浙江毫石银矿床成矿年代学和同位素地球化学  

MINERALIZATION CHRONOLOGY AND ISOTOPIC GEOCHEMISTRY OF THE HAOSHI SILVER DEPOSIT IN ZHEJIANG PROVNCE

作　　者：徐步台[1] 李长江[1] 陈好寿[1] 

机构地区：[1]浙江省地质矿产研究所,浙江大学地球科学系

出　　处：《矿床地质》1994年第3期271-281,共11页Mineral Deposits

基　　金：浙江省自然科学基金

摘　　要：文章通过矿脉中蚀变绢云母的Ｋ－Ａｒ年龄和石英流体包裹体的Ｒｂ－Ｓｒ等时年龄测定，得出毫石银矿床的成矿年龄为１００×１０￣６ａ。该成矿年龄相对于本区上侏罗统火山岩的成岩年龄要滞后≥３０×ｌ０￣６ａ。同时，对该银矿床进行了较系统的Ｈ、Ｏ、Ｓ及Ｐｂ等同位素地球化学研究，判别其成矿热液来自中生代大气降水成因的环流地热水，通过淋滤作用汲取岩石中的成矿物质，形成了浅成中低温热液充填型银矿床。The Haoshi deposit is a large-medium silver deposit newly discovered inthe Mesozoic volcanic area of eastern Zhejiang,Isotopic ages of fluid inclusionsin quartz and alteration minerals from ore veins and related volcanic rockssuggest that the time interval between the formation of host volcanic rocksand the silver mineralization is more than 30×l0￣6a,Therefore , the mineraliza-tion was not directly associated with the volcanic magmatic activity.Accordingto hydrogen and oxygen isotopic data of quartz from ore veins and of theirfluid inclusions and the variation curve for isotopic composition of water-rockexchange,it is believed that the ore-forming solution was a circulating geother-mal fluld derived from Mesozoic meteoric water. Sulfur and lead isotopiccompositions of ore minerals indicate that mineralizing materials were mainlyderived from the Mesozoic volcanic rocks. The two-component mixing modelfor lead isotope composition shows that about 95% ore lead came from theMesozoic volcanic rocks, while lead derived from metamorphosed rocks of thePrecambrian basement underlying the volcanic rocks was negligible in quantity,implying that mineralizIng materials were leached and drawn by circulatinggeothermal water at a relatively small depth and the main part of thecirculation was in the volcanic cover. However, the lead of the metamorphosedrock source has exerted a strong influence on the model ages of ore lead, andhence the model ages of ore lead no longer have the mineralization chronolo-gical significance; nevertheless, these ages may be used as one of the indica-tors for the formation of ore deposits through the leaching and drawing ofcirculating geothermal water,With the weakening of the wall rock alterationcaused by mineralizing fluids during the emplacement of orebodies, the water-rock ratios decrease and the δ￣(18)O values exhibit a“W”-shaped change coinci-ding with the variation of silver content in host rocks, Therefore, the oxygeniso tope geochemical method may be used to locate silver-rich orebod

关 键 词：银矿床 成矿年代 同位素 地球化学 

分 类 号：P618.520.2[天文地球—矿床学]