广西大瑶山古罗碱性辉长岩体LA-ICP-MS锆石U-Pb年龄、岩石学、地球化学及其构造意义

古罗碱性辉长岩体包括古罗、黄羌冲两个侵入体,主要由辉长岩、石英辉长岩(或石英闪长岩)组成。岩石以富碱、富集大离子亲石元素(LILE)、轻稀土元素(LREE)和高场强元素(HFSE),无Nb、Ta异常,是典型的板内钾玄岩。对古罗辉长岩体进行了高精度的LA-ICP-MS锆石U-Pb定年,获得石英辉长岩的206Pb/238U加权平均年龄为165.63±0.95 Ma。研究认为古罗碱性辉长岩体形成于中侏罗世,属典型的板内钾玄岩,形成于大陆地壳伸展拉张减薄的构造背景,为燕山期早期华南后造山阶段的地质记录。

Zircon LA-ICP-MS U-Pb age,petrog-raphy,geochemistry and tectonic implications of the Guluo alkaline gabbroic rock in the Dayaoshan,Guangxi

Guluo alkaline gabbroic magmatic rocks including Guluo and Huangqiangchong intrusive rocks are comprising of gabbro, quartz-gabbro（or quartz-diorite）. These rocks are enriched in alkalies, LILE, LREE and HFSE, characteristed by no Nb and Ta anomalies, which indicates belongs to typical intrapate-shoshonite series.Zircon LA-ICP-MS U-Pb dating of Guluo alkaline gabbroic rocks yields the206Pb/238 U age of 165.63±0.95 Ma.The geochronology data suggests that Guluo alkaline gabbroic rocks as typical intrapate-shoshonite series was formed in the Middle Jurassic Period, and indicated that the magma was generated in the tectonic settings of continental crust extension and thinning, which records post-orogenesis event of South China in the Early Yanshannian period.