Compositions and Pressure-Temperature Conditions of Metamorphic Fluids Overprinting the Talate VMS Pb-Zn Deposit, Southern Altay, China
Compositions and Pressure-Temperature Conditions of Metamorphic Fluids Overprinting the Talate VMS Pb-Zn Deposit, Southern Altay, China
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阿勒泰南部塔拉特VMS铅锌矿床覆印变质流体成分及压力-温度条件
DOI：
10.1111/1755-6724.12479
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发表时间：
2015
影响因子：
3.3
通讯作者：
Bian Chunjing
中科院分区：
文献类型：
--
作者：
Zhang Hui;Xu Jiuhua;Cheng Xihui;Guo Xuji;Lin Longhua;Yang Rui;Bian Chunjing
塔拉特铅锌矿床产于下泥盆统下康布铁堡组(D1k12)上第二岩性段变质岩系中，位于阿尔泰山南部泥盆纪Kelan火山-沉积盆地NW-SE伸展带的东部。铅锌矿体呈层状，叠加有晚期硫化物-石英脉。确定了两个不同的成矿期：海底火山沉积喷气成矿期和变质热液成矿期。变质叠加期可进一步划分为两个阶段：早期以含矿层位绿泥石片岩和轻铁矿中发育的层状平行透镜状石英脉为特征，晚期以黄铁矿-黄铜矿-石英脉横切绿泥石片和轻铁矿或块状铅锌矿为代表。早期变质石英脉中的流体包裹体主要为CO2-H2O-NaC l和碳酸盐(CO2±CH4±N 2)包裹体，并有少量的水包裹体。包裹体均一温度为294~368℃，Tm、CO2为-62.6~-60.5℃，Th、CO2为7.7~29.6℃(均一为液态)，盐度为5.5~7.4wt%氯化钠当量。碳质包裹体Tm、CO2为-60.1~-58.5℃，Th、CO2为-4.2~20.6℃，晚期硫化物石英脉流体包裹体主要为CO2-H2O-NaCl和CO2±CH4包裹体。CO_2-H_2O-NaCl包裹体的温度为142~360℃，Tm、CO_2of-66.0~-56.6℃，Th、CO_2of-6.0~29.4℃(均一为液态)，盐度2.4~16.5wt%的氯化钠当量。碳酸盐包裹体的Tm、CO_2为-61.5~-57.3℃，Th、CO_2为-27.0~28.7℃，水相包裹体(L-V)的Tm、Ce为-9.8~-1.3℃，Th为205~412℃，富CO_2流体包裹体的圈闭条件(100~370 Mpa，250~368℃)与区域晚期变质作用条件相当。富CO2流体可能来源于区域变质作用，参与了原生矿石的改造和金属富集。在此基础上，将塔拉特铅锌矿床划分为受变质流体改造的VMS矿床。块状铅锌矿发育于与伸展俯冲相关的弧后盆地的海底火山沉积喷流早期，含多金属硫化物的石英脉形成于二叠-三叠纪大陆碰撞变质热液叠加晚期。
The Talate Pb–Zn deposit, located in the east of the NW–SE extending Devonian Kelan volcanic‐sedimentary basin of the southern Altaides, occurs in the metamorphic rock series of the upper second lithological section of the lower Devonian lower Kangbutiebao Formation (D1k12). The Pb–Zn orebodies are stratiform and overprinted by late sulfide–quartz veins. Two distinct mineralization periods were identified: a submarine volcanic sedimentary exhalation period and a metamorphic hydrothermal mineralization period. The metamorphic overprinting period can be further divided into two stages: an early stage characterized by bedding‐parallel lentoid quartz veins developed in the chlorite schist and leptite of the ore‐bearing horizon, and a late stage represented by pyrite–chalcopyrite–quartz veins crosscutting chlorite schist and leptite or the massive Pb–Zn ores. Fluid inclusions in the early metamorphic quartz veins are mainly CO2–H2O–NaCl and carbonic (CO2±CH4±N2) inclusions with minor aqueous inclusions. The CO2–H2O–NaCl inclusions have homogenization temperatures of 294–368° C,Tm,CO2of –62.6 to –60.5°C,Th,CO2of 7.7 to 29.6°C (homogenized into liquid), and salinities of 5.5–7.4 wt% NaCl eqv. The carbonic inclusions haveTm,CO2of –60.1 to –58.5°C, andTh, CO2of –4.2 to 20.6°C. Fluid inclusions in late sulfide quartz veins are also dominated by CO2–H2O–NaCl and CO2±CH4inclusions. The CO2–H2O–NaCl inclusions haveTh,totof 142 to 360°C,Tm,CO2of –66.0 to –56.6°C,Th,CO2of –6.0 to 29.4°C (homogenized into liquid) and salinities of 2.4–16.5 wt% NaCl eqv. The carbonic inclusions haveTm, CO2of –61.5 to –57.3°C, andTh, CO2of –27.0 to 28.7°C. The aqueous inclusions (L‐V) haveTm,iceof –9.8 to –1.3°C andTh,totof 205 to 412°C. TheP–Ttrapping conditions of CO2‐rich fluid inclusions (100–370 MPa, 250–368°C) are comparable with the late‐ to post‐regional metamorphism conditions. The CO2‐rich fluids, possibly derived from regional metamorphism, were involved in the reworking and metal enrichment of the primary ores. Based on these results, the Talate Pb–Zn deposit is classified as a VMS deposit modified by metamorphic fluids. The massive Pb–Zn ores with banded and breccia structures were developed in the early period of submarine volcanic sedimentary exhalation associated with an extensional subduction‐related back‐arc basin, and the quartz veins bearing polymetallic sulfides were formed in the late period of metamorphic hydrothermal superimposition related to the Permian–Triassic continental collision.