粤北白石坳地区印支期过铝质花岗岩成因及其大地构造意义

Petrogenesis and Tectonic Implication of the Indosinian Peraluminous Granites in Baoshiao Region, NorthernGuangdong

本文选取粤北白石坳地区广泛出露的印支期过铝质花岗岩为研究对象,通过岩石地球化学、同位素地球化学及区域大地构造学等方法,分析了其物质来源、成因机制及区域构造演化。本文认为白石坳地区印支期过铝质花岗岩是古元古代地壳组分经部分熔融的产物,原岩为泥质岩和杂砂岩,形成于同碰撞构造环境。其成因模式为印支期的区域上陆-陆碰撞致使华南地区地壳由伸展机制向挤压机制转换,地壳加厚作用导致下地壳密度的增大,岩石圈重力不稳定而发生拆沉作用,引起地幔软流圈物质的上涌,从而促使富硅铝地壳物质发生大规模不同程度的部分熔融形成过铝质花岗岩。

The Indosinian peraluminous granites widely exposed in Baishi region, northern Guangdong Province, are selected as the research object in this paper. By the method of rock geochemistry, isotope geochemistry and regional geotectonics, the paper in detail analyses the material source and petrogenesis of the Indosinian granite, which could reflect the regional tectonic evolution.The Indosinian peraluminous granites, which consist of mudstone and sandstone, were the product of partial melting of the Paleoproterozoic crust. The Regional land-land collision caused the conversion from extension to extrusion of crust in south China during Indo Chinese epoch. And the peraluminous granites in Baishi region were formed in the collisional tectonic environment, which resulted in the rise of crustal thickness and density. The upwelling of asthenospheric material in the mantle, caused by delamination effect of lithosphere, provided the needed heat of crustal partial melting for the formation of peraluminous granites.