| 四川天宝山矿床闪锌矿Rb-Sr年代学、稳定同位素及地质意义 |
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| 引用本文： | 王健,张均,张晓军,刘文浩,仲文斌,杨清,刘重芃.四川天宝山矿床闪锌矿Rb-Sr年代学、稳定同位素及地质意义[J].地球科学,2019,44(9):3026-3041. |
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| 作者姓名： | 王健 张均 张晓军 刘文浩 仲文斌 杨清 刘重芃 |
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| 作者单位： | 1.中国地质大学资源学院, 湖北武汉 430074 |
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| 基金项目： | 中国地质调查局地质调查项目12120114019701 |
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| 摘 要： | 四川天宝山铅锌矿床是赋存于震旦系灯影组白云岩中的大型铅锌矿床，一直以来缺乏精确的成矿年龄数据，致使其成矿构造环境存在争议.获取了闪锌矿Rb-Sr年龄，联合H-O、C-O同位素数据，以确定其成矿年代、成矿物质来源及成矿构造环境.闪锌矿Rb-Sr年龄为348.5±7.2 Ma(MSWD=1.10)，表明矿床形成于早石炭世.热液矿物δDH2O、δ18O值分别为-19.3‰~-58.1‰、-1.4‰~0.6‰，沿海水与地层有机质反应线分布，并有向雨水线漂移的趋势，说明成矿流体中水是海水与地层有机质反应并加入雨水的混合体.热液方解石δ13C、δ18O值明显分为两群，分别为-1.7‰~-1.6‰、12.9‰~15.2‰和-6.5‰~-4.9‰、19.3‰~20.2‰，暗示成矿流体中C、O可能来源于赋矿围岩溶解作用和有机质脱羧基作用.闪锌矿(87Sr/86Sr)i值为0.710 42 ±0.000 13，高于赋矿围岩Sr同位素值而明显低于基底Sr同位素值，指示成矿物质主要来源于赋矿围岩与基底.结果表明川滇黔地区存在两期铅锌成矿作用，分别形成于晚泥盆世-早石炭世与古特提斯洋张开有关的伸展构造环境和晚三叠世-早侏罗世与古特提斯洋闭合有关的收缩构造环境.
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| 关 键 词： | 川滇黔地区 天宝山铅锌矿床 Rb-Sr定年 碳-氢-氧同位素 伸展构造环境 地球化学 |
| 收稿时间： | 2017-10-19 |
Rb-Sr Geochronology,Stable Isotopic Analyses and Geological Significance of the Tianbaoshan Pb-Zn Deposit in Sichuan Province,China |
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| Abstract: | Tianbaoshan deposit is a large Pb-Zn deposit hosted in the carbonate rocks of the Upper Sinian Dengyin Formation in Sichuan-Yunnan-Guizhou district,China. Due to the lack of accurate age data of the Pb-Zn mineralization,the related regional metallotectonic setting is still controversial. In this study,we used direct Rb-Sr chronometry of sphalerite,and combined H-O and C-O isotopic analyses to constrain the mieralizating age,the possible resources of ore-forming fluids and associated tectonic setting. An effective Rb-Sr sphalerite age of 348.5±7.2 Ma (MSWD=1.10) definitely indicates that the formation of the Tianbaoshan deposit is the Early Carboniferous. The δDH2O and δ18O values of the hydrothermal minerals (-19.3‰—-58.1‰ and 1.4‰-0.6‰,respectively) are plotted in the region of the sea water interacted with organic matter in the crustal water and the drifting to the rainwater line,indicating that the mineralizing hydrothermal fluids are mixed resources derived from interaction between seawater and organic matter of sedimentary rocks,added with meteoric water. The δ13C and δ18O values of hydrothermal calcite are divided into two different groups (-1.7‰—-1.6‰ and 12.9‰-15.2‰,and -6.5‰—-4.9‰ and 19.3‰-20.2‰,respectively),suggesting that C and O compositions of hydrothermal fluids may be derived from the dissolution of host carbonates and decarboxylation of sedimentary organic matters hosted in carbonates. The (87Sr/86Sr)i ratios of sphalerite (0.710 42±0.000 13) are higher than the those of ore-hosting carbonate rocks,whereas distinctly lower than the those of basement rocks,implying that the ore-forming material is mainly derived from the mixture of the host rocks and basement rocks. So this study highlights that there are two independent lead-zinc mineralization events in Sichuan-Yunnan-Guizhou district,in which one occurs in extensional geological environments during the Late Devonian to Early Carboniferous related to the opening of the Paleo-Tethys Ocean and the other is associated with compressional geological environments from the Late Triassic to Early Jurassic related to the closure of the Paleo-Tethys Ocean,respectively. |
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