东昆仑五龙沟金多金属矿集区晚二叠世-三叠纪岩浆岩年代学、地球化学及其构造意义

Geochronology and geochemistry of the Wulonggou orefield related granites in Late Permian-Triassic East Kunlun: Implication for metallogenic tectonic

五龙沟金多金属矿集区晚二叠世-三叠纪岩浆岩较为发育,花岗岩与金及多金属成矿关系不明,岩石成因,成岩成矿动力学背景仍然存在分歧。本文对该矿集区出露的侵入岩展开详细的年代学和地球化学研究。通过LA-ICP-MS锆石U-Pb定年,获得花岗闪长岩体、英云闪长岩体、石英闪长玢岩脉年龄分别为244.1±2.0Ma、241.9±0.5Ma、211.5±0.4Ma。岩石地球化学特征表明五龙沟矿集区侵入岩整体为一套高钾钙碱性岩石系列,具有轻稀土富集,富集大离子亲石元素(如Rb、Ba、Th),高场强元素出现不同程度的亏损特征,源区由下地壳角闪岩相部分熔融,演化过程中经历了分离结晶作用,岩浆为壳源岩浆与幔源岩浆在不同比例下混合的产物。基于本文最新研究成果及综合前人资料,构筑了五龙沟矿集区晚二叠世-三叠纪成岩成矿年代学格架,区内岩浆活动分为两期,早期260～235Ma,晚期225～210Ma,其中峰值分别为245Ma和220～215Ma;多金属矿化时代与早期岩浆岩活动一致,金成矿与早晚两期岩浆活动密切相关。五龙沟矿集区金及多金属成矿构造环境早期形成俯冲-碰撞转换阶段,晚期为后碰撞伸展。

The granite is well developed in the Wulonggou area,in Late Permian-Triassic East Kunlun. In order to study the genesis and tectonic of the rocks,a detailed geochronology and geochemical study were carried out in the intrusive rocks. The U-Pb zircon ages by LA-ICP-MS of the granodiorite,tonalite and quartz diorite porphyrite is 244. 1 ± 2. 0 Ma,241. 9 ± 0. 5 Ma and 211. 5 ± 0. 4 Ma,respectively. The chemical features show that the magmatic rock in the Wulonggou orefield is a series of high-K calc-alkaline rocks,and belong to the enrichment LREE type. The granite enriched in large ion lithophile elements（ such as Rb,Ba and Th）,but depletion of high field strong elements with different degrees. And the granite source region is the partial melting of the amphibolite phase and in the process of evolution with experienced crystallization. The magma has the same source region,which is the mixed product of crustal and mantle magma but different ratios. As a result,the gold and polymetallic metallogenic tectonic setting of Wulonggou orefield is early subduction and late post-collision extension. Through the research and collection of data,we build the Late Permian-Triassic chronology framework of Wulonggou intrusive rock. The magmatic activity in the area is divided into two periods,the early is 260 ~ 235 Ma,the later is 225 ~ 210 Ma,which 245 Ma is the main peak and the late peak is 220 ~ 215 Ma. The polymetallic mineralization age is consistent with the early magmatic activity,mainly occurring in 240 ~ 245 Ma and gold mineralization closely related late. The Wulonggou gold and polymetallic mineralization tectonic setting is subduction-collision transformation in the early stage,and the latter is post-collision extension.