| 扬子板块北缘马元铅锌矿床有机地球化学特征及成矿作用 |
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| 引用本文： | 高永宝,,李侃,张江伟,郭望,韩一筱,刘天航,朝银银.扬子板块北缘马元铅锌矿床有机地球化学特征及成矿作用[J].延边大学理工学报,2021,0(2):276-290. |
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| 作者姓名： | 高永宝 李侃 张江伟 郭望 韩一筱 刘天航 朝银银 |
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| 作者单位： | (1. 中国地质调查局西安矿产资源调查中心,陕西 西安 710100; 2. 中国地质调查局西安地质调查中心 自然资源部岩浆作用成矿与找矿重点实验室,陕西 西安 710054) |
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| 摘 要： | 近年来,有机质与金属成矿关系研究备受关注。扬子板块北缘马元矿床铅锌矿体分布与古油藏、沥青在空间上叠置,是探索有机质与铅锌成矿关系的理想地区。矿区发育分散有机质、沥青、气态烃类等不同赋存形式的有机质,生物标志化合物特征明显,以低碳数正构烷烃为主,具浅海环境藻类来源特征,均处于过成熟演化程度。沥青206Pb/204Pb值为17.946～18.071,207Pb/204Pb值为15.593～15.703,208Pb/204Pb值为37.812～38.072,Pb模式年龄为612～478 Ma,结合油-源对比结果,沥青主要来源于下寒武统郭家坝组烃源岩,郭家坝组烃源岩经历了较强的还原环境和缺氧的高盐度环境。各类有机质C同位素组成一致,δ13C值为-35.3‰～-31.4‰,与区内闪锌矿流体包裹体中甲烷、乙烷等C同位素一致,显示有机成因碳典型特征。综上所述,马元铅锌矿床成矿与有机质关系密切,古油藏热裂解和热化学硫酸盐还原(TSR)作用提供了还原硫,富含Pb、Zn的盆地卤水与富含CH4、H2S的有机还原性流体混合是其重要成矿机制。
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| 关 键 词： | 生物标志化合物 C同位素 Pb同位素 有机质 铅锌矿床 古油藏 流体混合 扬子板块北缘 |
Geochemical Characteristics of Organic Matters and Metallogenesis of Mayuan Pb-Zn Deposit in the Northern Margin of Yangtze Plate,China |
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| GAO Yong-bao,' target="_blank" rel="external">,LI Kan,ZHANG Jiang-wei,GUO Wang,HAN Yi-xiao,LIU Tian-hang,CHAO Yin-yin.Geochemical Characteristics of Organic Matters and Metallogenesis of Mayuan Pb-Zn Deposit in the Northern Margin of Yangtze Plate,China[J].Journal of Yanbian University (Natural Science),2021,0(2):276-290. |
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| Authors: | GAO Yong-bao " target="_blank">' target="_blank" rel="external"> LI Kan ZHANG Jiang-wei GUO Wang HAN Yi-xiao LIU Tian-hang CHAO Yin-yin |
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| Affiliation: | (1. Xi'an Center of Mineral Resources Survey, China Geological Survey, Xi'an 710100, Shaanxi, China; 2. Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits of Ministry of Natual Resources, Xi'an Center of Geological Survey, China Geological Survey, Xi'an 710054, Shaanxi, China) |
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| Abstract: | The relationship between organic matter and metal mineralization has attracted much interest in recent years. The spatial relationships between paleo-oil reservoirs, asphalt and Mayuan Pb-Zn deposit, which is an ideal area in the northern margin of Yangtze plate for studying the relationship between organic matter and Pb-Zn mineralization, are superimposed. The mineralized area is characterized by organic matter, asphalt, and hydrocarbons. The biomarker combinations have low-carbon n-alkanes characteristic of an algae source in the shallow sea environment, and all of them are over-mature evolution. The Pb isotope compositions of the asphalt are 17.946-18.071 206Pb/204Pb, 15.593-15.703 207Pb/204Pb, and 37.812-38.072 208Pb/204Pb with the model ages of 612-478 Ma, which indicate that the asphalt has a Cambrian source. The probable source is Lower Cambrian Guojiaba Formation deposited in a strongly reducing and anoxic highly saline environment, as deduced from the oil-source correlation. The C isotope compositions of various organic matter are the same with δ13C values of -35.3‰--31.4‰, which are consistent with the C isotope compositions for methane and ethane in sphalerite fluid inclusions. All these data are typical for organic carbon. The mineralization of Mayuan Pb-Zn deposit is therefore genetically related to organic matter, and the thermal cracking of the paleo-oil reservoir and TSR produces reduction sulphur. It is deposited in a reducing environment involving the mixture of Pb-Zn-rich brine and fluids containing CH4 and H2S. |
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| Keywords: | biomarker combination C isotope Pb isotope organic matter Pb-Zn deposit paleo-oil reservoir fluid mixing the northern margin of Yangtze plate |
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