柴达木盆地构造古地理分析

AN ANALYSIS ON TECTONO-PALEOGEOGRAPHY OF THE QAIDAM BASIN,NW CHINA

研究的目的是分析柴达木盆地显生宙构造古地理特征和盆地叠合过程。在寒武纪—泥盆纪 ,柴达木板块处于低纬度区 ,从寒武纪时的南纬 4 1°往北漂移到泥盆纪时的北纬 10 6° ,与塔里木、华北、扬子等块体有较大的纬度差 ,表明柴达木板块在该时期是一个并不隶属于其它任何板块的独立的块体 :与华北板块之间以北祁连洋相隔 ,与塔里木板块之间以阿尔金洋相隔 ,与中昆仑地块之间以东昆仑洋相隔 ,柴达木板块内部也被赛什腾—锡铁山洋所分隔。这些洋盆经历了寒武纪—早、中奥陶世张裂阶段和晚奥陶世—早、中泥盆世聚敛阶段 ,最终于中泥盆世末期闭合。该时期在柴达木盆地内部 ,叠合在震旦纪大陆裂谷盆地之上的是寒武—奥陶纪台地—陆棚相碳酸盐岩和碎屑岩建造 ,生物发育 ;志留纪—早、中泥盆世柴达木盆地以隆起为特征。石炭纪—三叠纪柴达木板块继续北移 ,石炭纪时位于北纬 11 9° ,二叠纪时位于北纬 12 7° ,三叠纪时位于北纬 2 2 2° ,该时期柴达木板块已与华北板块、塔里木板块拼合 ,但与羌塘板块之间以南昆仑洋相隔 ,柴达木处于南昆仑洋的弧后部位 ,叠加在早期盆地之上的是石炭纪—早二叠世滨岸—台地—陆棚相碳酸盐岩、碎屑岩夹煤线。晚二叠世—三叠纪柴达木盆地再度隆升。侏罗纪以来 。

The purpose of this paper is to analyze the tectono-paleogeography and basin composite process of Qaidam basin in Phanerozoic time The Qaidam plate was located at low latitude from Cambrian to Devonian (i.e. at 4 1°S in Cambrian and at 10 6°N in Devonian), which was different from the adjacent plates such as Tarim, North China and Yangtze (South China) plates North Qilian ocean existed between the Qaidam and North China plates, Altun ocean separated the Qaidam and Tarim plates, East Kunlun ocean isolated the Qaidam and Mid-Kunlun massif, and Saishiteng-Xitieshan ocean developed along the northern margin of present Qaidam basin These indicate that the Qaidam is an independent plate from the Early Paleozoic to Middle Devonian that was not subordinated to any other plates The oceans mentioned above underwent extension stage from Cambrian to Early Mid Ordovician and convergent stage from Late Ordovician to Early Mid Devonian, and the closure at the end of Mid Devonian, forming the ophiolite in the areas which represents the closed ocean at this time The carbonates and clastic rocks of the platform shelf environment from Cambrian to Ordovician superimposed on the continental rift basins of the Sinian, and the basin uplifted from the Silurian to Mid Devonian The Qaidam plate was located at latitude 11 9° N in Carboniferous, 12 7°N in Permian, and 22 2°N in Triassic The plate conjoined with the North China and Tarim plates was separated from Qiangtang plate by the south Kunlun ocean, and the Qaidam was a back-arc basin superimposed on the early basins, deposited the carbonates, clastic rocks and coal streak of the littoral platform shelf environment The basin uplifted again from the Late Permian to Triassic Since Jurassic, the plate migrated northward slowly, was located at latitude 29 8°N in Jurassic, 31 0°N in Cretaceous and 33 4°N in Neogene The continental basin from Jurassic to Quaternary superimposed on the marine basins of Paleozoic. The Jurassic is coal bearing series, the Cretaceous is red coarse clastics, and the Tertiary — Quaternary is thick sandstones, mudstones, gypsum and salts