摘要
赫章县天桥铅锌矿床位于扬子准地台西南缘的黔西北铅锌成矿区中部,是本区已发现的96处中、小型矿(床)点的典型代表。天桥铅锌矿床由三个矿体群组成,其金属资源量(Pb+Zn)超过0.2Mt。本文报道了该矿床矿石硫化物的硫和铅同位素组成及其稀土元素组成特征。矿石硫化物δ34SV-CDT值主要集中在8.4‰～14.4‰之间,总体具有δ34Spy>δ34Ssp>δ34Sga特征,表明成矿流体中硫已达到平衡。该矿床成矿流体中δ34S∑S值与不同时代地层中海相硫酸盐δ34S值(15‰)相近,表明成矿流体中硫来源于不同时代地层,为不同时代地层海相硫酸盐热化学还原(TSR)的产物。铅同位素组成相当均一,n(208Pb)/n(204Pb)值为38.875～39.057(平均38.945),n(207Pb)/n(204Pb)值为15.708～15.763(平均15.728),n(206Pb)/n(204Pb)值范围为18.481～18.544(平均18.516),与碳酸盐地层相近,在n(208Pb)/n(204Pb)—n(206Pb)/n(204Pb)和n(207Pb)/n(204Pb)—n(206Pb)/n(204Pb)图,落入碳酸盐地层范围内,表明铅来源于与矿物铅同位素组成相近的各时代碳酸盐地层。硫化物样品具有低ΣREE(<3×10-6)和负的Eu异常(0.13～0.88)特征。在稀土元素球粒陨石标准化配分模式图上,全部样品具有相似特征,且与地层中的黄铁矿(下石炭统大塘组C1d)、地层白云岩及蚀变围岩相比,具有一致的稀土配分模式和Eu负异常特征,表明成矿流体来源围岩及下伏碳酸盐地层。综合S、Pb同位素和REE地球化学特征认为该矿床成矿物质和成矿流体具有多来源特征,各时代地层均不同程度地为成矿提供物质和流体。
The Tianqiao Pb-Zn ore deposit,Hezhang County,is located in the southwest of the Yangtze craton,the center of the Northwestern Guizhou Pb-Zn metallogenic province,and is a representative of the Pb-Zn ore deposits in this area,where more than 96 ore （deposits） spots have been found.There are three mainly ore bodies in this deposit,whose Pb＋Zn reserves are more than 0.2 Mt.This paper analyzes the sulfur and lead isotopic compositions and REE contents of these ore-bodies.The data show that the ore minerals in these ore-bodies are enriched in heavy sulfur,with δ^3SV-CDT values concentrated between 8.4 ‰ and 14.4‰,and they have the feature of δ^3Spy〉δ^3Ssp〉δ^3Sga,which indicate the sulfur isotope in ore-forming fluids has attained equilibrium.The δ^3SV-CDT values of the deposits are similar to that of the sulfates from carbonate strata of different ages in the ore-field （15‰）,which suggests that the sulfur in the ore-forming fluids should be derived from the thermo-chemical sulfate reduction of sulfates from the sedimentary strata.The n （206^Pb）/n （204^Pb）,n （207^Pb）/n （204^Pb） and n （208^Pb）/n （204^Pb） values of the minerals are range from 18.481 to 18.544（average 18.516）,from 15.708 to 15.763（average 15.728） and from 38.875 to 39.057（average 38.945）,respectively,which mean the Pb isotope ratios are normal and similar to that of the host carbonate rocks of different ages strata,indicating that these rocks may provided metals together to the ore-forming metals.All samples have the low contents of ΣREE （〈3×10^-6）,and negative Eu anomaly（0.13～0.88）.On the chondrite-normalized REE patterns,the characteristic of sulfides are accord with the patterns of ores,altered dolostone rock,strata and the pyrite form C1d （the Datang Fm.）,which indicate that the ore-forming fluids maybe come from polycomponenet system,the different chronostratigraphic units maybe make an important contribution together,this accord with the S and Pb isotopes＇ result,that is the ore-forming fluids and ore-forming metals are poly-sources.
出处
《地质论评》
CAS
CSCD
北大核心
2010年第4期513-524,共12页
Geological Review
基金
国家重点基础研究发展计划(973计划)课题(编号2007CB411402)
国家自然科学基金资助项目(编号40573036)成果
关键词
S、Pb同位素
REE
成矿物质和成矿流体来源
天桥铅锌矿床
黔西北铅锌成矿区
sulfur and lead isotope
REE
the source of ore-forming fluids and ore-forming metals
the Tianqiao Pb—Zn ore deposit
Northwestern Guizhou Pb—Zn metallogrenic province
