西藏申扎县雄梅铜矿床的硫、铅同位素特征及其成矿意义

S,Pb isotopic characteristics of Xiongmei porphyry copper deposit in Tibet and their metallogenic significance

西藏雄梅斑岩型铜矿床位于班公湖-怒江成矿带中段的申扎县雄梅乡。矿区岩石类型由含矿花岗闪长斑岩、孔雀石化次生石英岩及含矿角岩化砂板岩组成。该矿床自2012年发现以来尚未开展成因方面的深入研究,作者旨在通过对矿区硫化物硫、铅同位素的系统研究,查明矿区的成矿物质来源,并通过与成矿带西段多龙矿集区斑岩铜矿成因的对比研究,对本地区的成矿潜力做出评价。测试结果表明,雄梅铜矿矿石硫化物的δ34S值为-2.5‰~6.1‰,硫同位素呈塔式分布,显示岩浆硫特征;铅同位素组成^(206)Pb/^(204)Pb、^(207)Pb/^(204)Pb、^(208)Pb/^(204)Pb比值分别为18.220~19.005、15.626~15.770、38.510~39.856,显示正常铅的特征。对铅同位素的源区分析,显示样品大致分布于上地壳端员。铅μ值在9.51~9.78之间,也表明硫化物样品具壳源的特征。与多龙矿集区成矿条件的对比研究,发现两者都是形成于造山带的碰撞后伸展环境,成矿物质来源上两者存在一些差异。良好的构造成矿环境,表明了本地区优越的找矿前景。

The Xiongmei porphyry copper deposit is located in the middle part of the Bangong Co-Nujiang metallogenic belt in Xiongmei Township,Xainza County,Tibet.Copper mineralization in the mining area is composed of orebearing granodiorite porphyry,malachitization secondary quartzite and ore-bearing hornfels sandy slate.The purpose of this study is to determine the source of ore-forming materials in this area by investigating the regional sulfur and lead isotopes.δ^（34）S values of the sulfide range from -2.5‰ to 6.1‰ with tower distribution,indicative of a magmatic source.The ^（206）Pb/^（204）Pb,^（207）Pb/^（204）Pb and ^（208）Pb/^（204）Pb ratios of Xiongmei ore-bearing sulfide range from 18.220 to 19.005,15.626 to 15.770 and 38.510 to 39.856,respectively,which fall in or near the upper crustal area on the Pb isotope source discrimination diagram.The μ values of lead are form 9.51 to 9.78,indicating a crustal source.Based on a comparative study of previous work in the Duolong mining area,the authors hold that both the Duolong mining area and the Xiongmei copper deposit were formed under an extension environment of closure/post-collision of the Bangong Co-Nujiang Meso-Tethys Ocean,indicative of a good ore prospecting potential in the Xiongmei area.