Genesis Of Clastic Intercalation In Salt-bearing Strata Of Qarhan Salt Lake In Qaidam Basin

Qarhan Salt Lake in Qaidam Basin is a large-scale potassium-magnesium salt deposit with potash salt as the main mineral,coexisting solid and liquid minerals.The liquid deposit has large scale and reserves,strong water-rich and easy to be mined.While the solid potassium-magnesium salt mine is low-grade ore,it has a wide distri-bution,but the ore layer is thin and the continuity is poor,which makes it difficult to mine.In order to ensure the sustainable development of the company,Qinghai Salt Lake Industry Co.,Ltd.has continuously strengthened its investment in solid/liquid conversion dissolving of low-grade solid ore in Qarhan Salt Lake.However,due to the strong heterogeneity of the ore body and the presence of more clastic interbeds in the salt-bearing strata,it is difficult for solvents to enter the ore bed steadily and continuously,which significantly reduces the efficiency of large-scale ore-dissolving mining.Therefore,to ascertain the genesis of clastic is of great significance interbeds in salt-bearing strata for guiding the next step of ore dissolution.This paper takes the salt-bearing sediment profiles with clastic interbeds in the shallow salt lake as the research object,based on the comprehensive analysis of mineralogy,granulometric analysis of sediments and geochemical analysis and other technical means,try to find out the evolution process of the salt-bearing strata and the genesis of the clastic interbeds.The lithofacies characteristics show that there is corrosion phenomenon in the four clastic interbeds in the lower part of the measured profile,while there is no obvious dissolution phenomenon has been observed in the upper salt layer.Geochemi-cal characteristics of evaporite indicate that four flood events occurred successively in the salt-bearing strata in the course of sedimentary evolution,in turn at the 31,29,25 and 23 layers of the profile.The grain size analysis of the sediments shows that the sediments in the four clastic interbeds are carried by flowing water and deposited in the lacustrine sedimentary environment.The sediments at the upper part of the measured profile were piled by transportation of different geologic agents.The early lacustrine sediments formed around the lake were transported to the salt lake by wind to participate in the deposition.The origin of clastic interlayer in salt-bearing strata is preliminarily determined as follows: during the evolution of salt lakes,the surrounding detritus is brought into the salt lake deposit by floods,forming thin clastic interlayer between lithium-salt layers.The small amount of debris inclusions in the upper salt layer should be the result of wind force bringing the surrounding sediments into the salt basin.The intermittent occurrence of debris is probably caused by seasonal climatic conditions in Qarhan area.It is of great significance to restore the formation process of salt-bearing strata,and also provides an important theoretical basis for the design of mining technology and scheme of low-grade solid potash mine.