哀牢山区太忠—李仙江带上二叠统(P_2)弧火山岩

ARC VOLCANIC ROCKS OF LATE PERMIAN (P 2) IN TAIZHONG LIXIANJIANG ZONE,AILAOSHAN AREA

太忠—李仙江带弧火山岩位于哀牢山浅变质带西侧，沿阿墨江—李仙江深大断裂续延伸达３００ｋｍ。火山岩形成时代为晚二叠世（Ｐ２），以火山碎屑岩为主（Ｅｐ为０．７～０．９）。拉斑系列，钙碱性系列及少量的钾质碱性系列并存，化学成分表现为高Ａｌ低Ｔｉ，产出环境为陆缘弧。此外，该带火山岩由东往西岩石系列还表现出由拉斑→钙碱性→钾质碱性的变化趋势，Ｋ２Ｏ含量，ΣＲＥＥ，Ｕ，Ｔｈ等的丰度表现出不断增加的特点。

The volcanic rocks in Taizhong Lixianjiang zone are tectonically situated the west of Ailaoshan epimetamorphic belt and right along stretching about 300 kilometres along Amojiang Lixianjiang deep fault.The volcanic rocks formed in late Permian(P 2) and mainly belong to pyroclastic rocks(E p=0.7￣0.9).which contain tholeiitic,calc alkaline and few K alkaline series.Its characteristics of petrochemical composition are obvious high in Al and obvious low in Ti,which indicative of formed in the marginal arc tectonic setting.In addition,from east to west,the volcanic rock series have revealed a changing trend from tholeiitic through Ca alkaline to K alkaline series,and K 2O contains,the abundances of ΣREE,U,Th gradually increasing.These facts indicate that the volcanic rocks in the belt resulted from Ailaoshan oceanic basin plate to subducted westwards below the Nanping Simao massif during Late Permian.