滇西南下景张地区花岗岩岩石特征与构造环境

THE LITHOLOGIC CHARACTER AND TECTONIC ENVIRONMENT OF GRANITE IN XIAJINGZHANG AREA,SW YUNNAN

滇西南下景张地区花岗岩属于临沧花岗岩中南段的一部分,位于昌宁-孟连结合带与澜沧江火山弧之间,其主要岩石类型为黑云二长花岗岩,另有少量花岗闪长岩和钾长花岗岩。前者获锆石U-Pb年龄232.9±1.4Ma。该黑云二长花岗岩为“高硅、富钾、铝过饱和”的“S”型花岗岩,为碰撞晚期-碰撞后构造环境,属昌宁-孟连洋盆向东俯冲,于晚三叠世碰撞晚期形成产物。

The granite in Xiajingzhang area,SW Yunnan belongs to a part of middle S section of Lincang granite,between Changning-Menglian conjunction zone and Lancangjiang volcanic arc.The main rock type is biotite adamellite with a little of granodiorite and kalifeldspare granite.The former has the zircon U-Pb age 232.9±1.4Ma,belonging to“high Si,rich in K,Al oversaturated”and“S”type granite,in late collision-postcollision environment,formed by Changning-Menglian ocean basin subduction eastward in Late T late collision period.