豫西沙沟脉状Ag-Pb-Zn矿床地质特征和成矿流体研究  

Geology and ore-forming fluid of silver-lead-zinc lode deposit of Shagou,western Henan Province

作　　者：高建京[1] 毛景文[2] 叶会寿[2] 陈懋弘[2] 郑榕芬 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037 [3]中海石油(中国)有限公司湛江分公司研究院,湛江524057

出　　处：《岩石学报》2010年第3期740-756,共17页Acta Petrologica Sinica

基　　金：全国危机矿山接替资源找矿项目(20089949,200841019);中国地质调查局项目“我国主要金属矿床模型研究(1212010634001)”;公益性行业科研专项经费项目(K0801)资助

摘　　要：豫西沙沟薄脉状Ag-Pb-Zn硫化物矿床位于华北陆块南缘熊耳山地区,主要由多金属硫化物-石英-碳酸盐脉型和石英-碳酸盐-绢云母-多金属硫化物蚀变岩型两种矿化类型组成。主要矿脉的矿物共生序列可以分为成矿前的石英-黄铁矿阶段(Ⅰ)、闪锌矿-石英-方铅矿-少量银矿物阶段(Ⅱ1)、方铅矿-石英-闪锌矿-含铁白云石-银矿物阶段(Ⅱ2)和成矿后的方解石-(石英)阶段(Ⅲ)。对不同阶段的成矿流体研究表明,石英-黄铁矿阶段(Ⅰ)中的含氯化钠子晶三相(LVH)包裹体(Ⅰ1)可能是直接从饱和水的结晶岩浆熔体中出溶形成或是由岩浆流体的减压沸腾形成,显示该区很可能存在岩浆流体端元。多金属硫化物阶段(Ⅱ1&Ⅱ2)捕获富液相包裹体(LV型)和个别CO2包裹体(C型),这两个阶段流体包裹体反映了主成矿阶段流体的基本特征,结合包裹体气相和液相成分色谱分析以及包裹体初融温度,认为成矿流体应该为中-低温低盐度含CO2的H2O-NaCl体系。其中,阶段(Ⅱ2)的均一温度(145～288℃,平均为194℃)比阶段(Ⅱ1)的均一温度(185～357℃,平均240℃)低46℃;同时,阶段(Ⅱ2)的盐度(1.91%～10.86%,平均6.38%)较阶段(Ⅱ1)盐度(4.65%～10.11%,平均7.77%)略低。对这一温度和盐度的总体下降趋势的合理解释是大气水的逐渐混入。多金属硫化物阶段(Ⅱ1&Ⅱ2)之后的方解石-(石英)阶段普遍为富液相包裹体(LV型),该阶段显著降低的温度(129～208℃,平均165℃)和盐度(1.40%～4.03%,平均2.50%),进一步佐证大气水的不断混入。而且,流体混合可能在引起矿石矿物从热液中沉淀方面起到重要作用。Shagou vein-type Ag-Pb-Zn ore deposit in the south margin of North China Craton is mainly composed of polymetallic sulphide ore type and quartz-carbonate-sericite replacement ore type. The main Shagou vein presents a paragenesis that can be divided into four stages:An early quartz-pyrite stage (Ⅰ) prior to polymetallic mineralization,a sphalerite-quartz-galena-minor silver minerals polymetallic stage (Ⅱ1),a galena-quartz-sphalerite-silver minerals polymetallic stage (Ⅱ2),and a calcite-(quartz) stage (Ⅲ) after polymetallic mineralization. The three phase (LVH) fluid inclusions (Ⅰ1) have been interpreted as the product of direct exsolution of a crystallizing magma or sudden decompression of the fluid exsolved by the magma,which indicates a possible magmatic fluid endpoint in the study area. Combined with melting temperature and inclusions composition determined by Quadrupole Mass Spectrometer,liquid-rich inclusions and minor 3-phase H2O-CO2 rich inclusions trapped in polymetallic stages (Ⅱ1&Ⅱ2) show that the ore forming fluid is a CO2 bearing H2O-NaCl system with a lower temperature. The fluid inclusion homogenization temperatures (145~288℃,194℃ in average) of stage (Ⅱ2) are lower 46℃ than the homogenization temperatures (185~357℃,240℃ in average) of stage (Ⅱ1),while the salinities (1.91%~10.86%,6.38% in average) of stage (Ⅱ2) is slightly lower than the salinities (4.65%~10.11%,7.77% in average) of stage (Ⅱ1). The systematic decreases in temperatures and salinities suggest a possible mixing with meteoric water,which is further supported by continuing cooling (homogenize at temperatures between 129~208℃,with an average of 165℃) and dilution (with a salinities of 1.40%~4.03%,2.50% in average) of calcite-(quartz) stage (Ⅲ). Decreases in salinity and temperature as result of the potential fluid mixing are supposed to have played an important role in triggering the precipitation of ore minerals from the hydrothermal solution.

关 键 词：银铅锌 流体包裹体 成矿流体 沙沟 熊耳山 

分 类 号：P618.2[天文地球—矿床学]