Altyn-Tagh, Astyn-Tagh, Altun Mountains, Altun Shan, A-erh-chin, A-erh-chin shan, or Aerjin Shan (Chinese: 阿尔金山; Altyn Tag is Gold Mountain in Turkic; Shan is Chinese for mountain ; Astyn- Tagh proper is a part of the range south of Lop Nor), is a mountain range in northwestern China that separates the eastern Tarim Basin from the Tibetan Plateau. The western third is in Xinjiang while the eastern part forms the border between Qinghai to the south and Xinjiang and Gansu to the north.
Altun Shan is also the name of a 5,830 metres (19,130 ft) mountain near the eastern end of the range.
A series of mountain ranges run along the northern edge of the Tibetan Plateau. In the west are the Kunlun Mountains. About half way across the Tarim basin, where the mountains begin to orient somewhat to the north, the border range becomes the Altyn-Tagh, while the Kunluns continue directly east, forming a "V". Inside the "V" are a number of endorheic basins. The eastern end of the Altyn-Shan is near the Dangjin Pass on the Dunhuang-Golmud road in far western Gansu. East of the Altyn-Tagh the border range rises to the Qilian Mountains. The range separates the Tarim Basin, to the north, and Lake Ayakkum, to the south. The range can be divided into three portions. The southwest portion borders the Kunlun Mountains, is very rugged, with peaks reaching more than 6,100 metres (20,000 ft) and many perrenial snow fields. The central portion is lower in elevation, around 4,000 metres (13,000 ft), and the eastern portion. The eastern portion is higher in elevation, about 5,000 metres (16,000 ft) and consists of a group of smaller ranges oriented in a south-east to north-west trend.
Along the northern side of the mountains ran the main Silk road trade route from China proper to the Tarim Basin and westward. The Altun-Tagh and Qilians were sometimes called the Nan Shan ('south mountains') because they were south of the main route. Near the west end of the Altun-Shan the Gansu or Hexi corridor ends and the silk road splits. One branch follows the Altun-Tagh along the south side of the Tarim Basin while the other follows the north side.
The southwestern part of the Altyn-Tagh range reaches snowy peaks of up to 6295 m, although it descends to an average of 4000 m in the narrow middle and eventually rises up to average 5000 m as it meets the Nan Shan.
There are a dearth of rivers and streams in these mountains, due to the aridity of the region. The western portion has some small streams that either head north into the dessert or south into Lake Ayakkum. The remainder of the range is lacking in rivers.
Intermontane endorheic basins 
The two main lakes in this basin are the saline Lake Aqqikkol (also Ajig Kum Kul, Achak-kum; Chinese: 阿其克库勒湖; pinyin: Āqíkèkùlè Hú; 37°05′N，88°25′E, 4,250 m elevation) and Lake Ayakkum (Chinese: 阿牙克库木湖; pinyin: Āyákèkùmù hú); 37°30′N，89°30′E; elevation 3,876 m). These lakes are two of the few noticeable bodies of water in this extremely arid area; the area around them is officially protected as the Altun Shan Nature Reserve.
Farther east, in northwestern Qinghai, the much larger Qaidam Basin starts between the Altyn-Tagh and the Kunlun and extends almost to the east side of the plateau; the Altyn-Tagh separates the west side of this basin from the Kumtagh Desert.
Major Peaks 
- "A-erh-chin Mountains". Encyclopedia Britannica. I: A-Ak - Bayes (15th ed.). Chicago, IL: Encyclopedia Britannica, Inc. 2010. p. 1. ISBN 978-1-59339-837-8.
- See e.g. the map in Fig. 1 in Meng & Fang 2008, p. 2
- Holdich, Sir Thomas Hungerford (1906), Tibet, the mysterious, F.A. Stokes Company, p. 288
- E.g. 阿其克库勒湖 on Baidu.com
- Li, Bosheng (2000), "Chapter 11, Nature Conservation", in Zheng, Du; Zhang, Qingsong; Wu, Shaohong, Mountain geoecology and sustainable development of the Tibetan Plateau, Volume 57 of GeoJournal library, Springer, pp. 230–231, ISBN 0-7923-6688-3
- Or 3,870 m, according to 阿牙克库木湖 (Ayakkum Lake) on Hudong.com
- Peakbagger.com (1 November 2004). "Altun Shan". Retrieved 17 July 2010.
- Peaklist. "Sinkiang - Xinjiang 53 Mountain Summits with Prominence of 1,500 meters or greater". Archived from the original on 23 August 2010. Retrieved 24 July 2010.
- National Geographic Atlas of China, 2008
- Meng, Qing-Ren; Fang, Xiang (2008), "Cenozoic tectonic development of the Qaidam Basin in the northeastern Tibetan Plateau", in Burchfiel, B. C.; Wang, Erchie, Investigations into the tectonics of the Tibetan plateau, Volume 444 of Special paper - Geological Society of America, Geological Society of America, pp. 1–3, ISBN 0-8137-2444-9
- Zheng, Mianping (1997), An introduction to saline lakes on the Qinghai-Tibet plateau, Springer, p. 229, ISBN 0-7923-4098-1 Unknown parameter
- NASA photos of Ayakkum Lake and surrounding area