塔里木板块东南缘多坝沟金矿区花岗岩类年代学、地球化学特征及找矿意义

Geochemical Characteristics and Prospecting Significance of the Granites from the Duobagou Gold Deposit in the Southeast Tarim Basin

多坝沟金矿是近年来塔里木盆地东南缘新发现的一处具有一定规模的金矿床,矿区内出露的英云闪长岩侵入闪长岩中,金矿体主要赋存在英云闪长岩体内部的构造蚀变带中。笔者对矿区闪长岩、英云闪长岩和金矿石进行了岩石学和地球化学研究,闪长岩具有埃达克型花岗岩特征,英云闪长岩具有喜马拉雅型花岗岩特征,全岩δ^(18)O_(V-SMOW)‰为11.0‰~13.4‰。通过金矿石的LA-ICP-MS锆石U-Pb测年,获得具有多期峰值的变质年龄,^(206)Pb/^(238)U年龄值在422~1 284 Ma,这组年龄显示出闪长岩形成年龄为(497±13)Ma,英云闪长岩的形成年龄为(435.9±6.6)Ma,伴随构造热液活动的年龄,成矿年龄稍晚于英云闪长岩的年龄,矿区的2期岩浆活动与塔里木东南缘—阿尔金北缘早古生代2期主要成矿阶段一致,多坝沟金矿成矿阶段主要集中在第二阶段,表明在塔里木盆地东南缘寻找与早古生代形成的埃达克型和喜马拉雅型花岗岩有关金铜矿床具有一定的潜力。

The Duobagou gold deposithas been newly discovered in the southeastern margin of Tarim Basin witha certain scale, and the gold orebodies were mainly occurred in the tectonic alteration zone of tonalite that intrude into the diorite. In this paper, the petrological and geochemical features of diorite, tonalite and gold ore have been studied. The results show that the diorite has the properties of adakitic rocks,while the tonalite has the characteristics of the Himalayan type granite, and the δ^18OV-SMOW values of whole rocks range from 11. 0‰ to 13. 4‰. The LA-ICP- MS zircon U-Pb dating for gold ore has revealed multiphase peak metamorphism age, the obtained ^206Pt/^238u ges vary from 422 Ma to 1284 Ma, suggesting that the diorite and tonalite were formed at （497±13） Ma and （435.9±6.6） Ma, respectively. Followed the age of the tectonic hydrothermal activity, the metallogenetic age is later than the formation age of tonalite. The ages of two-phases magma activities in this mining area are consistent with two main metallogenic stages of Southeast Tarim-North Alty in Early Paleozoic. The formation of Duobagou gold deposit had correlation with the second metallo- genic stages, indicating that there is certainly potential to disepver Au-Gu deposits related adakitic and Himalayan-type granites in Southeast Tarim Basin.