龙木错-双湖-澜沧江板块缝合带与石炭二叠纪冈瓦纳北界

1982—1983年间,作者在改则幅和日土幅1:100万区域地质调查中,发现在黑头山—冈玛错—角木日—双湖一带,存在严重解体的蛇绿岩带。后经进一步工作,获悉该带明显地控制了冈瓦纳相和特提斯相石炭、二叠系的分布,并有高压变质带的岩石出露。因此,该带为一条北西西—南东东向的板块缝合带,它应是目前国内外地质界都在寻找的冈瓦纳大陆的北界。

THE LONGMUCUO-SHUANGHU-LANCANGJIANG PLATE SUTURE AND THE NORTH BOUNDARY OF DISTRIBUTION OF GONDWANA FACIES PERMO-CARBONIFEROUS SYSTEM IN NORTHERN XIZANG,CHINA

It is important for earth science community at home and abroad to look for the northern boundary of Gondwana facies of Permo-Carboniferous system in Qing-Xizang Plateau.Through large scale of geological research a west cast direced ophiolite zone, a high pressure metamorphic zone and a Gondwana facies of Permo-Carboniferous system were discovered with the Gondwana facies of Permo-Carboniferous system controlled by the ophiolite zone and the high pressure metamorphic zone.lt follows that the suture between Longmucuo and Shuanghu plates was primarily extending southeastward to connect with the Lancangjiang suture west of Yunnan Province,to Malaysia and then the boundary between Gondwana facies and Tethys facies of Permo-Carboniferous systems has been fairly established.Data show that there had been a supercontinent during Tournaisian stage in early Carboniferous and the rifting of which started from late Visean or Namur-ian stage. Sedmentation and volcanism of late Carboniferous epoch found in the region south of Qiangtang and Phuket Group found in Malaysia might be products of the Visean stage. The Metamorphic age of blueschist from Lancangjiang west of Yunnan province is 2.4 or 2.6Ma,the high pressure mineral assemblageonly appears in basic rocks of late Carboniferous to early Permian in the middle of Qiangtang plateau where the biota had been changed completely to warm-water fauna since late stage of early Permian,are all facts indicating the age for the rifted continents to reunite ought to be early Permian.Other evidence is:1) The Longmucuo-Shuanghu-Lancangjiang suture was formed in Permian;2) This suture clearly controls the distribution of Gondwana-Tethys facies. So that the Longmucuo-Shuanghu-Lancangjiang suture is considered as the boundary between Gondwana and Kurasia.