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河南桐柏老湾金矿床上上河矿段矿床地质和成矿流体地球化学

发布时间:2019-01-22 19:58
【摘要】:河南桐柏老湾金矿床是桐柏-大别(北坡)金银成矿带内大型造山带型金矿床之一。本文对老湾金矿上上河矿段的矿床地质和流体地球化学特征进行了研究,旨在查明该矿段的流体成矿过程。根据矿脉穿插关系、矿石结构构造、矿物共生组合关系以及黄铁矿粒度和晶形,将老湾金矿床上上河矿段成矿过程划分为:石英粗粒自形黄铁矿(Ⅰ)、石英细粒半自形-他形黄铁矿(Ⅱ)、石英多金属硫化物(Ⅲ)及石英碳酸盐(Ⅳ)四个阶段。镜下观察显示,矿床中的包裹体类型有含CO2包裹体(LH2O+VCO2+LCO2)、纯CO2(VCO2+LCO2)包裹体、液相(LH2O+VH2O)包裹体及少量含子晶包裹体(LH2O+VH2O+S)。第Ⅰ、Ⅱ和Ⅲ阶段均可见含CO2、纯CO2和液相包裹体,有时可见含CO2包裹体和液相包裹体共生。流体包裹体显微测温结果显示,成矿流体可近似看做中低温、低盐度、富CO2的NaCl-CO2-H2O体系,捕获纯CO2和液相包裹体的流体是由含CO2包裹体所代表的NaCl-CO2-H2O流体经不混溶形成的,三者在寄主矿物沉淀时,被同时捕获而共存。从第Ⅰ阶段到第Ⅳ阶段,成矿流体温度从303~379℃逐渐降低到138~195℃,盐度从4.07%~9.59%NaCl.eq逐渐降低到1.06%~2.74%NaCl.eq。第Ⅰ阶段成矿流体产生了不混溶作用,到第Ⅱ和第Ⅲ阶段CO2起泡再次激发了不混溶作用。从第Ⅰ阶段到第Ⅲ阶段,成矿流体δ18OH2O从6.56‰~9.71‰经1.89‰~4.01‰变化到0.08‰,δDH2O从-78.1‰~-64.2‰经-79.5‰~-76.3‰变化到-72.6‰,表明老湾金矿床上上河矿段早期成矿流体主要是岩浆热液,第Ⅱ阶段成矿流体中有少量大气降水加入,到第Ⅲ阶段成矿流体中大气降水的比例明显加大。
[Abstract]:Tongbai Laowan gold deposit is one of the large orogenic type gold deposits in Tongbai-Dabie (North Slope) gold-silver metallogenic belt. In this paper, the geological and fluid geochemical characteristics of the Shangshanhe formation in Laowan gold deposit are studied in order to find out the fluid metallogenic process in the section. According to the ore vein intercalation relationship, ore structure, mineral symbiotic assemblage relationship, pyrite granularity and crystal shape, the ore-forming process of Shangshanhe formation of Laowan gold deposit is divided into quartz coarse grain self-shaped pyrite (鈪,

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