The fault-controlled skarn W–Mo polymetallic mineralization during the main India–Eurasia collision: Example from Hahaigang deposit of Gangdese metallogenic belt of Tibet     

《Ore Geology Reviews》2014

The Hahaigang W–Mo polymetallic skarn deposit is located in the central-eastern part of Gangdese tectono-magmatic belt in Lhasa terrane, Tibet. The deposit was discovered in 2007 with currently proven 46 million tons of WO₃ ores, 12 million tons of Mo ores, and 1.31 million tons of combined Cu–Pb–Zn ores, at an average grade of 0.20% WO₃, 0.07% Mo, 0.026% Cu, 0.49% Pb, and 3.1% Zn. Ore bodies occur in veins or disseminations, and are confined within the NE-striking Dalong fault zone which is hosted by the Lower-Permian Pangna Group of dominantly quartz sandstone and slate. Several granitic plutons are exposed in the area or known from drill-holes. Ages of these granitic plutons are determined by using zircon U–Pb LA–ICP–MS method. For example, the biotite monzogranite yields a ²⁰⁶Pb/²³⁸U–²⁰⁷Pb/²³⁸U concordia age of 58.66 ± 0.90 Ma and a weighted mean ²⁰⁶Pb/²³⁸U age of 57.02 ± 0.42 Ma. The granite porphyry yields a ²⁰⁶Pb/²³⁸U–²⁰⁷Pb/²³⁸U concordia age of 109.1 ± 8.9 Ma and a weighted mean ²⁰⁶Pb/²³⁸U age of 114.0 ± 2.6 Ma. The biotite monzogranite yields a weighted mean ²⁰⁶Pb/²³⁸U age of 56.1 ± 1.1 Ma. Re–Os isochron age of 63.2 ± 3.2 Ma from 5 molybdenite samples collected from the W–Mo skarn ores is also obtained in this study. The zircon U–Pb and molybdenite Re–Os geochronological data suggest that the W–Mo mineralization was not temporally associated with any of the dated igneous plutons. However, the molybdenite Re–Os age of 63.2 ± 3.2 Ma indicates that the W–Mo mineralization might have occurred during the main India–Eurasia collision that was initiated around 65 Ma. Microprobe analysis of ilvaite that occurs in two generations in the W–Mo skarn ores reveals a close relationship to Ca–Fe–F-rich hydrothermal fluids, which were probably derived from deeply-seated magmas. We suggest that ascent of the fluids was strictly controlled by the ore-controlling Dalong fault zone, and that chemical interaction and metasomatism between the fluids and the Lower-Permian Pangna quartz-feldspathic host rocks produced the ilvaite and the W–Mo polymetallic skarn deposit during the main India–Eurasia collision. Although the majority of the polymetallic deposits in the Gangdese belt are reported to be either pre- or post-main collision, it is evident from this study that the main collision also produced W–Mo polymetallic mineralization within the belt.  相似文献   

Tectonic evolution of the Qinling orogen and adjacent orogenic belts     

《Gondwana Research》2016

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Partial least squares-discriminant analysis of trace element compositions of magnetite from various VMS deposit subtypes: Application to mineral exploration     

《Ore Geology Reviews》2016

The petrography and mineral chemistry of magnetite from fifteen volcanogenic massive sulfide (VMS) deposits in Canada, and the Lasail VMS deposit in Oman, as well as from two VMS-associated banded iron formations (BIF), Austin Brook (New Brunswick, Canada) and Izok Lake (Nunavut, Canada), were investigated using optical microscopy, electron probe micro-analyzer (EPMA), and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The method of robust estimation for compositional data (robCompositions) was applied to investigate geochemical censored data. Among thirty-seven elements analyzed by EPMA and/or LA-ICP-MS in magnetite from the studied deposits/bedrock lithologies, only the results for Si, Ca, Zr, Al, Mg, Ti, Zn, Co and Ni contain < 40% censored values, and thus could be imputed using robCompositions. Imputed censored data were transformed using centered log-ratios to overcome the closure effect on compositional data. Transformed data were classified by partial least squares-discriminant analysis (PLS-DA) to identify different compositional characteristics of magnetite from VMS deposits and BIFs. The integration of petrography and mineral chemistry identifies three types of magnetite in VMS settings: magmatic, hydrothermal, and metamorphic. Magmatic magnetite in VMS deposit host bedrocks is characterized by ilmenite exsolution and may be overprinted by metamorphism. Some VMS deposits contain hydrothermal magnetite, which is intergrown with sulfides, and shows a metamorphic overprint as it is partly replaced by common metamorphic minerals including chlorite, sericite, anthophyllite, and/or actinolite, whereas the majority of the deposits are characterized by metamorphic magnetite formed by replacing pre-existing sulfides and/or silicates, and is intergrown with metamorphic minerals. Among VMS deposits of the Noranda mining district, the West Ansil deposit is characterized by hydrothermal-metamorphic magnetite zoned by inclusion-free cores and Si- and Mg-rich rims. Magnetite from the studied VMS-associated BIFs is also metamorphic in origin. Aluminum, Ti and Zn contents of magnetite can separate BIF from the other mineralized and un-mineralized bedrock lithologies in the studied VMS settings.PLS-DA shows that variable compositions of magnetite slightly discriminate different studied deposits/bedrock lithologies. The geochemical observations suggest that the variation in magnetite chemistry from different VMS settings might be sourced from differences in: 1) the composition and temperature of parental magmas or hydrothermal fluids, 2) the composition of host bedrocks, 3) the composition of co-forming minerals, and 4) oxygen fugacity. PLS-DA distinguishes magnetite compositions from the studied VMS deposits and BIFs from that of the other ore deposit types including Ni–Cu, porphyry Cu-Mo-Au, iron oxide-copper- gold, iron oxide-apatite, and the Bayan Obo REE-Fe-Nb deposit. Magnetite from the VMS settings on average contains lower concentrations of Si, Zr, Al, Mg, Ti, Zn, Co and Ni relative to that from the other mineral deposit types. PLS-DA of magnetite data from VMS deposits and BIFs of the Bathurst mining camp as well as PLS-DA of magnetite compositions from various mineral deposit types yield discrimination models for application to mineral exploration for VMS deposits using indicator minerals in Quaternary lithified sedimentary rocks.  相似文献   

Apatite geochemistry of the Taihe layered intrusion,SW China: Implications for the magmatic differentiation and the origin of apatite-rich Fe-Ti oxide ores     

《Ore Geology Reviews》2016

The Taihe intrusion is one of the layered intrusions situated in the central zone of the Emeishan Large Igneous Province (ELIP), SW China. The cyclic units in the Middle Zone of the intrusion are composed of apatite-magnetite clinopyroxenite at the base and gabbro at the top. The apatite-rich oxide ores contain 6–12 modal% apatite and 20–50 modal% Fe-Ti oxides evidently distinguished from the coeval intrusions in which apatite-rich rocks are poor in Fe-Ti oxides. Most of apatites of the Taihe Middle and Upper Zones are fluorapatite, although four samples show slightly high Cl content in apatite suggesting that they crystallize from a hydrous parental magma. Compared to the apatite from the gabbro of the Panzhihua intrusion, situated 100 km to the south of the Taihe intrusion, the apatite of the Taihe rocks is richer in Sr and depleted in HREE relative to LREE. The calculated magma in equilibrium with apatite of the Taihe Middle and Upper Zones also shows weakly negative Sr anomalies in primitive mantle normalized trace element diagrams. These features indicate that the apatite of the Taihe Middle and Upper Zones crystallizes after clinopyroxene and before plagioclase. The apatite of the Taihe Middle and Upper Zones shows weakly negative Eu anomalies suggesting a high oxygen fugacity condition. The high iron and titanium contents in the oxidizing magma result in crystallization of Fe-Ti oxides. Crystallization of abundant Fe-Ti oxides and clinopyroxenes lowers the solubility of phosphorus and elevates SiO₂ concentration in the magma triggering the saturation of apatite. The positive correlations of Sr, V, total REE contents and Ce/Yb ratio in apatite with cumulus clinopyroxene demonstrate approximately compositional equilibrium between these phases suggesting they crystallized from the same ferrobasaltic magma. Early crystallization and accumulation of Fe-Ti oxide together with apatite produced the apatite-rich oxide ores at the base of the cyclic units of the Taihe Middle Zone.  相似文献   

Isotopic analysis of the super-large Shuangjianzishan Pb–Zn–Ag deposit in Inner Mongolia,China: Constraints on magmatism,metallogenesis, and tectonic setting     

《Ore Geology Reviews》2016

The super-large Shuangjianzishan Pb–Zn–Ag deposit is a newly discovered deposit located in the Huanggang–Ganzhuermiao polymetallic metallogenic belt of Inner Mongolia, NE China. The deposit's resource includes 0.026 Mt Ag, 1.1 Mt Pb, and 3.3 Mt Zn. The deposit is controlled by a NW-trending ductile shear zone and NE- and NW-trending faults in black pelite assigned to the lower Permian Dashizhai Formation. LREE enrichment, HREE depletion, Nb, Ta, P, and Ti depletion, and Zr and Hf enrichment characterize felsic magmatic rocks in the Shuangjianzishan Pb–Zn–Ag district. The ages of porphyritic monzogranite, rhyolitic crystal–vitric ignimbrite, and porphyritic granodiorite are 254–252, 169, and 130 Ma, respectively. Pyrite sampled from the mineralization has Re–Os isochron ages of 165 ± 7 Ma, which suggest the mineralization is associated with the ca. 169 Ma magmatism in the Shuangjianzishan district.Zircons extracted from the porphyritic granodiorite yield ε_Hf(t) values of − 11.34 to − 1.41, with t_DM2 dates of 1275–1901 Ma. The ε_Hf(t) values of zircons in the rhyolitic crystal–vitric ignimbrite and the ore-bearing monzogranite porphyry are 7.57–16.23 and 10.18–15.96, respectively, and their t_DM2 ages are 177–733 and 257–632 Ma, respectively. Partial melting of depleted mantle resulted in the formation of the ca. 254–252 Ma ore-bearing porphyritic monzogranite and the ca. 169 Ma rhyolitic crystal–vitric ignimbrite; dehydration partial melting of subducted oceanic crust resulted in the formation of the ca. 130 Ma porphyritic granodiorite. The porphyritic monzogranite was emplaced during the late stages of closure of the Paleo-Asian Ocean during the transformation from a collisional to extensional tectonic setting. The ca. 170 and ca. 130 Ma magmatism and mineralization in the Shuangjianzishan district are related to subduction of the Mongolia–Okhotsk Ocean and subduction of the Paleo-Pacific Ocean Plate, respectively.  相似文献   

Late Cretaceous magmatism and related metallogeny in the Tengchong area: Evidence from geochronological,isotopic and geochemical data from the Xiaolonghe Sn deposit,western Yunnan,China     

《Ore Geology Reviews》2016

Xiaolonghe is a poorly studied greisen-type tin deposit that is hosted by biotite granite in the western Yunnan tin belt. The mineralisation-related metaluminous and weak peraluminous granite is characterised by high Si, Al and K and low Mg, Fe and Ca, with an average A/CNK of 1.02. The granite is enriched in LILEs (K and Rb), LREEs and HFSEs (Zr, Hf, Th, U and Ce) and depleted in Ba, Nb, Sr, P, and Ti, with zircon εHf(t) = − 10.8 to − 7.5 (T_DM2 = 1.61–1.82 Ga). These characteristics indicate that the magma was generated by the partial melting of a thickened ancient crust. LA-ICP-MS U–Pb dating of igneous zircon and hydrothermal cassiterite yield ages of 71.4 ± 0.4 Ma and 71.6 ± 4.8 Ma, respectively. The igneous biotite and hydrothermal muscovite samples show Ar–Ar plateau ages of 72.3 ± 0.4 Ma and 70.6 ± 0.2 Ma, respectively. The close temporal relationship between the igneous emplacement and hydrothermal activity suggests that the tin mineralisation was closely linked to the igneous emplacement. The δ¹⁸O and δD values for the deposit range from + 3.11‰ to − 4.5‰ and from − 127.3‰ to − 94.7‰, respectively. The hydrothermal calcite C and O isotopic data show a wide range of δ¹³C_PDB values from − 5.7‰ to − 4.4‰, and the δ¹⁸O_SMOW values range from + 1.4‰ to + 11.2‰. The δ³⁴S_V-CDT data range from + 4.8‰ to + 8.9‰ for pyrite, and the ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios range from 18.708 to 18.760, from 15.728 to 15.754 and from 39.237 to 39.341, respectively. The stable isotopic (C–H–O–S–Pb) compositions are all similar to those of magmatic and mantle-derived fluids, which indicate that the ore-forming fluids and materials were mainly derived from magmatic sources that were accompanied by meteoric water. The tin mineralisation in the Xiaolonghe district was closely associated with the Late Cretaceous crustal-melting S-type granites that formed during the subduction of the Neo-Tethys oceanic lithosphere. Combined with the tin deposits in the Southeast Asian tin belt, Tengchong block and Central Lhasa, we interpreted that a giant intermittent tin mineralisation belt should be present along the Asian Neo-Tethys margin.  相似文献   

Mineralogy and mineral chemistry of Bi-minerals: Constraints on ore genesis of the Beiya giant porphyry-skarn gold deposit,southwestern China     

《Ore Geology Reviews》2016

The Beiya deposit, located in the Sanjiang Tethyan tectonic domain (SW China), is the third largest Au deposit in China (323 t Au @ 2.47 g/t). As a porphyry-skarn deposit, Beiya is related to Cenozoic (Himalayan) alkaline porphyries. Abundant Bi-minerals have been recognized from both the porphyry- and skarn- ores, comprising bismuthinite, Bi–Cu sulfosalts (emplectite, wittichenite), Bi–Pb sulfosalts (galenobismutite, cosalite), Bi–Ag sulfosalt (matildite), Bi–Cu–Pb sulfosalts (bismuthinite derivatives), Bi–Pb–Ag sulfosalts (lillianite homologs, galena-matildite series), and Bi chalcogenides (tsumoite, the unnamed Bi₂Te, the unnamed Ag₄Bi₃Te₃, tetradymite, and the unnamed (Bi, Pb)₃(Te, S)₄). Native bismuth and maldonite are also found in the skarn ores. The arsenopyrite geothermometer reveals that the porphyry Au mineralization took place at temperatures in the range of 350–450 °C and at log fS₂ in the range of − 8.0 to − 5.5, respectively. In contrast, the Beiya Bi-mineral assemblages indicate that the skarn ore-forming fluids had minimum temperatures of 230–175 °C (prevailing temperatures exceeding 271 °C) and fluctuating fS₂–fTe₂ conditions. We also model a prolonged skarn Au mineralization history at Beiya, including at least two episodes of Bi melts scavenging Au. We thus suggest that this process was among the most effective Au-enrichment mechanisms at Beiya.  相似文献   

湘西合仁坪金矿床硫、铅同位素地球化学   总被引：1，自引：0，他引：1  

邓穆昆  彭建堂  胡诗倩  李玉坤  张婷 《矿床地质》2016,35(5):953-965

湘西柳林汊一带广泛分布钠长石_石英脉型金矿,合仁坪金矿床是其典型代表。文章对合仁坪金矿床的硫、铅同位素进行了研究,并与区域石英脉型金矿床进行对比,探讨了该矿的成矿物质来源,并初步确定了其矿床成因。研究表明,合仁坪金矿床硫化物的δ34S值范围较窄(-4.8‰~4.4‰),平均为-0.6‰,该矿床的硫为深源硫,由深部变质流体带入;铅的同位素组成较均一,并表现出明显的造山带铅的特点。结合区域成矿作用,进一步研究揭示,合仁坪金矿床为一典型的造山型金矿,其成矿可能与湘西雪峰山地区加里东期的造山作用有关。  相似文献   

华北克拉通东部鲁西早白垩纪基性岩墙成因:来自锆石年龄、地球化学和Sr-Nd-Hf同位素的证据   总被引：2，自引：2，他引：0  

刘燊  冯彩霞  翟明国  胡瑞忠  赖绍聪  陈俊瑾  颜军 《岩石学报》2016,32(3):629-645

中生代基性辉绿岩墙广泛分布于华北克拉通东部山东地区。本研究给出代表性岩墙的U-Pb锆石年龄、地球化学和Sr-Nd-Hf同位素证据,4个代表性锆石的LA-ICP-MS年龄范围处于121.9±0.6Ma和124.3±0.5Ma之间(早白垩纪)。岩石的主量元素组成变化较小,岩石富集轻稀土元素和大离子亲石元素(如,Rb、Ba、U、K和Pb),以及亏损高场强元素(如,Nb、Ta和Ti)。另外,基性岩墙具有相对一致的(⁸⁷Sr/⁸⁶Sr)_i比值(~0.7098),负的ε_Nd(t)值(-14.7~-14.5)、ε_Hf(t)值(-31.4~-26.7)和高的Hf模式年龄(t_DM1=1817~2024Ma)。研究显示基性岩墙来自富集岩石圈地幔的部分熔融作用,并在上升侵位过程中经历了一定程度的地壳混染作用影响。总体研究表明,基性岩墙的成因机制与扬子克拉通与华北克拉通的碰撞有关,岩浆源区为晚中生代前受俯冲扬子地壳沉积物交代后的富集岩石圈地幔。  相似文献   

Tin partition behavior and implications for the Furong tin ore formation associated with peralkaline intrusive granite in Hunan Province,China     

Xiaoyan Hu  Xianwu Bi  Ruizhong Hu  Guosheng Cai  Youwei Chen 《中国地球化学学报》2016,35(2):138-147

Tin deposits are often closely associated with granitic intrusions. In this study, we analyzed tin partition coefficients between different fluids and melts (\({\text{D}}_{Sn}^{aq.fl./melt}\)) as well as various crystals and melts \({\text{D}}_{Sn}^{aq.fl./melt}\)(\({\text{D}}_{Sn}^{crystal/melt}\)) from the Furong tin deposit associated with the Qitianling A-type granite. Our experimental results indicate that tin partition behavior is affected by the chemical compositions of fluids, melts, and minerals. Tin is prone to partitioning into the residual magma in fractional crystallization or other differential magmatic processes if the magma originated from crustal sources with high alkali content, high volatile content, and low oxygen fugacity. Highly evolved residual peralkaline granitic magma enriched in tin can lead to tin mineralization in a later stage. Furthermore, the volatiles F and Cl in the magma play important roles in tin partitioning behavior. Low F contents in the melt phase and high Cl content in the aqueous fluid phase are favorable factors for tin partitioning in the aqueous fluid phase. High Cl content in the aqueous fluid catalyzes water–rock interaction and leads to the extraction of tin from tin-bearing minerals. All these findings support a hydrothermal origin for the tin deposits. In light of the geotectonic setting, petrochemical characteristics, and mineralizing physicochemical conditions of the Furong tin deposit, it is inferred that the ore-forming fluid of the Furong tin ore deposit could have derived from the Qitianling peralkaline intrusion.  相似文献