凤太矿集区八卦庙金矿区脉状铅锌矿化的物质来源研究:硫化物原位S-Pb同位素证据  

Sources of the ore-forming materials of vein-type Pb-Zn mineralization in Baguamiao gold deposit,Fengtai area:Evidences from in situ sulfide S-Pb isotopes

作　　者：高炫宇 李宇轩 梁文静 袁洪林[1] 安芳[1] Gao Xuanyu;Li Yuxuan;Liang Wenjiang;Yuan Honglin;An Fang(State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi'an 710069)

机构地区：[1]西北大学地质学系,大陆动力学国家重点实验室,西安710069

出　　处：《地质科学》2024年第5期1438-1452,共15页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金项目(编号:42130102);西北大学地质学系本科生创新基金项目资助。

摘　　要：秦岭造山带凤太矿集区内发育层状—似层状和脉状两种类型的铅锌矿化,部分脉状铅锌矿化伴生产于金矿床中,其成矿物质来源仍未得到较好的约束。论文以八卦庙金矿区的脉状铅锌矿体为主要研究对象,采用硫化物原位微区S-Pb同位素研究方法,探讨了脉状铅锌矿化的成矿物质来源。八卦庙金矿区的脉状铅锌矿化主要受NE和NW向断裂或裂隙控制,矿脉宽度通常为2~20 cm。矿石呈团块状或浸染状构造,其中矿石矿物以方铅矿和闪锌矿为主,另有少量黄铜矿和黄铁矿,脉石矿物有石英、白云母、绢云母和少量方解石、白云石等碳酸盐矿物。硫化物原位S-Pb同位素分析结果显示,矿石中闪锌矿的δ^(34)S值相对集中(15.03‰~17.11‰),而黄铜矿(14.76‰~19.91‰)和方铅矿(12.12‰~21.88‰)的δ^(34)S值则变化较大;方铅矿的铅同位素组成非常均一。通过与区内可能物质源区S-Pb同位素对比研究,认为八卦庙金矿区脉状铅锌矿化的成矿物质来自于围岩变质过程中释放的变质流体,并有印支期岩浆热液的贡献,总体具有与金矿化相似的成矿物质来源。金矿化和脉状铅锌矿化在八卦庙矿区共生富集但又独立产出,可能受铅锌和金元素在热液体系中明显不同的地球化学行为所控制。Pb-Zn mineralization in Fengtai area of the Qinling orogenic belt consists of layered and vein-type orebodies. Some vein-type Pb-Zn orebodies are associated with gold orebodies in gold deposits, which sources of ore-forming materials have not been well constrained. Here, we take vein-type Pb-Zn orebodies in the Baguamiao gold deposit as a case, discussed their ore-forming material sources based on sulfide in situ S-Pb isotope compositions. The vein-type Pb-Zn orebodies are mainly controlled by NE-trending faults, with vein widths ranging from 10 to 20 cm. The ore minerals in the ore are mainly galena and sphalerite, with small amounts of chalcopyrite and pyrite, while the gangue minerals include quartz, muscovite/sericite, and some calcite and dolomite. The in-situ S-Pb isotope analytical results show that the sphalerite grains have relatively concentrated δ^(34)S values (15.03‰~17.11‰), while the δ^(34)S values of chalcopyrite (14.76‰~19.91‰) and galena (12.12‰~21.88‰) are relatively variable, and the lead isotope compositions of galena are very uniform. By comparing the S-Pb isotopes of the vein-type Pb-Zn ore to possible sources, it is concluded that the ore-forming materials of the vein-type Pb-Zn orebodies are from metamorphic fluids generated by metamorphism of the wall-rocks, and also involve contributions from the coeval granitic magma, which are fully similar to those of the gold mineralization. The gold and vein-type Pb-Zn mineralization in the Baguamiao area are co-enriched but independently developed, which may be controlled by the distinct geochemical behavior of Pb-Zn and Au in the hydrothermal system.

关 键 词：脉状铅锌矿化 八卦庙金矿 硫化物原位S-Pb同位素 物质来源 

分 类 号：P618.4[天文地球—矿床学]