This area is located in the transition zone between the first landform step and the second landform step in China, and its main body is distributed in Hengduan Mountain area in the north-south direction, including the vast areas of eastern Tibet, western Sichuan and western Yunnan. There are Nujiang River, Lancang River and Jinsha River in the area, and the terrain is deeply cut. Mountains and rivers alternate with each other, forming the famous ridge landform of Hengduan Valley, with the height difference exceeding 1000m, which is a serious landslide and debris flow disaster area in the valley with serious soil erosion. This area has unique geological structure and rich mineral resources, but the overall development level is low, and there are few mining enterprises above medium size. The main mining minerals are copper, lead, zinc, tin, gold and non-metallic building materials, and the geological environment of the mine is landslide, ground collapse, debris flow, land resource destruction, soil erosion and other issues, which are now described in three blocks.

(1) Environmental Geology of Landslides, Debris Flows, Ground Collapses and Collapses in Mines in Western Yunnan

This area includes Nujiang, Diqing, Lijiang, Dehong, Baoshan, Dali, Xishuangbanna, Pu 'er and Lincang. The mineral resources in this area are extremely rich, and the mineral reserves of lead, zinc, cadmium, thallium and strontium rank first 1 in China. However, most of this area has inconvenient transportation, backward economy, low degree of mineral development, few medium-sized and above mining enterprises, and most of them are newly built mines in the 1980s and 1990s, with short mining history and generally small mining scale. Northwest Yunnan is a region rich in mineral resources. With the development of national economy, especially the improvement of traffic conditions, the conditions for large-scale exploitation of mineral resources are becoming more and more mature. The main minerals mined are lead, zinc, tin, copper and other non-ferrous metals. The serious impact on the geological environment is mainly the mining areas where group mining activities are out of control, such as Lanping lead-zinc mine area and Lushui Shiganghe tin mine area. The waste residue of Lanping lead-zinc mine often causes river blockage, with an area of 6.5km2 There are altogether 70 mine geological disasters1person in this area, and 7 1 person died due to the disasters (Table 3-22). The main types of disasters are landslide, debris flow, ground collapse and collapse.

Table 3-22 Environmental Geological Problems of Mines in Western Yunnan

(2) Geological disasters such as mine collapse, landslide, debris flow and soil-water flow in western Sichuan.

Western Sichuan, including Ganzi Prefecture and Aba Prefecture, belongs to plateau alpine landform and Songpan-Ganzi orogenic belt, with strong metamorphism and seismic activity. Hongyuan area in the northeast of Aba is a flat plateau with complex geological structure, and the annual precipitation is less than 800 mm. Due to poor traffic conditions and poor overall level of mineral development, the main environmental geological problems of the mine are collapse, landslide and debris flow. According to preliminary statistics, the annual output of mine wastewater in this area is 204.49× 104m3, and the accumulated waste residue is 666.56× 104t, occupying and destroying land area122.64hm2.

Tagong gold mine in this area is an open-pit gold mine. Mining and mineral processing have caused large-scale grassland destruction and pollution. According to preliminary statistics, the damaged area has reached 13.3km2, and a large amount of slag has formed a debris flow disaster. Manaoke gold mine is also an open-pit gold mine. Mining and mineral processing have caused large-scale mountain destruction, with an area of 7.8km2, and at the same time, unstable slopes and landslides have been formed, and surface water has been polluted, which has destroyed the mine and its surrounding ecological environment.

(3) The occupation of land resources in mines in eastern Tibet has destroyed the environment.

This area mainly refers to the Qamdo area in eastern Tibet, mainly mountainous and canyon landforms. The geological structure is complex. There are 8 mining enterprises in the area, including one large mine (Yulong Copper Mine) 1 mine, two medium-sized mines and five small mines, which mainly mine copper, lead, zinc, tin, coal and placer gold. Mine environmental geological problems are mainly the occupation and destruction of land resources. The total area of eight mines is 239.87hm2, including 89.23hm2 of stope and 35 piles of mine waste residue 150.64hm2. In addition, there are two small collapses in Yulong Copper Mine, which are newly-built mines and open-pit mines, which are prone to geological disasters.

In Maquhe placer gold mine in Gongjue County, mining residues accumulated along the river, forming hills and many deep pits, which caused great damage to the grassland. Heavy rainfall causes soil erosion, and it is easy to induce geological disasters of debris flow in flood season.

In the north of this area, the mining history is short, although there are few waste rocks and coal gangue piles, the geological environment is very fragile, and once it is destroyed, it will be difficult to recover, and the mining hidden danger is great. At the same time, the tailings dam of Mabuguo tin mine in the north of Saibei Nong is not firm, which is easy to form the hidden danger of dam-break and debris flow.