西昆仑大红柳滩二云母花岗岩地球化学和地质年代学研究及其地质意义

发布时间：2018-04-09 02:08

  本文选题：锆石U-Pb年龄　切入点：古特提斯洋　出处：《地球化学》2017年01期

【摘要】：大红柳滩花岗岩体位于康西瓦构造带南侧,甜水海地体的北部,是三十里营房-奇台达坂花岗岩带的主要岩体之一。该岩体具有明显的岩相分带,其东部-东北部为二长花岗岩,而西南部则为二云母花岗岩。本文对西南部二云母花岗岩进行了岩石学、元素和同位素地球化学及同位素年代学综合研究,同时对二长花岗岩进行了元素地球化学研究。二云母花岗岩明显富SiO_2、Al_2O_3和K_2O,贫MgO、CaO和TiO_2,属于高钾钙碱性系列岩石;二云母花岗岩的锆石LA-ICPMS U-Pb年龄为(209.6±1.5)Ma,与东部二长花岗岩年龄一致,表明两者是同一构造事件的产物。二云母花岗岩稀土总量低(∑REE 56.0~66.1μg/g),强烈亏损重稀土元素,Eu负异常不明显(δEu为0.81~0.98),低Y(~7μg/g)和Yb(~0.5μg/g),Sr/Y比值较高(~20),Nb、Ta和Ti含量低,Nb/Ta比值高(21~23),表明其源区有石榴子石和金红石残留,说明二云母花岗岩形成压力可能为1~1.5 GPa,是壳源物质部分熔融形成。研究显示,大红柳滩花岗岩形成于古特提斯洋闭合之后的同碰撞过程,是甜水海地体和西昆仑地体碰撞造山作用的产物,西昆仑造山带东部的古特提斯洋闭合以及碰撞造山时代可能晚于该造山带的中部和西部。
[Abstract]:The Dahongliutan granite body is located in the southern side of the Kangxiwa tectonic belt and the northern part of the sweet water Haitian body. It is one of the main rock masses in the 30-li barracks-Qidaidaban granite belt.The rock body has obvious lithofacies zonation, its east-northeast is monzonitic, and southwestern is dimica granite.In this paper, the petrology, element and isotope geochemistry and isotopic chronology of the monomorphite granites in the southwest of China are studied. At the same time, the elemental geochemistry of the monzogranites is also studied.The dimica granite is obviously rich in SiO-Sh _ 2Al _ 2O _ 3 and K _ 2O, MgO _ 2O _ (Cao) and Tio _ (2), belonging to the high-potassium calc-alkaline series rocks, and the zircon LA-ICPMS U-Pb age of the dimica granite is 209.6 卤1.5 Ma, which is consistent with that of the eastern monzogranite, indicating that the two rocks are the product of the same tectonic event.The amount of rare earth elements is low (鈭，

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