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General discussion on metallogenitic tectonic setting of beishan mountain, Northwestern China
Abstract
Beishan mountain area can be devided by Hongliuhe-Niuquanzi-Xichangjing ophiolite belt into two parts: Xingxingxia-Mingshui-Hanshan micro-plant and Dunhuang micro-plant. In Ordovician ocean basin and back-arc basin, volcano-sedimentary type copper-zinc minerals can be formed; in passive continental margin, lead-zinc minerals are hosted in volcano-sediment rock system. Silurian-Devonian island-arc volcanic formation may be hosted in rock full of porphyry copper deposits. The volcanosedimentary type iron minerals may occur in Carboniferous-Permian continental rift sedimentary formation, porphyry copper deposits and copper-nickel deposits of basic rock type. The palaeocontinunt crust melting type granite mass is metallogenetic matrix of W, Sn, rare metal deposits.
... Early studies suggested that Precambrian basement, referred to as the Beishan complex, was widespread in the Beishan Orogenic Belt (Fig. 1b;Zuo et al., 1990Zuo et al., , 1991Zuo et al., , 2003BGMRGP, 1993;Li, 1994;Mei et al., 1997Mei et al., , 1998Yang et al., 2008), but their protolith ages of the so called Precambrian rocks are speculative. Although recent zircon U-Pb dating has confirmed that some rocks in the Beishan Orogenic Belt are Precambrian (Fig. 1b;He et al., 2015He et al., , 2018Liu et al., 2015;Mei et al., 1999;Ye et al., 2013;Yuan et al., 2015Yuan et al., , 2019Zong et al., 2017), it has also shown that some rocks previously thought to have been Precambrian are Paleozoic in age (Song et al., 2013a(Song et al., , 2013b(Song et al., , 2013c(Song et al., , 2015(Song et al., , 2016Zheng et al., 2018). ...
... Up to now, the nature, tectonic architecture, and evolution of the Beishan Orogenic Belt are not well defined. Models proposed include Precambrian fragments rifted from different continental blocks (Zuo et al., 1990(Zuo et al., , 1991(Zuo et al., , 2003He et al., 2005;Yang et al., 2008Yang et al., , 2010, Precambrian fragments derived from a single, uniform microcontinent (He et al., 2018a), and Paleozoic island arcs or subduction and accretionary complexes (Xiao et al., 2010(Xiao et al., , 2020Song et al., 2013aSong et al., , 2013bSong et al., , 2013cSong et al., , 2015Song et al., , 2016Zheng et al., 2018). ...
... The Beishan Orogenic Belt is located in the southern part of the central segment of the CAOB (Fig. 1a), and is bounded by the Dunhuang Block to the south and the Mongolia Accretionary Collage to the north ( Fig. 1b; Zuo et al., 1991;Xiao et al., 2010). The Beishan Orogenic Belt is composed of several discrete arc terranes, namely, the Shibanshan, Shuangyingshan-Huaniushan, Mazongshan, Heiyingshan-Hanshan, and Queershan terranes, which are separated by the Liuyuan, Hongliuhe-Xichangjing, Shibanjing-Xiaohuangshan, and Hongshishan ophiolitic mélanges or rift zones (Fig. 1b;He et al., 2005He et al., , 2018Xiao et al., 2010;Yang et al., 2008, Zuo et al., 1990, 1991, 2003. ...
The distribution of Precambrian rocks and microcontinents is a key to understanding the architecture of the Beishan Orogenic Belt, southern Central Asian Orogenic Belt (CAOB). We present zircon U-Pb-Hf isotopic and whole-rock geochemical data for early Neoproterozoic granitic rocks from the eastern Shuangyingshan–Huaniushan Terrane in the Beishan Orogenic Belt. The zircon ages show that the granitic gneiss, the mylonitized granite, and the mylonitized monzonite formed at 895 Ma, 894 Ma, and 884 Ma, respectively. These ages confirm that the Shuangyingshan–Huaniushan Terrane is a microcontinental block and that Precambrian magmatic rocks are not restricted to the western Gubaoquan area. Both the gneiss and granite contain Al-rich muscovite, high SiO2 (69.59–78.10 wt%) contents, and show peraluminous features (molar Al2O3/(CaO + Na2O + K2O) values = 1.03–1.28), negative correlations of Th and Y with respect to Rb, typical features of S-type granites. The monzonite contains hornblende, and relatively low SiO2 (62.11–64.10 wt%), high CaO (5.33–5.41 wt%), Na2O (5.88–6.02 wt%), V and Cr contents, and low K2O/Na2O, Rb/Sr and Rb/Ba ratios, consistent with I-type granites. These studied granitic rocks are calc-alkaline to shoshonitic, and all exhibit similar LREE-enriched trace-element patterns, pronounced negative Eu anomalies, positive Rb, Th, U and K anomalies, negative Ba, Nb, Ta, Sr, P and Ti anomalies, evolved zircon εHf(t) values of −6.25 to + 1.09, and two-stage Hf model ages of 2.16–1.70 Ga. These characteristics suggest that they have mainly crustal sources, similar to coeval reported granitic rocks in the Beishan Orogenic Belt, and indicating an older crustal reworking event. The Precambrian basement of the Beishan Orogenic Belt shows evidence of Mesoproterozoic crustal growth and early Neoproterozoic crustal reworking, with zircon εHf(t) values plotting within the crustal evolution trend defined by 2.1–1.3 Ga crustal material, similar to the Yili, Central Tianshan and Northern Alxa blocks, and indicating an affinity with those blocks. Geochronological data from these blocks and terranes suggest that the southern CAOB contains an extensive assemblage of early Neoproterozoic magmatic rocks that are related to the assembly of Rodinia and can be trace over 2000 km as an east–west-trending belt.
... Based on the inferred occurrence of Alaskan-type complex, some proposed that the Beishan region represents an arc setting in Late Paleozoic (Mao, 2008;Xiao et al., 2009;Ao, 2010;Ao et al., 2010). However, more authors preferred an intra-continental rift setting (Xiao et al., 2000(Xiao et al., , 2004aJiang et al., 2006;Yang et al., 2008;Xu et al., 2009). But at present, they still have not got sufficient evidence, including the absence of bimodal igneous series, to support their opinion. ...
... Tectonic setting could be inferred from rock assemblages and their geochemical characteristics. The mafic-ultramafic intrusions in the Beishan region are construed to be derived from the upper mantle (Li et al., 2006a;Jiang et al., 2006;Mao et al., 2008;Pirajno et al., 2008;Yang et al., 2008;Su et al., 2009Su et al., , 2010a. Even though these rocks contain a wealth of information about petrogenetic evolution and related magmatic processes, few geochemical and geochronological works have been done on them. ...
... The Permian mafic-ultramafic complexes discovered so far are mainly distributed in the western part of the Beishan region and intrude the Proterozoic and Carboniferous strata (BGMRXUAR, 1993;Jiang et al., 2006;Su et al., 2009;Xu et al., 2009). From west to east, the mafic-ultramafic intrusions are distributed as follows: Luodong, Poshi, Poyi, Bijiashan, Hongshishan and Xuanwoling, and have been successively explored in the past decades ( Fig. 1B; Xiao et al., 2000Xiao et al., , 2004aJiang et al., 2006;Li et al., 2006a;Yang et al., 2008;Su et al., 2009Su et al., , 2010aAo et al., 2010) Jahn et al. (2000)). (B) Regional geological map of the Eastern Tianshan and Beishan regions showing the distribution of Paleozoic mafic-ultramafic complexes 2006a; Su et al., 2009Su et al., , 2010c. ...
The dacites and granites from the Beishan region are characterized by highly-fractionated REE, enrichments in LILE, and depletion in Nb, Ta and Sr. The dacites contain zircons with ages ranging from 265 to 748Ma. These features suggest that they were probably derived from the older lower continental crust and were later on subjected to significant crustal assimilation. The rhyolites, diorites and diabases, all of which share similar geochemical features such as trace element patterns, zircon U–Pb ages of ∼280Ma, positive εHf(t) and εNd(t), high initial (87Sr/86Sr)i and δ18O‰ values, were most likely derived from the juvenile crustal sources and subsequently experienced fractional crystallization and crustal contamination. These acidic igneous rocks (except dacites and granites) and coeval mafic–ultramafic intrusions form a bimodal igneous series. This implies that the Beishan region was a Late Paleozoic rift probably developed in association with the early Permian mantle plume activity in the Tarim Basin.
... Two episodes of magmatism related to coeval tungsten mineralization have been recognized in the Beishan orogenic belt: (1) 424-314 Ma (e.g., Hongjianbingshan, Guoqing, Yingzuihongshan, and Baixianishan deposits); the related intrusions were derived from the partial melting of Precambrian metasedimentary rock or juvenile lower crust [12,15,16,21,34,35]; ...
... Two episodes of magmatism related to coeval tungsten mineralization have been recognized in the Beishan orogenic belt: (1) 424-314 Ma; for example, the Hongjianbingshan, Guoqing, Yingzuihongshan, and Baixianishan deposits. The related intrusions were derived from the partial melting of Precambrian metasedimentary strata or juvenile lower crust [12,15,16,34,46]; and (2) 286-220 Ma; for example, the Liushashan (262-260 Ma; [36,37]), Huaheitan (226 Ma; [78]), and Yushan deposits [79]. The granites were derived from ancient crustal sediment [17,21,[36][37][38][39][40]79]. ...
The newly discovered Juyuan tungsten deposit is hosted in Triassic granite in the Beishan Orogen, NW China. The tungsten mineralization occurred as quartz veins, and the main ore minerals included wolframite and scheelite. The age, origin, and tectonic setting of the Juyuan tungsten deposit, however, remain poorly understood. According to the mineralogical assemblages and crosscutting relationships, three hydrothermal stages can be identified, i.e., the early stage of quartz veins with scheelite and wolframite, the intermediate stage of quartz veinlets with sulfides, and the late stage of carbonate-quartz veinlets with tungsten being mainly introduced in the early stage. Quartz formed in the two earlier stages contained four compositional types of fluid inclusions, i.e., pure CO2, CO2-H2O, daughter mineral-bearing, and NaCl-H2O, but the late-stage quartz only contained the NaCl-H2O inclusions. The inclusions in quartz formed in the early, intermediate, and late stages had total homogenization temperatures of 230–344 °C, 241−295 °C, and 184−234 °C, respectively, with salinities no higher than 7.2 wt.% NaCl equiv (equivalent). Trapping pressures estimated from the CO2-H2O inclusions were 33−256 MPa and 36−214 MPa in the early and intermediate stages, corresponding to mineralization depths of 3–8 km. Fluid boiling and mixing caused rapid precipitation of wolframite, scheelite, and sulfides. Through boiling and inflow of meteoric water, the ore-forming fluid system evolved from CO2-rich to CO2-poor in composition and from magmatic to meteoric, as indicated by decreasing δ18Owater values from early to late stages. The sulfur and lead isotope compositions in the intermediate-stage suggest that the Triassic granite was a significant source of ore metals. The biotite 40Ar/39Ar age from the W-bearing quartz shows that the Juyuan tungsten system was formed at 240.0 ± 1.0 Ma, coeval with the emplacement of granitic rocks at the deposit. Integrating the data obtained from the studies including regional geology, ore geology, biotite Ar-Ar geochronology, fluid inclusion, and C-H-O-S-Pb isotope geochemistry, we conclude that the Juyuan tungsten deposit was a quartz-vein type system that originated from the emplacement of the granites, which was induced by collision between the Tarim and Kazakhstan–Ili plates. A comparison of the characteristics of tungsten mineralization in East Tianshan and Beishan suggests that the Triassic tungsten metallogenic belt in East Tianshan extends to the Beishan orogenic belt and that the west of the orogenic belt also has potential for the discovery of further quartz-vein-type tungsten deposits.
... The deposits in Beishan metallogenic belt are closely associated with magmatism [11,12]. Different types of metal ore bodies have been documented in Shuangyingshan -Huaniushan arc Unit [13], which had developed an Au-W-Cu-Fe-Ni magmatic hydrothermal system. ...
... The Paleoproterozoic rocks contain migmatite, gneiss, quartzite, and granulite. The Neoproterozoic meta-sedimentary rocks, which are marble, linestone, and meta-sandstone, emerged in the area [11]. The Early Paleozoic rocks and Late Paleozoic rocks are composed by dolostone and clastic rocks, and volcanic -clastic rocks, lava and carbonates, respectively ( figure. ...
Hyperspectral information of altered minerals plays an important role in the identifications of mineralized zones. In this study, the altered minerals of two gold deposits from Fangshankou-Laojinchang regions of Beishan metallogenic belt were measured by ASD field Spectrometer. Many gold deposits would have a close relationship with Variscan magma intrusion, which have been found in study region. The alteration minerals have been divided six types by the spectral results, i.e. sericite, limonite, dolomite, chlorite, epidote and calcite. The distribution characteristics and formations of altered minerals were discussed here. By the ASD, the spectral curve of different geological units in the Jintanzi and Fangshankou gold deposits were analysed and summarized. The results show that the sericite and limonite are mainly related with the gold mineralization and widely occurred in the gold deposits. Therefore, we proposed that the sericite and limonite are the iconic alteration mineral assemblages for gold mineralization and the models of altered minerals for gold deposits could be established in this region.
... The ore body of Huaniushan Gold Deposits symmetrically occurred in the calcium siliceous hornstone and the interlayer fractured zone in the contact zone between marble and biotite felsic hornstone (whose original rock is argillaceous silty clastic rock) of third lithologic section in Jixian system, and also in the skarn zone of Indosinian-Yanshanian syenogranite and marble [1][2][3]. The mining area is the secondary anticlinal structure of east side. ...
The Beishan orogenic belt is located in the south rim of central Asia orogenic belt, the intersection of east Tianshan and Tarim plates. Thus, the geological structure is extremely complex. The gold deposits are widely distributed in various types and the met allogenic mechanism is complex. Overall, the gold deposits in Beishan orogenic belt are mostly developed in Palaeozoic continental plate collision and butting belt, which has a certain spatial and temporal distribution law. Huaniushan gold deposit is a typical gold deposit in Beishan Orogenic belt. This paper carried out a detailed study of the geology of Huaniushan gold deposit, to provide some basis for the classification of met allogenic stage.
... The mafic-ultramafic intrusions in the Pobei, such as Luodong, Poshi, Poyi, and Podong, have been successively explored in recent decades ( Fig. 1) (Jiang et al., 2006;Li et al., 2006;Yang et al., 2008;Ao et al., 2010;Yang, 2011;Su, 2014;Yang et al., 2014;Liu et al., 2015Liu et al., , 2016Xue et al., 2016;Zhang et al., 2017). The Pobei mafic-ultramafic complex is approximately 35 km in length and 8 km in width (Fig. 2). ...
The Poyi Cu-Ni deposit is hosted by the Early Permian Pobei mafic-ultramafic complex along the northern margin of the Tarim Plate. This series of multiple intrusions in the Poyi deposit can be divided into four lithologies: gabbro, dunite, hornblende peridotite, and wehrlite. The ore body consists mainly of disseminated sulfides hosted by hornblende peridotite. All the Poyi deposit sulfides show positive Δ³³S values from 0.004 to 0.221‰ and negative δ³⁴S values from −0.8 to −3.5‰. High Ni contents occur in the hornblende peridotites, which exhibit the highest Δ³³S value of 0.221‰ and the lowest δ³⁴S value of −3.5‰, indicating contamination by sulfides from Archean sedimentary rocks. This contamination was important during sulfide saturation in the Poyi intrusions and likely occurred at depth before the emplacement of the Poyi intrusions. The intrusions incorporated country rocks during their emplacement and consolidation, and the degree of assimilation increases from the central lithofacies (i.e., the hornblende peridotite) to the marginal lithofacies (i.e., the wehrlite, dunite, olivine gabbro, and gabbro). Higher Ni contents are correlated with lower degrees of contamination; thus, we infer that the contamination by the country Paleoproterozoic rocks, which contain significant amounts of gneiss and marble, hindered sulfide saturation.
The whole-rock Ni content is negatively correlated with the MgO and Fo contents in the olivine and positively correlated with the FeO and MnO contents in the olivine. During crystallization, olivine becomes gradually richer in FeO but poorer in MgO, and Mn tends to be enriched in the late stages of the melt. We infer that the fractional crystallization of olivine was an important factor during sulfide saturation.
... The majority of the ophiolites in the Beishan region are older than the Carboniferous (Yang et al., 2008;Ao, 2012). The Hongliuhe Ophiolite (Fig. 2) The identification and detailed description of peperites in Early Permian volcano-sedimentary successions in the Beishan region provides a significant approach in determining paleoenvironment and thus constraining regional tectonic setting, which is a valuable contribution to understand Late Paleozoic history of Beishan and the CAOB. ...
The Lower Permian volcano-sedimentary Zhesi Group has been investigated in the Hongliuhe and Liuyuan areas in Beishan, China, which is significant for the reconstruction of Late Paleozoic evolution in the southern part of the Central Asian Orogenic Belt. A variety of volcanic facies were distinguished in the Upper Zhesi Group: pillow basalt with interstitial limestone, thin-interbedded limestone and basalt, closely packed pillows, pillow-fragmented hyaloclastite breccia, and peperite. Laser 40Ar/39Ar whole-rock dating of the basalt yielding an age of 277±11Ma, as well as Early Permian brachiopod fossils in the limestone interbedded with the basalt, indicate that basalt was erupted in the Early Permian. The identification of the peperite and other facies originating from magma-sediment mingling reveals that the basaltic lava flows were derived from autochthonous basaltic magmatism and formed as part of the Lower Permian succession. The peperite also indicates that these subaqueous basaltic lava flows are not dismembered ophiolitic components, but formed in an autochthonous extensional setting in the Early Permian. The clastic rocks in the Lower Zhesi Group underlying the basaltic flows and peperites in the Hongliuhe and Liuyuan areas show a general fining-upwards sequence, indicating that they were deposited in a progressively deepening basin overlying the Devonian Hongliuhe suture zone. Subaqueous volcanism in a rift basin or basins, accompanied by coeval deposition of carbonate sediment and mud, built up the peperite-bearing volcanogenic-sedimentary successions. From among the various tectonic hypotheses for the Beishan region, this study demonstrates that by Early Permian the region was developing post-collisional rift basins.
... There are four important ophiolitic belts or sutures in the Beishan area which are also poorly understood. From south to north, they include the Late Paleozoic Yin'aoxia ophiolitic belt, the Early Paleozoic Xichangjing-Niujuanzi-Hongliuhe ophiolitic belt, the Early Paleozoic Xiaohuangshan-Shibanjing-Mingshui ophiolitic belt, and the Late Paleozoic Hongshishan ophiolitic belt (Ao et al., , 2011Dai and Tan, 2008;Guo et al., 2006;Ren et al., 2001;Song et al., 2008;Wang et al., 2007;Wu et al., 2011;Yang et al., 2008Yang et al., , 2009Yang et al., , 2010aYu et al., 2006;Zhang and Guo, 2008;Zuo and He, 1990;Zuo et al., 1991) (Fig. 1b). These ophiolitic belts are crucial for constraining the Paleozoic paleoenvironment and tectonic evolution of the Beishan area. ...
The Dongqiyishan granitic pluton is exposed in the Eastern Beishan area, in the central part of the Southern Central Asia Orogenic Belt. SIMS U–Pb zircon dating indicates that the Dongqiyishan pluton was emplaced at 356 ± 2 Ma. Geochemically the pluton is calc-alkaline and characterized by high SiO2 (> 65%), Al2O3 (mostly > 15%), Na2O/K2O ratios (1.3–3.9) and Sr (generally > 400 ppm). Samples display positive to weakly negative Eu anomalies (δEu = 0.81–2.32), low HREE, Y and Yb (Y < 18 ppm, Yb < 1.9 ppm), are enriched in LREE, LILE (Rb, Ba, Sr, U, and K), Zr, and Hf, and depleted in HFSE. They have relatively low εNd(t) values (–2.9–+ 0.6) and relatively high (87Sr/86Sr)i ratios (0.70581–0.70749). Together, these geochemical traits suggest an adakite-like composition that reflects melting of subducted oceanic crust and the involvement of older continental material. Assimilation and fractional crystallization (AFC) modeling requires significant crustal assimilation to modify an initial MORB-derived andesitic melt to produce the hybrid granitic melt, e.g. — the Dongqiyishan pluton. A back-arc basin to the south (represented by the Yueyashan–Xichangjing ophiolitic belt) closed before the Early Carboniferous Dongqiyishan adakite-like pluton was emplaced into the Silurian volcanic arc. Closure of the back-arc basin potentially provides the continental component seen in the isotopic signature of the Dongqiyishan pluton and required by the AFC modeling. Post-Ordovician flattening of the subducting slab together with crustal thickening from closure of the back-arc basin, led to the formation of a tightly coupled subducting slab and lower crust which resulted in the formation of Dongqiyishan adakite-like pluton. The Dongqiyishan pluton is consistent with southward subduction (represented by the Xiaohuangshan ophiolitic belt) and indicates that oceanic crust was still being produced in the Paleo-Asian Ocean during the Early Carboniferous. Adakite-like granitic rocks may be more abundant than previously thought in the Beishan region.
The Central Asian Orogenic Belt (CAOB) was generated through multiple collisional and accretionary events in the Paleo-Asian Ocean, a major global ocean that existed from the late Neoproterozoic into the late Paleozoic. Nevertheless, the question of when the Paleo-Asian Ocean finally closed has notoriously been enigmatic, especially due to the absence of large-scale investigations. The South Tianshan-Solonker Suture, is the largest and southernmost suture within the CAOB, and records the ultimate collision between the Tarim-North China cratons with the Siberia craton, and is commonly interpreted as marking the eventual closure of the Paleo-Asian Ocean. In this paper, we synthesize and evaluate relevant Chinese papers on the area, which are not readily available to an international audience, and extend this across the full length of the suture zone. Based on this review, we can divide the suture zone into four distinct segments, which are, from west to east: the South Tianshan Belt, the Beishan Belt, the Solonker Belt and the Yanji Belt. This enables us to provide a more systematic understanding of the nature and development of the South Tianshan-Solonker suture.
Geochronological data from Paleozoic cover rocks and high-pressure metamorphic rocks show that during the late Carboniferous, the western section of the Paleo-Asian Ocean closed when the Tarim Craton moved northward to collide with the Kazakhstan-Yili Block, thus marking the initial development of the South Tianshan Belt. The Beishan Belt to the east formed when the Dunhuang-Alxa blocks were transported northward to collide with the Tuva-Mongolia Block, with the youngest zircon UPb data from ophiolites indicating that closure of the local Beishan Ocean was in the early-middle Permian, although its final closure may not have been until the early late Permian along the northern margin of the Alxa Block, thus making it slightly younger than the South Tianshan Belt. Further to the east, the available petrographic, geochronological and paleontological data from the Solonker Belt indicate that this belt was formed in the middle-late Permian, during which time bi-directional subduction occurred and the North China and Siberia cratons were amalgamated during an ‘Appalachian-type’ orogeny. Furthermore, we observe that a transition in polarity from northward to bi-directional subduction occurred along the boundary between the Beishan and Solonker belts, which may be related to the East Gobi Transform Fault. In contrast, under the influence of the westward subduction of the Paleo-Pacific Ocean, the Jiamusi-Khanka Block moved southwestward along the Yilan-Yitong Fault in the middle-late Triassic (230–220 Ma) to amalgamate with the North China Craton.
The formation of the South Tianshan-Solonker Suture can be characterized by four distinct west-to-east accretion/collision events that lasted from the late Carboniferous to the late Permian. The South Tianshan Belt, the Beishan Belt and the Solonker Belt therefore demarcate, respectively, the amalgamation between the Tarim Craton and the Kazakhstan-Yili Block, the Dunhuang-Alxa Block and the Tuva-Mongolia Block, and the North China Craton with the Siberia Craton, representing the final closure of the Paleo-Asian Ocean. During the middle-late Triassic, the Yanji Belt in the far east was influenced by the Paleo-Pacific tectonic domain as a result of amalgamation between the Jiamusi-Khanka Block and the North China Craton.
The Xiqianluzi Pb–Zn polymetallic deposit is located in the southeast of the southern Beishan belt, whereas the ore‐forming metal sources are still unclear. Its Pb–Zn ore bodies mainly occur in the Changcheng system Qianluzigou Group metamorphic clastic rocks, showing zonation of Cu–Zn–Pb metals from deep to surface. The ore structures are mainly banded, massive and veined, which have the characteristics of syngenetic sedimentation. Au mineralization in silty slate is obviously controlled by WNW–ESE‐trending faults, and occurs as veined or lenticular type. The Pb, Zn, Cu, and Au are mainly enriched in quartz or siliceous veins. The biotite granodiorites are enriched in Si, Na, Rb, Ba and K, with A/CNK values less than 1.1, and depleted in Nb, P, Ti. They belong to calc‐alkalic series and weak peraluminous I‐type granite, formed in a post‐collision extensional environment and characterized by crust–mantle mixed source. The sulphide minerals in the Pb–Zn ores have δ34S values in the range of 17.7‰–21.0‰ with average of 19.2‰, reflecting seawater sulphate origin of sulphur. The sulphur of Pb–Zn ores was likely transformed from S6+ to S2− by thermochemical sulphate reduction. The Pb isotopic compositions of sulphide minerals in the Pb–Zn ores have 206Pb/204Pb ratios of 16.837–17.001, 207Pb/204Pb ratios of 15.437–15.557, and 208Pb/204Pb ratios of 36.377–36.889. In contrast, sulphide minerals in Au ores have δ34S values (5.4‰–7.6‰, with average of 6.5‰) lower than those of sulphide minerals in the Pb–Zn ores. The δ34S values of sulphide minerals in the Au ores are consistent with those of sulphide minerals in the Late Permian–Middle Triassic magmatic hydrothermal gold deposits in the southern Beishan belt, which imply a magmatic source for sulphur. Sulphide minerals in the Au ores have higher lead isotopic ratios, including 206Pb/204Pb of 18.249–18.325, 207Pb/204Pb of 15.583–15.598, and 208Pb/204Pb of 38.023–38.366, compared to those in the Pb–Zn ores. Geological and isotopic features indicate that the Xiqianluzi Pb–Zn polymetallic deposit comprises two mineralization types; namely, its Pb–Zn ores can be considered as Mesoproterozoic sedimentary exhalative type, while its Au ores are magmatic origin. These show that Au mineralization was closely related to the magmatic hydrothermal activities, and thus Au ores can be classified as Late Permian–Early Triassic magmatic hydrothermal Au mineralization. Xiqianluzi Pb–Zn polymetallic deposit underwent two types of mineralization, first the Mesoproterozoic sedimentary exhalative Pb–Zn mineralization and second the Late Permian–Early Triassic magmatic hydrothermal Au mineralization.
The Beishan orogen is an economically important gold mineralization belt that hosts more than 20 gold deposits. Most Au orebodies occur within large-scale fault zones, indicating a correlation between structural evolution and gold mineralization. Previous studies have demonstrated that Au mineralization generally developed in the Permian–Triassic; however, pre-Permian gold mineralization and its temporal relationship with tectonic evolution remain poorly understood. The Qingbaishan deposit, located in the Beishan orogen, NW China, is hosted by the Sanjiashan shear zone. A detailed field-based structural analysis revealed that the Sanjiashan shear zone has thrust and sinistral strike-slip characteristics, such as asymmetrical folds and S-C fabrics. The muscovite ⁴⁰Ar/³⁹Ar age from auriferous quartz shows that the Qingbaishan gold system formed around 399.7 ± 1.6 Ma, consistent with the time of Sanjiashan sinistral ductile shearing in the Beishan orogen. The carbon and oxygen isotope compositions of auriferous quartz suggest that the host rocks within the Precambrian Gudongjin Group would have been a significant source of ore metals and that the low δ¹⁸O values in quartz resulted from fluid reactions with ¹⁸O-poor host rocks. The Qingbaishan Au deposit is concluded to be a strike-slip-dominated orogenic-type system related to continental collision between the Tarim and Kazakhstan–Ili plates.
By integrating the age data obtained from this study with previous geochronological results, two episodes of gold mineralization in Beishan are distinguished: an early episode around 399 Ma, when sinistral strike-slip zone-related orogenic gold deposits formed in a syncollisional setting, and a late episode around 298–231 Ma, when dextral strike-slip deformation produced deposits in a postcollisional extensional setting.
Fossil remains of Dryopterites fern foliage were collected from the Lower Cretaceous Chijinbao Formation in the Zhongkouzi Basin, Beishan area, Northwest China. A new species, Dryopterites beishanensis Ren and Sun sp. nov., is described on the basis of gross morphological structure and details of reproductive characters. Fronds are tripinnate, the main rachis is broad, and pinnules are small, oval or long ovate, and attached at narrow angles to the rachis, with apices obtuse. Sporangia are rounded or rounded-reniform and borne on the lateral vein, with one to two pairs in number. Spores are suborbicular or oval and monolete, with laesura 28 to 41 µm long. The extine is not smooth. The new fossils represent the first record of Dryopterites from the Chijinbao Formation. Additionally, according to different fossil records, the genus Dryopterites most likely originated in East Asia in the Early Cretaceous (Hauterivian to Barremian age). The new fossil provides new evidence on concerning the origin of Dryopterites.
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.
Ordovician to Devonian sodic granites dominate the newly recognized Luotuojuan composite granite in the Lebaquan-Luotuojuan-Niujuanzi region of Beishan, along the southern margin of the Central Asian Orogenic Belt in NW China. The granites include sodic (K2O/Na2O > 0.5) tonalites with low Y (<7 ppm), Yb (<0.7 ppm), high Sr/Y (>68) that formed during at least two events at c. 435 and c. 370-360 Ma. Their compositions are consistent with high-pressure melting of basaltic crust, although relatively non-radiogenic Nd isotope compositions (εNd(t) + 0.9) require some crustal assimilation. The interpretation that these granites reflect melts of a subducted slab (i.e. adakite) is supported by independent local and regional geological evidence for an oceanic subduction-accretion setting, including a long history of calc-alkaline magmatism and the identification of a series of early Paleozoic ophiolite belts. Other sodic granites forming the Luotuojuan composite granite are mainly quartz-diorite and granodiorite formed between c. 391 and c. 360 Ma. These rocks are not adakites, having Sr concentrations and Sr/Y ratios too low and Y and Yb concentrations too high. They are low- to medium-K calc-alkaline rocks more typical of magmas derived through melting in a subduction modified mantle wedge. Compositional changes from sodic to potassic granites, over time frames consistent with subduction processes, suggest at least two separate cycles, or pulses, of hot subduction in the Lebaquan-Luotuojuan-Niujuanzi region. Although early Paleozoic adakites have been inferred to exist elsewhere in the Beishan region, many of the reported adakitic rocks have compositions inconsistent with melting of subducted oceanic lithosphere and so tectonic interpretation of hot subduction might not be valid in these cases. A study of regional granite data also shows not only that adakite magmatism does not extend into the Permian but that if subduction-accretion processes extended into the late Paleozoic, no typical subduction-related magmatism was preserved. New and published Nd isotope data from regional granites also requires at least the local presence of Proterozoic basement, or microcontinental slivers, in the evolution of the Beishan region.
The chert from Hongshan iron deposit is closely associated with the iron ore body, and some cherts are iron ores themself. Chemical analysis of the chert shows that it generally has the features of high content of Si and Fe, low content of Al, and higher content of K 2O than Na 2O, and the ratio of Fe/Ti is between 57.14-218. 74, (Fe+Mn)/Ti is between 57. 54-224.16, Al/(AH-Fe+Mn) is between 0. 05-0.14, which are all according with the features of hydrothermal sedimentary chert, but with little terrigenous materials. Trace element analysis of the chert shows that most of the trace elements are lower than the Clarke value and the total REE is lower. Normalized by the North American shale, HREE is richer than LREE, and the geochemical characteristics of the chert indicate that they are hydrothermally sedimentary origin, but with existence of certain continental sources. So it can be concluded that the Hongshan iron deposit is associated with hydrothermal deposite with terrigenous materials and it was formed in the environment of continental margin.
Hulunxibai gold deposit is located in the western of hulunxibai-zhusileng reverse "S"-type arcuate structure. The NW-striking faults are large in scale, not only the main rock-and ore-controlling structures, but also the important pathways for hydrothermal activity. The late superimposed NE-striking secondary structures related to sub-volcanic rocks activity or deep cryptoexplosion are important depositing ore structure. Metallogenic materials are mainly from Jurassic porphyry biotite granite, syenite porphyry and gabbro. Ore-bodies are hosted in different structure positions with Jurassic porphyry biotite granite, syenite porphyry-sub-volcanic rock activity (or deep crypto-explosion), and belong to post magmatic hydrothermal cataclastic altered rock type or subvolcanic type (magma crypto-explosion breccia type) gold deposit. The occurrence environment of the 13 gold veins having been discovered can be divided into two types; one is inner rock body or inner contact zone with wall rock, the other is outer contact interstratified fracture zone (weak zone). The major alterations closely related to ore-forming are silicification, pyritization, and chalcopyritization, and there is a positive correlation between gold grade and contents of metal sulfides. Based on the analysis of metallogenic geological conditions, the ore-forming model has been established preliminarily.
Heishan Ni-Cu deposit is situated on the Heishan-Jiznquanzi Fault which is the south margin of Mazongshan middle block within Kazakhstan paleo-plate. The fault has the characteristics of marginal rift on the edge of paleo-plate, and regionally, the fault and rock mass appear the obvious gravity and magnetic anomaly. The ore-bearing rock body intruded into dolomite marble of Qingbaikou Series Dahui-oluoshan Group, and Cambrian Shuanyingshan Formation carbonaceous-siliceous-slate, metamor-feldspar-quartz-sandstone and baritic rock. Viewing from the surface, the body is the pear shape with the outcrop area of nearly 0. 25 km2, slightly longer on the NW direction, about 800 m long and 470 m wide. It is a complex massif developed from multi-intrusive of the same source and period, mainly comprised of plagio-harzburgite, hornblende-olivinite, olivine-hornblende-gabbro, and hornblende gabbro. The first phase is hornblende-gabbro facies which consist of hornblende-gabbro and quartz-syenite block within gabbro. The second phase is olivine-hornblende- gabbro and plagio-harzzburgite facies which consist of olivine-hornblende- gabbro, hornblende-olivine-gabbro, hornblende gabbro, and plagio-harzburgite. The average of chemical composition is similar with ultrabasic rock. The basicity index σ is very low, average is 0. 05, TiO20.28, m/f (Wu Liren) 4.79, Zavaritskiivalues 6 = 56. 00, 5 = 39.77; m' = 81. 68; Na 2O>K2O, the basicity type is Pacific type. The protomagma is characterized of olivine-tholeiite, came from the upper mantle. The average value of Mg/Fe is 4. 79. Ni-Cu orebody with appearance of len, vein and stratiform-like mainly exist the middle and lower part of rock mass. Mother rock and ore-bearing rock mainly consist of harzbeugite, secondly hornblende-gabbro. The ore body is classified into 3 types; insitu liquation, late period injection and contact metamorphic body. The ore minerals include niccolite, chloanthite, chalcopyrite, millerite, magnetic pyrite, chalcocite, as' well as some pyrite, violarite and natural copper. The metal oxide is magnetite. The associated elements have Co, Pt, Pd, Au, Ag, Os, Ir, Ru, Rhodium, Se, Te, Cr etc. The harmful elements have Pb, Zn, As, Bi. The chemical composition of ore is characterized of poor alkali, lower aluminium and calcium. Although a little differences of scale and neme-racalvalues, Heishan Ni-Cu deposit has the same condition with Jnchuan Ni-Cu deposit on geological setting of diagenesis and metallogensis, gravity and magnetic anomaly, occurrence of ore-bearing rock body, feature of ore body, petrochemistry and metallogenic elements, generally, these reflected similarity and consistency of two deposits on diagenesis and metallogenesis. Heishan district would be expected to be potential in depth. Regionally, around the area of gravity and magnetic anomaly on the deep-great fault at the edge of archicontinent or old block, the prospecting targets for magmatic Ni-Cu deposit should be focused on multi-phase intrusive outcrop or small scale concealed basic-ultrabasic complex body with anomaly zone of Fe, Cr, Ni, Co, V, Cu, Zn, Mn.
This paper deals with petrologic and geochemical features and zircon U- Pb isotope ages of the intrusive rocks from Yantan belt in Beishan area,which are mainly composed of quartz diorite, granodiorite, monzonitic granite, K-feldspar granite, granite and granite-porphyry, belonging to high-K calc-alkaline and calc-alkaline series; All the rocks are characterized by enrichment of LREE, depletion of HREE and strong Eu negative anomalies. The trace elements are enriched in LILE(Rb, Th), and depleted in Sr, Nb, Ta evidently. The zircon SHRIMP U-Pb ages of the quartz diorite and granite are (296±4.1) Ma and (294±3.7) Ma respectively, both of the data are consistent within test errors, suggesting that the rocks were formed at the beginning of the early Permian period. An analysis suggests that these intrusive rocks are I-type granite which are indicative of the underplating of the mantle material into the lower crust and the formation of these rocks in the post-collision tectonic environment after the closure of Beishan rift. The result shows that the Beishan rift was closed in the early Permian in the study area.
The stratigraphic division of Beishan mountains and east Tianshan mountains, in the Conjunction Area of Xinjiang Uygur Autonomous Region, Gansu Province and Inner Mongolia Autonomous Region, is different, because they belong to different administrative regions. But the stratigraphic correlation indicates that the stratum of east Tianshan mountains and Beishan mountains is continuous, and this can provide an important basis for tectonic division. Theses tectonic units, such as Archean-Paleoproterozoic Beishan complex ( Ar2Pt1Bc), mesoproterozoic Changcheng system Xingxingxia group (ChX) and Gudongjing group (ChG), Jixian system Kawabulake group (J×K) and Pingtoushan formation constitute the center of Xingxingxia-Hanshan micro-plant, and Dunhuang micro-plant is mainly made up of ArcheanPaleoproterozoic Dunhuang complex (Ar2Pt1D c) and a little mesoproterozoic Changcheng system Qianluzi group (ChQ). The accessory basis what the Hongliuhe-Niuquanzi-Xichangjing ophiolite belt was confirmed Eopaleozoic suture zone is that there is Precambrian stratum of containing phosphorus-vanadium-uraniummanganese in the south side of this belt, which indicate the extension and shallow-subdeepwater sedimentary environment before cracking of the south plate and the north plate. This evidence proves that Hongliuhe-Niuquanzi-Xichangjing ophiolite belt lies in the location where the south plate and the north plate was splitted and aggregated.
The Central Asian Orogenic Belts (CAOB) resulted from evolution and final closure of the Plaeo-Asian Ocean(s). Located in the central segment of the southern portion of the CAOB, the Beishan area, which refers to the conjunction region of Inner Mongolia, Gansu and Xinjiang, is one of the most important metallogenic belts in China, with abundant Cu, Mo, Au, Fe and base metal deposits. Two collisional events took place in the Beishan area during Late Paleozoic-Early Mesozoic: one occurred at the end of Late Paleozoic, which was related to the final closure of the CAOB, and the other took place in Early Mesozoic, resulting from the closure of the Carboniferous-Permian rifts in southern Beishan. As a consequence, the Beishan area was involved, in terms of temporal relations, in a collision to post-collision stage in Indosinian epoch of Mesozoic period, during which large-scale ductile shear zones and intensive magmatism as well as associated metallic mineralization occurred. The Mesozoic magmatism, which is predominated by intermediate-felsic intrusions locally with minor basic ones, is characterized by plutonic intrusive facies, without extrusive counterpart. Petrogenically, S-, I- and A-type granites have been delineated in the area. Types of Mesozoic mineral deposits in the area mainly include porphyry-type Mo mineralization, which is associated with I-And/or A-type granites, W (Sn) deposits associated with S-type granites, skarn-type Au-Ag-Cu polymetallic deposits associated with intermediate-felsic intrusions, and Au deposits related to granitic intrusions and controlled by ductile shear zones. Indosinian epoch is the latest period of major magmatism and metallic mineralization in the area, to which more attentions should be paid since the Indosinian granitoid intrusions and associated mineral deposits may be much more extensive and abundant than recognized presently.
Xiaohongshan and Damião vanadium and ilmenite deposits in the Tianshan mountains-Yinshan belts in the similar latitude. The early Hercynian gabbro rock is the main mine body. The consistent income-based distribution of vanadium-titanium magnetite is shown mostly in the surface, and in the deep is the magma-shaped like layered sub-vanadium-titanium magnetite output. The ore body is stable and rich. The magnetite and ilmenite ore minerals are mainly symbiotic elements such as vanadium, which is a magma-differentiation and segregation-penetration superposition compound type of vanadium-titanium magnetite, and a new type of type between Panzhihua and Damião V-Ti magnetite-type ore-forming characteristics, the discovery of This type of mineralization has a certain scientific significance for the similar types of vanadium-titanium magnetite.
This paper summarizes the assemblege of rock types and geochemical characteristics of four ophiolite belts in Beishan region, and analyzes the the regional geological background conditions. The result shows that the Hongliuhe-Niujuanzi-Xichangjing ophiolite belt was formed in Early Palaeozoic and is part of the oceanic basin type and quite similar to the present oceanic ophiolite in characteristic. This ophiolite belt indicates the sutureline of the north-south plates because the Gongpoquan-dongqiyishan volcanic rocks in the north belongs to the inland volcanic rock series with active continental margin environment and the shallow sub-sea P-V-Mn-U-bearing sedimentary strata of the Cambrian in the south representing the extended tectonic before the plate becoming divergent. The Jijitaizi-Xiaohuangshan ophiolitic belt, formed in the Early Paleozoic back-arc basin environment, is distributed between Xingxingxia-Hanshan plate and Gongpoquan-Dongqiyishan arc belt. The Hongshishan-BaiheshanBengpeshan ophiolitic belt and Huitongshan-Zhangfangshan ophiolitic belt are similar to Red Sea in environment, which was formed from the stage with the maximum extensional rift to the initial stage of forming the small ocean basin in late Paleozoic.
The Hongliugou copper-nickel mineralized mafic-ultramafic rock is located in the Beishan rift belt on the northern margin of the Tarim plate. There are two regional deep fracture zones in the rock on both sides, i.e., Dashantou-Gangliunaozi and Fang-shankou-Miaomiaojing-Shuangyingshan. Rock mass was emplaced in the the Dunhuang rock group, copper-nickel mineralization usually occurs in lherzolite, whereas olivine two-pyroxene monzonite and olivine norite-gabbro. SHRIMP U-Pb dating of zircon from the olivine hornblende gabbro norite yielded an age of (396.7±3.8) Ma, which suggests that both the intrusion of the ore-bearing complex and the mineralization occurred in middle Devonian. Combined with the age of Heishan and Guaishishan copper-nickel ore-bearing rock, it is revealed that Beishan area of Gansu was in a continental margin rift extensional environment in the middle-Late Devonian.
The newly-discovered tungsten deposits are located in the Beishan Orogenic Belt, NW-China, Central Asian Orogenic Belt. There are three mineralized granitoid intrusives of them; the Pantuoshan, Yingzuihongshan and Yushan. By high-precision SIMS zircon U-Pb dating, we obtained the concordant age of 422.0 +/- 1. 5Ma and 417.0 +/- 1. 7Ma for monzogranite and K-feldspar granite of Pantuoshan ore-bearing intrusion, and K-feldspar granite of Yingzuihongshan emplaced at age of 424.0 +/- 1. 3Ma. In addition, we have got the age of 280. 8 +/- 3. 0Ma of Yushan granite. The geochemical data shows that the three intrusions characterized by high REE and LREE-rich pattern, enriched LILE (Th, Zr, Hf) and HFSE (U, Pb), depleted HFSE (Ta, Nb, Ti, P). In combination with the evolution of the Paleozoic Beishan Orogenic Belt, we suggest that the Guoqing and Yingzuihongshan tungsten deposits occurred by the collision between Gongpoquan and Huaniushan island arc, and Yushan tungsten deposit formed in the Late Paleozoic back-arc extension tectonic setting.
In this paper, a systematic study had been made for the intrusive rocks of the
southeast Heishan ridge in Xinjiang, in the ways of lithology, geochemistry and
zircon SHRIMP chronology. As a result, all the intrusive rocks are divided into
an independent rock mass and four related sequences. The former is a mylonitize
syenogranite mixed rock mass of proterozoiction (zircon SHRIMP dating is
(1422±7)Ma), and the latter contains maild metamorphic gabbro–tonalite–granite
sequence in the proterozoic era (zircon SHRIMP dating is (1349±160)Ma),
diorite–granite sequence in the late carboniferous, gabbro–diorite–granite
sequence in the early Permian (zircon SHRIMP dating is (296±4)Ma, (294±6)Ma
and (287±4.5)Ma) and gabbro–diorite–granodiorite sequence in the midpermian.
According to the characters of alkalic rate, A/CNK, felsic index,
magnesium–iron index, REE and trace element, these rocks sequences show
some relevance in the tectonic evolution, and their forming environment is
related to the intracontinental activities in that period.
Keywords: Beishan, southeast area of Heishan ridge, intrusive rocks sequence,
intracontinental rift.
Bandaoshan granites are exposed in the Southeastern Beishan area, in the
central part of the Central Asia Orogenic Belt (CAOB). LA-ICP-MS U-Pb
zircon dating indicates that Bandaoshan granites were emplaced into
Precambrian basement at 285 ± 4 Ma and their geochemistry
indicates that they are alkali-rich potassium-high granites. Initial
&z.epsiv;Nd values (-4.3 to -2.7) and
&z.epsiv;Hf values (-2.7 to +0.7) suggest that
Bandaoshan granites were derived from mantle-derived melt and an upper
continental crustal or sedimentary component. The latter plays a
significant role in their genesis. In combination with regional geology,
the Early Permian Bandaoshan pluton is interpreted to form in a
post-collisional environment. In the Southeastern Beishan area Late
Carboniferous Qiaowan granites, Early Permian Yin'aoxia granites and
Middle Permian Xijianquanzi granites are also considered as
post-collisional granites, and together with Bandaoshan granites
indicate that the region was in a post-collisional stage from the end of
Late Carboniferous to Middle Permian.
