滇西澜沧变质带的变形序列与变质作用初步研究

研究表明澜沧变质带由小黑江-西定混杂带和澜沧变质混杂带2个构造地层单元组成。前者经历了3期构造变形与2期变质作用,形成了呈南北向展布的区域性流劈理S1以及冲断-褶皱构造,主期蓝片岩相变质作用形成以蓝闪石、3T多硅白云母及黑硬绿泥石等高压相矿物为特征。后者在小黑江-西定混杂带变质变形之前业已普遍发育近东西向的褶皱构造及绿片岩相变质作用,尔后又经历了与前者相同的变形与变质历史。二者主期变质与变形作用发生在279-214Ma,与古特提斯构造发育密切相关,并形成了本带如今呈南北向展布的构造格局。

A PRELIMINARY STUDY ON DEFORMATION SEQUENCE AND METAMORPHISM IN LANCANG METAMORPHIC BELT OF WEST YUNNAN

Our detailed studies show that the Lancang metamorphic belt is actually composed of two different tectonic units. Xiao Heijiang-Xiding block and Lancang metamorphic complex. The former unit underwent three stages of structural deformation. characterized of regional flow cleaveages S1 and thrust-folded structures, NStrending and two-phases of metamorphism. with a main blue-schist phase characterized by high-pressure mineral assemblages consisting of glaucophane, 3T phengite and stilpnomelane. The later unit has generally experienced extensive green-schist phase metamorphism and deformation characterised by E-W-trending fold structures before the deformation and metamorphism in former unit. but its later deformational and metamorphic history is consistent with that in the former one. The major event of deformation and metamorphism in these two units took place during the period of 279-214Ma, and the cause of this event is the development of Tethyan tectonics. Furthermore. this event eventually resulted in the formation of a NStrending tectonic framework of the region.