内蒙古阿拉善北部地区碰撞期和后造山期岩浆作用

Magmatism of Collisional and Post-Orogenic Period in Northern Alaxa Region in Inner Mongolia

本文重点研究内蒙古阿拉善北部地区塔里木板块与华北板块碰撞期及后造山期的岩浆作用。发生于251.3 Ma左右的热事件是碰撞期Cs型岩浆作用,仅分布于缝合线之北,其产物不是典型的S型花岗岩。岩体中片麻理构造及围岩中的透入性劈理是同碰撞期造山作用的构造形迹。发生于228 Ma左右的热事件是后造山期A型岩浆作用,源岩是下地壳物质,按源岩差异研究的A型花岗岩分为As型和Ai型。前者受陆壳中沉积物混染较强,而后者受地幔物质混合作用较强。

The studied region in this paper involves northern Alaxa region,Inner Mongolia,China. Geo-tectonically it belongs to the Tarim and North China plates. This paper chiefly has studied the magmatism of collisional and post-orogenic period between the Tarim and North China plates. The thermal event occurred in 251. 3 Ma it is Cs-type magmatism of collisional period, it only is distributed in northern part of suture, and their products no are typical S-type granites. The gneissosity in body and penetrative cleavage in country rock are orogenic structural features of syn-collision. The thermal event taken place in 228 Mai is A-type magmatism of post-orogenic period, and their sources belongs to matter of lower crust. According to difference of their sources,the studied A-type granites can be divided into As type and Ai type. The former strongly are contaminated by sediments in continental crust,magmas had udergone fractional crystallisation. The latter strangle undergoes mixing with mantle matter.