广西西大明山渌井铅锌矿床成因——流体包裹体、硫化物矿物化学和硫同位素约束

The genesis of the Lujing Pb-Zn deposit: Constraints from fluid inclusions,sulfide mineral chemistry and S isotopes evidence

渌井矿床是广西西大明山地区内一个典型的脉状铅锌矿床,矿体赋存于寒武纪地层中,主要受断裂构造控制。本文在详细野外调查的基础上,通过对其流体包裹体、硫化物矿物化学和硫同位素的系统测定和分析,探讨了成矿流体性质和矿质来源。流体包裹体研究表明,渌井矿床主成矿阶段流体包裹体类型以富液相的气液两相包裹体和纯液相包裹体为主,主成矿期包裹体均一温度为237~281℃(平均值为256℃),对应盐度为3.54%~12.69%(均值为8.39%)。硫化物电子探针分析结果显示,闪锌矿以富集Fe、Cd、In而贫Mn、Ga、Ge等元素为特征,多属于形成温度偏高的含铁闪锌矿类型。硫化物硫同位素研究显示,δ34S值总体变化范围为-1.9‰~4.4‰,呈塔式分布,均值为1.7‰,位于零值附近,暗示渌井矿床硫化物的硫主要来源于岩浆。综合矿床地质、流体包裹体、硫化物矿物化学及硫同位素特征可知,渌井矿床应归属于热液脉型铅锌矿床范畴,在成因上与本区深部的隐伏岩体具有密切的联系,成矿时代可能为燕山晚期。

The Lujing deposit is a typical veined Pb-Zn deposit in west Damingshan area, and its orebodies are located in the Cambrian strata and strictly controlled by faults. Based on detailed field geological survey as well as analysis and interpretation of fluid inclusions, sulfide mineral chemistry and S isotope, the authors investigated oreforming fluid properties and sources of ore-forming mineral. Petrographic observations reveal that the inclusions at stage II of Lujing deposit primarily belong to liquid-rich, single-phase aqueous fluid inclusion. Microthermometric measurements indicate that homogenization temperatures are 237 - 281℃（ 256℃ on average）, with corresponding salinities of 3. 54% - 12. 69%（ 8. 39% on average）. Electron microprobe analysis indicates that, characterized by high content of Fe, Cd and Cd and low content of Mn, Ga and Ge, sphalerites should belong to high temperature iron sphalerite. The δ34 S values of sulfides vary from-1. 9‰ to 4. 4‰（ 1. 7‰ on average）, close to zero on average, which indicates that sulfur of the sulfide was derived from the magmatic source. Based on ore-forming geological characteristics, fluid inclusions, sulfide mineral chemistry and S isotope, the authors hold that the Lujing deposit should belong to hydrothermal vein type Pb-Zn deposit, that mineralization of Lujing was closely related to the magmatism, and that the deposit was formed in late Yanshanian period.