The Geological Characteristics And Genesis Of The Hadahexiu Saline Lake In Inner Mongolia

Inner Mongolia plateau is one of the most distributed areas of Saline Lake in China.Hadahexiu Salt Lake is located in the hinterland of Inner Mongolia Plateau.It is a typical sulfate-type Salt Lake in Inner Mongolia Plateau and one of the few porous brine deposits in Inner Mongolia Plateau.In this paper,the strata,structure,magmatic rocks,geological characteristics of solid and brine ore bodies in the Hadahexiu Salt Lake are studied in detail.The genesis of the deposit is discussed from the aspects of metallogenic basin,source of metallogenic material and climate.The basement of Hadahexiu Salt Lake Basin is dacite and tuff of Jinta Formation of Permian,and the upper part of it is covered with gravel-bearing coarse sandstone of Kuquan Formation of Neogene and Pliocene as bottom water barrier of brine ore body,The upper part is red sandstone with quaternary upper Pleistocene.The roof of the brine orebody is a yellow green,gray white,black silt layer of the Quaternary Holocene.The upper layer is the ore bearing horizon of the solid mirabilite rock deposit-quaternary Holocene lacustrine chemical sedimentary layer.This layer directly exposes the surface.The solid mirabilite ore bodies occur horizontally in the Quaternary Holocene lacustrine deposits with an average thickness of 3.16m.The main ore types are mirabilite,bloedite and salt.Sodium sulfate,magnesium sulfate and sodium chloride are the most beneficial components.The highest grade of sodium sulfate is 78.29%,the average grade is 22.97%;the highest grade of magnesium sulfate is 30.70%,the average grade is 12.88%;the highest grade of sodium chloride is 81.05%,the average grade is 24.72%.Bittern orebodies occur in the upper Pleistocene lacustrine sand layer of the Quaternary and show a horizontal production.The beneficial components are potassium chloride,sodium sulfate,Magnesium Sulfate and sodium chloride,and bromine and boron are associated with it.Among them,the average grade of sodium sulfate is 2.39%,sodium chloride is 4.29%,magnesium sulfate is 5.62%,and potassium chloride is 0.51%.The average value of PH is 7.87,which belongs to weakly alkaline brine.The average salinity is 151g/l.The chemical characteristics of brine in the study area show a certain horizontal zonation,while the vertical zonation is not obvious.The concentrating center of the Saline Lake basin is located in the north-east part of the study area.It belongs to SO₄·Cl-Mg·Na?SO₄·Cl-Na·Mg water.Hadada Saline Lake is controlled by Dabushu tectonic belts.The bromine chlorine coefficient of brine is less than 1.The origin of brine is dissolved water.The metallogenic materials are derived from the volcanic clastic rocks containing Na+,Mg²⁺,K⁺,Ca²⁺,Cl^-,SO₄^2-and Variscan intrusive rocks widely exposed in and around the basement of long-term leaching basins such as precipitation,surface water and groundwater.In the long-term geological evolution process,affected by humidity-dryness-heat and other climate changes,with the uplift-decline of the basin,the Hadahexiu modern inland lake evaporative salt lake deposit gradually formed.