Hydrochemistry and Minerals Assemblages of Salt Lakes in the QinghaiTibet Plateau, China
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    Abstract:

    The salinity of the lakes of the plateau is closely related to the natural environment of lake evolution, especially the climatic conditions. According to the available data and interpretation of satellite images, the salinity of the lakes of the plateau has a general trend of decreasing from north and northwest to south and southeast, broadly showing synchronous variations with the annual precipitation and aridity (annual evaporation/annual precipitation) of the modern plateau. The pH values of the plateau salt lakes are related to both hydrochemical types and salinities of the lake waters, i.e., the pH values tend to decrease from the carbonate type → sodium sulfate subtype → magnesium sulfate subtype → chloride type; meanwhile, a negative correlation is observed between the pH and salinities of the lakes. According to KurnakovValyashko classification and author's subclassifing for carbonate type, a complete and meticulous hydrochemical classification of the salt lakes of the plateau has been made and then a clear understanding of the N S hydrochemical zoning and EW hydrochemical differentiation has been obtained. There is a genetic association between certain saline minerals and specific salt lake hydrochemical types: the representative mineral assemblages of the carbonate type of salt lake is borax (tincalconite) and boraxzabuyelite (Li2CO3) and alkali carbonatemirabilite; the representative mineral assemblages of the sodium sulfate subtype are mirabilite (thenardite)halite and magnesium borate (kurnakovite, inderite etc.)ulexitemirabilite; the representative mineral assemblages of the magnesium sulfate subtype are magnesium sulfate (epsomite, bloedite)halite, magnesium boratemirabilite, and mirabiliteschoenitehalite, as well as large amount of gypsum; The representative mineral assemblages of the chloride type are carnallitebischofitehalite and carnallitehalite, with antarcticite in a few individual salt lakes. The abovementioned salt lake mineral assemblages of various types on the plateau have features of coldphase assemblages. Mirabilite and its associated coldphase saline minerals are important indicators for the study of paleoclimate changes of the plateau. A total of 59 elements have been detected in lake waters of the plateau currently, of which the B is intimately associated with Li, Cs, K and Rb and its concentration shows a general positive correlation with increasing salinity of the lake waters. The highest positive anomalies of B, Li, Cs, and K center on the Ngangla Ringco Lake area in the western segment of the southern Qiangtang carbonate type subzone (I2) and coincide with Miocene volcanicsedimentary rocks and highvalue areas of B, Li, and Cs of the plateau. This strongly demonstrates that special elements such as B, Li, and Cs on the plateau were related to deep sources. Based on recent voluminous geophysical study and geochemical study of volcanic rocks, their origin had close genetic relation to anatectic magmatism resulting from India-Eurasia continent-continent collision, and B Li (Cs) salt lakes in the Cordillera Plateau of South America just originated on active continental margins, both of which indicate that global specific tectonically active belts are the main cause for the high abundances of B, Li, and Cs (K and Rb) in natural water and mineralization of these elements.

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ZHENG Mianping, LIU Xifang.2010. Hydrochemistry and Minerals Assemblages of Salt Lakes in the QinghaiTibet Plateau, China[J]. Acta Geologica Sinica,84(11):1585-1600

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  • Received:August 28,2010
  • Revised:September 29,2010
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