary rocks and granitoid rocks in the late Neoarchean GGBs display formation ages of 2.60–2.48 Ga, followed by metamorphism at 2.52–2.47 Ga, corresponding to a typical modern-style subduction-collision system operating at the dawn of Proterozoic. The late Neoarchean komatiite (Dongwufenzi GGB), sanukitoid (Dongwufenzi GGB and Western Shandong GGB), BIF (Zunhua GGB) and VMS deposit (Hongtoushan-Qingyuan-Helong GGB) have closer connection to a combined process of oceanic slab subduction and mantle plume. The Neoarchean cratonization of the NCC appears to have involved two stages of tectonic process along the 2.75–2.6 Ga GGB and ∼2.5 Ga GGBs, the former involve plume–arc interaction process, and the latter involving oceanic lithospheric subduction, with or without arc-plume interaction.
The Xiahe-Hezuo district in the West Qinling orogen contains numerous Au-(As-Sb) and Cu-Au-(W) deposits. The district is divided into eastern and western zones by the Xiahe-Hezuo Fault. The western zone is exposed at a shallow level and contains sediment-hosted disseminated Au-(As-Sb) deposits, whereas the eastern zone is exposed at a deeper level and contains Cu-Au-(W) skarn and lode gold deposits within or close to granitic intrusions. The Laodou gold deposit in the eastern zone consists of auriferous quartz-sulfide-tourmaline and minor quartz-stibnite veins that are structurally controlled by fault zones transecting the Laodou quartz diorite porphyry stock and enveloped by potassic and phyllic alteration. Both the veins and alteration halos commonly contain quartz, sericite, tourmaline, pyrite, and arsenopyrite, with minor galena, sphalerite, chalcopyrite, tetrahedrite, and enargite. Gold occurs mainly as invisible gold in pyrite or arsenopyrite and locally as inclusions less than 50 μm in diameter. The zircon U-Pb age of 247.6 ± 1.3 Ma (2σ) on the host quartz diorite porphyry and the sericite 40Ar/39Ar plateau ages of 249.1 ± 1.6 and 249.0 ± 1.5 Ma (2σ) on two ore-related hydrothermal sericite samples are within analytical errors of one another. At the formation temperature (275 °C) inferred from microthermometric measurements of fluid inclusion, sericite and tourmaline yield calculated δDH2O values of −70 to −45‰ and δ18OH2O of 5.8 to 9.7‰, while quartz yields calculated δ18OH2O values of 5.1∼5.7‰. Hydrothermal tourmaline in quartz-sulfide-tourmaline veins has δ11B of −11.2 to −0.9‰ (mean of −6.3‰) that are similar to the values of magmatic tourmaline (−8.9 to −5.5‰ with a mean of −6.8‰) in the host quartz diorite porphyry. The δ34S values of sulfide minerals range from −5.9 to +5.8‰ with a mean of −0.6‰ that is typical of magmatic sulfur. Pyrite from hydrothermally altered quartz diorite porphyry and quartz-sulfide-tourmaline veins have relatively homogeneous lead isotopic compositions, compatible with granitic intrusions in the district. The geochronological and isotopic data combined support a magmatic origin for the Laodou gold deposit, most likely formed from fluids exsolved from the Laodou quartz diorite porphyry or associated intrusive phases at deeper levels beneath the stock. Orogenic and Carlin-like gold deposits in the West Qinling orogen have been commonly thought to have formed from metamorphic fluids. This study, however, highlights the role of magmatic-derived fluids in the formation of lode gold deposits. Synthesis of geochronological, geological, and geochemical data on magmatic rocks and ore deposits in and surrounding the Xiahe-Hezuo district indicates that gold mineralization predominantly occurred within a subduction-related magmatic arc prior to collision between the Yangtze and North China cratons that produced the West Qinling orogen.
The Xinghai-Zeku area of western China is one of the most important Au polymetallic metallogenic belts in Qinghai Province, China. To guide the mineral exploration in this area, log and isometric log-ratio (ilr) transformations of stream sediment data are evaluated using principal component analysis (PCA) combined with geological data to study the relationship among different elements. In addition, Mean + 2 standard deviations (Mean + 2STD), Median + 2 median absolute deviations (Median + 2MAD), and concentration-area (C-A) models are applied to identify pathfinder threshold values and geochemical patterns are decomposed using a spectrum-area (S-A) model. The results show that: (1) PCA for the ilr-transformed data can accurately describe three different geochemical assemblages, Au-As-Sb, that represent Au-As-Sb mineralization in fracture zones; (2) anomalies of Au + As + Sb are more suitable for targeting Au-As deposits than those of the single element Au; (3) the C-A model is useful for indentifying geochemical anomalies associated with mineralization because results obtained by the C-A fractal model and the geological characteristics are well correlated; (4) background and anomaly maps for Au + As + Sb from the S-A model in conjunction with the Mean + 2STD successfully identify weaker anomalies by reducing anomalous areas; and (5) using Au + As + Sb anomalies identified by C-A in conjunction with the S-A model and Mean + 2STD method are effective in exploration for Au deposits in the area. © 2016 The Author(s). Published by The Geological Society of London for GSL and AAG. All rights reserved.
Archean cratons have map patterns and rock associations that are diagnostic of the Wilson Cycle. The North China Craton (NCC) consists of several distinctly different tectonic units, but the delineation and understanding of the significance of individual sutures and the rocks between them has been controversial. We present an actualistic tectonic division and evolution of the North China Craton based on Wilson Cycle and comparative tectonic analysis that uses a multi-disciplinary approach in order to define sutures, their ages, and the nature of the rocks between them, to determine their mode of formation and means of accretion or exhumation, and propose appropriate modern analogues. The eastern unit of the craton consists of several different small blocks assembled between 2.6 and 2.7 Ga ago, that resemble fragments of accreted arcs from an assembled archipelago similar to those in the extant SW Pacific. A thick Atlantic-type passive margin developed on the western side of the newly assembled Eastern Block by 2.6-2.5 Ga. A > 1,300 km- long arc and accretionary prism collided with the margin of the Eastern Block at 2.5 Ga, obducting ophiolites and ophiolitic mélanges onto the block, and depositing a thick clastic wedge in a foreland basin farther into the Eastern Block. This was followed by an arc-polarity reversal, which led to a short-lived injection of mantle wedge-derived melts to the base of the crust that led to the intrusion of mafic dikes and arc-type granitoid (TTG) plutons with associated metamorphism. By 2.43 Ga, the remaining open ocean west of the accreted arc closed with the collision of an oceanic plateau now preserved as the Western Block with the collision-modified margin of the Eastern Block, causing further deformation inthe Central Orogenic Belt. 2.4-2.35 Ga rifting of the newly amalgamated continental block formed a rift along its center, and new oceans within the other two rift arms, which removed a still-unknown continental fragment from its northern margin. By 2.3 Ga an arc collided with a new Atlantic-type margin developed over the rift sequence along the northern margin of the craton, and thus was converted to an Andean margin through arc-polarity reversal.
Organic matter can be associated with mineralization in hydrothermal ore deposits. One hypothesis is that this organic matter represents remnants of organic fluids (crude oils) that were competing with aqueous fluids for metal transport and contributed to metal endowment. We investigated the transport of gold (Au) in model oil compounds (S-free n-dodecane, CH3(CH2)10CH3, DD; and S-bearing 1-dodecanethiol, CH3(CH2)10CH2SH; DDT) from 25 °C to 250 °C using in-situ synchrotron X-ray absorption spectroscopy (XAS) experiments to determine the speciation and the structural properties of gold complexes in the aqueous- and oil-based fluids. For most experiments, DD or DDT were in contact with Au-bearing acidified water, or acidified water plus 10 wt% NaCl (pH25°C = 1.85 in both cases). Gold rapidly partitioned from the aqueous phase into DD and DDT. Below 125 °C, Au(III)Cl is dominant in the DD and the adjacent water with a refined coordination number (CN) of chloride of 4.0(3) and an Au–Cl bond length of 2.28 Å consistent with the tetrachloroaurate complex (AuCl4⁻) being stable in both the aqueous and organic phases. In contrast, Au(III) is rapidly reduced in the presence of DDT and an Au(I) complex dominates in both water and adjacent DDT with a CN of sulfur ∼2.0, suggesting a [RS-Au-SR]⁻ (RS = DDT with deprotonated thiol group) complex with Au–S bond lengths ranging from 2.29(1) Å to 2.31(3) Å. In an open system of DDT in contact with water, of which the water and DDT were analyzed separately, AuCl4⁻ was dominant in the water phase, and Au(RS)2⁻ dominant in DDT, possibly due to different equilibration kinetics in the beaker and glassy carbon tube. Since sulfur and organothiol compounds are ubiquitous and abundant components in natural oils, this study demonstrates the potential of natural oils to scavenge and enrich gold from co-existing gold-bearing brines. In particular, Au(I) organothiol complexes may contribute to transport in low-temperature (<125 °C) ore fluids such as those in basinal environments – in both hydrothermal fluids and oils. At temperatures ≥125 °C, gold was reduced to metallic gold in all experiments, suggesting that organo-stabilized nanoparticles may be the major form of gold to be scavenged, concentrated or transported in crude oils at these conditions. The results imply that brine-oil interactions may enrich Au in oils, and that oils may be an effective ore fluid in sedimentary environments.
There was extensive Permian to Triassic magmatism in Hainan Island, southern part of the South China Block (SCB), which began earlier and exhibits different rock types and geochemical characteristics compared to the Indosinian magmatism in the hinterland of the SCB. Two stages of magmatism have been identified in central Hainan Island in this study. The first-stage magmatism (253–262 Ma) is characterized by strongly deformed granites. These gneissic granites exhibit SiO2 (64.0–69.8 wt%), MgO (0.97–1.60 wt%), Fe2O3T (2.68–6.78 wt%), A/CNK (most <1.1), zircon εHf(t) values (−2.08 to −0.41), the geochemical features of I-type granites. These early granites can be subdivided into high-REE and low-REE groups. Compared to the low-REE granites, the high-REE ones have higher K2O, Ba, K2O/Na2O, Gd/Yb and Th/Ta, low U, Rb/Ba, Nb/La and U/Pb. The low-REE granites show whole-rock εNd(t) (−4.33 to −3.96) and ISr (ca 0.7074), while the high-REE granites have lower εNd(t) (−7.34 to −6.33) and higher ISr (0.7096–0.7109). The gneissic granites probably derived from the partial melting of the Baoban Complex at different crustal levels. The second-stage magmatism (245–256 Ma) is characterized by weakly deformed to massive gabbroic-dioritic rocks. They exhibit relatively low SiO2 (48.9–59.7 wt%), high Fe2O3T (6.57–11.6 wt%), total alkalies (Na2O + K2O) (3.91–7.35 wt%), and variable MgO (2.74–7.05 wt%), Ni (3.84–60.1 ppm) and Cr (7.22–299 ppm) concentrations. They also have low whole-rock εNd(t) values (−7.92 to −5.11) and high ISr (0.7083–0.7118), and a range of zircon εHf(t) values (−5.55 to −1.11), suggesting that their parental magmas were derived from heterogeneous enriched-mantle sources, and experienced AFC processes. The rock assemblages and their geochemical features indicate that both granites and gabbroic-dioritic rocks were formed in a back-arc extensional environment, which was probably related to the subduction of Paleo-Pacific oceanic plate. Hence, the Indosinian intracontinental orogeny in the hinterland of the SCB probably was triggered by this subduction in the southeast, rather than the collision between the SCB and the Indochina Block in the southwest.
The NE-striking Dunhua–Mishan Fault Zone (DMFZ) is one of two branches of the continental-scale sinistral Tan–Lu Fault Zone in NE China. The field data presented here indicate that the ca. 1000 km long DMFZ records two phases of sinistral faulting. The structures produced by these two phases of faulting include NE–SW-striking ductile shear belts and brittle faults, respectively. Mylonite-hosted microstructures and quartz c-axis fabrics suggest deformation temperatures of 450 °C–500 °C for the ductile shear belts. Combining new zircon U–Pb dates for 14 igneous rock samples analyzed during this study with the geology of this region indicates these shear belts formed during the earliest Early Cretaceous. This phase of sinistral displacement represents the initial formation of the DMFZ in response to the northward propagation of the Tan–Lu Fault Zone into NE China. A phase of Early Cretaceous rifting was followed by a second phase of sinistral faulting at 102–96 Ma, as evidenced by our new U–Pb ages for associated igneous rocks. Combining our new data with the results of previous research indicates that the DFMZ records a four-stage Cretaceous evolutionary history, where initial sinistral faulting at the beginning of the Early Cretaceous gave way to rifting during the rest of the Early Cretaceous. This was followed by a second phase of sinistral faulting at the beginning of the Late Cretaceous and a second phase of local rifting during the rest of the Late Cretaceous. The Cretaceous evolution of the DMFZ records the synchronous tectonic evolution of the NE China continent bordering the Pacific Ocean. Two phases of regional N–S compression generated the two phases of sinistral faulting within the DMFZ, whereas two-stage regional extension generated the two phases of rifting. The two compressive events were the result of the rapid low-angle subduction of the Izanagi and Pacific plates, whereas the two-stage extension was caused by the roll-back of these respective plates. The final closure of the Mongol–Okhotsk Ocean at the beginning of the Early Cretaceous intensified the synchronous compression in NE China, causing the northward propagation of the Tan–Lu Fault Zone.
The Katebasu gold (Au)–copper (Cu) deposit is one of the extra large-scale Au–Cu deposits discovered in the western Tianshan Mountains in Xinjiang in the recent years. The geological characteristics of the deposit have not been systematically studied and summarized, and there is considerable debate about the deposit type and metallogenic epoch. In this paper, we studied the Katebasu Au–Cu deposit orebody production characteristics, ore mineral composition, structural tectonic, surrounding rock alteration, and metallogenic phases. We identified the deposit types, presented a new discussion on the metallogenic epoch combined with the study of garnet Sm–Nd chronology, and indicate that the deposit type is a skarn type–fracture zone alteration rock type. The skarn-type Cu–Au deposit is mainly distributed in the fault fracture zone and skarn in the contact zone between the rock mass and marble strata. The fracture zone alteration-type Au–Cu deposit is mainly distributed in the monzonite granite fracture zone. The mining area has two phases of metallogenesis, which are related to monzonite granite and diorite dykes, respectively, and have a certain degree of superposition in space. The early metallogenesis occurred at 334.3 ± 6.7 Ma. The above results provide direction for regional prospecting.
The Kunlun Orogen is generally divided into the East Kunlun Orogenic Belt (E-KOB) and the West Kunlun Orogenic Belt (W-KOB) by the Altyn Tagh fault. The E-KOB forms part of the western segment of the Central China Orogenic System (CCOS), and is considered to have formed by the collision between the Qaidam Block and Qiangtang or Bayanhar Terrane as a consequence of the closure of the Kunlun Ocean (branch of the Paleo-Tethyan Ocean). Based on a compilation recently published high-quality data, this contribution provides an overview of the composition, nature and ages of the principal tectonic elements, including ophiolitic mélanges and related volcanic rocks, intrusive plutons and sedimentary cover sequences in the E-KOB. According to multiple lines of evidence from these tectonic elements, we proposed herewith a Paleozoic-Triassic subduction and accretionary tectonic model to interpret the spatiotemporal tectonic framework, plate subduction polarity, and tectonic processes from accretion to collision of the E-KOB. Three main ophiolitic mélange zones are identified in the E-KOB, from north to south, they are the Qimantagh-Xiangride ophiolitic mélange zone (QXM), the Aqikekulehu-Kunzhong ophiolitic mélange zone (AKM) and the Muztagh-Buqingshan-Anemaqen ophiolitic mélange zone (MBAM). According to these ophiolitic mélange zones, the E-KOB is divided into four major tectonic units: the North Qimantagh belt, the Central Kunlun belt, the South Kunlun belt and the Bayanhar Terrane. Based on several lines of evidence from geology, geochemistry and geochronology, the South Kunlun belt is interpreted as a Paleozoic to Triassic fore-arc and accretionary complex related to northward subduction of the Kunlun Ocean during the Ordovician-Triassic time. The AKM, MABM and the South Kunlun belt constitute a wide accretionary complex along the Kunlun Suture zone that marks final closure of the major Paleo-Tethyan Ocean, while the QXM represents the best expression of another suture that records final closure of the Qimantagh back-arc basin. The Central Kunlun Belt, as a long-lived island-arc terrane from Ordovician to Triassic times, rifted from the Qaidam Block due to the spreading of the Qimantagh back-arc basin during the period of ca. 485-425. Ma. Taken into all the geological, geochemical and geochronological lines of evidence together, a trench / arc / back-arc basin tectonic system in the E-KOB was built up, and evolved into a protracted and long-lived northward-subduction and accretion along the Kunlun Suture during Paleozoic and Triassic time.
Central-western Hunan in South China hosts the largest antimony belt in the world with two types of Sb deposits identified: Sb-Au Woxi-type and Sb only Xikuangshan-type. Banxi is the most representative deposit in the region with vein-type Sb mineralization hosted in Neoproterozoic clastic rocks, stibnite developing in ores, and arsenopyrite mainly occurring in altered country rocks. Trace element contents (including rare earth elements; REE) and isotopic ratios (S, Pb, Sr, Nd, He and Ar) in stibnite and/or arsenopyrite were analyzed to determine the timing of ore formation and to elucidate fluid origin and evolution processes. Most sulfides have high ΣREE contents (45–103 ppm), moderate fractionation between LREE and HREE (LREE/HREE = 6.38–11.56) and slightly negative Eu anomalies (Eu/Eu* = 0.53–0.72). The δ³⁴S values are 3.88–5.81‰ for stibnite and 9.25–11.82‰ for arsenopyrite. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios range from 18.617 to 18.635, 15.695 to 15.739, and 38.965 to 38.981 for stibnite, and from 18.594 to 18.609, from 15.587 to 15.698, and from 38.893 to 38.926 for arsenopyrite. The ⁸⁷Rb/⁸⁶Sr and ⁸⁷Sr/⁸⁶Sr ratios are 0.3016–3.538 and 0.711463–0.717591, respectively for stibnite, and 0.2251–2.214 and 0.711244–0.711565, respectively for arsenopyrite. The ¹⁴⁷Sm/¹⁴⁴Nd and ¹⁴³Nd/¹⁴⁴Nd ratios are 0.1174–0.9816 and 0.511942–0.512768 for stibnite, with εNd(t) values (t = 130 Ma) ranging from − 12.4 to − 6.6, and two-stage model ages (T2DM) ranging from 1457 to 1932 Ma. The ⁴⁰Ar/³⁶Ar and R/Ra ratios (where Ra is the atmospheric ³He/⁴He ratio of 1.4 × 10− 6) are 409–545 and 0.0088–0.0348, respectively for stibnite. The Rb–Sr and Sm–Nd isotopic analyses of the sulfides yield isochron ages of 129.4 ± 2.4 Ma (2σ, MSWD = 1.3) and 130.4 ± 1.9 Ma (2σ, MSWD = 1.6), respectively. The combined trace element and isotopic data-set indicates that the ore-forming fluids were a mixture of dominantly deep basement-derived, solute-rich parent water and a small amount of dilute, heated meteoric water. The decreases in ΣREE, δ³⁴S, ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, ²⁰⁸Pb/²⁰⁴Pb, ⁸⁷Rb/⁸⁶Sr, ⁸⁷Sr/⁸⁶Sr, ¹⁴⁷Sm/¹⁴⁴Nd and ¹⁴³Nd/¹⁴⁴Nd and increases in ⁴⁰Ar/³⁶Ar and ⁴He contents in the stibnite from the earlier quartz-stibnite mineralization stage (Stage II) through to the later stibnite mineralization stage (Stage III) indicate that the influx of meteoric water increased during Sb mineralization. The deep-sourced, relatively high temperature, rock-reacted fluid mixed with increasing amounts of more oxidized, low temperature meteoric fluids, causing the precipitation of arsenopyrite and stibnite sequentially at the Banxi deposit. A two-period genetic model has been proposed for the world-class Sb mineralization in the central-western Hunan region. The Woxi-type Sb–Au deposits were derived from orogenic fluids generated from folding and shearing during the Caledonian and Indosinian Orogeny, whereas the Xikuangshan-type Sb deposits were formed by mixing heated basement-derived hydrothermal fluid circulating during the flare-up of magmatism in South China, with lower temperature meteoric water.
The Liyuan lode gold deposit is located in the Shanxi province, central North China Craton. Gold orebodies are mainly hosted in Archean metamorphic rocks and structurally controlled by the NNE-trending faults. Gold occurs in disseminated and auriferous quartz-sulfide veins and veinlets within hydrothermally altered rocks. Mineralization can be divided into three intervals: (1) quartz-pyrite stage, (2) quartz-polymetallic sulfides stage, and (3) quartz-carbonate stage. Gold formed mainly in the middle stage. Sericite sample associated with the middle stage pyrite from phyllic alteration zones yields an well-defined ⁴⁰Ar/³⁹Ar plateau age of 133.3 ± 1.2 Ma, which is remarkably consistent with zircon U-Pb age (133.4 ± 1.1 Ma) of the quartz porphyry dikes in the Liyuan mine, indicating a close relationship between gold mineralization and granitic magmatism in the area. The sulfur isotopic compositions of pyrite (Py1-2) from the early stage have a narrow range from −0.3 to 4.1‰, indicating a deep-seated magmatic source. However, the sulfides (Py3-5, sphalerite, galena) from the middle stage have lower δ³⁴SV-CDT values of −7.2 to 3.0‰, which is thought to be a result of fluid oxidation during gold mineralization. The Pb isotopic compositions of sulfides from Liyuan ores have ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios of 16.671–16.860, 15.236–15.255, and 41.452–44.159, respectively, indicting a high-thorium lower continental crust source of ore-forming materials. The δ¹³CVPDB and δ¹⁸OVSMOW values of late stage calcite ranging from −7.1 to −5.8‰ and 12.2 to 13.7‰, respectively, illustrating a deep-seated magmatic source of carbon-bearing portion. Given the absence of granite bodies at the present mining levels, we speculate that the ore-forming fluids may have been exsolved from a concealed granite pluton at greater depth. Based on the regional tectono-magmatic events, ore geology, geochronologic and isotopic data obtained in this study together with the previous published fluid inclusion data, we suggest that the Liyuan deposit is an orogenic gold deposit that is probably related to the early Cretaceous granite magmatism in the interior of the North China Craton.
The location and tectonic nature of the Solonker Suture in East Asia and hence the late Palaeozoic to early Mesozoic closure of the Palaeo-Asian Ocean have notoriously been enigmatic in the past decades due to limited rock exposure and the absence of unambiguous collision-related regional features. Several tectonic models have been proposed since, but in many cases these models were derived only from single key exposures or methodologies, often being over-simplified, or -interpreted, leading to questionable extrapolations on regional and global scales despite the complexity of the Palaeozoic accretionary tectonic framework. Now, the regionally consistent availability of geochronological, geochemical, stratigraphic and palaeo-geographic data enables us to integrate these into a highly detailed and coherent Palaeozoic tectonic review of the suture.
The region across the Solonker Suture can generally be subdivided into three major Palaeozoic tectonic provinces, e.g., (i) a Sino-Cratonic Province that resembles the active Palaeozoic northern margin of the North China Craton to the south of the suture, (ii) a Mongolian Province that comprises the south-eastern margin of the Mongolian Terrane to the north of the suture, and (iii) an East Asian Pre-Pacific Province in north-east China that accreted with the Late Permian initiation of Pacific Plate subduction. The Sino-Cratonic Province experienced episodic tectonic activity that includes the accretion of the initially ensialic Bainaimiao Arc onto the passive northern margin of the North China Craton at ~ 437–453 Ma, subsequent southward directed subduction activity beneath the amalgamated margin until at least ~ 400 Ma, followed by a temporary cessation of magmatic activity accompanied by a switch from north- to southward directed continental drift, and finally concluded by renewed subduction activity until the final closure of the Palaeo-Asian Ocean. The Mongolian Province is suggested to have been more closely associated with the Siberian Craton before the presumably Late Devonian opening of the Mongol-Okhotsk Ocean. The East Asian Pre-Pacific Province, originally rifted away from the eastern margin of Gondwana at ~ 600–750 Ma, recorded early Palaeozoic (~ 500 Ma) orogenic processes along the then northern margin of the Siberian Craton. The Baolidao arc system successively developed along the present-day south-eastern margin of the Mongolian Province due to continued subduction activity throughout the Palaeozoic. After the Middle Carboniferous opening of the Hegenshan back-arc basin renewed subduction beneath a matured Baolidao Arc during Carboniferous and Permian times led to the obduction of the Hegenshan ophiolite not earlier than ~ 270 Ma. Shortly after the Palaeo-Asian Ocean diachronously closed from west to east along the Solonker Suture in the Late Permian to Early Triassic. The East Asian Pre-Pacific Province re-attached itself by the mid-Mesozoic, followed by a change in the regional stress regime controlled by Palaeo-Pacific plate subduction.
A divergent double-sided subduction model for the closure of the Palaeo-Asian Ocean provides, based on the reviewed data, a tectonic model that is not only able to reasonably well explain the absence of typical collision-related features in the region but also the abundance of Mesozoic A-type granitic magmatism in north-east China.
Carlin-style gold deposits are widely distributed in Southwestern Guizhou, China. Research has dominantly focused on deposit-scale geology and structural control of mineralization. The relationship between the gold deposits and regional structures, in particular their control on the formation and distribution of those deposits is less well understood. Here we use seismic survey and gravity data to reveal the basin-scale structure control of the gold deposits in central Southwestern Guizhou. The seismic reflection profiles show strong reflection horizons including Upper Permian coal measures, and Dongwu and Guangxi unconformities. The seismic data provide important evidence of the basinal structural style and the relationship between fault-related folding and the Carlin-style gold deposits. Regional gravity data also revealed several paleo-uplifts, which appear to control the distribution of Carlin-style gold deposits.
The Carlin-style gold deposits are spatially and temporally associated with fault-related folds. Based on their location, we classify the gold deposits into two types, (1) low-angle thrust-controlled deposits; and (2) high-angle reverse fault-related deposits. In the low-angle thrust-controlled deposits, main thrusts are listric, strike NW-SE and dip southwest. These thrusts detach into coal measures, tuffs and volcanic rocks and are bedding-parallel in the vicinity of the Dongwu unconformity. Gold ore bodies are found in the thrusts and characterized by cutting-layer veins near the surface and bedding-parallel veins at depth. The high-angle reverse fault-related deposits are located in the hinge of northeast-southwest-striking fault-related folds, with high-angle reverse faults near the hinge of folds crosscutting the Upper Permian coal measures, volcanic rocks and Dongwu unconformity, and then into the limestone of Middle Permian Maokou Formation. Ore bodies are bedding-parallel in anticline culminations where interlayer fracture zones in Upper Permian coal measures and volcanic rocks are generated by high-angle reverse faulting.
We consider that the formation of the gold deposits is part of the tectonic evolution in the area. The two sets of NW-SE- and NE-SW-striking fault-related folds were successively formed during the closure of eastern Tethys Ocean in Late Triassic, and major gold deposits formed in the fault-related folds. The Dongwu unconformity and faults provided conduits for ore fluid flow, and the coal measures and the tuffs of Dachang Member acted as detachment layers and hosts for ore deposition.
The Wutai greenstone belt in central North China Craton (NCC) hosts a number of Precambrian gold deposits and ore occurrences. Based on the host rock association, these can be divided into Banded Iron Formation (BIF), meta-volcano-sedimentary and meta-conglomerate types. The two former types formed during ∼2.5-2.3 Ga and the third one at ∼1.85 Ga. The characteristics of these Precambrian gold deposits are broadly similar with those of the orogenic gold deposits. Based on available geochronological data, here we reconstruct the major tectonic events and their relationship with gold mineralization in the Wutai-Hengshan-Fuping region during Neoarchean to Paleoproterozoic as follows. (1) ∼2.6-2.5 Ga: widespread intrusion of tonalite-trondhjemite-granodiorite (TTG) magmas in the Hengshan terrane and Fuping continental arc, formation of the Wutai volcanic arc in the southern margin of Hengshan terrane with granitoids emplacement, and the Hengshan-Wutai intra-oceanic arc accretion to the Fuping arc at the end of Neoarchean. (2) ∼2.5-2.3 Ga: the subduction of Hengshan arc from north leading to persistent magmatism and orogenic gold mineralization. (3) ∼2.2-2.1 Ga: extension leading to the formation of graben structure in the Wutai and Fuping region, deposition of the Hutuo and Wanzi Group sediments, formation of placer gold through erosion of the orogenic gold deposits. (4) ∼2.2-2.0 Ga: widespread magmatism in the Wutai-Hengshan-Fuping region. (5) ∼1.95-1.8 Ga: regional metamorphism associated with collision of the Western and Eastern Blocks of the NCC and associated orogenic gold deposits. The multiple subduction-accretion-collision history and subsequent deep erosion has significantly affected most of the Precambrian gold deposits in the Wutai greenstone belt. © 2017 China University of Geosciences (Beijing) and Peking University.
The Song Hien rift basin is an important metallogenic area in NE Vietnam. This domain consists mainly of Triassic sulfide-rich black shale beds, which play a role as a sedimentary host for various mineral systems such as antimony, mercury and gold-sulfide deposits. Most of gold deposits are hosted in carbonaceous sedimentary rocks, however some deposits, which have similar characteristics, are hosted in fine-grained mafic magmatic rocks. An Ar-Ar isotopic dating of hydrothermal sericite from the sedimentary hosted Bo Va and Khung Khoang gold deposits and intrusion hosted orogenic Hat Han gold deposit yields plateau ages of 184.8±2.1 Ma, 211.63±2.3 Ma, and 209.12±2.3 Ma, respectively. The obtained Ar-Ar ages convincingly show that the orogenic gold deposits in the Song Hien domain were formed in Late Triassic to Early Jurassic, while the age of the Bo Va deposit is at least older than 184.8±2.1 Ma. Loss of argon by volume diffusion, supported by previously reported mineralogical and isotopic features of the Bo Va deposit may suggest that the Jurassic-Cretaceous (Yanshanian) tectonothermal events overprinted some deposits in the Song Hien domain. Formation of gold deposits in the Song Hien domain is linked to the same tectonic event as the Carlin-like gold deposits in SW China and is associated with an extensional tectonic regime that followed continental collision between the Indochina and South China Blocks. The similarity in geology setting and mineral composition of gold deposits of the Song Hien domain and the Golden Triangle region, as well as timing and kinematics of deformation, magmatic features, and stratigraphic sequence and bulk architecture, lead to conclusion that NE Vietnam and SW China is a single metallogenic zone. The study of gold deposits in Vietnam will provide a new data on the metallogenic history of this important part of SE Asia.
The Beishan orogenic belt is an important tectonic unit and a suitable target to investigate and understand the Paleozoic tectonic framework of the Central Asian Orogenic Belt. Paleozoic granitic rocks are widely distributed in the area and closely related to the tungsten deposits at Hongjianbingshan, Guoqing, Yingzuihongshan and Yushan. To understand the petrogenesis of the intrusions, we performed SIMS zircon U-Pb, O and whole rock major-trace element contents and Sr-Nd isotopic analyses. Two major suites of granitic intrusions associated with tungsten mineralization have been recognized during 424-314 Ma and 286-244 Ma. The former suite shows variable Sr-Nd and O compositions (average (⁸⁷Sr/⁸⁶Sr)i = 0.7149 or 0.7034, εNd(t) =-6.3 or 7.6, T2DM = 1.68 or 0.41 Ga, δ¹⁸O = 9.3 or 5.9 ‰) indicating an ancient crust or a juvenile lower crust origin, whereas the latter suite shows A-type affinity, and the Sr-Nd and O compositions (average (⁸⁷Sr/⁸⁶Sr)i = 0.7125, εNd(t) =-4.5, T2DM = 1.42 Ga, δ¹⁸O = 6.9 ‰) suggest the Precambrian metasedimentary strata may have exerted a significant role in the magma source. The proposed magma sources, combined with the geochemical differences between these two suites of intrusions, indicating the Silurian-Carboniferous mineralization such as Hongjianbingshan, Guoqing and Yingzuihongshan are closely associated with subduction-accretion and generation of Gongpoquan arc-accretionary system, while the Permian mineralization including Yushan deposit are attributed to continuing accretion and subsequent post collision. These tungsten-related granitic rocks are enriched in LREE and depleted in HREE and Ba, Sr, Nb, P, Eu and Ti, suggesting they may have experienced advanced fractional crystallization. Furthermore, a spectacular tetrad effect in their REE distribution patterns has been discovered, showing the granites are highly evolved rocks with strong hydrothermal interaction. The prolonged fractional crystallization and magmatic-hydrothermal interactions have contributed to the formation of the Silurian-Permian tungsten mineralization.
The Huachanggou gold deposit in Shaanxi province is located at the south of Mianlue Suture Zone. The ore bodies, which are mainly controlled by a series of EW trending ductile-brittle shear zones and reverse faults, are hosted in the spilite and limestone. To constrain the metallogenic age, fuchsite ⁴⁰Ar/³⁹Ar geochronological analyses were carried out. Two fuchsite samples from the gold bearing quartz veins and altered spilite ore yielded ⁴⁰Ar/³⁹Ar isotopic plateau ages of 209.4±2.3 Ma and 211.5±2.5 Ma, respectively, representing the mineralization age of gold polymetallic sulfides. By summarizing the characteristics of ore geology and the geotectonic location, it can be inferred that the Huachanggou gold deposit was formed during the collision between the Yangtze Block and Qinling micro Block which might have been took place before 209 Ma.
Located in the southeastern margin of the Yangtze Block and generally interpreted as the Neoproterozoic collisional product of the Yangtze with the Cathaysia Blocks of South China, the Jiangnan Orogenic Belt (JOB) contains a number of gold (Au) (-polymetallic) ore deposits and mineral showings, mostly hosted by Neoproterozoic low-grade metamorphic volcaniclastic and sedimentary rocks. The mineralization styles mainly include aurifeous quartz veins and disseminated mineralization in altered mylonite and cataclasite that are developed along shear zones, fracture zones and inter- or intra-formational fault zones closely related to regional folding and shearing deformation. Three gold mineralizing epochs are recognized in the JOB. The ca. 423 – 397 Ma mineralization was associated with the early Paleozoic tectonothermal event(s), which induced widespread emplacement of Silurian S-type granites, low-grade metamorphism and enrichment of gold in the Neoproterozoic rocks (i.e., forming Au source beds). The second Au mineralization epoch, occurring at ca. 176 – 170 Ma (Jurassic), was related to the subduction of the Paleo-Pacific plate beneath the South China continental margin. The third and most important Au mineralization epoch took place at ca. 144 – 130 Ma (early Cretaceous), when a Basin-and-Range tectonic pattern was developed, characterized by NE–NNE-trending strike-slip faults, granitic domes and metamorphic core complexes (MCC), and basins filled with red bed lithologies. C, H, O, He-Ar, S and Pb isotopic and fluid-inclusion data suggest that the ore fluids were predominantly metamorphic and/or magmatic, with variable input of mantle-derived fluids and the progressive involvement of meteoric waters in the later stages of mineralization. Ore materials were mostly contributed by the Neoproterozoic source beds, plus a possible contribution from mantle- or magma-derived components. The Au (-polymetallic) deposits in the JOB, particularly those formed in the early Cretaceous, share many geological and geochemical features with the orogenic-type and Carlin-type deposits. In the context of tectonic evolution of South China, the gold mineralization in the JOB may be considered an “intracontinental reactivation type”, characterized by synchronous development of Au–polymetallic mineralization, reactivation of stuctures developed in Neoproterozoic metamorphic rocks, and widespread granite emplacement in the late Mesozoic.
The eastern margin of the Xing'an-Mongolian Orogenic Belt is characterised by widespread Phanerozoic granitic magmatism, some of which is closely related to significant ore mineralisation. This paper presents new geochronological, petrogenetic, and tectonic data for selected intrusions. Zircon U-Pb geochronology for five granitoid plutons indicates they were emplaced during the middle-late Permian (264-255Ma) and Cretaceous (106-94Ma), and thus granitic magmatism occurred throughout the Phanerozoic, Permian (268-252Ma), Early-Middle Triassic (248-240Ma), Early Jurassic (183Ma), and Cretaceous (112-94Ma). The Permian granitoids consist of monzogranite, granodiorite, tonalite, and quartz diorite, characterised by enrichment in Na2O (3.60-4.72wt.%), depletion in K2O (0.97-2.66wt.%), and a negative correlation between P2O5 and SiO2. Together with the presence of hornblende, these geochemical features are indicative of an I-type affinity. The Permian granitic magmatism is associated with quartz-vein-type tungsten deposits (252Ma; unpublished Sm-Nd isochron age), which formed in an active continental margin setting related to subduction of the Palaeo-Asian Ocean. The Cretaceous quartz diorites have an adakitic affinity, having relatively high Sr (374-502ppm), low Yb (0.51-0.67ppm) and Y (8.7-10.7ppm), and high Sr/Y (39.4-46.8) and (La/Yb)N values (16.2-34.7), suggesting that they were related to the partial melting of subducted oceanic crust. In addition, they are associated with porphyry Au-Cu deposits. We conclude that the Cretaceous granitic rocks and associated porphyry Au-Cu mineralisation occurred in an extensional tectonic setting related to the subduction of the Palaeo-Pacific Plate beneath the Eurasian Plate. In addition, the large-scale Early-Middle Triassic syn-collisional granite belt at the eastern margin of the Xing'an-Mongolian Orogenic Belt extends from the middle of Jilin Province to the Wangqing-Hunchun region, constraining the timing of the final collision between the North China Craton and the Jiamusi-Khanka Massif, and suggesting that the Xra Moron River-Changchun Suture likely extends eastward into the eastern Hunchun region. This collision caused the Middle Triassic mesothermal lode gold mineralisation.
The Haigou lode deposit contains 40t of gold at an average grade of 3.5g/t, and is one of the largest deposits in the Jiapigou gold belt located along the eastern segment of the northern margin of the North China Craton. The deposit comprises 15gold-bearing quartz veins hosted in a Carboniferous monzonite-monzogranite stock. Cretaceous dikes consisting of diorite, diabase, and granodiorite porphyries are well developed in the deposit. The diorite porphyry dikes (130.4±6.3Ma) occur together with gold-bearing quartz veins in NNE- and NE-striking faults. Gold-bearing quartz veins crosscut the diorite porphyry dikes, and the veins are in turn crosscut by E-W-striking 124.6±2.2Ma granodiorite porphyry dikes. The mineralization mainly occurs as auriferous quartz veins with minor amounts of sulfide minerals, including pyrite, galena, chalcopyrite, and molybdenite. Gold occurs as either native gold or calaverite. Common gangue minerals in the deposit include quartz, sericite, and calcite. The deposit is characterized by various types of hydrothermal alteration, including silicification, sericitization, chloritization, potassic alteration, and carbonatization. Three stages of hydrothermal activity have been recognized in the deposit: (1) a barren quartz stage; (2) a polymetallic sulfide (gold) stage; (3) a calcite stage. Fluid inclusions in hydrothermal pyrites have ³He/⁴He ratios of 0.3 to 3.3 Ra and ⁴⁰Ar/³⁶Ar ratios of 351 to 1353, indicating mixing of fluids of mantle and crustal origin. Hydrothermal quartz yielded δ¹⁸O values of -1.3‰ to +7.2‰ and δD values of fluid inclusions in the quartz vary between -80‰ and -104‰. These stable isotope data also suggest mixing of magmatic and meteoric fluids. Noble gas and stable isotopic data suggest that the ore fluids have a predominant mantle source with a significant crustal component. Based on the spatial association of gold-bearing quartz veins with early Cretaceous intrusions, and the H-O-He-Ar isotopic data from the deposit and intrusions, we propose that gold mineralization in the Haigou deposit was formed in an extensional setting and was related to the early Cretaceous, mantle-derived intrusions.
Lithospheric subduction prior to the assembly of the South China and North China blocks is traditionally considered to be directed northward. However, some critical geological and geochemical data cannot be reconciled with this northward subduction. This paper presents new lines of evidence against the traditional models and proposes a new and revolutionary tectonic model to explain the distribution and exhumation of high pressure (HP)-ultra-high pressure (UHP) metamorphic rocks of the Dabie-Sulu Belt. We emphasize the following: 1) The Triassic tectonic environment of the southern margin of the North China Block was passive, not active, based on the stratigraphy; 2) In the southern margin of the North China Block no arc magmatism was recorded. 3) Many Paleoproterozoic slices of Jiaobei affinity of the Jiao-Liao-Ji Belt in the North China Block were located in the Triassic Dabie-Sulu Orogen. 4) Many 1.85 Ga metamorphic zircons are preserved in the Dabie-Sulu high pressure-ultra-high pressure (HP-UHP) metamorphic rocks. 5) The geometric asymmetry of many structural patterns in the HP-UHP slices indicates top-to-the northwest thrusting during the exhumation of HP-UHP slices. 6) Blueschists occur in the south of the UHP eclogite slices. 7) In the eastern segment of the North Qinling Orogen, no components with an affinity of the South China Block have been found. Along the Shangdan Suture of the Qinling Orogen has been recorded an apparent northward subduction. We consider that the suture is just a lateral subduction zone rather than a major collisional zone. Along the Shangdan Suture, the rarity of I-type plutonism can be attributed to a transform-type continental margin. The Bureya-Jiamusi-Xinkai Block has an affinity to the South China Block based on its similarity regarding the Paleozoic history of deformation and Triassic blueschist metamorphic facies metamorphism. The Bureya-Jiamusi-Khingan Block could be the northern extension of the Dabie-Sulu Belt, and this gigantic belt could be interpreted as an orocline related to the southeastward subduction of the North China Block beneath the Greater South China Block.
West Africa, with presently an approximate 10,000-metric ton (t) gold endowment, is one of the world’s great gold provinces and the largest Paleoproterozoic gold-producing region. The gold resources are concentrated within the 2250 to 2000 Ma greenstone belts of the Man-Leo shield, forming the southern part of the West Africa craton. Most of the major orebodies are best classified as orogenic gold deposit types, although there are paleoplacer and porphyry-skarn deposits within some of the greenstone belts, and perhaps local intrusion-related gold systems. The gold-hosting, mainly greenschist metamorphic facies greenstone belts are dominated by tholeiitic volcanic rocks, with clastic and chemical sediments filling adjacent subbasins. The Paleoproterozoic sequences formed in what was likely a rift or series of rifts in a Precambrian cratonic block; it is not clear whether significant Late Archean lithospheric roots occur below these Paleoproterozoic arcs that formed in the resulting ocean subbasins. Although diachronous across West Africa, the Eburnean orogeny is typically indicated to have been initiated at ca. 2130 Ma, with closure of the subbasins, amalgamation of the Paleoproterozoic arcs, and their accretion back to the continental margin of Archean rocks. Compressional tectonics took place for about 25 to 30 m.y., with widespread crustal thickening along orogen-parallel, commonly NE-trending, first-order thrust fault systems. This was followed by more than 100 m.y. of transcurrent tectonism and associated exhumation; gold ores mainly formed late during the Eburnean deformation.
The most productive orogenic gold deposits are located in greenstone belts in Ghana, Mali, Senegal, Burkina Faso, Cote d’Ivoire (or Ivory Coast), and Guinea. Yielding about 200 t Au per year, West African production has exceeded that of the Yilgarn craton of Western Australia since 2007 and, if grouped together, current annual production from these relatively small countries would only be surpassed by China, Australia, and Russia, demonstrating the global significance of the gold mineralization within this region. With an endowment of >2,500 t Au, the Obuasi deposit represents the largest single Precambrian gold deposit discovered in the world to date, exclusive of the Witwatersrand paleoplacers. More than 25 of the deposits in the Man-Leo shield contain resources in excess of 100 t Au. The gold-bearing brittle-ductile quartz veins, stockworks, breccias, and disseminated orebodies are located adjacent to major faults, typically in areas of second-order shears, large dilational jogs, regional fold systems, and rheological contrast. Mineralogy, alteration, structural geology, stable isotope geochemistry, and P-T conditions of gold deposition are typical of those observed in most orogenic gold provinces. Well-constrained absolute ages for much of the orogenic gold formation remain lacking, but there seems to be a temporal association with the 2100 Ma onset of transpression/strike-slip and exhumation. However, ore deposition was likely spread over at least 130 m.y. throughout the shield, with some ores as old as ca. 2160 Ma (e.g., Wassa) and some no older than ca. 2030 Ma (e.g., Damang).
It is unclear as to exactly why such a large gold endowment is present in West Africa and, in particular, the Birimian sequences of the Man-Leo shield, although it is likely the consequence of a combination of key regional factors. Relative to other Paleoproterozoic orogens, the abundance of carbonaceous oceanic sediments that overly the Birimian basalts may represent an exceptionally fertile source of both fluid and metal. The fact that many of the orogenic gold deposits formed from ore fluids with at least 70 to 80 mol % CO2, quite different from deposits elsewhere in the world where H2O >CO2, hints at an atypically large volume of carbon being released during metamorphic devolatilization. A series of closing and subsequently inverting basins, which were important sinks for the carbonaceous material, also resulted in a favorable structural architecture with development of many orogen-parallel, deep-crustal shear zones. Two hundred million years of orogenesis represented a lengthy period of deformation, including strike-slip reactivation events along the older thrusts that may have allowed for diachronous gold-forming events throughout the Eburnean.
Continent–continent collision between the North China Block (NCB) and South China Block (SCB) took place along the Qinling–Tongbai–Hong'an–Dabie orogens during the Triassic. A micro-continent with Paleozoic arc magmatism has been recognized in the northern Qinling–Tongbai orogens; however, it remains unclear whether the micro-continent extended to the Dabie Orogen to form a ribbon-shaped micro-continent, due to later burial by the Hefei Basin in the north. To solve this problem, we conducted LA–ICP–MS UPb dating of zircons from Silurian to Cretaceous sandstones and volcanic rocks from the southern margin of the basin. The age spectra of detrital zircons suggest that the Dabie Orogen and later basin cover were the sources of the analyzed sandstones. The detrital and inherited zircons indicate Neoproterozoic, early and late Paleozoic magmatism in the Beihuaiyang unit in the north of the Dabie Orogen. The zircon and previous geophysical data show that a micro-continent bounded by the Feizhong Suture in the north and the Xiaotian–Mozitang Suture in the south existed between the NCB and the Triassic Dabie Orogen, and its northern half is buried by the Jurassic–Paleogene Hefei Basin. The Beihuaiyang micro-continent experienced early Paleozoic arc magmatism caused by southward subduction of the Erlangping oceanic crust and late Paleozoic magmatism related to northward subduction of the Paleotethyan oceanic crust. The micro-continent was accreted to the southern edge of the NCB at the end of the Early Devonian (ca. 400 Ma) via arc–continent collision. Similarly to the Qinling–Tongbai orogens, the Dabie Orogen contains a Paleozoic accretionary system in the north and a Triassic collisional system in the south; thus, it is suggested that a ribbon-shaped micro-continent, > 900 km long and 50–100 km wide, was present along the entire Qinling–Tongbai–Hong'an–Dabie orogens prior to the middle Paleozoic. This micro-continent might have originated as a result of middle Neoproterozoic rifting along the margin of the SCB.
Precise geochronological constraints of the Irtysh tectonic belt between the Saur Island Arc and the Altay Terrane are crucial to a better understanding of the tectonic evolution of the Central Asian Orogenic Belt (CAOB). Recently, we discovered repeatedly deformed arc-related and collisional granitoids in the Kalaxiangar tectonic belt (KTB), which is located in the eastern part of the Irtysh tectonic belt. In this study, we report new whole-rock geochemical, zircon U-Pb and Hf isotopic data of the arc-related and collisional granitoids. Our data reveal that 1) arc-related granodioritic porphyries formed at ca. 382-374 Ma. Recrystallized zircon grains from a (ultra-)mylonitic granodiorite of the Laoshankou zone in the southern KTB display a U-Pb age of ca. 360 Ma; 2) syn-collisional granodioritic porphyries, which distribute along faults and parallel to the cleavage, were emplaced at ca. 367-356 Ma, with εHf(t) values varying from + 7.8 to + 14.2 and Hf model ages from 873 to 459 Ma; 3) a post-collisional A-type granodioritic porphyry, which crosscuts the NW-NNW trending schistosity of the metasedimentary country rocks at a low angle, has an age of ca. 324-320 Ma, while the εHf(t) values range from + 7.6 to + 14.4 with Hf model ages from 850 to 416 Ma; 4) post-collisional strike-slip A-type granite dykes, exposed along strike-slip faults, gave ages between 287 and 279 Ma, whereas the εHf(t) values range from + 4.9 to + 12.7 and the Hf model ages from 995 to 500 Ma; and 5) A-type biotite granite dykes, which intruded along conjugate tension joints, have ages of 274-271 Ma, and the εHf(t) values from + 1.5 to + 13.2 with Hf model ages from 1196 to 454 Ma. Consequently, we propose that the collision between the Saur Island Arc and the Altay Terrane occurred in the Early Carboniferous (ca. 367-356 Ma) and the subsequent post-collisional tectonic process continued to the Late Carboniferous (ca. 324-320 Ma). It is further suggested that the Irtysh tectonic belt underwent large-scale strike-slip deformation during the mid-Permian between 287 and 279 Ma. The termination of the Irtysh tectonic belt orogeny is thought to have also occurred during the mid-Permian between 274 and 271 Ma.
Geohistory of the Yunkai massif in South China Block is important in understanding the geodynamics for the build-up of this block during the Phanerozoic orogenies. To investigate this massif, we conduct EMP monazite and U-Pb zircon geochronological determinations on mineral inclusions and separate for seventeen samples in four groups, representing metamorphic rocks from core domain, the Gaozhou Complex (amphibolite facies, NE-striking) and the Yunkai Group (greenschist facies, NW-striking) of this massif and adjacent undeformed granites. Some EMP monazite ages are consistent with the NanoSIMS results. Monazite inclusions, mostly with long axis parallel to the cleavage of platy and elongated hosts, give distinguishable age results for NW- and NE-trending deformations at 244–236 Ma and 236–233 Ma, respectively. They also yield ages of 233–230 Ma for core domain gneissic granites and 232–229 Ma for undefomed granites. Combining U-Pb zircon ages of the same group, ~ 245 Ma and ~ 230 Ma are suggested to constrain the time of two phases of deformation. Aside from ubiquity of Triassic ages in studied rocks, ages of detrital monazite in the meta-sandstone match the major U-Pb zircon age clusters of the metamorphic rock that are largely concentrated at Neoproterozoic (1.0–0.9 Ga) and Early Paleozoic (444–431 Ma). Based on these geochronological data, Triassic is interpreted as representing the time for recrystallization of these host minerals on the Early Paleozoic protolith, and the also popular Neoproterozoic age is probably inherited. With this context, Yunkai massif is regarded as a strongly reactivated Triassic metamorphic terrain on an Early Paleozoic basement which had incorporated sediments with Neoproterozoic provenances. Triassic tectonic evolution of the Yunkai massif is suggested to have been controlled by converging geodynamics of the South China and Indochina Blocks as well as mafic magma emplacement related to the Emeishan large igneous province (E-LIP).
The Yangtze and Cathaysia blocks in South China are separated by the ca. 1500 km long Jiangnan Orogen. The Lianyunshan complex, located in the central segment of Jiangnan Orogen, includes wide exposures of late Mesozoic granites. Here we report geological, geochronological and geochemical data from the Lianyunshan late Mesozoic granites and their Neoproterozoic host rocks belonging to the Lengjiaxi Group. Detrital zircon U–Pb ages reveal a single prominent peak at ca. 840 Ma in the metamorphosed and deformed Lengjiaxi Group samples. Ten of the youngest zircon grains in these rocks have a weighted mean age of 828.8 ± 7.1 Ma, which is tentatively interpreted as the maximum depositional age of the Lengjiaxi Group. Two stages of late Mesozoic S-type granites are dated at ca. 150 Ma and ca. 140 Ma from the Lianyunshan domain. From early to late, these rocks show decreasing MgO, CaO, Fe2O3T, TiO2 contents and increasing SiO2, K2O, Eu/Eu*, Rb/Sr ratios and differentiation index, suggesting continuous magmatic evolution dominated by fractional crystallization. The εHf(t) values of zircons with late Mesozoic ages are all negative, with their two-stage model ages mainly ranging from 1.9 to 1.4 Ga, which is significantly different from the model age of the host rocks belonging to the Lengjiaxi Group. These results indicate that the late Mesozoic granites were mainly derived from the partial melting of Paleo-Mesoproterozoic basement rocks that are older than Lengjiaxi Group. Major and trace element features suggest that the protoliths of these early stage granites in Lianyunshan are probably mixed greywacke and shale. The arc-like trace elements signature of all the late Mesozoic granites were possibly inherited through crustal contamination during the magma genesis caused by slab rollback associated with Paleo-Pacific subduction during 150- to 140 Ma beneath the central Jiangnan belt.
The South China Craton was formed by amalgamation of the Yangtze and Cathaysia Blocks during the Neoproterozoic. During the Mesozoic, voluminous granitic plutons and associated W-Sn polymetallic deposits were formed in the Cathaysia Block. The giant South China low-temperature metallogenic domain (LTMD) includes an area of ∼500,000 km² in the Yangtze Block and is composed of the Chuan-Dian-Qian Pb-Zn, Youjiang Au-As-Sb-Hg and Xiangzhong Sb-Au metallogenic provinces. The Chuan-Dian-Qian Pb-Zn province contains numerous MVT Pb-Zn deposits, whereas the other two provinces are characterized by Carlin-type Au deposits and vein-type Sb, Hg and As deposits. These epigenetic deposits, which formed under low temperature conditions (∼100-250°C), are typically hosted in sedimentary rocks and are locally controlled by faults and fractures. The deposits formed dominantly at 200-230 Ma and 130-160 Ma, corresponding to Indosinian (Triassic) and Yanshanian (Jurassic to Cretaceous) orogenies, respectively. Indosinian mineralization is recognized in all three provinces, but Yanshanian mineralization occurred only in the Youjiang and Xiangzhong provinces. The Indosinian orogeny, which involved collision of the Indochina Block with the South China Craton, resulted in circulation of basinal brines that leached ore-forming elements from adjacent sedimentary strata to form the Chuan-Dian-Qian Pb-Zn province. Deep-seated granitic magmas generated during this orogeny caused extensive circulation of meteoric water that mobilized ore-forming elements from the sedimentary strata to form the Carlin-type Au deposits in the Youjiang province, and the Sb-Au deposits in the Xiangzhong province. The Indosinian orogeny was the key factor in establishing the metallogenic framework of the LTMD. It produced widespread mineralization in the three metallogenic provinces, each of which has unique features reflecting differences in the nature and composition of the basement rocks. The Yanshanian metallogeny was less important and overprinted the older ore deposits in the Youjiang and Xiangzhong provinces.
The newly discovered Katbasu gold deposit in the South Tianshan region has a gold reserve of 76 t at an average grade of 3.84 g/t. It is the first large gold deposit in the central segment of the South Tianshan. Gold mineralization is hosted within granite, and is associated with potassic, phyllic and chloritic alteration. Gold-bearing pyrite occurs as disseminations in the host rock and as quartz-sulfide veins cross-cutting the potassic and phyllic alteration assemblage. Rubidium (Rb) - strontium (Sr) analyses on sericite within five individual pyrite grains from a phyllic alteration sample yield an isochron age of 322.5 ± 6.8 Ma (MSWD = 3.2). The host granite has a SIMS U-Pb zircon age of 351.4 ± 1.1 Ma (MSWD = 0.13). The Rb-Sr isochron age represents the mineralizing age of the Katbasu gold deposit, which significantly postdates the ore-hosting granite but is consistent with the age of regional porphyry type mineralization at ~ 320 Ma in the South Tianshan. Discovery of the Katbasu gold deposits indicates huge potential for gold exploration in the central segment of the South Tianshan as it is geologically similar to the western and eastern segments of the South Tianshan, which both host many world-class gold deposits.
The Sawayaerdun deposit, located in the southern Tianshan orogenic belt in Xinjiang, NW China, is one of many orogenic gold deposits in the Central Asian Orogenic Belt (CAOB). The deposit is controlled by reverse faults and hosted in highly deformed carbonaceous turbidites that have undergone pyritic, arsenopyritic, silicification, carbonate and sericitic alteration. Gold occurs mainly in the form of electrum and native gold, and is also present in pyrite and arsenopyrite as “invisible gold”. Three generations of auriferous pyrite have been recognized through detailed petrographic studies and EMPA analyses. The pyrite with framboidal texture (Py0) is disseminated in the host rock, and is locally enriched in gold. The anhedral pyrite (Py1), associated with silicification and quartz veins that experienced strong deformation, has an average Au content of 0.021 wt.%. The euhedral–subhedral pyrite (Py2), showing octahedron cube and pyritohedron habits, is associated with least deformed quartz veins that are best developed in the main orebodies, and has an average Au content of 0.023 wt.%. The Py0 is interpreted to have formed contemporaneously with the ore-bearing rocks, with a maximum depositional age of 355 ± 7.3 Ma based on U–Pb dating of detrital zircons. Re–Os isotopic analyses of four Py1 samples yielded an isochron age of 324 ± 4.8 Ma, and those of five Py2 samples yielded an isochron age of 282 ± 12 Ma. Py1 is interpreted to have formed in the syn-tectonic stage, during the collision between the Tarim craton and the Central Tianshan terrane in Late Carboniferous, whereas Py2 was formed in a later mineralization event, during the late- to post-tectonic stage in Early Permian. These study results suggest that multiple stages of gold mineralization have developed in the Sawayaerdun deposit, and similar mineralization processes may have taken place in other parts of the Western Tianshan Orogen.
The Tethyan tectonic domain hosts numerous world-class mineral deposits. Among these, the Dewulu skarn copper deposit in Western Qinling, China belongs to the Paleotethys ore belt. The skarn and orebodies here occur as stratoids or lenses at the contact between the Triassic Dewulu intrusive complex and Permian marine clastic and carbonates. Alteration minerals include prograde skarns (garnet, diopside, wollastonite), plagioclase, hornblende, actinolite, tremolite, epidote, chlorite, calcite, quartz and sericite. The main ore types include early disseminated skarn-type replacement orebodies and late-stage quartz-sulfide veins. Chalcopyrite is the major ore mineral, along with pyrite, bornite and sphalerite. The Dewulu intrusive complex comprises quartz diorite, quartz diorite porphyry and dioritic mafic microgranular enclaves (MME). The MMEs are spheroidal in shape, and have igneous mineral assemblages, acicular apatites, complex oscillatory zoned plagioclase and quartz megacrysts surrounded by mafic minerals. The MMEs are metaluminous and calc-alkaline to high-K calc-alkaline, and possess relatively high Ni, Cr and MgO contents and Mg# values. They display sub-parallel patterns in trace element spider diagrams and rare earth element (REE) plots. They are also characterized by the enrichment of Rb, U and Th, depletion of Ba, Sr, Nb and Ta and negative Eu anomaly. Zircon LA-ICP-MS U-Pb dating of the dioritic MME yields an age of 247.0±2.2Ma, coeval with the host quartz diorite, quartz diorite porphyry and ore-related sericite ⁴⁰Ar/³⁹Ar plateau ages within analytical uncertainties. Oxygen fugacity estimated from trace element compositions of zircons from the dioritic MME shows FMQ±3.3. The zircons have negative εHf(t) values in a range of -8.0 to -3.3, corresponding to two-stage model ages ranging from 1.48 to 1.78Ga. The integrated data from petrology, geochronology and bulk geochemistry suggest that the Early Triassic granitoids associated with Cu skarn mineralization at Dewulu were products of arc magmatism and involved magma mixing in an active continental margin setting. The magma was sourced through partial melting of enriched sub-continental lithospheric mantle that had been previously modified by slab-derived melt during the continuous northward subduction of the Paleotethys oceanic slab.
Sancha mining area located Qilian landmass among Qilian orogenic belt, which is a landmass and magmatic arc stacked construction units. It is Neoproterozoic-Early Paleozoic of middle-late stage magmatic arc, sandwiched between North Qilian suture zone and Shulenan Mountain-Laji Mountain suture zone. Based on detailed studies of field deposit geology, through petrography, microthermometry analysis, inclusions constituents LRM analysis, carbon-hydrogen-oxygen isotope analysis and comparison research on the fluid inclusions of each stage closely associated with ore-forming fluids, the results showed that: cryptoexplosive quartz breccia of early mineralization stages has three types fluid inclusions, i. e. gas-liquid two-phase inclusions, daughter minerals-bearing three-phase inclusions and liquid-rich CO2 inclusions. Its homogenization temperatures concentrates in the range of 200-280℃, salinity in the range of 6.00%-18.00% NaCleqv, density in the range of 0.64-0.73 g/cm³. Pyrite phyllic of the main mineralization stage and Quartz veins of late stage mainly has one type fluid inclusions, i. e. gas-liquid two-phase inclusions. The main mineralization stage homogeneous temperature varies from 160 to 240℃, salinity from 2.00% to 6.00% NaCleqv, density from 0.80 g/cm³ to 0.95 g /cm³. Late stage homogenization temperatures concentrates in the range of 120-190℃, salinity in the range of 2.00%-6.00% NaCleqv, density in the range of 0.76-0.86 g/cm³. Carbon-hydrogen-oxygen isotopic composition reveals early ore-forming fluid of Sancha deposits is mainly magmatic water. In the late stage of the evolution, ore-forming fluid is obviously involved the meteoricwater, and sulfur isotope studies reflect that ore-forming material has characteristics of deep source. Therefore, Sancha gold deposit genetic type is mesothermal vein-type deposit.
The Baiyun gold deposit is one of the most important large gold deposits in the Liaodong rift. However, no directly chronological dating result has been reported for it yet. On purpose of dating the mineralization of the deposit, rhenium and osmium isotopes in eight gold bearing pyrite separates from different types of ores in the deposit have been analyzed. The results yielded Re-Os isochronal age of 225.3±7.0 Ma (MSWD=5.8), with an initial ¹⁸⁷Os/¹⁸⁸Os rate of 2.1±2.8. Combined with the previous researches, it is concluded that the Baiyun gold deposit is a magmatic hydrothermal deposit, which was formed in the Indo-Sinian period and the ore-forming materials were mainly originated from the crust. It is also suggested that the deposit was formed in the intracontinental post-collisional setting subsequent to the subduction of the Mongolia-Okhtsk seas. This study may shed light on the future exploration of similar ore deposit (relate to the Indo-Sinian magmatism) in the Liaodong rift.
The Jiapigou gold mineralization hosted in a Neoarchean granite-greenstone belt in the southern Jilin Province, at the easternmost part of the northern margin of the North China Craton (NCC), is one of the important gold deposits in China. However, its evolution, in particular the initial Au source and enrichment, have not been well constrained. The initial gold enrichment defined by Au concentrations of Neoarchean unaltered gneisses of this region, range from <0.005 ppm to 0.001 ppm, increasing to 0.006-0.031 ppm Au for the ore-hosting Neoarchean altered mylonite gneisses. A combined study of zircon trace element, U-Pb dating, Hf isotope compositions, as well as whole rock chemical compositions was performed for dioritic gneisses from both ore-bearing (close to the ore body) and ore-barren zones (within the nearby rock body) with a view to constrain the gold initial enrichment. The dioritic gneisses have varied SiO2 contents (54.19-61.34 wt.%), Al2O3 (13.06-16.75 wt.%) with moderate to high K2O/Na2O ratios (0.7-1.3) and MgO (2.20-3.77%). Based on their chemical compositions, positive zircon εHf(t) values, and their formation ages of 2512 ± 9 Ma, we infer that these dioritic rocks were generated by partial melting of a juvenile source, most likely thickened mafic lower continental crust (LCC) with residual plagioclase associated with minor amphibole. The ore-bearing sample (H5) from a ductile shear zone has been extensively altered by fluids and is the sample containing zircons with blurred zoning and reverse discordance. Zircons from H5 have much higher radiogenic Pb but lower U and Pb contents than those in the ore-barren sample (H3), which contains zircons with oscillatory zoning and represents the basement rock. Based on the available petrological, geochronological and geochemical constraints, we propose the following model for Au initial enrichment within the Neoarchean granite-greenstone belt. At ca. 2.54 Ga, associated with the accretionary processes in the proto-NCC, subduction-related fluids infiltrated the metasomatised subcontinental lithospheric mantle (SCLM), scavenging Au and Pb (mainly radiogenic Pb, henceforth Pb*) and triggering partial melting. The resulting basaltic magmas underplated the LCC and were re-melted at 2512 ± 9 Ma, when the onset of an extensional regime permitted the advection of heat and melts/fluids into the LCC. This generated voluminous dioritic magmas with juvenile Hf isotope signatures with little evidence of interaction with the mantle. Subsequent ca. 2505 Ma re-melting of some granodioritic rocks led to the formation of potassic granite and residual fluids further enriched in Au and Pb*, both focused into ductile shear zones and other lithospheric weak zones. The fluids with anomalous U-Pb fractionation resulted in the rarely reported zircon reverse discordance, alteration and also enrichment in Au, as observed in sample H5 and H4, representing the initial stage of Au enrichment within the Neoarchean granite-greenstone belt.
Numerous gold deposits and occurrences in Hainan Province of South China, predominantly of Mesozoic age account for more than 143 t of proven gold reserves. The Au mineralization occurs either along a group of NE-, NNW- and WNW-trending shear zones or within NW- to NNW-trending intraformational detachment faults which are closely related to folding, shearing and transpressional to transtensional deformation. Combined with the Mesozoic tectonics and associated magmatism, the ore geology, fluid inclusion geochemistry, C-H-O-S-(Pb) isotopes and geochronology consistently indicate that there are at least two gold deposit-types in Hainan Island, i.e., orogenic-type and intrusion-related.
The predominant orogenic gold mineralization, which produces more than 95% of gold metal reserves in Hainan Island, formed in the Early Mesozoic (ca. 228–224 Ma). This ore deposit-type, represented by the Baolun, Gezhen, and Wangxia deposits, is generally hosted by metamorphosed volcaniclastic sedimentary rocks of the Paleo- to Mesoproterozoic, the Silurian and the Permian ages, and is closely associated with brittle-ductile shearing. These deposits, with native gold as main gold occurrence and low sulfide abundance (<5% by volume), are derived from the CO2-rich (mainly 4.8–16.8 mol%), near neutral (pH = ∼7), low-salinity (generally 3–10.5 wt.% NaCleq.), and intermediate-temperature ore fluids. In combination with the paleomagnetism, sedimentation, and petrographical and geochemical features of the Late Paleozoic to Early Mesozoic granitoids, the orogenic gold mineralization is considered to be formed in a post-collisional tectonic setting, in response to the Indosinian orogeny in South China triggered by the closure of the Paleotethys Ocean. Abundant Bi-As-Te-Mo-S phases, which grew synchronously with the gold minerals, suggest a possible involvement of magmatic fluids, especially for the large-scale, high-grade Baolun deposit.
The Fuwen Au-dominated Au-Ag deposit, which is hosted by Lower Cretaceous continental clastic rocks, was interpreted as an intrusion-related deposit and most likely formed in the Late Cretaceous. This deposit is endowed with high gold grade (average 28–95 g/t Au), extremely high sulfide abundance (>50% by volume), Au-Ag-Cu-Pb-Zn metal association, and small amounts of alteration minerals (pyrite, quartz, sericite, chlorite and calcite). The rare isotopic data of O-H-S-Pb, and the ore occurrences mainly in the intraformational detachment fault zones and subordinately within the Late Cretaceous adakite-like granitoids (zircon U-Pb age of ca. 100 Ma), suggest that the Fuwen deposit had an intimate genetic link to the arc-related extension-type magmatism, due to asthenospheric upwelling triggered by the slab roll-back of the subducted Paleo-Pacific plate beneath the South China Block.
In China, there are 12 types of gold deposits in 57 class-III metallogenic zones, formed in 7 main metallogenic periods. Most gold deposits are small or occur as ore spots; very large deposits are rare with relatively poor quality, mainly medium to low grade. Only 35% of the total gold reserves is identified, while a large amount of reserves is yet to be identified. In recent years, China Geological Survey has organized or conducted mineral resources survey and evaluation project, replacement resources prospecting for deposits in crisis, old mines prospecting and commercial prospecting funded or encouraged by the Central Government. These efforts have been fruitful. According to the temporal and spatial allocation of gold resources, and experiences from recent prospecting efforts, western China and the deep layers and peripheries of the-sits in eastern China have relatively high prospecting potential. The government should give even more support to the gold industry and strengthen technological innovation to help address difficulties in gold exploitation and processing. The government should also formulate consistent plans, consolidate mining rights, and promote integrated exploration, so as to achieve new major breakthroughs in gold prospecting.