青藏高原北部地质构造演化初论

PRIMARY DISCUSSION ON GEOLOGICAL TECTONIC EVOLOTION OF THE NORTHERN QINGHAI—XIZANG PLATEAU

青藏高原北部泛指班公湖—怒江以北地区。该区经历了元古代末期古陆解体后的秦祁昆和戈木日-他念他翁早古生代海槽发育阶段,将联合古陆分裂为北部塔里木—华北古陆、中部唐古拉—扬子古陆、南部“西藏古陆”。志留经末期海槽闭合、形成造山带和新的联合古陆,与此同时,由于造山期相伴的裂谷作用,致使秦祁昆造山带南缘产生木孜塔格—中秦岭泥盆纪坳陷带和内陆海盆地。石炭纪进入特提斯演化阶段,由西金乌兰—玉树—金沙江裂陷槽起主控作用,在唐古拉古陆之上和扬子古陆的西北部,形成石炭纪—早二叠世一系列裂陷槽,并与陆表海沉积盆地相联系,构成北特提斯海域。此期裂陷槽于晚二叠世、闭合,相继形成可可西里—巴颜喀拉三叠纪内陆海盆地,并与陆表海沉积盆地相联系,构成青藏高原北部三叠纪特提斯海域。晚三叠世末,可可西里—巴颜喀拉三叠纪内陆海盆地闭合,形成造山带和青藏高原北部新的联合古陆;与此同时,南侧班公湖—怒江侏罗纪海槽形成,并以此首次成为特提斯大洋盆地。

The northern Qinghai—xizang plateau in general is considered as the north of BangongLake-Nujiang and went through the early palaeozoic trough devoloping-stage of Qinling-Qilian-Kunlunand Gemuri-Taniantaweng after the pangea disintergrated in the end of Proterozoic,so Tarim-NorthChina old land occured in thd north,Tangguia-Yangzi old land in the middle,Xizang old land in thesouth.At the end of Silurian the trough was closed and formed orogenic belt and new pangea,in themeantime,duo to the rifting in the orogenic period,Muzitage-Middle Qinling Devonian depression andcontinent sea basin was developed in the southmagin of Qinling-Qilian-Kunlun orogenic belt.In Carbniferous it was entered Tethys devoloping stage.Since the Xijinwulan-Yushu-Jinshajiangrift geosyncline playing a main control function,above Tanggula old land and in northwest Yangzi oldland a series of Carboniferous-Early Permian rift geosynclines were formed and combined with the epi-continental sea depositioned basin to constitute North Tethys sea area.The rift geosyncline was closedin Late Permian,formed in turn Hob Xil and Bayanhar Trassic continent sea basin and connected withthe epicontinental sea depositional basin to constitute Trassic Tethys sea area in the Northern Qinghai-Xizang plateau.In the end of Trassic Hoh Xil-Bayanhar Trassie continental sea basin closed and formed orogenicbelt and a new pangea in the Northern Qinghai-Xizang plateau,at the same time,the Bangong lake-Nu-jiang Trassic trough developed in south and from that on Tethys ocean Basin was first formed.