Evolutionary characteristics of the sedimentary environment of the lithium-rich strata in the Permian Daoshitou Formation in the Anning area of the central Yunnan, China

In recent years, the newly discovered clay-type lithium deposits in the central Yunnan are characterized with large scale, widely distributed area and huge lithium resource potential. The sedimentary environment is believed as a key controlling factor for the lithium enrichment of those deposits. However, it is still unclear regarding the coupling relationship between the sedimentary environment and lithium enrichment of those lithium ore-bearing rock series in the Anning area of the central Yunnan. In this study, by taking samples of the Daoshitou Formation from cores of two typical drilling holes in the Anning area of the central Yunnan, we have carried out investigation on the characteristics of sedimentary environment changes using sensitive ratios such as ratios of Sr/Ba, Rb/K, U/Th, V/Cr, V/(V+Ni), Sr/Cu, Rb/Sr and Mo isotopes, in order to restore the sedimentary environment of the lithium-rich strata and to constrain the lithium enrichment condition. The results show that the lithium-rich strata within the Daoshitou Formation were mainly formed in terrestrial environment characterized with dry and hot climate, relatively closed oxidation-weak reduction REDOX conditions. The enrichment of lithium in these ore-bearing rock series had undergone the weathering and erosion stage of original rocks, the migration and transportation stage of original weathered crusts, the deposition-diagenesis stage of the ore-bearing sequences, and the late reworking stage of ore-bearing rocks by the infiltration process of fluids. Among these stages, the deposition-diagenesis stage of the ore-bearing sequences was believed the main stage for the lithium enrichment within the Daoshitou Formation which was closely related to the proper sedimentary environment.