关键词: 准噶尔盆地, 二叠纪, 咸化湖盆, 菌藻, 古亚洲洋

Abstract: Following the formation of Eurasian Plate and the closure of Paleo-Asian Ocean, the Kazakhstan Plate (Orocline) was formed in the late Paleozoic. As influenced by the closure of the Junggar-Balkhash Ocean and the hot and arid paleoclimate, a series of residual oceanic and coastal continental margin saline lacustrine basins were formed during the Early to Middle Permian along the oceanic-continental closure zone in Junggar Basin located at the eastern margin of Kazakhstan Plate. The comprehensive analyses of lithology, sedimentary facies, geochemistry, seismic stratigraphy, and seismic lithology show the following. (1) The Lower-Middle Permian Fengcheng Formation, Lucaogou Formation, Hongyanchi Formation and Pingdiquan Formation in Junggar Basin are mainly composed of saline sediments (including residual oceanic and saline lacustrine sediments). Specifically, Fengcheng Formation is mainly distributed in Mahu sag, Penyijingxi sag, Shawan sag and Fukang sag along the closure zone of the western Junggar residual ocean and northern Tianshan residual ocean, Lucaogou Formation and Hongyanchi Formation are mainly distributed in Fukang sag and Bogda Mountain region along the northern Tianshan-Solunke residual ocean, and Pingdiquan Formation is mainly distributed in Wucaiwan sag, Shishugou sag and Shiqiantan sag along the Kalamaili residual ocean. (2) The saline sediments are distributed regularly, and gradually migrated from west to east and from bottom to top from Early to Middle Permian. (3) Fengcheng Formation, Lucaogou Formation and Pingdiquan Formation are the main source rocks of Permian in Junggar Basin, which contain bacteria-rich algal organic matter and are typically characterized by saline lacustrine sediments. (4) The formation and migration of the Early to Middle Permian residual oceans and saline lacustrine basins in Junggar Basin controlled the distribution of sedimentary facies and high-quality source rocks. Petroleum exploration practices reveal that the high-quality saline lacustrine source rocks in Mahu sag in the west and Jimusaer sag in the east of the basin control the formation of hydrocarbon accumulation areas with 1 billion to billions of tons reserves, indicating that there may be great oil-gas resource potential in the distribution centers of saline sedimentary source rocks in Penyijingxi Sag, Shawan sag, the southern margin area of the basin and Fukang sag. Although there is no deep drilling to confirm those at present, their exploration prospects are worth looking forward to.

Key words: Junggar Basin, Permian, saline lacustrine basin, bacteria and algae, Paleo-Asian Ocean