澳大利亚爱博(Abra)铅-铜多金属矿床成矿流体性质及对矿床成因的制约  

Characteristics of the Ore-forming Fluids and its Constraints on the Genesis of Abra Pb-Cu Deposit, Western Australia

作　　者：李洁兰[1] 王明艳 何玲 

机构地区：[1]中南大学地球科学与信息物理学院,湖南长沙410083 [2]中国五矿湖南有色金属控股集团矿山管理部,湖南长沙410015 [3]Abra Mining Pty Ltd, West Perth, WA 6005 [4]华北地质勘查局综合普查大队,河北燕郊065201

出　　处：《大地构造与成矿学》2014年第3期598-608,共11页Geotectonica et Metallogenia

基　　金：国土资源部“2010年度境外矿产资源风险勘探财政补贴”项目;国家科技攻关计划课题(编号:2003BA612A-05);国家自然科学基金项目(批准号:41002027)资助

摘　　要：爱博（Abra）Pb-Cu矿床位于西澳洲Bangemall盆地中,产于中元古界Edmund群浅海相碎屑岩地层中,矿体上部呈层状、似层状,下部呈网脉状。由于该矿床地质特征复杂,研究程度不高,矿床成因和成矿流体来源尚存在争议。本文拟探讨成矿流体的性质、来源及演化。流体包裹体显微测温研究表明矿石中石英所捕获的流体包裹体为两相H2O溶液包裹体、含CO2和CH4的流体包裹体、含子矿物三相包裹体等3种类型。上部赤铁碧玉岩段和磁铁石英岩段矿石中流体包裹体均一温度为162.0-194.7℃,盐度为5.8%-13.0%;下部绿泥石化石英砂岩段均一温度为172.7-250.7℃,盐度为7.0%-17.0%。各岩性段中温度和盐度变化都较大,指示有多期流体的存在。锶、硫同位素研究表明：成矿流体为海水与变质水的混合,成矿物质主要来自围岩地层,围岩岩性制约着矿床类型。由盐度和均一温度计算出流体密度为0.885-1.012 g/cm^3,成矿深度为0.22-1.39 km,因此确定爱博矿床为一中低温热液矿床。The Abra Pb-Cu deposit was discovered in 1981 in the Bangemall Basin, north-western of Western Australia. The ore body is hosted in the Meso-proterozoic Edmund Group shallow marine clastic sequences. The layered ores present in the upper section, and the veined ores occur in the lower section. Because of its complicated geology and lack of detailed investigations, the genesis of the Abra deposit is debatable. In this paper, the characteristics, origin and evolution of the ore-forming fluid are investigated. Based on the results of micro-thermometry, the fluid-inclusions in the quartz can be divided into three groups： two phases H2 O fluid-inclusions, fluid inclusions with CO2 and CH4, and fluid inclusions with mineral crystals. The homogenization temperatures of these fluid inclusions in the upper hematite jasperite and magnetic quartzite vary from 162.0 ℃ to 194.7 ℃, and the salinities vary in the range of 5.8%-13.0% wNaCl; while the homogenization temper- atures of the inclusions in the lower chloritized quartz sandstone vary from 172.7 ℃ to 250.7 ℃, and the salinities vary within the range of 7.0%-17.0% wNaCl. The wide range of homogenization temperatures and salinities in different sections demonstrated that there was more than one phase of ore-forming fluid activities. The data of S and Sr isotopes show that the ore-forming fluid was the mixture of sea water and metamorphic water, and the ore-forming elements were leached from the host strata. And the host rocks have contributed to the ore deposit formation. The calculated densities of the fluid inclusions are from 0.885 g/cm^3 to 1.012 g/cm^3 based on the homogenization temperatures and salinities. The theoretical ore forming depth is around 0.22 to 1.39 km below the surface, and the Abra deposit can be categorized as a meso- and epithermal deposit.

关 键 词：爱博矿床 流体包裹体 锶同位素 硫同位素 西澳州 中低温热液矿床 

分 类 号：P611.1[天文地球—矿床学]