投稿时间：2014-10-10
修订日期：2015-05-20
网络发布日期：2015-10-29
中文摘要:弄屯矿床发育在华南钦杭成矿带西南端广西境内,它是近年来广西在大规模找矿勘查中新发现的一处大型铅锌矿床。野外地质调查发现,弄屯矿床铅锌矿体主要呈脉状和似层状充填于断裂破碎带中,矿体产状严格受断裂控制,矿体及围岩中硅化和碳酸盐化蚀变大量发育。依据矿物组合及脉体穿插关系,矿床中的热液流体活动可划分为4个阶段:石英-黄铁矿阶段(Ⅰ)、闪锌矿-黄铁矿阶段(Ⅱ)、铅锌硫化物阶段(Ⅲ)和碳酸盐阶段(Ⅳ)。流体包裹体岩相学观察表明,矿床中主要发育气液两相包裹体和单相水溶液包裹体,仅在Ⅰ、Ⅱ阶段出现少量富气相包裹体。显微测温分析表明,由早阶段至晚阶段流体包裹体均一温度和盐度逐步降低,分别为276～342℃(Ⅰ)、209～301℃(Ⅱ)、140～272℃(Ⅲ)和116～172℃(Ⅳ),对应盐度w(NaCleq)分别为8.81%～15.07%(Ⅰ)、5.26%～11.58%(Ⅱ)、3.23%～9.98%(Ⅲ)和0.88%～4.34%(Ⅳ)。与国内外典型铅锌矿床的流体包裹体参数对比,弄屯矿床的成矿流体特征与SEDEX型、MVT和Skarn型铅锌矿床明显不同,而与热液脉型矿床十分相似,结合该矿床产于细碎屑岩建造并且受断裂构造控制等一系列的证据,将弄屯矿床定为热液脉型铅锌矿床。氢同位素(δD=-97‰～-54‰)和氧同位素(δ18OH2O=0.98‰～3.83‰)证据指示,成矿期流体与岩浆源流体具有一定的亲缘关系。从早成矿阶段到晚成矿阶段,成矿流体的温度、盐度出现同步降低的演化趋势,暗示了岩浆源流体与天水流体的混合作用可能是矿质沉淀的主要机制。
Abstract:Located in Xidaming Mountain of Guangxi on the southwest margin of the Qin-Hang metallogenic belt, the Nongtun ore deposit is a large-size Pb-Zn deposit discovered during large-scale prospecting in recent years. In this paper, detailed field investigation and fluid inclusion as well as hydrogen and oxygen isotope study were carried out. Geological survey reveals that orebodies are mainly in vein or layered forms filling faults, and are strictly controlled by faults. Carbonatization and silicification are well developed in orebodies and country rocks. Based on mineral assemblages and crosscutting relations of veinlets, four stages of hydrothermal fluid activity can be divided, i.e., quartz-pyrite stage (Ⅰ), sphalerite-pyrite stage (Ⅱ), lead-zinc sulfide stage (Ⅲ), and carbonate stage (Ⅳ), respectively. Three types of fluid inclusions can be distinguished from the petrographic study, being two-phase liquid-rich, two-phase vapor-rich (stage Ⅰ and Ⅱ), and single-phase aqueous fluid inclusions respectively. Microthermometric measurements indicate that temperatures and salinities gradually decrease from the early stage to the last stage, with the temperatures being 276～342℃ (Ⅰ), 209～301℃ (Ⅱ), 140～272℃ (Ⅲ) and 116～172℃ (Ⅳ), and the corresponding salinities of w(NaCleq) being 8.81%～15.07% (Ⅰ), 5.26%～11.58% (Ⅱ), 3.23%～9.98% (Ⅲ) and 0.88%～4.34%(Ⅳ), respectively. Characteristics of ore-forming fluids in the Nongtun deposit are different from those of SEDEX, MVT and skarn-type Pb-Zn deposits apparently, and are in accordance with features of hydrothermal vein-type deposits, as shown by the comparative studies in China and abroad. The Nongtun deposit can be genetically classified as hydrothermal vein-type Pb-Zn deposit according to the nature of fluids, the geological characteristics of clastic sedimentary rocks and the tectonic ore-controlling nature. H (δD=-97‰～-54‰) and O (δ18OH2O=0.98‰～3.83‰) isotopic compositions indicate that the source of ore-forming fluids had a genetic relationship with magmatic fluids at the hydrothermal mineralization stage; combined with the evolutionary characteristics of temperatures and salinities, the authors have reached the conclusion that the mixture between magmatic fluids and meteoric water probably played a critical role in the deposition and enrichment of Pb-Zn and other elements.
keywords:geochemistry hydrothermal vein-type Pb-Zn deposit fluid inclusion H-O isotope Nongtun Pb-Zn deposit Xidaming Mountain Guangxi
文章编号：
中图分类号：P618.42;P618.43
文献标志码：
基金项目:本文得到国家自然科学基金(编号:41462005)、广西壮族自治区大规模地质矿产勘查项目(编号:桂国土资函[2014]256号)和广西高等学校优秀中青年骨干教师培养工程项目联合资助
引用文本：
柴明春,付伟,冯佐海,徐文忠,乐兴文,李赛赛,陆建辉,刘武文,庞运权.2015.广西西大明山弄屯铅锌矿床的成矿流体特征及矿床成因指示意义[J].矿床地质,34(5):948~964CHAI MingChun,FU Wei,FENG ZuoHai,XU WenZhong,LE XingWen,LI SaiSai,LU JianHui,LIU WuWen,PANG YunQuan.2015.Characteristics of ore-forming fluids of Nongtun Pb-Zn deposit in Xidaming Mountain of Guangxi and their implications for ore genesis[J].Mineral Deposits34(5):948~964
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