广西凤凰山浊积岩型银矿床铅同位素地球化学──成矿物质来源  

LEAD ISOTOPE GEOCHEMISTRY OF TURBIDITE-TYPE SILVER DEPOSIT AT FENGHUANGSHAN, GUANGXI, CHINA

作　　者：李泽琴[1] 董宝林[2] 雷英凭 陈海 林德 

机构地区：[1]中国科学院地球化学研究所,贵阳550002 [2]广西第四地质队,南宁530031

出　　处：《矿物学报》1998年第4期473-482,共10页Acta Mineralogica Sinica

基　　金：中国地质矿产部8.5定向科研项目

摘　　要：首次对广西西大明山凤凰山银矿床及相关地质体进行系统铅同位素地球化学研究。研究结果表明，凤凰山银矿床成矿物质来源具有多源性。成矿物质，如Ag、Fe、Mn、S、SiO2等，主要来自赋矿层寒武系上统黄洞口组（h）浊积岩；而Ph、Zn、Ag、Ca及其相关元素主要来自下泥盆统莲花山组岩石及赋存于泥盆系与寒武系接触带部位的铅锌矿化富集体，或与其同源的矿源物质，并由此提出凤凰山银矿床系两种成分不同的成矿热液流体叠加成矿的观点。研究结果还表明，该区深部隐伏花岗岩基及其浅成岩相石英斑岩脉与银矿化未显示出有铅同位素的亲缘关系。The Fenghuangshan silver deposit is hosted in the Cambrian turbidites. The lead iso-topic compositions of alabandite, pyrite, galena,sphalerite and quartz in the deposit fall into two different isotopic groups. Alabandite, pyrite and quartz form the lower cluster around 208Pb/204Pb=39. 21, 207Pb/204Pb=15. 80, and 206Pb/ 204Pb=18. 73, Whereas galena and sphalerite form the upper cluster with a long array,208Pb/204Pb = 39. 791 - 39. 019,207Pb/204Pb =16. 065 - 15. 793, and 206Pb /204Pb =18. 532-18. 942. The small cluster of alabandite, pyrite and quartz approximately corre-sponds to the isotopic composition of the Upper Cambrian Huangdongkou Formation (h) which hosts the silver deposit. The upper cluster of galena and sphalerite shows the relationship with the isotopic compositions of the Lower Devonian (D,1), and lead-zinc deposits and occurrences mainly hosted at the contact of Devonian with Cambrian in the regional area. The characteristics of lead isotopic composition indicate that there are two minerallzing solutions, represented by the two lead clusters: the lower cluster solution circulated dominantly in the basement fau1t system of Cambrian and mainly extracted Ag, Mn, Fe, S and Si from the Huangdongkou Formation (h), whereas the upper cluster solution was dominated in the cover fault system of Devonian and obtained Pb,Zn and Ag from the Lower Devonian (D11 ), and the lead-zinc deposits and occurrences. The two overprinted and mixed solutions in the conjunctions of the basement fault system with the cover fault system, where higher grade silver ore bodies were formed. This study also shows that there is no relationship in lead isotopic composition between quartz porphyry veins and comagmatic gran-ites with silver mineralization.

关 键 词：浊积岩型 银矿床 铅同位素 矿质来源 地球化学 

分 类 号：P618.520.4[天文地球—矿床学]