Modern nonmarine evaporite deposition, Quaidam basin, China: An overview
- SUNY Binghamton, NY (United States)
- Univ. of Calgary, Alberta (Canada)
- Inst. of Salt Lakes, Xining (China)
Dabusun Lake (200 km{sup 2}) is a shallow ({lt}1 m) perennial saline lake in the high altitude Qaidam basin (120,000 km{sup 2}) of western China. It is underlain by {gt}40 m of salt and siliciclastic sediments ({approximately}54,000 years old). Petrographic features in two 50 m cores (chevron halite, halite cumulates, rafts, and siliciclastic mud, minor solution and no subaerial exposure features except in the top meter) indicate continuous shallow perennial lake conditions. The chemical composition of fluid inclusions trapped in halite crystals show lakewaters have generally undergone progressive concentration to the present. Modern Dabusun Lake is chemically uniform (Na-Mg-Cl-rich), nonstratified, and at or near halite saturation. Evaporites accumulate in zones on the restricted lake margins as halite (cumulate and raft layers with rippled surfaces and chevron mounds), halite + carnallite (KCl{center dot}MgCl{sub 2}{center dot}6H{sub 2}O), and finally carnallite (ephemeral fine-grained crystal mush). The carnallite zone merges with a 25 m wide shoreline facies, highlighted by a 1 m wide zone of halite ooids/pisoids that border a 20-30 cm tall overhanging salt crust (1967 shoreline). Lower lake levels since that time have produced vadose diagenetic features in the shoreline halites including: pendant cements, meniscus cements, halite 'popcorn,' and solution voids with muddy geopetal fills. A large flood (July-September 1989) expanded Dabusun Lake to 800 km{sup 2}, and dissolved all surface carnallite deposits. Diagenetic carnallite cements, formed by downward migration and cooking of carnallite saturated surface brines, however, remain in the subsurface to depths of 13 m. These potash mineral cements are similar in texture to many ancient potash evaporites.
- OSTI ID:
- 7013226
- Report Number(s):
- CONF-910403--
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Vol. 75:3; ISSN AABUD; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580000* -- Geosciences
ASIA
BRINES
CHEMICAL COMPOSITION
CHEMISTRY
CHINA
EVAPORITES
GEOCHEMISTRY
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
HALIDE MINERALS
HALITE
INCLUSIONS
MINERALS
PETROGRAPHY
PRECIPITATION
ROCKS
SALT DEPOSITS
SATURATION
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
SEPARATION PROCESSES