Acta Petrologica et Mineralogica

There are abundant brine-type lithium resources hosted in the Upper Cretaceous Zhoutian Formation of the Jitai Basin, Jiangxi Province. However, its sedimentary evolution and depositional model remain controversial. On the basis of previous studies, through the detailed description of the cores of five boreholes in Meigang area of the Jitai Basin, combined with petrology, mineralogy and sulfur isotopes of gypsum, the lithofacies associations were analyzed, sedimentary facies types and sedimentary characteristics were identified, and the sedimentary evolutionary processes of the Zhoutian Formation were summarized. According to the lithofacies associations and sedimentary structures, the sedimentary system of the Zhoutian Formation can be divided into shore-shallow lake sedimentary system in the lower part and salt lake sedimentary system in the upper part. In the early deposition stage of the Zhoutian Formation, the depositional center was located between Taihe and Zhixia areas in the southeast basin, and was mainly composed of conglomerate, fine sandstone, muddy siltstone and silty mudstone. The alluvian-fluvial facies developed at the edge of the lake basin, transitioning to delta facies in the intra-basin, and to the sedimentary center of the lake basin, shore-shallow lake facies. In the late deposition period of the Zhoutian Formation, the climate gradually became arid, and a salt lake environment was formed by the continuous evaporation of the lake water. The rhythmic deposition of mudstone and gypsum rocks was developed, indicating the periodic salinization and desalination process of the lake water. The δ³⁴S value of gypsum is of 8.0‰~15.4‰, mainly concentrated in the range of 10.1‰~12.8‰, indicating that the gypsum was formed in an open salt-forming environment, and almost unaffected by the bacterial reduction process. In the Meigang area, the salt-bearing strata thicken towards the northwest, with well-developed fractured reservoirs, presenting a promising prospect for lithium brine-type deposit exploration.

sedimentary evolution; depositional model; salt lake; sulfur isotope; Jitai Basin