内蒙古维拉斯托铜多金属矿床流体包裹体研究

Fluid Inclusion Study of the Weilasituo Cu Polymetal Deposit in Inner Mongolia

对内蒙古维拉斯托铜多金属矿床地质特征、流体包裹体和氢、氧同位素的研究表明,成矿具有多阶段性,根据矿脉穿插关系和矿石结构构造特征可以分为4个阶段：石英-黄铁矿阶段、多金属硫化物阶段、黄铜矿-磁黄铁矿-石英阶段和石英-碳酸盐阶段。流体包裹体类型以富液相包裹体为主,含有少量富气相包裹体和含子矿物包裹体以及含CO2三相包裹体。包裹体形态多为椭圆形、负晶形或近圆形,数量较多,呈不规则分布。均一温度变化区间为106~389℃,盐度为1.23%~9.86%NaCl eqv.,显示成矿流体具有中温、低盐度和低密度的特点。激光拉曼光谱分析包裹体成分主要为CO2、CH4和H2O。氢、氧同位素分析结果表明成矿热液是岩浆水和大气降水的混合作用来源。综合对比研究认为,维拉斯托铜多金属矿床与该区燕山期中酸性岩浆活动密切相关,为深部岩浆在上升过程中与下渗的大气降水发生混合,矿质在构造有利部位沉淀富集的结果。矿床为与燕山期岩浆活动有关的中温热液矿床。

The studies on geologic characteristics,fluid inclusion,H and O isotopes of the Weilasituo Cu polymetal deposit showed that mineralization had experienced many stages.Based on cross-cutting relationship of veins and ore structure,four stages can be identified：quartz-pyrite stage,polymetallic sulfide stage,chalcopyrite-pyrrhotite-quartz stage and quartz-carbonate stage.There are four types of the fluid inclusions：liquid-rich inclusion,gas-rich inclusion,polyphase inclusion bearing daughter-mineral crystals and CO2 three-phase inclusion.The fluid inclusions are oval or nearly round in shape,which are of majority and distributed disorderedly.The homogenized temperatures and salinity are from 106 ℃ to 389 ℃,and 1.23% to 9.86% NaCl eqv.,respectively,which indicate characters of intermediate temperature,low salinity and low density for the fluid.The analytic results through Laster Laman Spectroscopy suggest that the fluid is rich in CH4,CO2 and H2O.The analytic results from H and O isotopes implied that the mineralizing fluids originated from magmatic water and accompanied with participation of meteoric water.It is concluded that the Weilasituo Cu polymetal deposit was formed by the precipitation of mineralizing materials in advantaged structures.It is an intermediate temperature hydrothermal polymetal type related to the Yanshanian magmatism.