| 新疆克因布拉克铜锌矿床富CO_2-N_2流体及地质意义 |
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| 引用本文： | 边春静,杨凯,徐九华,张辉.新疆克因布拉克铜锌矿床富CO_2-N_2流体及地质意义[J].大地构造与成矿学,2017,41(6). |
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| 作者姓名： | 边春静 杨凯 徐九华 张辉 |
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| 作者单位： | 北京科技大学土木与资源工程学院,北京,100083 |
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| 摘 要： | 克因布拉克铜锌矿床位于新疆阿尔泰山南缘冲乎尔盆地。矿体主要赋存于早二叠世花岗岩外接触带的下泥盆统康布铁堡组上亚组内。克因布拉克矿床经历了两个成矿期:海相火山喷流沉积成矿期和变质热液叠加成矿期。变质热液叠加成矿期可包括2个阶段:早阶段顺层透镜状石英脉(Q1)和晚阶段切层含黄铁矿?黄铜矿石英脉(Q2)。石英脉中流体包裹体以富CO_2-N_2为特征,流体包裹体组合(FIA)发育。流体包裹体类型包括CO_2-N_2包裹体、H_2O-CO_2(±N_2)包裹体和水溶液包裹体(L-V型)。显微测温结果显示,Q1中CO_2-N_2包裹体三相点温度(T_(m,CO_2))范围在-61.2~-59.1℃,部分均一温度(T_(h,CO2))的范围是-42.3~-36.0℃。Q2中CO_2-N_2流体包裹体的T_(m,CO_2)为-61.6~-58.1℃,T_(h,CO_2)范围是-30.0~10.4℃;Q2中H_2O-CO_2(±N_2)包裹体的T_(m,CO_2)为-61.4~-58.1℃,T_(h,CO_2)为-11.9~5.3℃,CO_2笼合物融化温度(T_(m,clath))范围是2.9~13.1℃,完全均一温度(T_(h,total))为312℃,伴生的L-V包裹体T_(h,total)为201~389℃,求得CO_2相密度为0.91~0.97 g/cm~3,盐度为1.62%~12.02%NaCl_(eqv)。计算得到流体包裹体的最低捕获压力范围为250~320 MPa,具有极富CO_2-N_2、低盐度的特点,属于变质流体。变质热液期早阶段石英脉δD值为-90.5‰,δ~(18)O_(H_2O)值为7.8‰;晚阶段石英脉δD值为-82.1‰~-80.4‰,δ~(18)O_(H_2O)为6.2‰~8.6‰。海相火山沉积期硫化物的δ~(34)S为0.9‰~2.1‰,硫来自火山岩浆活动;变质热液叠加期硫化物的δ~(34)S为0.1‰~1.1‰,显示了与造山变质深源流体有关的来源。克因布拉克铜锌矿床矿石变形变质结构特征以及石英脉中富CO_2-N_2流体的大量出现,说明变质流体对矿床具有一定的叠加改造,矿床具有多阶段的特点。
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| 关 键 词： | 克因布拉克矿床 CO2-N2流体 稳定同位素 变质流体 |
CO2-N2 Fluids and their Geological Significance in Keyinbulake Cu-Zn Deposit,Burjin, Xinjiang |
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| BIAN Chunjing,YANG Kai,XU Jiuhua,ZHANG Hui.CO2-N2 Fluids and their Geological Significance in Keyinbulake Cu-Zn Deposit,Burjin, Xinjiang[J].Geotectonica et Metallogenia,2017,41(6). |
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| Authors: | BIAN Chunjing YANG Kai XU Jiuhua ZHANG Hui |
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| Abstract: | The Keyinbulake Cu-Zn deposit is located in the Chonghuer basin at the southern Altaids in Xinjiang. Ore bodies mainly occur in the exocontact zones between the Early Permian granite and the Lower Devonian Kangbutiebao Formation sedimentary rocks. Two mineralization periods can be distinguished based on ore occurrences, which include the submarine volcanic sedimentary exhalation and the metamorphic hydrothermal superimposition. Metamorphic hydrothermal superimposition period could be divided into two stages: an early bedded foliated quartz vein stage (Q1) and the later pyrite-chalcopyrite quartz vein stage (Q2) which cut across the foliation of biotite quartz schist. Fluid inclusion types include CO2-N2 fluid inclusion, H2O-CO2(±N2) inclusion and aqueous inclusion (L-V type). Microthermometric studies showed that the CO2-N2 inclusions in Q1 have solid CO2 melting temperatures (Tm, CO2) from?61.2 to?59.1℃, partial homogenization temperatures (Th, CO2) from?42.3℃ to?36.0℃ . TheTm, CO2 of CO2-N2 fluid inclusions in Q2 vary from?61.6℃ to?58.1℃ , andTh, CO2 are in the range of?30.0℃ to 10.4℃ . The H2O-CO2(±N2) fluid inclusions in Q2 haveTm, CO2 from?61.4℃ to?58.1℃ ,Th, CO2 from?11.9℃ to 5.3℃ , and the final homogenization temperature (Th, total) of 312℃ , with densities of CO2 phase from 0.91 to 0.97 g/cm3 and salinities of 1.62%–12.02%NaCleqv. The fluids forming the quartz veins are characterized by rich-CO2-N2, low salinities and low densities. The measuredδD values of fluid inclusions in Q1 and Q2 quartz veins range from?90.5‰, and?82.1‰ to?80.4‰ and the calculatedδ18OH2O values range from 7.8‰, and 6.2‰ to 8.6‰, respectively. TheδD-δ18OH2O data are fall in the magmatic and metamorphic fields. Theδ34S values of the early original volcanic sedimentary sulfides vary from 0.9‰ to 2.1‰, and those from the later metamorphic hydrothermal superimposed period fall in a narrow range of 0.1‰ to 1.1‰. The fluid inclusion and stable isotope data of this study indicate that superimposition of the metamorphic fluids is an important part of the multi-stage hydrothermal ore mineralization for the Keyinbulake Cu-Zn deposit. |
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| Keywords: | Keyinbulake deposit CO2-N2 fluids stable isotope metamorphic fluids |
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