大别造山带核部两处燕山期花岗岩体的成因演化模式

根据对大别山核部牛占鼻和木子店两处燕山期花岗岩体进行的元素地球化学分析和岩浆演化的模拟分析,结果显示,牛占鼻和木子店两处燕山期花岗岩体都具相似的主量和微量元素特征,它们和天堂寨的同期花岗岩具有相似的成因模式和源岩,其主要的形成演化模式可能是增厚的下地壳发生部分熔融所致,源岩可能是太古代TTG片麻岩或奥长花岗岩。同时这样的结果也说明大别山燕山期花岗岩的成因与造山后的地壳叠覆、基性岩浆底侵和随后的地壳拆沉作用具有密切的联系。模拟中也发现有的样品具有异常的地化特征,尤其对是Na2O/K2O>1的花岗岩的模拟结果不理想,暗示可能存在不同的源岩和岩浆演化作用。

The geochemical characteristics and genesis of two Yanshanian granitoids in the core of Dabie orogenic belt and their tectonic applications

Based on the analysis on the geochemical characteristics of the granites in Niuzhanbi and Muzidian and the comparison with the granites in Tiantangzhai,it's concluded that the granites in Niuzhanbi and Muzidian are similar in main and trace elements.And it's highly possible that the granites in Niuzhanbi and Muzidian have the same source and genesis as the Yanshanian granites in Tiantangzhai,whose genesis is the low thickened crust that was formed by the collision between the Yangtze Plate and the North China plate.Combining with previous researches,it's possible that the TTG gneiss or trondhjemite is the material source for the granites in these locations.Furthermore,it shows the causal relationship between the crust-thickening in the post-collision period,the mafic magmaintrusion,and the delamination of the low crust and the genesis of Yanshanian granitoids in the core of Dabie orogenic belt.Considering some samples that don't fit this model,especially the samples with Na2O/K2O>1,it's possible for Yanshanian granitoids that there is another genesis and magma evolution model in Dabie orogenic belt.