Geological Characteristics And Genesis Of Potash Deposits In Haixiafeng,Laos

Laos is a landlocked country in Southeast Asia,which is adjacent to China's Yunnan province in the north,Vietnam in the east,Myanmar in the south and Thailand in the west.Laos has undulating terrain in the country,with the Truong Son Mountain Range in the Northeast,the northwestern margin of the Sakhon Nakhon basin in the Midwest,and the Haixiafeng potash deposit in the northern margin of the Sakhon Nakhon basin.Based on the exploration project,this paper has studied the mineralogical and geochemical characteristics of Haixiafeng potash salt deposit by using the data and achievements of the Geological exploration projects,combined with the mineralogical geochemical test and analysis,and discussed the genesis and environment of the deposit.The study shows that the strata in the study area of Haixiafeng potash deposit mine are simple,with the Permian to Quaternary strata exposed,and the strata are mainly Jurassic,Cretaceous,Paleogene and Quaternary,in which the surface is mostly covered by Quaternary,the salt-bearing Paleogene strata are locally visible,and the surrounding Jurassic and Cretaceous strata are visible.The complete sequences of the deposition of potash salt in xia haifeng solid potash deposits provides an excellent research base for the study of the formation reason,metallogenic conditions and salt forming mechanism of fossil brine.The potash layers occur in the Tagong group?E₁tg?in Palaeogene.This formation has three sedimentary cycles,which are successively from bottom to top:rock salt layer-mudstone layer-rock salt layer-mudstone layer-rock salt layer-mudstone layer.Each salt layer and mudstone layer is called a sedimentary cycle.In which,potash deposits occur at the top of the first sedimentary cycle,namely,the rock salt layer.The mineral deposits are mainly carnallite and sylvite.Among them,both the base primary potash salt and the top secondary potash salt are not strong continuous and the thickness is not stable,but the central carnallite layer is stable in thickness and large in distribution area.The results of mineral identification and geological characteristics analysis show that the authigenic minerals in Haixiafeng potash deposit are mainly chloride carnallite potash,belonging to chloride type salt deposit and formed by chloride type brine.The drilled ore profile can be divided into two types:sylvite profile and carnallite profile,and the original brine composition of the carnallite profile is more rich in MgCl2 components than that of sylvite profile.In the process of the formation of the Haixiafeng potash deposit,salt halogenated water has four stages of desalination process,but generally presents a continuously concentrated evolution process.Br?Br×10³/Cl in sylvite and carnallite indicate that the main source of potash mineral material is from seawater.Based on the study and analysis of the regional geology,mineral features and metallogenic conditions of the Haixiafeng potash deposit in Vientiane city,Laos,it is believed that the deposit type is a solid potash deposit by evaporation of marine facies in Paleozoic.The genesis of the deposit is closely related to the closed basin formed by geotectonics.