Huanggang Intrusive Complexin Northern Tongbai Area:Island-Arc Tectonic Environment and Its Geological Significance

The Huanggang intrusive complex in northern Tongbai area was formed in Early Paleozoic. It mainly consists of ultra basic, basic, intermediate and acid rocks, dominated by intermediate and basic rocks. The complex belongs to calc alkaline series. Geochemical characteristics of major and trace elements show that the complex was derived from the fractional crystallization of co source magma. It is suggested that the complex was formed in island arc tectonic environment and was closely related to the northward subduction of the Erlangping back arc basin. Thus, the subduction of the back arc basin can induce the island arc type magmatism similar to the one formed in the setting of ocean plate subduction.

桐柏北部二朗坪蛇绿岩片中花岗岩:地球化学、成因及对地壳深部物质的指示

本文对产于桐柏北部二朗坪蛇绿岩片中加里东期桃园岩体和燕山期梁湾岩体花岗岩进行了系统的主量元素、微量元素和Ｓｒ－ Ｎｄ－ Ｐｂ 同位素地球化学研究。研究表明，桃园花岗岩与二朗坪基性岩具有相同的岩浆来源，两者均来自于亏损地幔源区，其中桃园花岗岩浆来自于基性岩浆的分异结晶，是与蛇绿岩共生的岩浆侵入单元，形成于与洋壳消减作用有关的弧后盆地环境，从而支持了二朗坪蛇绿岩属弧后盆地型蛇绿岩的认识。梁湾花岗岩的岩浆物质来自于南部（南秦岭）陆壳物质的部分熔融，指示在桐柏北部（北秦岭）的深部地壳中含有南秦岭陆壳物质，从而进一步证明了早期南秦岭陆壳向北俯冲叠置于北秦岭块体之下的认识。