豫西吉家洼金矿成矿作用过程:来自成矿流体的约束

Metallogenic Process of the Jijiawa Gold Deposit in Western Henan:Constraints from Fluid Inclusions

豫西吉家洼金矿位于熊耳山金多金属矿集区西部，是一构造蚀变岩-石英脉混合型金矿床。其热液成矿过程包括4个矿化阶段：黄铁矿-石英阶段（Ⅰ）、石英-黄铁矿阶段（Ⅱ）、石英-多金属硫化物阶段（Ⅲ）和石英-碳酸盐阶段（Ⅳ）。通过流体包裹体显微测温、拉曼光谱和H、O同位素分析，获得了成矿流体的温度、盐度、密度和成矿流体的类型和来源，探讨了成矿作用的机理。其结果显示如下：Ⅰ、Ⅱ阶段发育CO2三相包裹体和气液两相包裹体，Ⅲ、Ⅳ阶段主要发育气液两相包裹体。从第Ⅰ阶段到Ⅳ阶段，流体包裹体的均一温度分别为232～333℃、143～266℃、135～227℃和106～166℃；对应的盐度为3.76％～16.05％、1.74％～17.34％、0.7％～17.26％和0.35％～11.34％。表明成矿流体由早阶段中低温、中低盐度的CO2-H2 O-NaCl体系，向晚期的低温、低盐度的H2 O-NaCl体系演化。H、O同位素组成特征显示，成矿流体以岩浆水为主，有不同比例大气降水混合。流体混合作用和流体不混溶作用是促使金发生沉淀、富集的重要因素，水-岩反应对金的沉淀也有促进作用。

The Jijiawa gold deposit is located in the western part of Xiong＇er mountain gold polymetallic ore dis-trict,Henan Province.It represents a mixing gold deposit,consisting of structure-controlled alteration type,as well as the quartz vein type.The ore-forming process can be divided into four stages：pyrite-quartz vein stage （Ⅰ）,quartz-pyrite vein stage（Ⅱ）,quartz-polymetallic sulfides stage（Ⅲ）,quartz-carbonate vein stage（Ⅳ）. Through the studies of fluid inclusion microscopic temperature measurement,Laser-Raman spectra and H and O isotopes,we obtained the ore-forming fluid temperature,salinity,density and the type and source of ore-forming fluid,and discussed the mechanism of mineralization.The results show as follows：Two types of fluid inclusions in stage Ⅰ and Ⅱ are indentified as CO2 type and gas-liquid type;but stage Ⅲ and Ⅳ quartz contain exclu-sively gas-liquid type fluid inclusions.The homogenization temperatures of ore-forming fluids from stage Ⅰ to stage Ⅳare 232-333 ℃,143-266 ℃,135 -227 ℃and 106-166 ℃respectively,with the corresponding salinities being 3.76%-16.05%,1.74%-17.34%,0.7%-17.26% and 0.35%-1 1.34%.In general, the ore-forming fluid was evolved from CO2-H2 O-NaCl system,which is characterized by medium-low tempera-ture and medium-low salinity,to H2 O-NaCl system.The H-O isotopes composition reveals that in the Jijiawa gold deposit,the hydrothermal system gradually transited from a magmatic-dominated fluid to a meteoric-domi-nated fluid.Fluid mixing action and fluid immiscibility are the most important factors that caused the gold pre-cipitation and enrichment,and fluid-rock interaction also contributes to the gold precipitation and enrichment.