内蒙古拜仁达坝及维拉斯托银多金属矿床的硫和铅同位素研究  

Sulfur and lead isotopic compositions of Bairendaba and Weilasituo silver-polymetallic deposits,Inner Mongolia

作　　者：江思宏[1] 聂凤军[1] 刘翼飞[1] 云飞[1] 

机构地区：[1]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

出　　处：《矿床地质》2010年第1期101-112,共12页Mineral Deposits

基　　金：中央级公益性科研院所基本科研业务费专项资金(编号:K0704);全国危机矿山项目(编号:20089948);地质大调查项目(编号:1212010911029)的资助

摘　　要：拜仁达坝和维拉斯托是近年来在内蒙古东部地区发现的2个大型银多金属矿床,文章对其开展了硫和铅同位素研究。结果表明,拜仁达坝矿床矿石中硫化物的δ34S值为-4.0‰～+1.6‰,维拉斯托矿床矿石中硫化物的δ34S值为-0.8‰～+2.0‰,与岩浆热液型矿床的硫同位素值接近,表明这2个矿床中的硫主要来自岩浆。拜仁达坝矿区43件金属硫化物的206Pb/204Pb值为18.333～18.515,207Pb/204Pb值为15.532～15.656,208Pb/204Pb值为38.057～38.610;维拉斯托矿区20件金属硫化物的206Pb/204Pb值为18.304～18.377,207Pb/204Pb值为15.520～15.610,208Pb/204Pb值为38.112～38.435。拜仁达坝东矿区矿石中的铅同位素组成与维拉斯托矿区相似,变化范围小,相对贫放射性铅同位素,并且均为混合铅。矿石中的铅可能来自围岩地层及深源岩浆。The Bairendaba and Weilasituo ore deposits are two silver-polymetallic deposits discovered in eastern Inner Mongolia in recent years. Researches on the sulfur and lead isotopes of the sulfides from these two deposits are reported in this paper. It is shown that the δ^34S values of the sulfides from the Bairendaba and the Weilasituo deposit vary from -4.0‰ to ＋1.6‰ and from -0.8‰ to ＋2.0‰,respectively,close to the sulfur isotopic composition of the magmatic hydrothermal fluid,suggesting that the sulfur in both the Bairendaba and the Wei-lasituo deposit were mainly derived from the magma. Lead isotope studies of 43 sulfide separates from the Bairendaba deposit and 20 sulfide separates from the Weilasituo deposit demonstrate that the lead isotopic composition of sulfides from ores in these two deposits is characterized by low radiogenic values and narrow ranges of ratios,with ^206Pb/^204Pb ranging from 18.333 to 18.515 and from 18.304 to 18.377 respectively,^207Pb/^204Pb from 15.532 to 15.656 and from 15.520 to 15.610 respectively,and ^208Pb/^204Pb from 38.057 to 38.610 and from 38.112 to 38.435 respectively. It is thus inferred that the lead in ores from these two deposits might have mainly come from the wall rocks of gneiss and deep magma.

关 键 词：地球化学 硫同位素 铅同位素 成矿物质来源 拜仁达坝 维拉斯托 内蒙古 

分 类 号：P618.52[天文地球—矿床学]