川西雀儿山花岗杂岩体锆石U-Pb年龄、地球化学特征及其成矿专属性

Zircon U-Pb ages and geochemistry of Que'ershan granitic complex in western Sichuan and metallogenic specialization

川西义敦岛弧碰撞造山带北段雀儿山复式花岗杂岩体的年代学和全岩地球化学研究表明,雀儿山杂岩体主要由花岗闪长岩、二长花岗岩和正长花岗岩组成。锆石LA--ICP--MS U--Pb测年结果显示,该岩体中的花岗闪长岩形成时代为晚三叠世(224±3 Ma),二长花岗岩则形成于早白垩世(102±1 Ma)。地球化学数据表明,晚三叠世花岗闪长岩为火山弧岩石序列,形成环境为碰撞前俯冲环境;早白垩世二长花岗岩和正长花岗岩为后碰撞岩石序列,形成于造山期后板内或陆内环境。结合区域地质资料,认为雀儿山杂岩体为印支期—燕山期义敦岛弧碰撞造山带经历俯冲--碰撞--隆升过程中的产物。

The study of geochronology and whole-rock geochemistry in Que＇ershan granitic complex from the northern Yidun arc collision-orogenic belt,western Sichuan shows that Que＇ershan complex consists mainly of granodiorite,monzogranite and syenogranite.The results of zircon LA--ICP--MS U--Pb data indicate that the granodioriteof this granitic complex formed in the Late Triassic（224 ± 3 Ma）,and the monzogranite was emplaced in the Early Cretaceous（102 ± 1 Ma）.The geochemical data suggest that the Late Triassic granodiorites belong to the volcanic arc granite series,and might form in a pre-collision subduction setting,whereas the Early Cretaceous monzogranites and syenogranites belong to post-collisional rock serious,and probably formed within plate or continent during the post-orogeny stage.In combination with regional geological data,the authors propose that the Que＇ershan granitic complex were results of subduction-collision-uplift of Yidun arc collision-orogenic belt during Indosinian-Yanshanian period.