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张明玉,丰成友,武广,王辉,吴玉,韩梅梅,武文恒. 2018. 赣北大湖塘地区昆山钨-钼-铜矿床流体包裹体研究和稳定同位素特征. 岩石学报, 34(9): 2615-2631
赣北大湖塘地区昆山钨-钼-铜矿床流体包裹体研究和稳定同位素特征
作者单位E-mail
张明玉 中国地质科学院矿产资源研究所, 国土资源部成矿作用与资源评价重点实验室, 北京 100037  
丰成友 中国地质科学院矿产资源研究所, 国土资源部成矿作用与资源评价重点实验室, 北京 100037 fengchy@cags.ac.cn 
武广 中国地质科学院矿产资源研究所, 国土资源部成矿作用与资源评价重点实验室, 北京 100037  
王辉 长安大学地球科学与资源学院, 西安 710054  
吴玉 中国地质科学院地质力学研究所, 北京 100081  
韩梅梅 中国地质科学院地质力学研究所, 北京 100081  
武文恒 The Faculty of Science, the University of Melbourne, Melbourne 3010  
基金项目:本文受国家重点研发计划课题(2016YFC0600205)、中国地质调查局高层次地质人才培养计划(201309)和青年地质英才计划(201112)联合资助.
摘要:
      昆山矿床位于大湖塘钨多金属矿田的南部,产出石英细脉带型W-Mo-Cu矿体。该矿床的成矿过程可以划分为黑钨矿-石英阶段(Ⅰ)、辉钼矿-石英阶段(Ⅱ)、黄铜矿-石英阶段(Ⅲ)及石英-方解石阶段(Ⅳ)。本文通过流体包裹体岩相学、显微测温、激光拉曼光谱和稳定同位素研究,探讨了昆山矿床的成因机制。研究结果表明,昆山矿床发育纯气相型(PG)、纯液相型(PL)、富液两相水溶液型(WL)三类包裹体。Ⅰ阶段主要发育WL型流体包裹体,并有少量PG型包裹体,均一温度为236~388℃,盐度为0.5%~13.8% NaCleqv,密度为0.54~0.90g/cm3;Ⅱ阶段亦主要发育WL型和少量PG型包裹体,其均一温度为221~390℃,盐度为0.5%~12.7% NaCleqv,密度为0.51~0.93g/cm3;Ⅲ阶段主要发育WL型包裹体,均一温度为228~376℃,盐度为0.7%~11.2% NaCleqv,密度为0.57~0.91g/cm3;Ⅳ阶段主要发育WL型包裹体,并有少量的PL型包裹体,其均一温度为173~288℃,盐度为0.4%~11.8% NaCleqv,密度为0.76~0.97g/cm3。主成矿阶段流体属于中高温、中低盐度、中等密度流体,成矿晚阶段流体属于中低温、中低盐度、中高密度流体。包裹体气相成分主要是H2O,亦有少量CH4和CO2,成矿流体总体上属于H2O-NaCl-(CH4-CO2)体系。Ⅰ、Ⅱ和Ⅲ阶段成矿流体的δD值为-92‰~-56‰,计算获得的δ18O值为3.8‰~6.4‰;石英-方解石阶段的δD值为-68‰~-58‰,δ18O值为0.5‰~0.7‰。H-O同位素结果表明,昆山矿床主成矿阶段的流体以岩浆水为主,成矿晚阶段有少量的大气降水加入。金属硫化物的δ34S值分布集中,其值为-1.5‰~3.0‰,表明成矿流体中的硫主要来自深源岩浆。辉钼矿-石英阶段的石英包裹体中CO2δ13CV-PDB值为-6.6‰和-5.9‰,平均-6.3‰;晚阶段石英-方解石脉中方解石的δ13CV-PDB值为-12.3‰~-10.2‰,平均-11.0‰,表明昆山矿床主成矿阶段流体中的碳主要由花岗岩浆提供,且受低温蚀变作用的影响,而晚阶段方解石脉中的碳还受到了双桥山群沉积有机物质的影响。成矿流体的冷却作用是导致昆山矿床钨、钼和铜沉淀的主要机制。
英文摘要:
      The quartz veinlet-type Kunshan W-Mo-Cu deposit is located in the southern part of the Dahutang ore field, situated in the central area of the Jiuling tungsten-polymetallic ore cluster in northern Jiangxi Province. The ore-forming process of the deposit can be divided into four stages:wolframite-quartz stage (Ⅰ), molybdenite-quartz stage (Ⅱ), chalcopyrite-quartz stage (Ⅲ) and quartz-calcite stage (Ⅳ). In this paper, based on the previous research results and field geological survey, a systematic study of fluid inclusions and H-O-C-S isotopes was conducted. Three types of fluid inclusions (FIs) have been distinguished in various quartz veins including pure liquid (PL), pure gas (PG), liquid-rich two-phase (WL) inclusions. The FIs in the stage I are mainly WL-type with minor PG-type, and their homogenization temperatures, salinities and densities vary from 236℃ to 388℃, 0.5% to 13.8% NaCleqv and 0.54g/cm3 to 0.90g/cm3, respectively. The FIs in the stage Ⅱ are also mainly WL-type with minor PG-type, and their homogenization temperatures, salinities and densities vary from 221℃ to 390℃, 0.5% to 12.7% NaCleqv and 0.51g/cm3 to 0.93g/cm3, respectively. The FIs of the stage Ⅲ are composed of WL-type FIs, and their homogenization temperatures, salinities and densities vary from 228℃ to 376℃, 0.7% to 11.2% NaCleqv and 0.57g/cm3 to 0.91g/cm3, respectively. The FIs in the stage Ⅳ are mainly WL-type with minor PL-type, and their homogenization temperatures, salinities and densities vary from 173℃ to 288℃, 0.4% to 11.8% NaCleqv and 0.76g/cm3 to 0.97g/cm3, respectively. The main ore-forming stage (stages Ⅰ, Ⅱ and Ⅲ) fluid is characterized by medium-high temperature, medium-low salinity and medium density, while the fluid of the stage Ⅳ is characterized by medium-low temperature, medium-low salinity and medium-high density. The gas-phase composition of the FIs is mainly H2O with minor amounts of CH4 and CO2, indicating that the ore-forming fluid of the Kunshan deposit belongs to an H2O-NaCl-(CH4-CO2) system. The δ18OH2O and δDH2O values of the main ore-forming stage vary from 3.8‰ to 6.4‰ and -92‰ to -56‰, respectively; the δ18OH2O and δDH2O values of the stage Ⅳ vary from 0.5‰ to 0.7‰ and -68‰ to -58‰, respectively; indicating that the fluid of the main ore-forming stage mainly consists of magmatic water and that the fluid in late stage is a mixture of magmatic and meteoric water. The δ34S values of chalcopyrite, pyrite and molybdenite samples range from -1.5‰ to 3.0‰, indicating that the ore-forming metals and sulfur mainly came from magma. The δ13C values are in the ranges varying from -6.6‰ to -5.9‰ for FIs in quartz of the stage Ⅱ and -12.3‰ to -10.2‰ for calcite in the stage Ⅳ, respectively, suggesting that the carbon is mainly derived from the magma. Moreover, the carbon derived from the magma was affected by low-temperature alteration in the main ore-forming stage and mixed with sedimentary organic material of the Shuangqiaoshan Group in the late stage. The cooling of the ore-forming fluids was the dominant mechanism for precipitation of tungsten, molybdenum and copper in the Kunshan deposit.
关键词:流体包裹体  H-O-C-S同位素  昆山W-Mo-Cu矿床  大湖塘矿田  赣北
投稿时间:2017-03-17  修订日期:2018-04-01
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主办单位:中国矿物岩石地球化学学会
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