东昆仑祁漫塔格地区库德尔特金矿区花岗闪长岩的时代、成因及其构造意义

Age,Petrogenesis and Tectonic Significance of Granodiorite in Kudeerte Gold Deposit,Qimantage Area,East Kunlun

库德尔特金矿床是东昆仑祁漫塔格新发现的一处中型金矿床,金矿赋存于花岗闪长岩中。通过对花岗闪长岩开展岩石地球化学、锆石U-Pb年代学和Hf同位素研究,探讨该矿床成岩时代、成因类型和构造环境。研究结果显示:花岗闪长岩为一套准铝质高钾钙碱性岩石系列,呈现轻稀土富集的右倾分配模式,具有较明显的负Eu异常,富集大离子亲石元素(Rb、K)、活泼不相容元素(Th、U)和LREE元素,相对亏损高场强元素(Nb、Ta、Ti、P)、HREE元素和Sr元素,成岩年龄为(242.9±1.3)Ma。结合前人研究成果,认为库德尔特花岗闪长岩是在中三叠世大洋板块俯冲与碰撞转换环境中形成的I型花岗岩。

The Kudeerte gold deposit is a medium-sized gold deposit newly discovered in the western section of East Kunlun.Granodiorite is the host rock of gold deposit,but the petrogenesis,tectonic background and its relationship with mineralization are still unclear.The above questions have been discussed by studying the petrogeochemistry,U-Pb zircon geochronology,and Hf isotopes of the granodiorite in Kudeerte.The petrogeochemical characteristics show that the Kudeerte granodiorite is a set of quasi-aluminum-potassium basalt rocks,showing a right-inclined distribution pattern of light rare earth enrichment,with obvious negative Eu anoalies.The relative enrichment of elements such as large-ion lithophile elements Rb and K,the active incompatible elements Th and U,the depleted high field strength(Nb,Ta,Ti),HREE,and Sr elements,with the characteristics of shell-derived magma.Zircon LA-ICP-MS U-Pb dating showes that the age of granodiorite was(242.9±1.3)Ma(n=20,MSWD=0.65).The Kudeerte granodiorite is aⅠ-type granitic rock series of aluminous high potassium calc-alkaline rocks formed in the Middle Triassic.The tectonic environment is the transition environment between subduction and collision of oceanic plate.