Abstract:

Based on studies of depositional environment, assemblage of heavy mineral and stability factor of heavy mineral of the lower member of lower Ganchaigou Formation in the western Qaidam Basin, there are 5 source directions:(1)Akatengneng Mountain direction in the north of the Altun slope；(2)southern Datongshan -Annanba-Altun Mountain direction in the north of Xiaoliangshan-Niubiziliang；(3)Yuejin direction in the west of Qimantage Moumtain；(4)Dongchaishan-Huangshi direction in the east of Qimantage Moumtain；(5)Alar direction between Altun Mountain and Qimantage Moumtain. Different source areas control the development of sedimentary systems.There are 4 sedimentary systems in western Qaidam Basin:(1)the alluvial fan-delta fan-sublacustrine fan-deep lake sedimentary system in the west of Altun Mountain;(2)the alluvial fan-braided river-delta-littoral lake sedimentary system in the middle of Altun Mountain;(3)the alluvial fan-river-delta-littoral lake sedimentary system in front of Qimantage Moumtain;(4)the ancient Alar river-delta-littoral lake sedimentary system. According to the theory of sedimentary system distribution and oil and gas accumulation, fan delta, delta,beach bar and sub-lacustrine fan have good oilgenerating strata and reservoirs,where are the most prospective areas for exploration.

Key words: the western Qaidam Basin, lower member of lower Ganchaigou Formation, sedimentary system, source provenance analysis, assemblage of heavy mineral, stability factor