A Fluid Inclusion Study of Vein‐type Copper Mineralization in the East Wulasigou Pb–Zn–Cu Deposit, Altay, Northwestern China
A Fluid Inclusion Study of Vein‐type Copper Mineralization in the East Wulasigou Pb–Zn–Cu Deposit, Altay, Northwestern China
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DOI：
10.1111/1755-6724.12814
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发表时间：
2016-10
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影响因子：
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通讯作者：
Chunjing Bian;Jiuhua Xu;Deping Chen;Hui Zhang;Xihui Cheng
中科院分区：
文献类型：
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作者：
Chunjing Bian;Jiuhua Xu;Deping Chen;Hui Zhang;Xihui Cheng
乌拉斯沟铜铅锌存款矿床位于新疆阿勒泰市西北15 km处，是阿尔泰山南部克兰火山-沉积盆地内众多铜铅锌多金属矿床之一。可划分为两个成矿期：海相火山沉积铅锌成矿期和变质热液铜矿化期，后者又可进一步划分为早期层状片理化石英脉阶段（Q1）和横切片理化的晚期硫化物石英脉阶段（Q2）。乌拉斯沟存款东矿体Q1和Q2石英中的流体包裹体可分为4种类型：H2O-CO2包裹体、碳质流体包裹体、水成流体包裹体和含子矿物流体包裹体。显微测温研究表明，Q1中H2O-CO2包裹体的固体CO2熔融温度（Tm，co2）为−62.3°C ~ −58.5°C，为包合物熔融温度（Tm，clath）为0.5°C至7.5°C，部分均质化温度（Th，co2）为3.3°C至25.9°C（至液体），总均质温度（Th，tot）从285°C到378°C不等，盐度为4.9%-15.1%NaCl当量。并且CO2相密度为0.50-0.86 g/cm 3。Q2中的H2O-CO2包裹体的Tm，c 02为−61.9°C至−56.9°C，Tm，clath为1.3°C至9.5°C，Th，co2为3.4°C至28.7°C（至液体），Th，tot为242°C至388°C，盐度为1.0%至15.5%NaCl eqv。并且CO2相密度为0.48-0.89 g/cm 3。Q1和Q2流体包裹体的最低捕获压力分别为260-360 MPa和180-370 MPa。火山沉积期黄铁矿的δ 34 S值在2.3‰ ~ 2.8‰（CDT）之间，硫化物石英脉的δ 34 S值在-1.9 ‰ ~ 2.6‰（CDT）之间。Q2流体包裹体的δD值为−121.0‰ ~ −100.8‰（SMOW），由石英δ 18 O计算的δ 18 OH 2 O值为−0.2‰ ~ 8.3‰（SMOW）。δD-δ 18 OH 2 O数据与岩浆区和变质区接近。流体包裹体和稳定同位素资料表明，乌拉斯沟铅锌铜存款矿床脉状铜矿化形成于造山变质环境。
The Wulasigou Cu–Pb–Zn deposit, located 15km northwest of Altay city in Xinjiang, is one of many Cu–Pb–Zn polymetallic deposits in the Devonian Kelan volcanic‐sedimentary basin in southern Altaids. Two mineralizing periods can be distinguished: the marine volcanic sedimentary Pb‐Zn mineralization period, and the metamorphic hydrothermal Cu mineralization period, which is further divided into an early bedded foliated quartz vein stage (Q1) and a late sulfide‐quartz vein stage (Q2) crosscutting the foliation. Four types of fluid inclusions were recognized in the Q1 and Q2 quartz from the east orebodies of the Wulasigou deposit: H2O–CO2 inclusions, carbonic fluid inclusions, aqueous fluid inclusions, and daughter mineral‐bearing fluid inclusions. Microthermometric studies show that solid CO2 melting temperatures (Tm,co2) of H2O–CO2 inclusions in Q1 are from −62.3°C to −58.5°C, clathrate melting temperatures (Tm,clath) are from 0.5°C to 7.5°C, partial homogenization temperatures (Th,co2) vary from 3.3°C to 25.9°C (to liquid), and the total homogenization temperatures (Th,tot) vary from 285°C to 378°C, with the salinities being 4.9%‐15.1% NaCl eqv. and the CO2‐phase densities being 0.50–0.86 g/cm3. H2O–CO2 inclusions in Q2 have Tm,c02 from −61.9°C to −56.9°C, Tm,clath from 1.3°C to 9.5°C, Th,co2 from 3.4°C to 28.7°C (to liquid), and Th,tot from 242°C to 388°C, with the salinities being 1.0%‐15.5% NaCl eqv. and the CO2‐phase densities being 0.48–0.89 g/cm3. The minimum trapping pressures of fluid inclusions in Q1 and Q2 are estimated to be 260–360 MPa and 180–370 MPa, respectively. The δ34S values of pyrite from the volcanic sedimentary period vary from 2.3‰ to 2.8‰ (CDT), and those from the sulfide‐quartz veins fall in a narrow range of −1.9‰ to 2.6‰ (CDT). The δD values of fluid inclusions in Q2 range from −121.0‰ to −100.8‰ (SMOW), and the δ18OH2O values calculated from δ18O of quartz range from −0.2‰ to 8.3‰ (SMOW). The δD‐δ18OH2O data are close to the magmatic and metamorphic fields. The fluid inclusion and stable isotope data documented in this study indicate that the vein‐type copper mineralization in the Wulasigou Pb–Zn–Cu deposit took place in an orogenic‐metamorphic enviroment.