新疆多拉纳萨依金矿一带花岗岩类形成时代及其对金矿成矿作用的制约

新疆阿尔泰造山带西南缘分布有多拉纳萨依、赛都、哲兰德等大中型金矿床,近年又发现沃多克等小型金矿.这些金矿主要赋存于糜棱岩化石英闪长岩中,岩石地球化学特征表明沃多克和多拉纳萨依金矿含矿石英闪长岩特征基本一致,属同一期岩浆活动的产物,而明显不同于两矿床之间的萨热乌增英云闪长岩.沃多克金矿含矿石英闪长岩和萨热乌增英云闪长岩LA-ICP-MS锆石U-Pb年龄分别为(299.4±4.1) Ma和(317.7±1.5) Ma.二者分别属于后造山和后碰撞花岗岩.沃多克含金石英闪长岩年龄限定了多拉纳萨依一带金矿形成时代不早于300 Ma,结合前人的研究成果分析,表明其主要成矿时期为290 Ma左右.萨热乌增等岩体的形成早于金矿形成时代,金的成矿作用与该期大规模花岗岩体的侵位无关.

The age of the granitoids in the Dolanasayi gold ore district in Xinjiang and its constraints on gold mineralization

Abstract: Medium- to large-sized gold deposits, such as Dolanasayi, Saidu and Zhelande, are distributed along the southwestern margin of the Altay orogenic belt. In recent years, exploration work has let to the discovery of the Vodok deposit and some other small-sized gold deposits in this belt. These gold deposits mainly occur in the mylonitic quartz diorite. The quartz diorites in the Vodok and the Dolanasayi gold deposits share similar geochemical features, and they are genetically related to a common magmatic activity. On the other hand, the Sarewuzeng tonalite outcropped between the the Vodok and the Dolanasayi gold deposits show very different petrography and structure. LA-ICP-MS U-Pb zircon ages reveal that the gold-bearing quartz diorite in the Vodok deposit and Sarewuzeng tonalite crystallized at (299.4±4.1) Ma and (317.7±1.5) Ma, respectively, indicating that the quartz diorite and the tonalite were formed at post-orogenic and post-collision settings individually. The age of gold-bearing quartz diorite in the Vodok deposit constrains the lower limit of the formation age of the Dolanasayi gold deposit. In combination with previous studies and the age obtained in this study, the mineralization of the Vodok and the Dolanasayi gold deposits most probably took place at about 290 Ma. The Sarewuzeng tonalite was emplaced earlier than the gold mineralization and was of no significant relationship with gold mineralization in this area.