Abstract: A suit of highly potassic basalt bearing deep-source xenoliths has been discovered recently in the Siziwangqi area, Inner Mongolia. The host rock shows black and compact structure, characterized by alkaline-rich(w(K₂O)+w(Na₂O)>5%), high K (w(K₂O) 2.5%～3.19%) and high Ti (TiO₂ 2.03%～2.71%). The whole rock K-Ar isotopic age is early Cretaceous. After the close of petro-asian ocean, the North China Craton(NCC) has experienced intensive intra-continental contraction and extension. In the late early Cretaceous ,the NCC turned into contraction stage again by the influence of the subduction of Pacific plate and Indian plate. Siziwangqi area is on the joint of NCC and Siberia. The discovery of the shoshonite is important to research Mesozoic tectonic and deep-inside substance evolution of the NCC.

Key words: Early Cretaceous, Shoshonite, Siziwangqi area

摘要： 内蒙古四子王旗地区发现含有深源捕虏体的富钾玄武岩。玄武岩为黑色致密块状，以富碱（w(K₂O)+w(Na₂O)>5%）、高钾（w(K₂O)）在2.50%～3.19%之间)和较高的钛含量（w(TiO₂)在2.03%～2.71%之间）为特征，岩石分类上属钾玄岩系列，全岩K-Ar表观年龄为108～128Ma，为早白垩世。古亚洲洋闭合后华北板块在早中生代经历了由强烈的陆内挤压缩短作用转入造山后伸展作用阶段。早白垩世晚期该区受太平洋板块和印度洋板块俯冲作用影响，华北板块再次转入挤压作用阶段，开始了滨太平洋域的演化。内蒙古四子王旗地处华北板块与西伯利亚板块结合部，本次发现的早白垩世钾玄岩系列对于研究华北板块北缘在中生代构造转化中的物质及深部构造演化具有重要意义。

关键词: 早白垩世, 钾玄岩, 四子王旗