| The development of national economy has brought benefits to mankind,while resulted in the loss of natural resources.In recent years,increasingly depleted bauxite resources have constrained the development of the aluminum industry in our country.If there is no sufficient bauxite reserves,the development of national economy will be hindered.With rich mineral resources,open mining policies and low geological work,Laos is a hotly-requested mineral exploration site in the world.The volcanic activity in the area of the Boloven Plateau in southern Laos is intense,and the magmatic rock condensed on the surface of the original stratum is resulted in the enrichment of ferro-aluminous minerals by weathering and leaching,therefore,there is a lateritic bauxite-bearing area.Boloven Plateau is researched in this paper,and a combination of geology,remote sensing,and geographic information analysis techniques is used to establish Metallogenic Conceptual Model,Favorable Metallogenic Information Model and Comprehensive Metallogenic Prognosis Model,thus reached the mineralization prediction of laterite bauxite in study area.The main conclusions and methods for the laterite bauxite metallogenic conditions and establishment of prospecting model in Boloven Plateau are summarized as follows:?1?Referencing the known mining areas in Pasong County and related literatures,the metallogenic regularities in study area are analyzed as follows:Basalt is the parent rock of bauxite in Boloven Plateau Laos,and the component of which is mainly felsic;The best terrain landform of laterite bauxite formation for altitude is ranged from700m to 1300m,for gradient 5°to 25°,and for topographic relief 10m to 85m with180m horizontal distance;Most bauxite in plateau occurs where vegetation is scarce.The water system in Boloven Plateau is distributed uniformly and densely,the radiate formed water system in the bauxite enrichment area is obvious,and the terrain in valley is slightly deep and clear in outline,which is beneficial for the chemical reaction in rock to take away the silicon products in the weathering crust and promote the enrichment of aluminum and iron.?2?The laterite in the plateau is mainly composed of iron and gibbsite,but the information of Al3+in remote sensing image is too weak to identify bauxite,so the information of Fe2+,Fe3+and OH-is extracted.Based on the OLI remote sensing data,this study analyses the spectral characteristics of the aluminum and iron,combines ratio,principal component analysis,color synthesis and spectral angle classification methods,refers the distribution of all kinds of minerals in 1:100 million geological maps,comprehensively analyses the results of alteration distribution obtained by ratio-density division,principal component analysis-density division,ratio-principal component analysis-color synthesis-spectral angle classification,obtains the alteration information of bauxite in study area.?3?According to the Metallogenic Conditions of bauxite in Boloven Plateau Laos,establishing the Metallogenic Conceptual Model,the Boolean logic method is used to exclude the conditional restricted area and output the favorable areas for mineralization.Based on the reduced prospecting range of bauxite,analys the bauxite alteration information and hydrogeological conditions,builds the Comprehensive Metallogenic Prognosis Model as follows:For the alteration information,the altered patch area greater than 0.3km2and the patch density greater than 5%are prefered to select as the metallogenic prediction area;For the valley information,the bauxite metallogenic prediction area is focused on the regions with radiate water system and valley cutting depth in 3-68m.Finally,this study predicts 19 bauxite prospect area,and the prediction accuracy is up to 86%according to the field verification,which can provide scientific theoretical basis for regional geological work and following prospecting. |
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