藏南扎西康铅锌多金属矿床成因——硫化物原位硫同位素证据  

Genesis of Zhaxikang Pb-Zn Polymetallic Deposit in Southern Tibet:Evidence from in Situ S Isotopes of Sulfides

作　　者：李洪梁 李光明[2,3] 丁俊[2,3] 张志[2] 卿成实[2] 付建刚[2] 凌晨 刘宇奇 Li Hongliang;Li Guangming;Ding Jun;Zhang Zhi;Qing Chengshi;Fu Jiangang;Ling Chen;Liu Yuqi(Institute of Exploration Technology,Chinese Academy of Grological Sciences,Chengdu 611734,China;Chengdu Center,China Geological Survey,Chengdu 610081,China;College of Earth Science,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]中国地质科学院探矿工艺研究所,成都611734 [2]中国地质调查局成都地质调查中心,成都610081 [3]成都理工大学地球科学学院,成都610059

出　　处：《吉林大学学报（地球科学版）》2020年第5期1289-1303,共15页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金项目(41702080,91955208,41602214);中国地质调查局项目(DD20190644,DD20190147);国家科学技术部科技支撑计划重点项目(2016YFC060308,2018YFC0604103)。

摘　　要：藏南扎西康铅锌多金属矿床是特提斯喜马拉雅构造带(TH)东段发现的首个大型铅锌矿床,但其成因备受争议。本文在详细研究矿床地质特征的基础上,对矿硐内具有"同心环带"或"热水蛋"构造的铅锌矿石中的黄铁矿、方铅矿和闪锌矿进行了原位微区硫同位素分析。结果显示:铅锌矿石硫同位素组成变化范围在8.88‰~11.83‰之间,平均为10.50‰,总硫同位素组成(δ^34S∑S)约为10.07‰。其中:7个黄铁矿(Py)测点的δ^34SPy值为10.29‰~11.14‰,平均为10.70‰;6个闪锌矿(Sp)测点的δ^34SSp值为10.78‰~11.83‰,平均为11.49‰;5个方铅矿(Gn)测点的δ^34SGn值为8.88‰~9.18‰,平均为9.04‰。总体表现为δ^34SSp>δ^34SPy>δ^34SGn,指示硫同位素未达到分馏平衡。利用方铅矿与闪锌矿矿物对硫同位素温度计计算可得,铅锌成矿温度介于224~280℃之间,平均值为259℃。结合前人研究成果,进一步得出扎西康铅锌多金属矿床主成矿期硫源主要来自日当组(J1r)围岩地层,并可能有少量岩浆硫的混入,属受控于地层-构造-岩浆热液作用的中温热液矿床。Zhaxikang Pb-Zn polymetallic deposit is the first large-scale Pb-Zn deposit discovered in the eastern Tethys Himalaya(TH),but its genesis is still controversial.Based on the detailed study of the geological characteristics,the authors analyzed the in situ S isotope of pyrite,galena,and sphalerite in the Pb-Zn ore with"concentric ring zone"or"hot water egg"structure in the mine chamber.The results of in situ S isotopic analysis show that the isotopic composition of Pb-Zn ore varies from 8.88‰-11.83‰,with an average of 10.50‰,and the total sulfur isotopic composition(δ^34S∑S)is about 10.07‰.Among them,theδ^34SPy of seven pyrite measuring points is 10.29‰-11.14‰,with an average of 10.70‰;theδ^34SSp of six sphalerite measuring points is 10.78‰-11.83‰,with an average of 11.49‰;and theδ^34SGn of five galena measuring points is 8.88‰-9.18‰,with an average of 9.04‰.It shows a trend ofδ^34SSp>δ^34SPy>δ^34SGn,indicating a status of fractionation disequilibrium.Using S isotope thermometer between galena and sphalerite,the Pb-Zn mineralization temperature is constrained between 224℃and 280℃with an average of 259℃.Combined with the results of previous studies,it is concluded that the sulfur source of Zhaxikang Pb-Zn polymetallic deposit is mainly from the surrounding strata of Ridang Formation(J1r)with minor magma sulfur,and Zhaxikang Pb-Zn polymetallic deposit belongs to the filling metasomatic mesothermal deposit controlled by the stratigraphic,tectonic and magmatic hydrothermal processes.

关 键 词：原位硫同位素 矿床成因 中温热液矿床 扎西康铅锌多金属矿床 藏南 

分 类 号：P59[天文地球—地球化学] P618.4[天文地球—地质学]