西藏斯弄多银-铅-锌矿床流体包裹体研究和稳定同位素特征  

Fluid Inclusion Study and Stable Isotope Characteristics of the Sinongduo Ag-Pb-Zn Deposit, Tibet

作　　者：李海峰[1] 唐菊兴[2] 丁帅[3] 李壮[2] 胡古月[2] 谢富伟 周会林 杨宗耀[3] 施硕[3] LI Hai-feng;TANG Ju-xing;DING Shuai;LI Zhuang;HU Gu-yue;XIE Fu-wei;ZHOU Hui-lin;YANG Zong-yao;SHI Shuo(School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083;Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037;College of Earth Sciences, Chengdu University of Technology, Chengdu, Sichuan 610059;Regional Geological Survey Party, Sichuan Bureau of Geology and Mineral Development, Chengdu, Sichuan 610213)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国地质科学院矿产资源研究所,北京100037 [3]成都理工大学地球科学学院,四川成都610059 [4]四川省地质矿产勘查开发局区域地质调查队,四川成都610213

出　　处：《地球学报》2017年第5期670-686,共17页Acta Geoscientica Sinica

基　　金：中国地质调查局工作项目(编号:12120114068401);中国地质科学院基本科研业务费(编号:k1603);西藏中瑞矿业发展有限责任公司项目(编号:XZZR-2015)联合资助~~

摘　　要：斯弄多银铅锌(金)矿床位于拉萨地体隆格尔—工布江达弧背断隆带南侧上,是冈底斯北缘Pb-Zn-Ag成矿带中段上发现的首例低硫化型浅成低温热液矿床。矿体赋存在林子宗群火山岩中,受火山活动形成的近南北向次级断裂控制。成矿过程可划分为伊利石-绢云母-玉髓-碧玉±铁锰碳酸盐(Ⅰ),石英-黄铁矿±方铅矿±闪锌矿(Ⅱ),方铅矿-闪锌矿-石英-黄铁矿-绢云母±银矿物±碳酸盐(Ⅲ),辉银矿-硫砷铜银矿-方铅矿±深红银矿±自然银±闪锌矿±黄铜矿(Ⅳ),以及石英±碳酸盐±绢云母(Ⅴ)等五个阶段。本次选取了34件Ⅲ阶段和12件V阶段样品进行包裹体岩相学、显微测温、包裹体的气相及离子色谱和Si-H-O同位素研究,探讨了斯弄多矿床的成矿流体性质、来源和成矿沉淀机制。研究结果表明:斯弄多矿床主成矿期石英和闪锌矿中发育纯液相型(PL)、富液相水溶液型(WL)和富气相水溶液型(WG)三种类型的包裹体,后期无矿石英脉中仅发育PL和WL两种类型。其中Ⅲ阶段石英均一温度为185.6~290.7℃,盐度介于1.57%~5.71%,密度为0.76~0.92 g/cm^3;闪锌矿均一温度为197.2~280.8℃,盐度介于1.22%~5.71%,密度为0.75~0.99 g/cm^3;Ⅴ阶段石英均一温度147.6~218.7℃,盐度介于2.07%~8.94%;密度为0.88~0.98 g/cm^3。成矿流体均具有低温、低压、低密度的特点。Ⅲ阶段石英包裹体中气相成分主要以H_2O和CO_2为主;液相成分中阳离子以Ca^(2+)、K^+为主,阴离子以SO_4^(2–)、Cl~–和F~–为主。Ⅱ阶段成矿流体的δ^(30)Si分布范围为–0.2‰~0.1‰,δD值介于–151‰~–177‰,计算获得的δ^(18)O H_2O值介于–5.02‰~–0.63‰。Si-H-O同位素结果表明,斯弄多矿床成矿流体主要为大气降水;包裹体中大量CO_2和SO_4^(2–)、F~–等酸性气体和离子成分表明流体中仍保留微弱岩浆水的特征。斯弄多矿床Ⅲ阶段流体为不混溶流体,流体沸腾、气体逃逸、热液隐爆是�The Sinongduo silver-lead-zinc(gold)polymetallic deposit is located on the southern side ofLongge’er–Gongbujiangda arc fault belt of the Lhasa terrane.It is the first discovered low sulfidation epithermaltype deposit in the middle of the Pb-Zn-Ag metallogenic belt on the northern margin of Gangdise.The orebodyoccurs in the volcanic rocks of the Linzizong Group,and is controlled by the secondary northwest faults formedby the northwest volcanic activity.The mineralization process can be divided into five stages:illite-sericite-chalcedony-jasper±iron-man carbonates(I);quartz-pyrite±galena±sphalerite(II);galena-sphaleritequartz-pyrite-sericite±silver minerals±carbonate(III);argentite-peaceite-galena±pyrargyrite±sphalerite±chalcopyrite(IV);and quartz±carbonates±sericite(V).In this paper,systematic studies of fluid inclusions from34samples ofstage III and12samples of stage V and Si-H-O isotopes of inclusions were conducted.Based on the previousresearch,this paper discussed the nature and source of mineralization and the mechanism of mineralizationprecipitation.Three types of fluid inclusions were distinguished in various kinds of quartz and sphalerite of themain ore-forming period in this deposit,which primarily include the pure liquid(PL),liquid-rich two-phase(WL)and gas-rich two-phase(WG)inclusions.There are only PL and WL types in the late barren quartz-vein.Thehomogenization temperatures,salinities and densities of the quartz in stage III vary from185.6℃to290.7℃,1.57%NaCl eqv to5.71%NaCl eqv and0.76g/cm3to0.92g/cm3,respectively.The homogenization temperatures,salinities and densities of the sphalerite in stage III vary from197.2℃to280.8℃,1.22%NaCl eqv to5.71%NaCl eqv and0.75g/cm3to0.99g/cm3,respectively.The homogenization temperatures,salinities and densitiesof the quartz in stage V vary from147.6℃to218.7℃,2.07%NaCl eqv to8.94%NaCl eqv and0.88g/cm3to0.98g/cm3,respectively.Ore-forming fluids are characterized by low temperature,low pressure and lowdensity.The gas composition of the quartz i

关 键 词：流体包裹体 Si-H-O同位素 银铅锌矿床 斯弄多 冈底斯 西藏 

分 类 号：P575[天文地球—矿物学] O611.7[天文地球—地质学]