(Yunnan) Zhaotong Coalfield

Zhaotong coalfield is the largest one of the Triassic Period in china, which lies in Zhaotong City, the northeast of Yunnan Province .The city is in the center of the coalfield .Highway plays an important role on transportation, and there is a small airport in the outskirt. The landform is a basin whose shape is approximate ellipsoid. There are 20km from northeast to southwest and 8-15 km from northwest to southeast. The area is 230km².Some low mountains distributed in the basin, such as Fenghuang Mountain. There are four areas for exploration and development and they are haizi, Lotus, Zhugeying and hongwei.

1. Geological structure

Zhaotong Coalfield is the erosion basin of New Triassic Period .Yangxin and Emei Mountain Formation of Permian Period and Xuhe Formation of the later Triassic Epoch are in the base and periphery; the coal bearing strata of Zhaotong Formation of the Pliocene Epoch sediment in the basin; Fenghuang mountain is a basalt mountain of Emei Mountain Formation, controlling the near sedimentation of the New Triassic Period. The Quaternary system covers the surface of the basin, and is about 10m thick .Zhaotong Formation is a wide and gentle synclinorium, containing Haizi, Lotus and Zhugeying Syncline of sub-grade and the small anticlines on the ridges of Fenghuang Mountain and Lion Mountain .The dip angle of rock stratum is 3º-10º and a little sharp near the outcrop of the coal seams on the fringe of the coalfield, 20º-30º.The structure of the coalfield is simple and there is few fault. The fault whose drop in elevation is 1-2m can be seen occasionally.

2. Coal systems

Zhaotong Formation is 350-480m thick and can be divided into two parts. The lower part is conglomerate and clay rock; the clay rock in upper party has more than ten layers of thin seams and carbon clay rocks; the upper part contains three layers which are ultra thick seams and carbon clay rocks. Their codes from up to down are M1, M2 and M3, and the M2 is the main part .The development situation of the coal seams is different in every district. The largest number is 193.77m about the thickness in Haizi District.

3. Coal resources

The total coal resources are about 10Gt, and all proved .But the carefully proved deposit is less than 1/5.The type is brown coal, middle ash, low to middle sulfur and the calorific value of 16.7 MJ/kg or so.