云南金沙厂铅锌矿床硫同位素地球化学特征  

Characteristics of Sulfur Isotope Geochemistry of Jinshachang Pb-Zn Deposit in Yunnan Province, China

作　　者：白俊豪[1,2] 黄智龙[1] 朱丹[1] 严再飞[1] 罗泰义[1] 周家喜[1] 

机构地区：[1]中国科学院地球化学研究所矿床地球化学国家重点实验室,贵州贵阳550002 [2]中国科学院大学,北京100049

出　　处：《矿物学报》2013年第2期256-264,共9页Acta Mineralogica Sinica

基　　金：中国科学院重点方向项目(KZCX2-YW-Q04-05);矿床地球化学国家重点实验室自主课题(KCZX20090103)

摘　　要：金沙厂铅锌矿床位于云南省东北部,川-滇-黔铅锌成矿域的西北部,矿体主要赋存于下寒武统和上震旦统的碳酸盐地层中。该矿床的主要矿石矿物是闪锌矿和方铅矿,主要脉石矿物是重晶石、萤石和石英。闪锌矿的δ34S值分布于3.9‰～11.2‰之间,平均为5.7‰;方铅矿的δ34S值在6.0‰～9.0‰之间,平均为7.1‰;两个重晶石的δ34S值分别为34.8‰和34.5‰。重晶石的δ34S值与下寒武地层硫酸盐的一致,排除其他可能来源,认为重晶石的硫来源于下寒武统地层。硫化物的硫不可能来自细菌硫酸盐还原作用,因为流体包裹体均一温度远高于细菌的存活温度。硫酸盐热化学还原作用产生的同位素分馏至多为20‰,由此可知下寒武统地层中硫酸盐发生热化学还原作用产生的还原硫δ34S值至少应为14‰,这个值远高于该矿床硫化物δ34S值,因此这种机制不是还原硫的唯一来源。矿区周围广泛分布玄武岩,并且与岩浆有关的硫化物δ34S值比较低,所以硫化物中的硫可能来自岩浆活动。在方铅矿和闪锌矿共生的样品中,闪锌矿的δ34S值大于方铅矿的δ34S值,说明成矿流体的硫同位素局部达到平衡。利用矿物对硫同位素组成计算的硫化物平衡温度与流体包裹体均一温度一致。Jinshachang Pb-Zn deposit,located in Yunnan province and the northwest of Sichuan-Yunnan-Guizhou（SYG） Pb-Zn-Ag multi-metal mineralization area,is mainly hosted in the Upper Neoproterozoic carbonate rocks of Dengying Group.The ore minerals mainly contain sphalerite and galena,and the gangue minerals mainly contain barite,fluorite and quartz.The δ34S values of sphalerite minerals are in the range between 3.6‰ and 13.4‰ with an average value of 5.7‰.The δ34S values of galena range from 6.0‰ to 9.0‰ with an average value of 7.1‰.Two δ34S values of barite are 34.8‰ and 34.5‰ and consistent with that of sulfate from the Lower Cambrian stratum,indicating that the sulfur of barite were derived from this stratum.Because the homogenization temperatures of fluid inclusions exceed the suitable temperature for bacterial sulfate reduction,therefore this process is not an efficient path for the production of reduced sulfur in this district.If sulfides were derived from the Cambrian stratum due to thermochemical sulfate reduction,sulfides in this deposit should preserve a minimum δ34S value of 14‰ which exceeding that of sulfide from Jinshachang deposit.Therefore,this process is not the only source of reduced sulfur.Considered the fact that the ore district is surrounded by basalts and δ34S values of sulfide related to magmatic activities are relatively low,the reduced sulfur of sulfide may be derived from magmatic activities.The δ34S values of sphalerite are higher than that of coexisting galena,indicating that sulfur isotopic composition in ore-forming fluid had partly reached equilibrium.The equilibrium temperatures calculated by using the δ34S values of surfur-bearing mineral pairs are consistent well with the homogenization temperature of fluid inclusions.

关 键 词：金沙厂铅锌矿床 硫同位素 硫酸盐热化学还原作用 平衡温度 

分 类 号：P578.2[天文地球—矿物学] P618.4[天文地球—地质学]