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藏北商旭造山型金矿床成矿物质来源探讨:C、S、Pb同位素证据
投稿时间:2018-02-02  修订日期:2018-06-27  点此下载全文
引用本文:刘洪,李光明,黄瀚霄,肖万峰,闫国强,马东方,张海,张红.2018.藏北商旭造山型金矿床成矿物质来源探讨:C、S、Pb同位素证据[J].地质论评,64(5):1285-1301
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作者单位E-mail
刘洪 1)中国地质调查局成都地质调查中心成都610081 cugliu@foxmail.com 
李光明 1)中国地质调查局成都地质调查中心成都610081  
黄瀚霄 1)中国地质调查局成都地质调查中心成都610081 hanxiaohuang@126.com 
肖万峰 2) 河南省地质调查院郑州450007  
闫国强 3) 中国地质调查局天津地质调查中心天津300170  
马东方 2) 河南省地质调查院郑州450007  
张海 1)中国地质调查局成都地质调查中心成都610081  
张红 1)中国地质调查局成都地质调查中心成都610081  
基金项目:本文为国家重点研发计划(编号:2016YFC0600308,SQ2018YFC060162)、中国地质调查项目(编号:DD20160015,DD20160026)、中国地质调查局成都地质调查中心青藏高原国际大科学计划和国家自然科学基金资助项目(编号:41702080,41702086)的成果。
中文摘要:西藏双湖县商旭金矿床位于班公湖—怒江缝合带中段。矿床受近东西向断裂控制,赋存于中—下侏罗统木嘎岗日群浅变质增生混杂岩中。本文研究主成矿阶段石英流体包裹体中CO2的C同位素及共生硫化物的S—Pb同位素组成特征,并与木嘎岗日群、虾别错—木嘎岗日山花岗岩等主要地质体对比。含金石英脉流体包裹体中CO2的δ13CV- PDB值范围为-17.8‰~-23.1‰,均值为-21.3%,接近沉积岩或者变质岩源有机碳,表明商旭金矿床的成矿流体可能来自于木嘎岗日群的变质流体,而含金石英脉中发育着与虾别错—木嘎岗日山花岗岩同时代的少量岩浆锆石,暗示成矿流体还有岩浆热液的加入。共生硫化物δ34 SV- CDT值变化于-4.5‰~4.6‰,均值为-1.6‰,具有深源硫(地幔或下地壳,δ34SVCDT=-3‰~+3‰)的特征;共生硫化物Pb同位素位素\[n(206Pb)/ n(204Pb)=18.350~18.690、n(207Pb)/n(204Pb)=15.632~15.700、n(208Pb)/n(204Pb)=38.570~38.980\]与早白垩世虾别错—木嘎岗日山花岗岩\[n(206Pb)/n(204Pb)=18.558~19.169、n(207Pb )/ n(204Pb)=15.616~15.651、n(208 Pb)/n(204 Pb)=38.838~39.154\]基本一致,同时向侏罗统木嘎岗日群\[n(206Pb)/n(204Pb)=18.630~18.970、n(207Pb )/ n(204Pb)=15.619~15.673、n(208 Pb)/n(204Pb)=38.887~39.260\]略有漂移,暗示商旭金矿床的Pb可能来源于早白垩世岩浆活动,同时还有部分来自木嘎岗日群中铅的加入。本次研究认为,商旭金矿的成矿物质部分来自深部壳幔岩浆作用,并被成矿热液携带至浅部。木嘎岗日群围岩也贡献了部分成矿物质,被地层中的变质热液携带到成矿流体中。
中文关键词:西藏  班公湖—怒江  商旭金矿  造山型金矿床  物质来源  稳定同位素
 
Sources of Ore-forming Materials in the Shangxu Orogenic Gold Deposit, Northern Xizang(Tibet): Constraints form C, S, and Pb Isotopes
NameInstitution
LIU Hong1) Chengdu Center, China Geological Survey, Chengdu, 610081
LI Guangming1) Chengdu Center, China Geological Survey, Chengdu, 610081
HUANG Hanxiao1) Chengdu Center, China Geological Survey, Chengdu, 610081
XIAO Wanfeng2) Henan Institute of Geological Survey, Zhengzhou, 450001
YAN Guoqiang3) Tianjin Center, China Geological Survey,Tianjin, 300170
MA Dongfang1) Chengdu Center, China Geological Survey, Chengdu, 610081
ZHANG Hai1) Chengdu Center, China Geological Survey, Chengdu, 610081
ZHANG Hong1) Chengdu Center, China Geological Survey, Chengdu, 610081
Abstract:Objectives: The Shangxu gold deposit in the Shuanghu County, Xizang(Tibet), is located in the central segment of the Bangong Lake — Nujiang River suture. The deposit is controlled by EW trending faults, and is hosted in melange of the Middle—Lower Jurassic Mugagangri Group. In this study we focus on the sources of ore forming materials in the Shangxu orogenic gold deposit, was beneficial for the study of genesis for the ore deposit, and provide new constraints for understanding the dynamic background of orogenic gold metallization in the Bangong Lake — Nujiang River suture.Methods: n this study, the Carbon isotopes of the CO2 inclusions in ore stage quartz, and the sulfur and lead isotopes of sulfides are analyzed for discuss the sources of ore forming materials in the Shangxu orogenic gold deposit.Results:The δ13CCO2(V PDB) values of fluid inclusions range from -178‰ to -231‰, with a mean of -213%, which is similar to that of the sedimentary or metamorphic rocks. This indicate that the ore forming fluids of the Shangxu gold deposit may originated from the Mugagangri Group. Meanwhile, a few magmatic zircons, which yield the same U Pb age with the Xiabie Co – Mogagangri San granite, are detected in auriferous quartz veins, suggesting that the magmatic hydrothermal fluids may have been involved during the ore forming process. The δ34SV CDT values of sulfides vary from -45‰ to 46‰, with a mean of -16‰, which is characteristic of a deep sulfur source, The Pb isotopic compositions of the sulfides(n(206Pb)/ n(204Pb)=18350~18690, n(207Pb)/n(204Pb)=15632~15700, n(208Pb)/n(204Pb)=38570~38980) are similar to those of the Xiabie Co – Mogagangri San granite(n(206Pb)/n(204Pb)=18558~19169, n(207Pb )/ n(204Pb)=15616~15651, n(208 Pb)/n(204Pb)=38838~39154) and slightly drifting to the Jurassic Mugagangri Group (n(206Pb)/n(204Pb)=18630~18970, n(207Pb )/ n(204Pb)=15619~15673, n(208 Pb)/n(204Pb)=38887~39260), implying that Pb in the Shangxu gold deposit may have been sourced from the magmatic activity in Early Cretaceous, with minor contribution from the Mugagangri Group.Conclusions: According to the above discussions, we suggest that the ore forming materials of the Shangxu gold deposit were mainly derived from deep crustal — mantle magmatism, and were carried by deep seated fluids to the shallow crust. The Mugagangri Group also contributed part of the ore forming materials, which were brought by the metamorphic hydrothermal fluids.
keywords:Xizang(Tibet)  Bangong Lake — Nujiang River suture zone  Shangxu gold deposit  orogenic gold deposits  source of ore forming materials  stable Isotope
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