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Late Jurassic to Early Cretaceous age of the Daqiao gold deposit, West Qinling Orogen, China: implications for regional metallogeny

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Ya-Fei Wu at China University of Geosciences
Ya-Fei Wu
Jian-Wei Li
Jian-Wei Li
Jian-Wei Li
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Katharine Anne Evans at Curtin University
Katharine Anne Evans
P. M. Vasconcelos at The University of Queensland
P. M. Vasconcelos
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Abstract and Figures

The West Qinling Orogen is endowed with more than 100 sediment-hosted gold deposits with an estimated resource of > 2000 t Au. Previous radiometric dating results have shown that most deposits formed during a Late Triassic to Early Jurassic period of contractional deformation over the orogen. However, here we show that the newly discovered Daqiao gold deposit (> 105 t at 3–4 g/t) in the southern belt of the West Qinling Orogen formed in latest Jurassic to Early Cretaceous under a different tectonic regime. The Daqiao gold deposit is hosted in weakly metamorphosed Triassic turbidites and is spatially associated with hydrothermally altered granodiorite and diorite porphyry dykes. Six granodiorite dykes have similar zircon U–Pb ages ranging from 215.0 ± 1.1 to 211.5 ± 1.5 Ma (1σ), whereas one diorite porphyry dyke has a zircon U–Pb age of 187.5 ± 2.1 Ma (1σ). The age of gold mineralization is constrained by two types of sericite: sericite aggregates coexisting with disseminated auriferous pyrite in relatively high-grade breccia ores and sericite coexisting with auriferous pyrite in weakly mineralized granodiorite dykes. Sericite aggregates from the breccia ores have ⁴⁰Ar/³⁹Ar plateau ages ranging from 150.7 ± 3.1 to 142.3 ± 2.5 Ma (2σ), whereas grains from the altered granodiorite dykes and low-grade breccia ores have ⁴⁰Ar/³⁹Ar plateau ages of 130.8 ± 3.1 to 127.2 ± 0.6 Ma (2σ). The ⁴⁰Ar/³⁹Ar ages thus suggest two periods of gold mineralization in the latest Jurassic and Early Jurassic that are likely related to repeated brecciation at Daqiao. These Jurassic-Cretaceous mineralization ages coincide with discounted ages from several other gold deposits in the region and suggest that there is an underappreciated gold event in the West Qinling Orogen that may not have been associated with the orogenic deformation but is genetically related to the far-field effects of plate reorganization during Paleo-Pacific subduction beneath the eastern Eurasian continent.
A simplified map of geotectonic terranes in the Qinling-Dabie orogenic belt (modified from Dong and Santosh 2016). Also shown is the distribution of the major faults, plutons, gold deposits, and the location of Daqiao gold mine study area (red box). The inset shows the location of the Qinling orogen in China. Abbreviations: LLWF = Lingbao-Lushan-Wushan Fault, LLF = Luonan-Luanchuan Fault, SDS = Shangdan Suture; HLLF = Hezuo-Lintan-Liangdang Fault, ZCHF = Zhouqu-Chengxian-Huixian Fault, CHFF = Chengxian-Huixian-Fengxian Fault; MLS = Mianlue Suture; MBXF = Mianlue-Bashan-Xiangguang Fault; S-NCC = Southern North China Craton; NQB = North Qinling Belt; SQB = South Qinling Belt; N-SCB = Northern South China Block; Dabie UHP = Dabie ultrahigh-pressure terrane; WQO = West Qinling Orogen; EQO = East Qinling Orogen
A simplified map of geotectonic terranes in the Qinling-Dabie orogenic belt (modified from Dong and Santosh 2016). Also shown is the distribution of the major faults, plutons, gold deposits, and the location of Daqiao gold mine study area (red box). The inset shows the location of the Qinling orogen in China. Abbreviations: LLWF = Lingbao-Lushan-Wushan Fault, LLF = Luonan-Luanchuan Fault, SDS = Shangdan Suture; HLLF = Hezuo-Lintan-Liangdang Fault, ZCHF = Zhouqu-Chengxian-Huixian Fault, CHFF = Chengxian-Huixian-Fengxian Fault; MLS = Mianlue Suture; MBXF = Mianlue-Bashan-Xiangguang Fault; S-NCC = Southern North China Craton; NQB = North Qinling Belt; SQB = South Qinling Belt; N-SCB = Northern South China Block; Dabie UHP = Dabie ultrahigh-pressure terrane; WQO = West Qinling Orogen; EQO = East Qinling Orogen
… 
⁴⁰Ar/³⁹Ar age spectra of sericite from weakly mineralized dykes in and around the Daqiao gold mine
⁴⁰Ar/³⁹Ar age spectra of sericite from weakly mineralized dykes in and around the Daqiao gold mine
… 
A sketch illustrating the timing of tectonic events (Ren et al. 1992; Niu et al. 2003; Dong et al. 2011; Dong and Santosh 2016) and gold mineralization in the WQO (Wang 2000; Shao and Wang 2001; Qi et al. 2003, 2006; Lu et al. 2006; Yin and Zhao 2006; Zeng et al. 2012; Liu et al. 2014; Wang et al. 2014; Hu 2015; Zhang 2016; Lin et al. 2017; Yue et al. 2017)
A sketch illustrating the timing of tectonic events (Ren et al. 1992; Niu et al. 2003; Dong et al. 2011; Dong and Santosh 2016) and gold mineralization in the WQO (Wang 2000; Shao and Wang 2001; Qi et al. 2003, 2006; Lu et al. 2006; Yin and Zhao 2006; Zeng et al. 2012; Liu et al. 2014; Wang et al. 2014; Hu 2015; Zhang 2016; Lin et al. 2017; Yue et al. 2017)
… 
Geologic map of the Daqiao gold deposit (modified after Zhang et al. 2018)
Geologic map of the Daqiao gold deposit (modified after Zhang et al. 2018)
… 
Photographs showing typical features of the granodiorite and diorite porphyry dykes at Daqiao. a Granodiorite dyke intruding silicified slate of the Triassic Huashiguan Formation. b Altered granodiorite dyke with intense sericitization and sulfidation crosscut by quartz-pyrite vein. c Diorite porphyry dyke of about 2-m thickness showing relatively weak hydrothermal alteration. d Diorite porphyry dyke with carbonation of feldspar phenocrysts. Abbreviations: Cc = calcite, Py = pyrite, Qz = quartz, Ser = sericite
+6
Photographs showing typical features of the granodiorite and diorite porphyry dykes at Daqiao. a Granodiorite dyke intruding silicified slate of the Triassic Huashiguan Formation. b Altered granodiorite dyke with intense sericitization and sulfidation crosscut by quartz-pyrite vein. c Diorite porphyry dyke of about 2-m thickness showing relatively weak hydrothermal alteration. d Diorite porphyry dyke with carbonation of feldspar phenocrysts. Abbreviations: Cc = calcite, Py = pyrite, Qz = quartz, Ser = sericite
… 
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ARTICLE
Late Jurassic to Early Cretaceous age of the Daqiao gold deposit, West
Qinling Orogen, China: implications for regional metallogeny
Ya-Fei Wu
1,2,3
&Jian-Wei Li
1,3
&Katy Evans
2
&Paulo M. Vasconcelos
4
&David S. Thiede
4
&Denis Fougerouse
2
&
Kirsten Rempel
2
Received: 28 January 2018 / Accepted: 6 August 2018 /Published online: 16 August 2018
#Springer-Verlag GmbH Germany, part of Springer Nature 2018
Abstract
The West Qinling Orogen is endowed with more than 100 sediment-hosted gold deposits with an estimated resource of > 2000 t
Au. Previous radiometric dating results have shown that most deposits formed during a Late Triassic to Early Jurassic period of
contractional deformation over the orogen. However, here we show that the newly discovered Daqiao gold deposit (> 105 t at 3–
4 g/t) in the southern belt of the West Qinling Orogen formed in latest Jurassic to Early Cretaceous under a different tectonic
regime. The Daqiao gold deposit is hosted in weakly metamorphosed Triassic turbidites and is spatially associated with hydro-
thermally altered granodiorite and diorite porphyry dykes. Six granodiorite dykes have similar zircon U–Pb ages ranging from
215.0 ± 1.1 to 211.5 ± 1.5 Ma (1σ), whereas one diorite porphyry dyke has a zircon U–Pb age of 187.5 ± 2.1 Ma (1σ). The age of
gold mineralization is constrained by two types of sericite: sericite aggregates coexisting with disseminated auriferous pyrite in
relatively high-grade breccia ores and sericite coexisting with auriferous pyrite in weakly mineralized granodiorite dykes. Sericite
aggregates from the breccia ores have
40
Ar/
39
Ar plateau ages ranging from 150.7 ± 3.1 to 142.3 ± 2.5 Ma (2σ), whereas grains
from the altered granodiorite dykes and low-grade breccia ores have
40
Ar/
39
Ar plateau ages of 130.8 ± 3.1 to 127.2 ± 0.6 Ma (2σ).
The
40
Ar/
39
Ar ages thus suggest two periods of gold mineralization in the latest Jurassic and Early Jurassic that are likely related
to repeated brecciation at Daqiao. These Jurassic-Cretaceous mineralization ages coincide with discounted ages from several
other gold deposits in the region and suggest that there is an underappreciated gold event in the West Qinling Orogen that may not
have been associated with the orogenic deformation but is genetically related to the far-field effects of plate reorganization during
Paleo-Pacific subduction beneath the eastern Eurasian continent.
Keywords Daqiao gold deposit .
40
Ar/
39
Ar dating .Multistage gold mineralization .West Qinling Orogen .Paleo-Pacific plate
Introduction
The West Qinling Orogen (WQO) formed during the closure of
the Paleo-Tethys and subsequent orogenesis in Late Triassic
and is one of the largest and most prospective gold provinces
in China with over 2000 t of proven gold reserves (Fig. 1;Mao
et al. 2002;Chenetal.2004;Zengetal.2012;Goldfarbetal.
2014; Liu et al. 2015b). Previous
40
Ar/
39
Ar dates and Rb/Sr
isochron dates on K-bearing alteration minerals or fluid inclu-
sions extracted from quartz and Rb/Sr isochron dates on pyrite
have a large range as follows: 210 to 170 Ma (Mao et al. 2002),
220to100Mawithapeakat170Ma(Chenetal.2004), and
233and210Ma(DongandSantosh2016). However, based on
detailed textural characterization of several major gold deposits
in the WQO (e.g., Liba, Baguamiao, Liziyuan, Huachanggou,
and Jianchaling; Fig. 1), recent ore-related sericite and fuchsite
40
Ar/
39
Ar, carbonate Sm–Nd, and sphalerite Rb–Sr dates
Editorial handling: R. Hu
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s00126-018-0835-z) contains supplementary
material, which is available to authorized users.
*Jian-Wei Li
jwli@cug.edu.cn
1
State Key Laboratory of Geological Processes and Mineral
Resources, China University of Geosciences, Wuhan 430074, China
2
School of Earth and Planetary Sciences, The Institute for Geoscience
Research (TIGeR), Curtin University, GPO Box U1987,
Perth, WA 6845, Australia
3
School of Earth Resources, China University of Geosciences,
Wuhan 430074, China
4
School of Earth Sciences, The University of Queensland,
Brisbane 4072, Australia
Mineralium Deposita (2019) 54:631–644
https://doi.org/10.1007/s00126-018-0835-z
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Accurate dating of different intrusive events and their associated ore and alteration minerals using the U-Pb, Re-Os, and 40 Ar/ 39 Ar methods constitutes the basis of a successful estimation of the duration of single magmatic hydrothermal events (Valencia et al., 2005;Harris et al., 2008;Zhao et al., 2022), which can further be verified against the time interval bracketed by the U-Pb ages of such pre-/syn-and post-ore intrusions (Vry et al., 2010;Spencer et al., 2015). Gold deposits occurring as sulfide-quartz veins in association with granites in various volcano-sedimentary basins (Morelli et al., 2007;Zhang et al., 2018a;Wu et al., 2019;Chugaev et al., 2022) are notoriously difficult to date because they rarely generate dateable minerals. Nevertheless, measurement of precise ages for such deposits are essential to reveal their specific genesis (Ackerman et al., 2019;Zhou et al., 2022). ...
... Nevertheless, measurement of precise ages for such deposits are essential to reveal their specific genesis (Ackerman et al., 2019;Zhou et al., 2022). In recent years, hydrothermal zircon grains have been employed to be an effective tool for the dating of hydrothermal mineral deposits (Hoskin, 2005;Pettke et al., 2005;Zhai et al., 2022), with corroboration of mica Ar-Ar or sulfide Re-Os dating methods (Valley et al., 2009;Wu et al., 2019). These robust isotopic systems, together with the analytical and methodological developments (such as secondary ion mass spectroscopy [SIMS], sensitive high-resolution ion microprobe analysis, and chemical abrasion-isotope dilution-thermal ionization mass spectrometry), bring great opportunities to date minerals with high internal precisions (Chiaradia et al., 2013;Spencer et al., 2015;Ouyang et al., 2023). ...
... The closure temperature for argon diffusion in muscovite has been experimentally shown to be higher than 350 °C for muscovite crystals formed and cooled in a hydrothermal environment (Harrison et al., 2009), and thus, muscovite is one of the most useful minerals for 40 Ar/ 39 Ar dating of hydrothermal mineralization formed at or under this temperature (Wu et al., 2019). Micro-observations have identified widespread muscovite in the gold orebodies of the Qi-V gold deposit, which coexists with Qz2, gold-bearing pyrite, ankerite, and is associated with zircons in the stage II gold-bearing sulfide-muscovite-carbonate-Qz2 veins (Figs. ...
New precise age constraints of the Hatu gold belt, west Junggar, NW China: Implications for a 300 Ma magmatic hydrothermal event in post-collisional setting
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A 300 Ma magmatic hydrothermal ore-forming process is identified in the Hatu gold belt in west Junggar, northwest China, based on precise age constraint by secondary ion mass spectroscopy U-Pb dating of hydrothermal zircon and Ar-Ar dating of muscovite. The gold deposits in the Hatu belt (Hatu, Qi-V, Huilvshan, etc.) are similar in geology, with NE- and NW-trending orebodies composed of gold-bearing quartz veins and auriferous altered tuffaceous wall-rocks. Hydrothermal zircon grains separated from gold-bearing quartz veins in the Qi-V gold deposit provide a concordia age of 299.6 Ma and a nearly identical weighted mean 206Pb/238U age of 300 ± 2 Ma. Muscovite samples also from the gold-bearing quartz veins yield 40Ar/39Ar plateau ages of 299.6 ± 1.7 Ma, 299.9 ± 1.8 Ma, and 300.6 ± 1.9 Ma. By comprehensive compilation of geological and geochemical characteristics, tectonic evolution, and geochronology of the gold deposits in the Hatu gold belt, our new precise age data confirm that the gold deposits in the Hatu belt formed simultaneously at ca. 300 Ma, and likely formed during a post-collisional extensional setting by magmatic hydrothermal fluid from cooling magmatic sources.
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... The WNW-striking West Qinling Orogen in central China is tectonically bounded by the Qilian Orogen and the North China Block to the north, and by the Songpan-Ganzi Terrane, the Bikou Terrane, and the South China Block to the south ( Fig. 1A; Chen and Santosh, 2014;Dong et al., 2021;Li et al., 2018b). It is subdivided into North Qinling Terrane and South Qinling Terrane by the early Paleozoic Shangdan Suture (Dong et al., 2021;Wu et al., 2019). Precambrian metamorphic rocks exposed in the North Qinling Terrane include Proterozoic ophiolite units, gneisses, amphibolites, quartz-rich micaschists, marbles, and sedimentary cover units (Chen, 2010;Shi et al., 2012). ...
... The later orogenic mineralization event occurring at 136 Ma is related to NE-SW minimum principal stress in the Zaozigou deposit. Late Jurassic to Early Cretaceous hydrothermal events were also reported in the Daqiao (151-142 Ma and 131-128 Ma; Wu et al., 2019) and Zhaishang (131-126 Ma; Lu et al., 2006) deposits in the West Qinling Orogen. In addition, Early Cretaceous intraplate volcanic rocks are distributed in the northwesternmost part of the West Qinling Orogen. ...
... summarized that these latest Jurassic to Early Cretaceous events are closely related to the Early Cretaceous tectonic transition from compression to extension in the Qinling Orogen. This tectonic transition is interpreted to be related to the far-field effects of the paleo-Pacific Plate rollback (Deng et al., 2020b;Qiu et al., 2023b;Wu et al., 2019;Zhang et al., 2019), which triggered upwelling of the asthenosphere, potentially leading to significant devolatilization and related orogenic gold mineralization (Deng et al., 2023;Qiu et al., 2023cQiu et al., , 2024. Thus, we attribute D3 to the Early Cretaceous tectonic transition from contractional to extensional regime resulting from the roll back of the westward subducted paleo-Pacific oceanic slab (Fig. 13C). ...
The Zaozigou orogenic gold-antimony deposit, West Qinling Orogen, China: Structural controls on multiple mineralization events
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Orogenic gold deposits are generally thought to represent one perhaps protracted event. However, recent research on orogenic gold deposits increasingly offers evidence for some deposits forming through multiple and clearly discreet hydrothermal episodes. The giant Zaozigou orogenic Au-Sb deposit in the Triassic to Cretaceous West Qinling Orogen, central China, includes both steeply dipping and gently dipping orebodies. The two distinct mineralization styles provide a valuable setting for investigating a multiple mineralization model by integrating structural analysis within a robust geochronological framework. Through fieldwork and geochronology, we define a progression of major tectonic events in the area of the Zaozigou deposit. The deposit is hosted within a well-bedded sequence of Early Triassic metasedimentary rocks of the South Qinling Terrane. Pre-mineralization E-W shortening (D1) during subduction of the Mianlue oceanic slab include folding with resulting axial planes striking N-S, emplacement of Triassic ENE-striking and WNW-striking dacite dikes accompanied by Middle Triassic greenschist facies metamorphism. Late Triassic gold-stibnite quartz vein and disseminated mineralization formed along ENE-striking and steeply dipping D2 brittle to ductile sinistral faults. Their orientations suggest a link to the regional NNE-SSW maximum principal stress coinciding with transpression caused by the Late Triassic collision between the South China Block and South Qinling Terrane. Overprinting Early Cretaceous quartz-stibnite veins developed along gently dipping (20° to 40°) brittle D3 normal fault zones, which exhibit a NE-SW minimum principal stress. This younger deformation event is interpreted to be related to the Early Cretaceous tectonic transition from shortening to extension of the West Qinling Orogen. Therefore, the Zaozigou deposit reveals a model of multiple orogenic gold mineralizing events, with migration of hydrothermal fluids during discrete deformation episodes and the resulting formation of a single composite deposit formed along overprinting structures at separate times of orogenesis.
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... The western Qinling region is one of the most important regions for Carlin-type and Carlin-like gold deposits in China, and it contains > 100 gold deposits with reserves of over 2000 t (Chen et al. 2004;Wu et al. 2018). The Zhaishang Carlin-like gold deposit with reserve of 127 t is located in the north metallogenic sub-belt of the Qinling Orogen . ...
... In addition, determining the precise and accurate timing of ore-forming events is a persistent challenge due to the lack of ideal ore minerals and dating methods in this important district. Although the 40 Ar-39 Ar of ore-related alteration minerals has been the most widely used approach for western Qinling region (e.g., Wu et al. 2018;Ma et al. 2021), the complex and poorly understood relationship between alteration and ore minerals severely limits obtaining the actual mineralization age. It is rare to obtain reliable ages by directly dating ore minerals in this district, such as the 187 Re-187 Os chronometer in molybdenite, pyrite or arsenopyrite (Yue et al. 2022). ...
Scheelite texture and geochemistry as a recorder of nature and timing of metallogenesis: an example from the Zhaishang Au–Sb–W deposit, western Qinling, central China
Article
Full-text available
  • Jan 2024
  • CONTRIB MINERAL PETR
Scheelite, one kind of common REE-rich and U-bearing hydrothermal mineral, is extensively developed in various types of gold deposits, which can be used to record nature and timing of metallogenesis. The Zhaishang Carlin-like gold deposit in the Qinling Orogen is a giant Au deposit, hosting 127t of Au @ 2.67 g/t with economic concentrations of tungsten and antimony. The study reports two types of scheelite based on the characteristics of petrography and geochemistry. Sch A shows significant oscillatory zoning with dark gray cathodoluminescence (CL) response, whereas Sch B displays patchy textures with brighter CL response. Systematic LA-ICP-MS U–Pb dating of Sch A and Sch B yields ages of 227.1 ± 3.2 Ma and 226.2 ± 6.9 Ma, respectively. The new dates, constraining the Zhaishang Au–W mineralization to ~ 227Ma, coincide well with the western Qinling magmatism, metallogenic and tectonic events. There are significant variations in concentration, the Sch A has low REE content (mean = 41.3 ppm), negative Eu-anomaly with slightly positive Ce-anomaly, whereas Sch B, with small negative or positive Eu-anomaly, has higher REE content (mean = 247 ppm) and higher positive Ce-anomaly. The positive correlation of EuN and EuN* records oxidizing condition during the whole W mineralization event. Additionally, Sch B intergrown with selenides with an increase in the Ce-anomaly supports that the latter has higher oxygen fugacity environment. The Sr isotope signature for scheelite supports that ore-forming metals mostly inherited the host rock component, while the proportion of magma-derived Sr increased in the Sch B. Fluid–rock interactions co-precipitated Au and W caused by the release of Fe and Ca cations and the increase of pH. The study highlights that scheelite as a recorder can help in deciphering the nature and timing of metallogenesis of the studied Au–Sb–W deposit, and thus other similar Au–W deposits.
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... Stein et al. 2001), and techniques such as Pb-Pb often only yield model ages that rely upon assumed terrestrial evolution models (Cumming and Richards 1975;Frei and Pettke 1996). Indirect dating methods rely on clear petrogenetic evidence for synchrony; minerals such as monazite (U-Pb), sericite ( 40 Ar/ 39 Ar) and biotite (Rb-Sr) have been commonly employed (Vielreicher et al. 2015;Wu et al. 2019;Olierook et al. 2020bOlierook et al. , 2021, but these are not always present in mineralized samples and some of these isotopic systems are susceptible to resetting in polymetamorphic terrains. In the absence of commonly dated minerals associated with ore deposit formation, the envelope of geochronology needs to be expanded to solve issues regarding the timing of metal endowment. ...
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Full-text available
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  • MINER DEPOSITA
Porphyry Cu and Mo deposits are two economically important types of metal deposits worldwide, but factors controlling their difference remain enigmatic. Compared with the well-studied large porphyry Mo province in the south margin of the North China Block (S-NCB), the origin of newly discovered porphyry Cu deposits in the South Qinling (SQB) is poorly constrained. Integrated zircon LA–ICPMS U–Pb and molybdenite Re–Os ages and geological evidence indicate three stages of magmatism at Lengshuigou: (1) late Neoproterozoic (718 to 704 Ma) quartz diorite + albitite + granite association during the pre-ore stage, (2) 146 to 145 Ma granodiorite porphyry during the syn-ore stage, and (3) 145 Ma granite porphyry during the post-ore stage. Elemental and Sr–Nd isotopic evidence provide important constraints on their magma source. Pre-ore Neoproterozoic quartz diorite + albitite + granite was derived by re-melting of a mixture of crustal and juvenile mantle materials, and stronger fractional crystallization was involved in these ore-hosting intrusions than in contemporary granitoids hosted in the Douling Group. Syn-ore granodiorite porphyry was derived from mantle-derived magma with contributions from different proportions of crustal components. Post-ore granite porphyry was derived mainly from a crustal source. Nearly contemporaneous porphyry Cu and Mo systems were identified in Qinling Province, including the 147–139 Ma porphyry Mo systems in the S-NCB and 150–146 Ma porphyry Cu systems in the SQB. Granitic stocks related to porphyry Cu systems in the SQB are characterized by moderate SiO2 contents (58.01–69.07 %) and less radiogenic Nd–Hf isotopes (εNd(t) = −3.8 to −6.3, εHf(t) = −4.5 to +1.6), whereas the granitic stocks related to porphyry Mo deposits in the S-NCB have high SiO2 concentrations (64.00–76.00 %) and more radiogenic Nd–Hf isotopes (εNd(t) = −18.0 to −11.6, εHf(t) = −26.3 to −13.5). In addition, molybdenite from the Chigou and Lengshuigou porphyry Cu deposits in the S-NCB show higher Re contents (77.50–394.3 ppm) than those from nearly contemporaneous porphyry Mo deposits (9.34–49.7 ppm) in the S-NCB. These lines of evidence indicate that a higher proportion of mantle component was involved in the formation of porphyry Cu deposits in the SQB than nearly contemporaneous porphyry Mo deposits in the S-NCB. It is most likely that the nature of the magma source plays an essential role in the differences between porphyry Cu and Mo deposits.
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Full-text available
  • Jan 2005
We describe the temporal-spatial distribution of the main Mesozoic metallogenic belts and regions in North China, comprising the Middle Lower Yangtze River valley, the Xiaoqinling-Xiong'ershan (eastern Qinling) and western Qinling, North margin of the North China craton, and southern part of the Daxing'anling as well as the eastern Shandong peninsular and Wulugetu-Jiawula (Manzhuli). After collecting and documenting the precise radiometric age data of the ore deposits there appear three metallogenic pulses, i. e. 190 ∼ 160 Ma, ca. 140 Ma, and ca. 120 Ma. Almost all the gold only depoists in eastern Shandong peninsular formed at time of ca. 120 Ma. It is obvious there are two pulses of mineralization at ca. 140 Ma and ca. 120 Ma in the Middle Lower Yangtze River valley, and Xiaoqinling-Xiong'ershan region, where the porphyry-skarn-manto Cu-Au-Mo-Fe and Mo-(W) deposits occurred at the age of ca. 140 Ma whereas the gold deposits and terrestrial volcanic rock related iron deposits appeared at age of ca. 120 Ma. The Mesozoic mineralization in the northern margin of the North China craton developed in three pulses and their ages are getting older from the eastern margin of the Euroasian continent inward. The gold deposits in the western Qinling are dated to be an age range of 190 ∼ 160 Ma. In southern part of the Daxing'anling the granite-related Cu-Ag and Pb-Zn-Cu deposits are ca. 160 ∼ 177 Ma, granite-related Sn-Cu-Pb-Zn and Sn deposits are ca. 140 Ma, and Nb-Y-Zr deposit is 127 Ma. Based on the study of Mesozoic tectonic evolution, we propose these three pulses of large-scale mineralization are the consequences of the postcollisional process of the Triassic convergence between the northern China craton and the Yangtze craton, late stage of the tectonic regime changing its main stress from NS-trending to EW-trending, and lithosphere thinning process, repectively. The gold deposits associated with S-type granite of 200 ∼ 160Ma develop in the extension setting of postcollisional stage. At ca. 140 Ma a great amount of I-type granite porphyry derived from the upper mantle and lower crust empleaced at the shllow crust and are accompanied by porphyry-skarn-(manto) Cu-Mo-Fe-Au and Mo-W mineralization. Due to lithosphere rapid thinning at ca. 120 Ma the asthenosphere got into the curst, which gave up to the mixed fluids from the mantle, metamorphic process, and crust to leach the metallic elements so as to form the gold ore-forming system as well as the iron deposit association related to terrestrial volcanic activity.
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Ore-Forming Processes of the Daqiao Epizonal Orogenic Gold Deposit, West Qinling Orogen, China: Constraints from Textures, Trace Elements, and Sulfur Isotopes of Pyrite and Marcasite, and Raman Spectroscopy of Carbonaceous Material
Article
  • Aug 2018
The Daqiao gold deposit is hosted in organic-rich Triassic pumpellyite-actinolite facies metamorphosed turbidites in the West Qinling orogen, central China. Gold mineralization is characterized by high-grade hydraulic breccias (B and C ores) that overprint an earlier tectonic breccia (A ore). A complex paragenesis is defined by four sulfide stages: S1 diagenetic preore pyrite (py), S2 hydrothermal early ore disseminated pyrite and marcasite (mc), S3 main ore pyrite and marcasite aggregates, and S4 late ore coarse-grained marcasite with minor pyrite and stibnite. However, multiple generations of pyrite and marcasite may develop within one individual stage. Ore-related hydrothermal alteration is dominated by intensive silicification, sulfidation, sericitization, and generally distal minor carbonatization. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) trace element analyses show that the stage S1 py1 from the shale interlayers within turbidites contains low gold contents (mean of 0.05 ppm) and other trace elements (Mn, Co, Ni, Cu, Mo, Bi, and Pb), indicating an anoxic to euxinic sedimentary environment. Stage S2 contributed only minimally to the gold endowment with relatively low gold in various sulfides including py2 (mean of 0.09 ppm), py3 (0.84 ppm) to py4 (0.70 ppm), along with mc1 (0.02 ppm) and mc2 (0.14 ppm). Most of the gold was deposited in stage S3, which formed rapidly crystallized, irregular (e.g., framboids, colloform and cyclic zonation) cement-hosted py5a (mean of 27.35 ppm), py5b (9.71 ppm), and mc3 (5.94 ppm) during repeated hydraulic fracturing. Other trace elements (e.g., Ag, As, Sb, Hg, Tl, and W) are also significantly enriched in the main ore-stage pyrite and marcasite. Little or no gold is detected in the S4 py6 and mc4. Sulfur isotopes determined from in situ LA-multicollector (MC)-ICP-MS analyses of hydrothermal pyrite and marcasite from the Daqiao deposit vary significantly from –31.3 to 22.0 (δ34S values) but fall mostly between –10 to 10 and provide important information on the source and evolution of sulfur and of the ore-forming fluids. The results show that S2 ore fluids (mean δ34Ssulfide = –0.8 to 5.2) were most likely derived from deep-seated Paleozoic carbonaceous sediments during regional metamorphism associated with orogenesis of the West Qinling orogen. Main ore S3 fluids (mean δ34Ssulfide = –9.7 to –6.0) are relatively depleted in ³⁴S relative to those of S2, presumably due to fluid oxidation associated with hydraulic fracturing caused by the overpressurized fluids. The textural, chemical, and isotopic data indicate two distinct gold-introducing episodes at Daqiao, forming sulfide disseminations during early ore S2 and cement-hosted sulfide aggregates during main ore S3. The S2 mineralization took place in a tectonic breccia beneath low-permeability shale seals that capped the flow of deep-seated metamorphic fluids, facilitating reaction with preexisting carbonaceous material and the host turbidites to form sulfide disseminations and pervasive silicification. Raman spectroscopy analysis suggests that carbonaceous material in the ores is poorly crystallized, with low maturity, giving estimated temperatures of 283° to 355°C that are much higher than those of the ore fluids (100°–240°C). This temperature difference indicates an in situ sedimentary origin modified by the regional pumpellyite-actinolite facies metamorphism for the carbonaceous material in the host rocks, rather than a hydrothermal origin. In S3, continuous flux of hydrothermal fluids caused fluid overpressure and consequent hydraulic fracturing of the competent silicified rocks. Subsequent rapid fluid pressure fluctuations led to phase separation and thus massive oxidation of ore fluids, which triggered fast precipitation of gold and other trace elements within the fine-grained irregular sulfides. Results presented here, in combination with geologic evidences, suggest that the Daqiao gold deposit can be best classified as the shallow-crustal epizonal orogenic type, genetically associated with orogenic deformation and regional metamorphism of the West Qinling orogen.
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Fuchsite 40Ar/39Ar Geochronology of the Huachanggou Gold Deposit and its Tectonic Implications
Article
  • Apr 2017
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.
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Geological characteristics, ore-forming ages and geological significance of Donggou-Jinlongshan gold deposit, South Qinling belt
Article
  • Jul 2016
Donggou-Jinlongshan gold deposit located in flysch folded-thrust belt brachyanticline in southern Qinling orogen is considered to be a typical Carlin-type gold deposit and its metallogenic epoch yet to be determined. The regional tectonic system analysis showed that the brachyanticline is a dome structure which was formed by the superposition of east-west closed dome and north-east broad top anticline; the mineralization was mainly controlled by the late north-east brittle structure and east-west heterolithic facies unconformity interface. The geochemistry result of regional exploration shows that the anomalies of Au, As, and Sb register better, and that the anomalies distribute along north-east in beaded presentation and register obviously with the dome structure and the annular structure of remote sensing interpretation. The 40Ar/39Ar plateau age of sericite is 142.34±0.83 Ma, and the isochron age is 141.6±2.8 Ma, which shows that the mineralization happened in the early stage of the Late Mesozoic. The formation of pyrite has the characteristics of three periods; the auriferous pyrite has a symbiotic relationship with arsenopyrite and stibnite. Combining with regional date that the mineralization has a relationship with deep buried rock, and the deposit type is a remote epithermal deposit which is related to the deep hydrothermal fluid after the magmatic stage; the mineralization occurred in the squeeze-extended transition period at 141-142 Ma in the early Late Mesozoic; it suggests that the decompression and warming environment at the squeeze-extended transition period is the most favorable metallogenic geodynamic background. © 2016, Editorial Office of Earth Science Frontiers. All right reserved.
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