内蒙古苏左旗地区晚古生代构造-岩浆活动及地壳演化特征

THE FEATURES OF LATE PALEOZOIC TECTONO MAGMATIC ACTIVITY AND CRUSTAL REVOLUTION IN THE SOUTHERN SUZUOQI AREA

华北地台北缘内蒙古中部地区晚古生代曾发生过造山后伸展作用，在晚泥盆世—早石炭世，本区经历了短暂的造山作用，形成前陆盆地并推积了滨浅海相磨拉石建造，同时伴有同碰撞期花岗岩产生。中石炭世—早二叠世，本区进入造山后的陆内伸展作用阶段，并发育大量火山岩。火山岩碱质含量高，碱质成分中Ｎａ２Ｏ＞Ｋ２Ｏ，且显示双峰分布特征；碎屑岩成分熟度和结构熟度降低。

Post orogenic extension had occurred in Late Paleozoic at northern margin of the North China Platform.The orogeny occurred in late Devonian Early Carboniferous and foreland basin is formed and accumulated littoral epicontinental sea fecies molasse deposition and formed a lot of synorogenic granites.Intracontinental extension tectonics process occurred in Middle Carboniferous Early Permian which formed a lot of volcanic rocks.The alkalian content of volconic rocks is high(Na 2O>K 2O) and the differentiation index of volcanic rocks is characterized by bimodality.Composition and texture maturity of clastic rocks indicates that extensional process occurred from Middle Carboniferous to Early Permian.