Source of potassium in shizigou deep potassium-rich brine, Western Qaidam Basin

Key words: 
• Shizigou in western Qaidam Basin /
• deep-seated potassium-rich brine /
• geochemical characteristics /
• continental sedimentary environment /
• rock salt leaching

Abstract: The Shizigou anticline structure is located in the west of the Qaidam Basin.There are abundant brine resources in the upper part of the Paleogene Lower Ganchaigou Formation, and the content of K, B and Li in brine is high, which has development prospects. In this paper, through the detection of major, trace elements and strontium isotope of the brine, it is found that: The content of K+ in the brine in the study area is 1.058~15.87g/L, of which 70% exceeds 3g/L ; the chemical type of brine is mainly chloride type; By calculating the characteristic coefficient of brine and analyzing the phase diagram of water-salt system, it is considered that the leaching salt layer is the main cause of the high salinity brine. At the same time, the relationship between strontium isotope characteristics of brine and salt layer and the correlation between K+ and Li+ reflect that the source of deep thermal fluid K also has a certain contribution. Through analysis, the metallogenic model of brine potassium in the study area is preliminarily established: During the Paleogene Xiaganchaigou period, the Shizigou area was in a weak extensional environment, and the sedimentary environment was relatively stable. The halite and potassium-magnesium salt deposits of the upper member of the Xiaganchaigou Formation in the late Eocene were deposited. In the later period, the tectonic activity intensified, and the potassium-rich thermal fluid rose into the lake along the tensile fault, providing some deep material source K, and causing the dissolution of the existing potassium-magnesium salt and some halite deposits, which in turn provided another important source of dissolved potassium for the brine in this area.