The Constraints Of Tectonic Activity During Potassium Mineralization And The Later Stage In The Lower Congo Basin

Potash resources is one of the target minerals in Strategy of "going out" in China,because of the lack of potash.In the tide of the exploration of overseas potassium,the Lower Congo potash basin become the hot research area.The Lower Congo basin is located in the middle west African passive continental margin rift basin group,distributing in the north west-south east zonality,paralleling to the coast.There are gigantic thick evaporite deposits widely developed in the Cretaceous formation.The thick mineral layer of potash sedimentary in the Congo and Gabon coastal basin,which with industrial value.The Lower Congo basin is a typical rift-potassium basin.Some researcher already had some study on it and summarized some metallogenic regularities.On the basis of previous studies,we have carried on the detailed study on the relationship of the potash metallogenic and tectonic activities in the study area,by using physical,chemical,remote,drilling exploration data in this paper.Combined with the regional tectonic setting,tectonic and sedimentary evolution history,evaporite sedimentary sequence,etc.,we summarized the metallogenic evolution rules,origin of ore deposit,and built a potash metallogenic model in the Lower Congo basin.Under the premise of “tectonics-source-climate” three key factors coupling effect,the mode potassium metallogenic evolution process is mainly divided into three stages in the study area: metallogenic stage;Evaporation deposit metallogenic stage;Metallogenic after transformation stage.Variety of geological data indicate that tectonic activity as a core element in the Lower Congo basin occupies very important status in the metallogenic model,and through potassium mineralization process.The geochemical data shows that ore-forming material sources is supplied priority from marine,secondly from the mixture of deep and terrigenous sources.The Lower Congo basin are generally flat,due to the effect of tilted of the passive continental margin,which brings the structure high in the northeast and structure low in southwest,inclined to the sea with low angle,the geometric center of the basin in the southwest of the study area.Tectonic environment of the basin is generally stable,and it recorded a detail information of the sedimentary succession of the basin.In the system of brine migration and deposition distribution rules of the study area,it shows apparent direction.The migration direction is directly related the tectonic background of the occurrence and development of south Atlantic rift.Native rock salt crystals within the uniform temperature of the fluid inclusions can represent its crystallization precipitation of ancient brine interface temperature.According to the test,ancient temperature of the evaporite sediments in the study area is higher than30 ?,suggests that the era of evaporite deposits ancient climate should be extremely dry,conducive to the formation of evaporite.The metallogenic model will enrich the rift-potassium model which put forward by the predecessors,and enhance research metallogenic regularities of basin.It provides necessary theoretical support during the study of building a 3D model of potash deposit sediment and exploring potassium orientationally in the future.