关键词: 南疆, 土壤, 氟, 白云石, 碳酸盐矿物

Abstract: The oasis soil around the Tarim Basin in southern Xinjiang has developed a large amount of carbonate minerals, meanwhile the regional fluorine content in soil and groundwater is high, which poses a huge risk of fluorine pollution. Exploring the coupling relationship between the two is significant for comprehensive utilization of soil inorganic carbon sinks in arid regions and improving the prevention and control of regional fluoride pollution. This study sampled 15 typical surface soils from Tiemenguan, Xinjiang, and conducted a systematic study on the mineralogical and geochemical characteristics of the samples, using XRD, scanning electron microscopy, and other instrumental analysis methods. With the major and trace element content as well as carbonate Sr isotope compositions analyzed, combined with indoor selective dissolution experiments, geological evidence for the coupling mechanism of fluoride and carbonate minerals were obtained. Our study found that the mineral composition of the soil from Tiemenguan is relatively complex, with the major element content similar to that of the upper continental crust (UCC) and the chemical weathering index (CIA) value between 50 and 60 which indicates a relatively weak weathering. The soil contains a relatively large portion of carbonate minerals such as calcite and dolomite, with average Sr and Mn contents of 1434 ppm and 1736 ppm, respectively, and a 87Sr/86Sr ratio of 0.710. Fluorine in soil is highly correlated with elements related to carbonate minerals, and exhibits a good coupling relationship with dolomite. It is speculated that the fluorine anomaly in the soil mainly comes from the magnesium fluorite in the source area, which is subject to combined migration with dolomite due to geological and climatic factors.

Key words: Southern Xinjiang, soil, fluorine, dolomite, carbonate minerals