East Xinjiang Region After The Gap - Bogda Carboniferous Basin Analysis

Houxia-Bogda mountain chain is one of the most important components of Northern Tianshan Mts. Carboniferons period is the crucial period in the evolution of Northern Tianshan Mts. Clarifying the geological evolution of Houxia-Bogda region in Carboniferons period has great significance in understanding the evolution of the Tianshan Mts. So it has been one of the most important geological problems.Great progress has been made in probing and understanding the evolution of Tianshan Mountains. Through hardwork of several generations of geologists. However, they have different opinions on this hard nut.Based on the geological studing of "1:50000 regional geological surveying in Saridoca area and 1:50000 regional geological surveying in Awill-gou area in Changji City" which sponsored by the special Fund of Xinjiang Uygur Autonomous Region Government.We study the geology evolution of Houxia-Bogda region in Carboniferous period as a basin.We come to the conclusion that: Houxia-Bogda region was a back arc basin in Carboniferous period. The earlier stage of Carboniferous is the stage of expansion of the basin. The later period of Carboniferous is the stage of closing of the basin.Stratigraphic classification and analysis of Carboniferous system is the first step in studing the evolution of the basin in Carboniferous period in Houxia-Bogda region. Qijiaojing Formation is a formation of volcanic rocks which was formed in earlier period of Palaeocarboniferous. Liushugou Formation is a formation of clastic rock and Bimodal rift volcanic rocks. This Formation was formed in the cracking stage of Northern Tianshan back arc basin. Qiergusitao Formation is a flysch formation which has the characteristics of turbidite. Houxia formation is a bioclastic limestone formation which was the bioclastic limestone formation which was formed in the last stage of the Carboniferous back arc basin.The Carboniferous granite intrusions that exist in the area of Houxia-Bogda have the characteristics as fellows:These granite intrusions spread alone two sides of Arqikudouk Fault the dividing line of Northern and middle Tianshan Mountains. The Anti-carboniferous granite masses mainly existed in the area of middle Tianshan Mts.