赣东北地区中晚元古代的岩浆作用与构造环境

Middle-Late Proterozoic magmatism and its tectonic settings in northeastern Jiangxi Province

通过调研认为赣东北地区中晚元古代岩浆岩包括 :蓟县纪—青白口纪早期的斜长花岗岩、蛇绿岩套、拉斑玄武岩、钙碱性火山岩、强过铝花岗岩 ;青白口纪晚期的双峰式火山岩、岩浆混合岩、钾玄岩和基性岩墙 ;南华纪的碱长花岗岩和地幔岩等。它们分别是与B型俯冲作用有关的弧盆系、与造山后伸展的的裂谷系及非造山大地构造环境中产生岩浆岩组合 ,显示该区在蓟县纪—青白口纪早期发生两次B型俯冲作用和青白口纪晚期的大规模裂陷以及南华纪造山活动的已趋稳定。中晚元古代是一个分期明显、岩类完整、演化连续的造山旋回。

The Middle Late Proterozoic magmatic rocks in northeastern Jiangxi can be classified into three assemblages: the Jixianian early Qingbaikouan(1100～1000 Ma) plagiogranite,ophiolite,tholeiite,calc alkaline volcanic rocks and strongly peraluminous granite;the late Qingbaikouan(1000～900 Ma) bimodal volcanic rocks,magmatic migmatite,shoshonite and basic dikes and Nanhuaian(800～750 Ma) alkali feldspar granite and pyrolite. They are related respectively to B type subduction,post orogenic rifting and anorogenic settings,showing Jixianian early Qingbaikouan twice B type subduction and a large scale late Qingbaikouan rifting happened in this area where became stable during the Nanhuaian Period.The Middle Late Proterozoic magmatism and orogeny in this region make up a tectonomagmatic cycle.