Lower Permian formations of different geodynamic environments in A'nyemaqen ophiolitic zone (Buqingshan Mts., eastern Kunlun, Qinghai Province, China)  

作　　者：I. I. Pospelov E. Ya. Leven BIAN Qian-tao O. A. Korchagin 

机构地区：[1]Geological Institute, Russian Academy of Sciences, Moscow 119017, Russia [2]Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

出　　处：《Journal of Geoscientific Research in Northeast Asia》2005年第1期15-32,共18页东北亚地学研究（英文版）

摘　　要：Lower Permian formations within the Buqingshan Mountains （A＇nyemaqen ophiolitic zone, eastem sector of the eastern Kunlun） were formed in the following paleogeodynamic environments （from north to south） ： （ 1 ） shelf and slope of a passive continental margin in a marginal sea; （2）partially Permian metamorphic rocks of subduction-accretion complexes and volcanogenic rocks of an ensimatic island arc, of the age limited from above by the Asselian - Sakmarian; and （3） an island are slope and oceanic trench. Subduction-accretion complexes and the island are volcanites are overlain with a sharp angular unconformity by a carbonate-conglomerate sequence, which presents as local molasse of the Early Permian age. Based on fusulinids from the basal limestone, the age of the local molasse is first defined as the Yakhtashian-Bolorian, i.e, Artinskian-Kungurian （？）. The thorough investigations revealed that the initial closure of the eastern Paleotethys within the eastern Kunlun corresponded to the Sakmarian-Yakhtashian （Artinskian） boundary, whereas in the western Paleotethys sector （Northern Pamirs） the closure occurred considerably earlier, prior to the Late Bashkirian. Thus, the idea that the Paleotethys in the eastern Kunlun reached its maximum width in the Permian, is highly questionable. During the Early Permian the A＇nyernaqen branch of the Paleotethys intensely decreased. Beginning from the Bolorian （Kungurian） and up to the end of the Permian this branch represented its relict in the form of a marginal sea depression. It may be suggested that the Paleotethys closure in the A＇nyemaqen took place gradually from the west to the east and covered a long period from the Late Carboniferous to the terminal Early Permian.Lower Permian formations within the Buqingshan Mountains (A'nyemaqen ophiolitic zone, eastern sector of the eastern Kunlun) were formed in the following paleogeodynamic environments (from north to south): ( 1 ) shelf and slope of a passive continental margin in a marginal sea; (2) partially Permian metamorphic rocks of subduction-accretion complexes and volcanogenic rocks of an ensimatic island arc, of the age limited from above by the Asselian - Sakmarian;and (3) an island arc slope and oceanic trench. Subduction-accretion complexes and the island arc volcanites are overlain with a sharp angular unconformity by a carbonate-conglomerate sequence, which presents as local molasse of the Early Permian age. Based on fusulinids from the basal limestone, the age of the local molasse is first defined as the Yakhtashian-Bolorian, i.e. Artinskian-Kungurian (?). The thorough investigations revealed that the initial closure of the eastern Paleotethys within the eastern Kunlun corresponded to the Sakmarian-Yakhtashian (Artinskian) boundary, whereas in the western Paleotethys sector (Northern Pamirs) the closure occurred considerably earlier, prior to the Late Bashkirian.Thus, the idea that the Paleotethys in the eastern Kunlun reached its maximum width in the Permian, is highly questionable.During the Early Permian the A'nyemaqen branch of the Paleotethys intensely decreased. Beginning from the Bolorian (Kungurian) and up to the end of the Permian this branch represented its relict in the form ora marginal sea depression. It may be suggested that the Paleotethys closure in the A'nyemaqen took place gradually from the west to the east and covered a long period from the Late Carboniferous to the terminal Early Permian.

关 键 词：Lower Permian formations ophiolitic zone PALEOTETHYS eastern Kunlun China 

分 类 号：P534.46[天文地球—古生物学与地层学]