投稿时间：2022-02-26
修订日期：2022-11-15
网络发布日期：2023-01-07
中文摘要:陕西旬阳盆地南缘是南秦岭中部重要的铅锌成矿带，带内发育一大批赋存在志留系中的铅锌矿床。为了进一步厘清区域内铅锌成矿的物质来源和成因机制，文章选取区内典型的关子沟铅锌矿床开展流体包裹体和H-O-S-Pb同位素研究。关子沟铅锌矿体主要以层状、似层状赋存于双河镇组二段和三段千枚岩地层中，根据矿物组构和穿插关系，将成矿过程划分为3个阶段：石英-黄铁矿阶段（Ⅰ阶段）、石英-多金属硫化物阶段（Ⅱ阶段）和石英-碳酸盐（Ⅲ阶段）。其中，Ⅱ阶段原生流体包裹体均一温度为215~393℃，盐度w（NaCleq）为2.2‰~10.1‰； Ⅲ阶段均一温度为124~255℃，盐度w（NaCleq）为1.8‰~6.6‰，具有中高温、中低盐度的成矿流体特征。石英H-O同位素结果（δ18OH2O值为6‰~10.9‰，δD值为-82.9‰~-73.6‰）显示成矿流体主要为海水和有机水，伴有大气降水的混合。原位S同位素显示硫化物δ34S值变化范围为4.63‰~8.73‰，暗示主要硫化物的S源于海相硫酸盐的热化学还原，志留系黑色岩系中的有机质提供了还原剂。矿石硫化物的206Pb/204Pb为17.8254~17.9470，207Pb/204Pb为15.6233~15.6396，208Pb/204Pb为38.1706~38.3143，指示Pb主要源于沉积盖层。综合矿床地质特征、流体包裹体及H、O、S、Pb同位素特征，认为关子沟矿床为热水沉积成因，志留系裂陷盆地内热水沉积作用控制着铅锌成矿过程。
Abstract:The southern margin of the Xunyang Basin in Shaanxi Province is an important lead-zinc metallogenic belt in the central part of the South Qinling, in which many lead-zinc deposits hosted in Silurian strata are developed. To further clarify the source and genetic mechanism of lead-zinc mineralization in the region, the typical Guanzigou lead-zinc deposit was selected to carry out the study of fluid inclusions and H-O-S-Pb isotopes. The ore bodies occur as a layered shape or stratoid in the phyllite strata of the second and third members of the Shuanghezhen Formation. According to the mineral assemblage and crosscutting relationship, the mineralization process of the Guanzigou Pb-Zn deposit can be divided into three stages:early quartz-pyrite stage (stage-Ⅰ), quartz-polymetallic sulfide stage (stage-Ⅱ), and late quartz-carbonate stage (stage-Ⅲ). Fluid inclusions show that the ore-forming fluid of the deposit is characterized by medium-high temperature (215~393℃ of stage-Ⅱ, 124~255℃ of stage-Ⅲ) and medium-low salinity (2.2‰~10.1‰ w(NaCleq) of stage-Ⅱ, 1.8‰~6.6‰ w(NaCleq) of stage-Ⅲ). The H-O isotopes (6‰~10.9‰ of δ18OH2O, -82.9‰~-73.6‰ of δD) indicate that the ore-forming fluids are mainly seawater and organic water, which mixed with atmospheric water during the migration process. The in-situ S isotope shows that δ34S values of the sulfide vary from 4.63‰ to 8.73‰, suggesting that S was derived from the thermochemical reduction of marine sulfate, and the organic matter in the Silurian black rock series provided a reducing agent. The 207Pb/204Pb (15.6233~15.6396), 206Pb/204Pb (17.8254~17.9470), and 208Pb/204Pb (38.1706~38.3143) values of ore minerals show a crustal Pb origin, indicating that the ore-forming metals were derived from sedimentary rocks. Based on the geological characteristics of the deposit, fluid inclusions, and H-O-S-Pb isotopes, it is proposed that the Guanzigou Pb-Zn deposit is of syngenetic hydrothermal sedimentary origin and the hydrothermal sedimentation in the Silurian rift basin contributed to the mineralization of the deposit.
keywords:geochemistry fluid inclusions H-O-S-Pb isotopes genetic mechanism Guanzigou Pb-Zn deposit South Qinling
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基金项目:本文得到中国地质调查局项目（编号：ZD20220303）资助
引用文本：
吴欢欢,黄河,高永宝,魏立勇,李志丹,张振,范堡程,孟五一,李国英.2022.南秦岭关子沟铅锌矿床成因：流体包裹体和H-O-S-Pb同位素证据[J].矿床地质,41(6):1200~1216WU HuanHuan,HUANG He,GAO YongBao,WEI LiYong,LI ZhiDan,ZHANG Zhen,FAN BaoCheng,MENG WuYi,LI GuoYing.2022.Genesis of Guanzigou lead-zinc deposit in South Qinling: Evidence from fluid inclusions and H-O-S-Pb isotopes[J].Mineral Deposits41(6):1200~1216
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