新疆西昆仑独尖山地区二云母二长花岗岩岩石地球化学、锆石U-Pb年龄与Hf同位素特征

张宇; 唐名鹰; 何玉良; 崔霄峰; 张东阳; 朱明帅

doi:10.12029/gc20200714001

新疆西昆仑独尖山地区二云母二长花岗岩岩石地球化学、锆石U-Pb年龄与Hf同位素特征

Geochemistry, zircon U-Pb age and Hf isotopic characteristics of two-mica monzonitic granites in Dujianshan area of Western Kunlun, Xinjiang

摘要

摘要:
研究目的 为了进一步了解西昆仑松潘—甘孜陆块西北缘巴颜喀拉弧后盆地的构造演化。
研究方法 对西昆仑东缘独尖山地区二云母二长花岗岩进行了岩相学、地球化学、LA-ICP-MS锆石U-Pb年龄和Hf同位素测试。
研究结果 LA-ICP-MS锆石年代学研究揭示独尖山地区二长花岗岩成岩年龄为(219.9±1.2)~(227.1±1.5)Ma，为晚三叠世花岗岩。岩石主量元素、微量元素和Hf同位素分析结果揭示该二长花岗岩属高钾钙碱性系列，准铝质—弱过铝质，具岛弧和同碰撞花岗岩特征，物质来源具有壳幔物质混合的特点。
结论结合区域大地构造演化，推测独尖山地区在晚三叠世末期处于碰撞后伸展环境，早期洋-陆俯冲阶段形成的岛弧和同碰撞物质通过部分熔融在研究区内形成了后碰撞花岗岩。

Abstract:
This paper is the result of geological survey engineering.
Objective The study aims to further understand the tectonic evolution of the back-arc basin of Bayankera, the northwestern margin of Songpan-Ganzi block, Western Kunlun.
Methods In this paper, the authors present petrographical, lithogeochemical, LA-ICP-MS zircon U-Pb geochronological and Hf isotopic data for the two-mica monzogranite in Dujianshan.
Results LA-ICP-MS zircon geochronology study reveals that the monzogranites in the Dujianshan area crystallized at (219.9±1.2)-(227.1±1.5) Ma, indicative of the Late Triassic plutons. The results of major elements, trace elements and Hf isotope reveal that the monzogranites are metaluminous-weakly peraluminous rocks, belongs to the high potassium calcium alkaline series and exhibit characteristics of island arc and collisional granites. The source rocks of granites were generated from partial melting of a mixture of crust-mantle materials.
Conclusions Combined with the regional tectonic evolution, it is speculated that the Dujianshan area is in a post collision extension environment at the end of the Late Triassic, and the island arc and syn-collision materials formed in the early ocean continent subduction stage partially melted to form post collision granite in the area.

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