Anthracite

Anthracite

　　Anthracite is a dominant mineral resource in Zhaotong City, with reserves ranking first in the province. The coal-bearing area spans 5,269 square kilometers, accounting for 23.5% of the total regional area. The estimated reserves amount to 11.376 billion tons, representing 55.9% of the province's total for this type of coal. Its distribution is relatively concentrated in four counties—Zhenxiong, Weixin, Yanjin, and Yiliang—followed by Zhaotong City and Daguan County. The main coal-bearing formations are the Upper Permian Xuanwei Formation, followed by the Lower Carboniferous Wanshou Mountain Formation and the Lower Permian Liangshan Formation. These are widely distributed across twelve major synclines, including the Zhenxiong Syncline, Muxiang Syncline, Shikan Syncline, Luowang Syncline, Niujie Syncline, Cheluo Syncline, Datianba Syncline, and Xinglong Syncline. By the end of July 1989, proven reserves classified as A+B+C+D grades totaled 181,249 million tons. Of these, Grade A accounted for 78.17 million tons, Grade B for 173.51 million tons, Grade C for 340.81 million tons, and Grade D for 1,220 million tons. Among the proven reserves, based on coal-forming periods, 178,819 million tons were from the Upper Permian, 22.62 million tons from the Lower Carboniferous, and 1.68 million tons from the Lower Permian. The anthracite seams in the region are stable, mostly consisting of multiple coal layers, with 1–4 workable seams ranging from 1 to 4 meters in thickness individually, and totaling 3–9 meters, typically around 6 meters. The seam dips are gentle, with many upslope seams, favorable terrain, and suitability for adit mining and small-scale collective extraction. The surrounding rock is stable, resulting in low timber consumption. Since most seams are medium to thick, covering a broad area, mines with an annual output below 300,000 tons can be widely developed. The coal quality is also excellent, mostly medium-ash, low-sulfur, or low-ash, low-sulfur anthracite, with a few being extra-low sulfur. It has high fixed carbon content, with a low calorific value of 21.5–33.5 kJ/kg, generally around 27.2 kJ/kg—close to the calorific value of standard coal, making it an ideal thermal coal. However, due to depositional environment controls, there are the following patterns in thickness and coal quality variation: (1) From Zhenxiong northwestward to areas north of Yanjin—i.e., from east to northwest—the coal-bearing strata thin out, the number of coal layers and workable seams decreases, ash content in the coal increases, and coal quality declines. However, sulfur content gradually decreases from medium to low, or even extra-low sulfur. (2) Seam thickness is proportional to the thickness of the coal-bearing strata. In the eastern regions where the coal-bearing strata are thicker, the seams are thicker, mostly medium-thick, while in the thinner northwest regions, the seams are mostly thin. Zhaotong City has a long history of anthracite mining. However, regarding the production, supply, and sales of coal, since the dredging of the Guanhe River during the Qianlong period of the Qing Dynasty, aside from some coal from Yanjin County being transported by wooden boat to Yibin, Sichuan for external sales, the rest was mainly for local production and consumption—as fuel for urban and rural industrial and domestic use. Since the founding of the People’s Republic of China, annual output increased from 23,600 tons in 1952 to 1.1 million tons in 1978. Especially since 1979, driven by new industrial needs such as power station coal for the Yunnan Natural Gasification Plant, newly built thermal power plants, and carbide production, anthracite production has been further boosted. By 1990, the annual anthracite output of the 11 cities and counties in the region had reached 1.9 million tons. (Zhaotong)