扬子北缘马元铅锌矿床闪锌矿微量元素及S-Pb-He-Ar-C同位素地球化学研究  

Trace elements,S,Pb,He,Ar and C isotopes of sphalerite in the Mayuan Pb-Zn deposit,at the northern margin of the Yangtze plate,China

作　　者：高永宝[1] 李侃[1] 钱兵[1] 李文渊[1] 郑敏昌 ChenGuang ZHANG 

机构地区：[1]中国地质调查局西安地质调查中心,国土资源部岩浆作用成矿与找矿重点实验室,西安710054 [2]汉中天鸿基矿业有限公司,汉中723102 [3]加拿大女王大学地质科学与地质工程系

出　　处：《岩石学报》2016年第1期251-263,共13页Acta Petrologica Sinica

基　　金：国家自然科学基金青年项目(41102050);国家"十一.五"科技支撑计划项目(2006BAB01A01);陕西省自然科学基础研究计划项目(2013JM5010);陕西省科学技术发展研究计划项目(2015KJXX-71);中国地质调查局地质调查项目(1212011121088)和中国地质调查局青年地质英才计划(2013)联合资助

摘　　要：马元铅锌矿床是近年扬子陆块北缘铅锌找矿的新突破。矿体呈层状、似层状产于碑坝隆起翼部震旦系灯影组角砾状白云岩层间构造带中,围岩蚀变很弱。矿石中硫化物以闪锌矿、方铅矿为主,中粗粒晶质结构,充填于白云岩角砾间。闪锌矿富集Cd、Ge、Ag,贫In、Tl、Se,Ga/In为6~132,Ge/In多>1000,成矿温度以中-低温为主。金属硫化物ε^(34)S值相对集中,为12.9‰~19.4‰,平均为17.4‰,来自于海相硫酸盐的还原。铅同位素组成稳定,^(206)Pb/^(204)Pb为17.858~17.918:^(207)Pb/^(204)Pb为15.603~15.694;^(208)Pb/^(204)Pb为37.756~38.046,具有造山带和上地壳铅的特征,震旦系可能提供了金属成矿物质。闪锌矿中流体包裹体的~3He/~4He为0.03Ra^1.05Ra,^(40)Ar/^(36)Ar为326.1~765.1,^(38)Ar/^(36)Ar为0.183~0.204,表明成矿流体主要为地壳流体和饱和大气水(大气降水或海水)的混合。闪锌矿内流体包裹体挥发分δ^(13)C_(CH_4)值为-36.01‰^-28.80‰,δ^(13)C_(C_2H_6)值为-27.72‰^-22.44‰,δ^(13)C_(CO_2)值为-23.24‰^-9.68‰,表明有机流体参与了成矿作用。石英、方解石的H-O同位素结果表明具有海水和有机水混合的特征。可见,成矿流体具有两种流体混合的特征,一为蒸发海水与围岩反应所形成的盆地卤水,二为有机流体。推测矿区可能存在一个古油气藏,由于TSR生成一高硫气藏,为区内还原性有机流体的主要来源。当富含Pb、Zn等成矿物质的成矿流体运移至富含CH_4和H_2S的还原性流体的矿区角砾岩带时,两种流体混合,Pb、Zn等遇到H_2S发生反应而沉淀成矿,并伴生热液白云石等,形成了马元铅锌矿床。综上所述,我们认为马元矿床属MVT型铅锌矿床。The Mayuan Zn-Pb deposit is an exploration breakthrough at the northern margin of the Yangtze plate in recent years. The layered or layered-like orebodies occur in brecciated dolomites of Sinian Dengying Formation at the wings of the Beiba uplift, and the alterations are weak. The ore minerals are mainly sphalerite and galena, with medium to coarse crystalline structure, filling in open-space of dolomite breccias. Characterized by high contents of Cd, Ge and Ag, low contents of In, Ti and Se, high Ga/In （6 - 132） and Ge/In （mostly 〉 1000） values, sphalerites may have been formed at medium to low temperature. The 834S values of suIphides are from 12.9‰ to 19.4‰ with an average of 17.4‰, which are relatively concentrated, and may be formed by reduction of marine sulphate. Lead isotope compositions are stable. The 206pb/204Pb values are from 17. 858 to 17. 918, the 207Tpb/204pb values are from 15. 603 to 15. 694, and the 208sPb/204apb values are from 37. 756 to 38.046. The lead isotopes plot between orogen and upper crust. Sinian strata may have provided ore-forming materials. The 3 He/4 He, 40Ar/36 Ar and 3s At/36 Ar of fluid inclusions in sphalerite are from 0. 03Ra to 1.05Ra, 326. 1 to 765.1, and 0. 183 to 0. 204, respectively, suggesting that the ore-forming fluids were mainly a mixture of crustal fluid and atmospheric water （ meteoric water or seawater）. The 813 Cc,4, 3＇3 Cc2.6 and 813 Cco2 values of volatiles in fluid inclusions from sphalerite are from - 36. 01%v to - 28.80%v, - 27. 72%0 to - 22.44%0, and - 23.24%o to - 9. 68%0, respectively, which indicate that the organic fluid mixed in ore-forming process. The compositions of H-O isotopes from quartz and calcite show the characteristics of fluid mixing of seawater and organic water. So, the ore-forming fluid may be a mixture of two types of fluid i.e. the basin brine formed by the seawater evaporation and the reaction with wall-rocks, and the organic fluid. It is speculated that the ancient gas reservoir became the high-sulfur gas res

关 键 词：闪锌矿 微量元素 S-Pb-He-Ar-C同位素 马元铅锌矿床 扬子北缘 

分 类 号：P618.42[天文地球—矿床学]