喀喇昆仑地区沉积岩特征及岩相变化

喀喇昆仑地区从二叠纪开始,广泛沉积不同类型的碎屑岩、泥质岩、硅岩、碳酸盐岩和混积岩。沉积层序发育完整,白垩纪之前基本上属于稳定的连续造海建造系列。经初步研究,除西部二叠系出现半深水陆架边缘-岛弧盆地相、陆架区冷水型冈瓦纳相沉积和东部下三叠统有具复理石或重力流性质的外陆架半深水碎屑岩-硅泥质岩建造沉积外,大部分都是以细屑岩-碳酸盐岩建造为主的地台型浅海陆棚相和浅海平原相沉积,直到保罗纪末才形成早白垩世,以红色粗碎屑岩为主的陆相磨拉石建造,从而结束了长达1.5亿年连续沉积历史。

THE CHARACTERISTICS OF SEDIMENTARY ROCK AND ITS LITHOFACIES CHANGE IN THE KARAKORUM REGION

Since Permian period the sedimentry beds of the Karakorum region had welldeveloped. The Permian deposits overlaped on the Proterozoic metamorphic rocks,which are composed of elastic rocks, siliceous argillite and carbonate rocks withlight metamorphic slate and pabble-bearing slate as the represent atives. Some times with intercalations of cafe-clkaline island-arc volcanics in certain area. Theybelong to the sedimentary factes of typical shallow-water continental shelf, bathyalecontinental shelf margin and island-arc basin including the Gondwana cold-water deposition factes.From Triassic to Jurassic the sedimentary beds were mainly composed of elastic, fine-grained elastic and carbonate rocks. But the siliceous rocks also occurredin some localized area. With the exception for a Lower Triassic thick series ofrolastic rocks and siliceous argillite formation of gravity flow deposition with typi'cal flysch marks, which may belong to the outer continental shelf bathyal factes, tthe principal part was composed of fine-grained detrital rock-carbonate rock formation of shallow marine continental shelf sedimentary factes. All of them are con'sidered as the sedimentary series of stable continuous thalassogenic formation.An abrupt change of sedimentary factes did not happened until the end of Jurassic in the Karakorum region. Thick continental red coarseclastic rocks of molas.se sedimentary factes were altimately formed in early Cretaceous thus stoping thecontinued marine sedimentary history lasting for 1.5 handred million years.The big and sudden change of sedimentary factes after a stable continued deposition obviously resulted from the Yanshan movement being the product of platecollision along the second suture zone. Therefore, this is the most important geological event during the evolution of the region authentically recording the historyof the change and development of the region.