Geological Characteristics,Genesis And Metallogenic Prediction Of The Gypsum Deposits In Liaoning Province

Liaoning Province is located in the south of northeast,with a relatively high degree of geological work,which is one of the provinces with an earlier development of mineral resources in China.Liaoning province is rich in mineral resources with more than 100types of iron ore,coal mines,non-ferrous metal ores,non-metal ores and various energy minerals.The geotectonic location of Southeast Liaoning,where this research is located,is located in the eastern part of the northern margin of the North China Craton,and belongs to one of the key metallurgy and nonmetallic mineralization areas in the Northeast.The tectonic structure in the western part of Liaoning Province is located in the southern half of the Central Korean quasi-platform???Yanshan platform fold belt???Western Liaoning platform depression???Chaoyang dome fold fault bundle???.Based on the analysis of regional metallogenic geological background,this study selected the most representative gypsum deposits in the region?Dongjingling Gypsum Mine,Wanbaoqiao Gypsum Mine,Huolianzhai Gypsum Mine,Lingyuan Gypsum Mine?for systematic ore deposit geological characteristics.Researches on comparison and resource reserve estimation have further determined the genesis of the deposit and summarized the ore-forming laws.The main results and progress achieved are as follows:The genesis of gypsum deposits in Liaoning Province can be roughly divided into two types of genesis:metamorphic hydrothermal fissure-filling metasomatic and sedimentary gypsum deposits.We will take the widely distributed and large-scale marine evaporite-type gypsum deposits as the main research object this time,and discuss the four significant gypsum deposits in Liaoning province.The Taizi River Basin was denuded in the late Sinian period,the seawater invaded the Taizi River area during the early Cambrian alkali plant period.After a long period of geohistory,the sedimentary rocks were mainly carbonate rocks,clastic rocks and evaporites.The Cambrian strata followed closely,forming shallow land sediments with stable thickness.Later in the alkali plant,the seawater gradually receded and phytoliths appeared successively.By the end of the alkali plant,the seawater in the coastal lagoon gradually concentrated,the salt gradient increased,and some gypsum and anhydrite were separated and precipitated,forming the Lower Cambrian alkali plant gypsum deposit in this study area?PeiYongwan etc,2007?.During the Mantou formation period,the basal lifting movement was frequent,the climate was hot,and the evaporation was greater than the seawater recharge.The four obvious cycles of the Mantou stage have similar lithological units in various sections.Despite their differences in thickness,arrangement sequence,and some characteristics,the overall sedimentary characteristics are basically the same.The four paste layers?groups?formed in the mandible stage are formed in the corresponding four revolving segments.The carnallite and potassium salt layers are developed in the upper part of the gypsum ore horizon in the Dengta area.Although the grade of the carnallite and potassium salt layers is not very high,the metallogenic thickness of the salt layers is relatively large.This type of salt ore has stronger evaporation in the later stage than the pure gypsum ore.As evaporation continues,the sanddam rises to expose the water surface,the gulf is isolated from the ocean,and the potassium salt layers and the carnallite salt layers are deposited above the gypsum layer.Although there are no large-scale carnallite and potassium salt metallogenic layers in most mining areas,there are obvious mineralization indications.The thin mineral layers can be formed locally in the Dengta area,and then covered with a salt mud cover layer,which can be preserved.The multi-layered appearance of the gypsum layer reflects the cyclical interaction of relatively dry and relatively humid environments in the basin.Most other gypsum deposits are dolomite or dolomite limestone.Thicker layers of relatively pure gypsum deposits may have similar genesis as the thick gypsum deposits in the seaside Sabkha region of the Persian Gulf.The details are as follows:Seawater and terrestrial water supplement the groundwater,and evaporation increases groundwater salinity,in which Mg²⁺replaces Ca²⁺in the limestone to form dolomite or dolomite limestone,and the replaced Ca²⁺and SO₄^2-combine to form gypsum and anhydrite.According to comprehensive research,the genesis type of the deposit is marine salt evaporative sedimentary gypsum deposit.In the prospecting work of gypsum deposits in the future,the geochemical characteristics of the gypsum-bearing formations and the surface reference signs are crucial clues for gypsum prospecting.Where the Lower Cambrian Mantou Formation and the Alkali Formation have developed,the lithology is brick red.Dolomite mudstone,fuchsia argillaceous dolomite,and gray gypsum dolomite are predominant.Faults and fold structures are not developed,and areas with deep burial depth have prospects for gypsum prospecting.Prospecting direction in the future:Based on the results of this study,two prospect areas for gypsum deposits are located in the southern and western Liaoning areas of the Dongjingling deposit in the Liaoyang-Benxi area,with a distribution area of about 1600km².The gypsum strata in the Lower Cambrian Lower Touto Formation and the Alkaline Formation are relatively complete in the prediction area.The tectonic location is a complex syncline of the Taizihe-Hunjiang River in the Liaodong platform anticline of the Central North Korean platform is relatively stable,which has good future prospect for gypsum mineralization.