川西雀儿山印支晚期岩浆事件:花岗闪长岩锆石U-Pb年代学证据

Late Indosinian Magmatic Events of Queershan Area,Western Sichuan Province: Evidence from U-Pb Zircon Dating of Granodiorite

雀儿山花岗岩体位于川西义敦岛弧北端,由似斑状花岗岩、伟晶质和细晶质花岗岩脉以及岩体边部的花岗闪长岩组成。这些花岗闪长岩石属于高钾钙碱性的花岗岩石系列,其稀土元素配分曲线呈向右缓倾型,轻稀土元素富集明显,Eu负异常明显,表明岩浆演化过程中经历了部分斜长石结晶分离过程。花岗闪长岩LA-ICP-MS锆石U-Pb年龄值为217.2~223.6 Ma,表明其成岩年龄为晚三叠世。构造环境判别图解显示,川西雀儿山花岗闪长岩形成于与甘孜—理塘结合带向西俯冲有关的火山弧构造环境。

Queershan granitoids, located in the north of Yidun island arc belt, western Sichuan province, consist chiefly of porphyry-like granites, pegmatic and aplitic ganites as veins, and granodiorites distributing in the margin of the plutonic intrusion. These granitoids in the Queershan pluton have high-K calc-alkaline granite series, and rare earth element distribution curve reveals the characteristics of right deviation, Light rare earth element enrichment with negative Eu anomalies. It has experienced part of plagioclase crystallization separation process in magma evolution. LA-ICP-MS zircon U-Pb dating result of granodiorite was from 217.2 to 223.6 Ma, which represented diagenetic age was late Triassic epoch. Tectonic environment discrimination diagram shows Queershan granodiorite pluton formed in volcanic island arc environment in related to Ganzi - Litang belt subduction in the west.