Geochemical Discrimination of Early Permian Sedimentary Environment in Jimunai Area, Southern Altai

The elements that are sensitive to the depositional environment have been selected for analyzing the major elements, trace elements and rare earth elements of 14 dark mudstone samples from early Permian Kalagang Formation at Zhuwankala section in Jimunai area. And then, the relationship between the contents and ratios of the strata's trace elements and the related sedimentary environment in the studying area has been analyzed. Finally, the sedimentary environment characteristics of Jimunai area in Early Permian, such as lake-basin climatic conditions, salinity, redox conditions, have been discussed. The results show that the Paleo-salinity indexes such as w(B),m(Sr)/m(Ba) andm(B)/m(Ga) are 51.32×10^-6, 0.29% and 2.42%, respectively, indicating a freshwater sedimentary environment in Jimunai area during Early Permian, with multiple secondary cycles of brackish water. The V/(V+Ni), Th/U and &U values are 0.82%, 3.62% and 0.92%, respectively, which suggest that the Jimunai area developed under an anaerobic environment during Early Permian. After standardizing by North America shale, it's found that the REE contents in mudstone is lower than North America shale, and it's speculated that the paleoclimatic environment was dry climate sedimentary condition with weak chemical weathering and calm water.