Element Geochemical Characteristics of Sedimentary Rocks and Its Geological Significance from the Upper Permian Linxi Formation in the Songliao Basin

The Permian Linxi Formation of Well Mg1 in Songliao Basin revealed a set of gray and black mudstone deposits. In order to solve the sedimentary environment background of this set of black and gray mudstone, the trace elements and rare earth elements in the drilling clastic sedimentary rock samples were detected and comprehensively applied. The study shows that the sedimentary rocks of Linxi Formation have high light and heavy REE diversity, δEu showed significant negative abnormality (mean 0.66) δCe is normal (mean 0.99), and the chondrite is generally characterized by light rare earth enrichment, right dip, heavy rare earth depletion, and nearly flat type. The fluctuation of trace element Sr, Cu content and Sr/Cu ratio in the section of sedimentary rocks shows that the paleoclimate in the study area experienced an evolution process from dry and hot climate to warm and humid climate in the late Permian. The comprehensive study on the mass fraction of elements Sr, Ga, Li, Sr/Ba, Y/Ho ratio and other indicators shows that the water body during the sedimentation period of Linxi Formation was mainly continental freshwater environment. Determination indexes of redox environment V/Cr, Ni/Co, U/Th Δu, δEu and δCe and other comprehensive studies show that in the study area, the sedimentary period of Linxi Formation in the late Permian is dominated by oxidation environment, but it does not exclude the existence of weak oxidation and weak reduction environment.