景洪变质岩带中绿片岩特征及其构造环境

澜沧江断裂以东的景洪变质岩带中的绿片岩分布较为广泛,其原岩为基性火山岩。主量元素表现为低碱、低钛、低FeO*/MgO、富纳、稀土配分曲线呈平坦型。微量元素比值蛛网图上,不相容元素亦具平坦型特点。显示作为绿片岩原岩的基性火山岩属大洋拉斑玄武岩。经构造环境判别,进一步证实为N型洋中脊玄武岩,其形成与原特提斯澜沧江洋密切相关。

CHARACTERISTICS OF GREENSCHIST IN JINGHONG METAMORPHIC ZONE AND ITS STRUCTURAL ENVIRONMENT

The greenschist is widely distributed in the Jinghong metamorphic zone east of Lancangjiang fault, whose original rock is basic volcanic rock. The major element is characterized by low alkalinity, low Ti, low FeO/MgO, rich in Na and flat REE distribution curve. On the web diagram of trace element ratio, the conflicting element is also characterized by the flat type, which shows the basic volcanic rock as the original rock of greenschist belongs to the oceanic tholeiite. And it is the mid-oceanic ridge basalt of N-type, which has been confirmed by the discrimination of structural environment. Its formation is close related with the original Tethys Lancangjiang ocean.