Structure and stratigraphy of the Juhugeng coal district at Muli, Tianjun County, Qinghai Province

Since gas hydrates were found in the permafrost of the Juhugeng ore district (JHG) in the Muli coalfield of Qinghai Province, the JHG has become one of the hot spot areas in the Tibetan Plateau. This paper has investigated the geological structure, coal-bearing stratigraphy and depositional facies of the Jurassic coal measures in the JHG area. The JHG area is structurally located in the western section of the Qilian depression-folding zone. Controlled by the thrusting faults along the northern margin of the Datongshan and the southern margin of the Tuolaishan, the structures in the JHG area extend from northwest to southeast, and find expression in two synclines, i.e., northern syncline and southern syncline. Coal resources are preferentially preserved in the northern syncline. Coals were formed in the Middle Jurassic Muli Formation and Jiangcang Formation, and the regionally minable coals are preserved in the Upper Member of the Muli Formation. Coal accumulations mainly occur in the swamp environment developed in the abandoned braided river system and in the swamp environment developed by shallowing of the lacustrine and subaqueous delta.