Chaganur Salt Lake, Mongolia

The Chaganur (Qagan Nur) soda-ash lake deposit, discovered in 1966, is located in the Gobi Desert, in the central part of the Inner Mongolia Autonomous Region, some 80 km southeast of Erenhot. At an elevation of 1000 meters, it is a lacustrine sump in the lowest part of an arid deflation basin, situated at an erg edge, in the cool arid steppes (BSk) of the Inner Mongolian plateau. Winters are long and frigid with typical temperature ranges of -27 to 0ºC in January, while summers are short and cool with a a range of 18-28ºC in July. Annual evaporation today is ten times that of precipitation.

The nearby city of Erenhot receives 3,232 hours (about 73% of the possible total) of bright sunshine per year, and clear, sunny, dry weather dominates year-round. Due to the aridity, the diurnal temperature variation frequently approaches and exceeds 15 °C. Over two-thirds of the sparse 142 millimetres of annual rainfall occurs from June to August. With monthly percent possible sunshine ranging from 67% in July to 78% in February, the city is one of the sunniest in China.

Today the salt lake it has an area of 21 km2 and is made up of a smaller northeastern sub-basin (East Chaganur), and a larger southwestern sub-basin (West Chaganur) joined by a narrow channel. Two intermittent rivers discharge into the lake, one from the northeast and the other from the southeast. The lake is also fed by direct precipitation.

Regionally Chagan Nur is the largest of a series of 16 alkaline salt lakes (e.g. Hushunur, Wulannur, Huguonur, Halefushuyingnur, Muyingnur, Wulannur, Wenduobunur, South Chaganur) that are relicts of a formerly more extensive palaeolake Chagannur.

Lake Chaganur a Quaternary trona lake, Inner Mongolia autonomous region, China.

At its maximum extent, which is thought to have been during the early to mid- Holocene, this palaeolake occupied an area of some 2,640 km2. The total area of the various lakes in the basin today is ~ 156 km2, and the area of the current catchment is 2,800 km2. The basin low, which is controlled by two faults running SW-NE, is a tectonic sump with a Cretaceous bedrock of sandstone and mudstone.  The natural soda beds (halite with variable amounts of thenardite, mirabilite, trona) in the Chaganur lake accumulated during climatically-induced shrinkage events, occupy an area of 21 km2 and are underlain by some 20 m of sandy clay. The targeted deposit consists of nine soda beds with interstitial hypersaline brines that are interlayered with black muds (see Warren, 2016; Chapter 12 for detailed literature compilation). Today, the lake is the site of a soda ash factory (with several coal-fired kilns) located on the north edge of the lake, along with a small town built to accommodate workers.

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