燕山地区早中生代陆壳的改造:兼论印支运动

The Early Mesozoic continental crust reformation in Yanshan area:Giving discussion to Indosinian movement

文中结合近年的研究成果,从玄武质岩浆的底侵作用及壳幔岩浆的混熔作用、地壳不同深度层次的变形-变质、地表的隆升-剥蚀与沉积-建造等方面,由深到浅阐明华北克拉通北缘中段印支期不同圈层的地壳运动。通过研究区晚三叠世和早白垩世火成岩εNd(t)-ISr同位素特征的对比,认为晚三叠世出现的新构造格局是从深部启动的,是对全球深部构造格局转折的响应。深部构造热活动引起地壳加厚以及均衡状态的破坏,并导致断块的差异隆升,是一次陆内造山作用,有别于传统意义上的挤压造山运动。地幔物质与热输入的结果使华北岩石圈从早中生代开始了改造过程。

Combined with recent studies,this paper represents the crustal movements of different layers from shallow to deep in the middle segment of the northern margin of the North China Craton during Indosinian epoch through studying underplating of basaltic magma,crust-mantle mixing,deformation and metamorphism at different depths,upwelling and denudation,and sedimentation and formation.Comparison ofεNd（t）-ISrof igneous rocks of Late Triassic and Early Cretaceous suggested that the threshold of a new tectonic framework at Late Triassic from the depth as a response to the transformation of the global deep tectonic framework.It was the deep tectono-thermal activities that caused crustal thickening and isostatic adjustments and resulted in differential uplifts of the fault blocks,which was an intracontinental orogeny that was essentially different from conventional compressional orogeny.Meanwhile,input of the mantel materials and heat also initiated the reconstruction of the lithosphere in the North China in the Early Mesozoic.