| 西藏邦布石英脉型金矿床的成因: 流体包裹体及氢-氧同位素证据 |
| Received:February 17, 2012 Revised:February 10, 2013 点此下载全文 |
| 引用本文：SUN QingZhong,ZHENG YuanChuan,HOU ZengQian,YANG ZhuSen,LI Wei,HUANG KeXian,ZHANG Song.2013.Genesis of Bangbu orogenic gold deposit in Tibet: Constraints from fluid inclusions and isotopic composition[J].Mineral Deposits,32(2):353~366 |
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| Author Name | Affiliation | E-mail | | SUN QingZhong | Geological Survey of Jiangsu Province, Nanjing 210018, Jiangsu, China | | | ZHENG YuanChuan | China University of Geosciences, Beijing 100083, China | zheng-yc@126.com | | HOU ZengQian | Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China | | | YANG ZhuSen | Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China | | | LI Wei | China University of Geosciences, Beijing 100083, China | | | HUANG KeXian | China University of Geosciences, Beijing 100083, China | | | ZHANG Song | China University of Geosciences, Beijing 100083, China | |
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| 基金项目:本文得到国家重点基础研究发展计划(973计划)"青藏高原南部大陆聚合和成矿作用"(2011CB403100);中国地质调查局地质调查项目"青藏高原碰撞造山及成矿地质背景研究"(1212011121253)和国家自然科学青年基金"藏南北喜马拉雅中新世镁铁质岩浆活动及其对淡色花岗岩成因的约束"(41102033)的联合资助 |
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| 中文摘要:西藏邦布石英脉型金矿床是产于印度-亚洲板块陆-陆造山主碰撞汇聚环境下、与大洋俯冲无关的新型造山型金矿床。该矿床位于雅鲁藏布江缝合带南侧朗杰学增生楔的东段南缘,矿体受区域内EW向金地-鲁农复向斜和错古-折木朗壳型脆-韧性剪切带及其次级构造的控制。金矿化主要与石英脉密切相关,并包裹于脉内细粒/粗粒硫化物中。矿区内主要分布有3期石英脉:成矿前钩状石英脉、成矿期石英大脉和成矿后陡立状石英脉。文章对3期石英脉流体包裹体形态、形成温度、密度及H-O同位素等方面进行了详细的对比研究,试图查明成矿流体来源以及金的沉淀机制等问题。研究表明,钩状石英脉内包裹体主要为液相(L)包裹体,成分主要为H2O溶液,其流体可能为早期区域变质的产物;石英大脉内包裹体主要为含CO2气液(VL)两相包裹体,体积较大,成分主要为H2O+CO2+CH4±N2,成矿流体为深源变质流体,并与变质地层中的有机质发生强烈反应;陡立状石英脉内包裹体主要为气液两相包裹体,体积较小,其主要成分为H2O+CO2,流体主要与后期区域变质事件有关,为成矿后变质作用的产物。邦布金矿的主要成矿流体源自深部变质流体,流体不混溶作用可能是导致金矿沉淀的主要原因。 |
| 中文关键词:地球化学 流体包裹体 H-O同位素 碰撞造山 邦布金矿 西藏 |
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| Genesis of Bangbu orogenic gold deposit in Tibet: Constraints from fluid inclusions and isotopic composition |
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| Abstract:The Bangbu quartz-vein type gold deposit is located in Jiacha County, southern Tibet, lying in the southeastern segment of the Langjiexue accretionary wedge on the south side of the Yarlung-Zangbo suture. Muscovite Ar/Ar geochronological study indicates that it was formed at (49.5±0.5) Ma, consistent with the period of the onset of the Indo-Asian collision. The gold ore bodies are jointly controlled by the Jindi-Lunong synclinorium and Cuogu-Zhemulang large-scale brittle-ductile shear zone as well as its secondary structures. The mineralization of gold was mainly associated with quartz veins in the mining area. According to the attitudes, the quartz veins can be divided into three types, namely, the pre-metallogenic hook-like veins,the metallogenic large quartz veins and the post-metallogenic NS-striking quartz veins. The authors made microthermometric measurement, laser Raman analysis of fluid inclusions and H-O isotopic analysis of the three types of the quartz veins. Microthermometric measurements indicate that the three types of fluid inclusions in the Bangbu gold deposit are characterized by low salinity, low temperature and low density. Laser Raman analysis indicates that the inclusions in the pre-metallogenic hook-like quartz veins are dominated mainly by liquid, and H-O isotope analyses of these quartz veins indicate that the fluids trapped in the quartz were derived from regional metamorphism in the early phase. Inclusions in the mineralized large quartz veins are mainly VL inclusions characterized by larger volume. Analysis indicates that these inclusions mainly contain H2O+CO2+CH4±N2, and H-O isotopic data indicate that the ore-forming fluids were mainly derived from metamorphic fluids which were interacted with organic materials during their passing through the regional sedimentary strata. Fluid inclusions in the post-metallogenic quartz veins associated with STDS are chiefly VL inclusions in small volume and mainly contain H2O+CO2, and H-O isotopes, suggesting that these fluids might have resulted from post-ore metamorphism. The main mineralizing fluid was derived from the deep metamorphic fluid, and the main factor responsible for the deposition of Au was probably the boiling process. |
| keywords:geochemistry fluid inclusions H-O isotope collisional orogen Bangbu gold deposit Tibet |
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