Holocene Sedimentary Environment And Potash Mineralization Of Mahai Salt Lake,Qaidam Basin

Mesozoic and Cenozoic continental salt lake basins are widely developed in China.It is of great significance to study the stratigraphy of salt lake basins.Mahai Basin is located in the western section of the eastern subsidence area of qaidam Basin,a rare large inland salt lake basin in the world.It is a secondary basin formed by the tectonic activities of folds and faults.The area is high in the southwest and low in the northeast,which makes the major drainage systems and salt mineral components around the basin converge in the sedimentary center in the northeast of the basin.The strata in the study area are from old to newly exposed,which are early Pleistocene,middle Pleistocene,Late Pleistocene and Holocene strata in sequence.The Holocene is the potassic mineralization period,so the paper will select the Holocene strata in the study area as the main research object.As a large continental salt lake,the salt formation mechanism of Mahai Salt Lake is mainly evaporation salt formation,which is mainly controlled by climate.Due to the complex changes of sedimentary environment,the Mahai salt lake basin contracted continuously and formed a potassium salt deposit with the coexistence of solid and liquid.Therefore,the study of sedimentary environment is of great significance to the mineralization of continental salt lake.In order to reveal the controlling significance of sedimentary environment on potash mineralization in Mahai Salt Lake,this paper mainly studied the lithology of core sediments and the morphological characteristics and combinations of salt minerals in 16 geological holes in the study area,and divided and compared the sedimentary strata in the study area by sedimentary rhythm,so as to establish the regional stratigraphic framework.On the basis of depositional rhythm division,the salt content of the strata was analyzed and compared to reveal the migration process of the depositional center in the study area and further improve the depositional facies distribution.In this paper,fluid inclusion experiment is used to restore the composition of the ancient salt lake brine and reveal the evolution of the salt lake brine since the Holocene.Finally,combining the sedimentary environment with the deployment of water solution mining engineering in Mahai mining area,the mineralization of potassium salt in the sedimentary environment is discussed,and the deployment of water solution mining engineering in the study area is briefly evaluated.Based on the previous researches of geologists in the study area,the sedimentary strata of Mahai Salt lake in holocene can be divided into four sedimentary rhythm layers,indicating the evolution process of saltwater lake environment,salt lake environment and dry salt flat environment,thus the sedimentary facies is shallow lake facies,salt lake facies and dry salt flat facies.According to the analysis of fluid inclusions,the paleo-brine of The Mahai Salt Lake only reached the stage of salting-out in holocene.Through the analysis and comparison of the chemical composition of the strata,the genesis of potassium salt minerals is revealed.Finally,combined with the sedimentary characteristics of the study area and the deployment of water-soluble mining engineering,it shows that the sedimentary environmental factors play a controlling role in water-soluble mining.