Application Of The Weights-of-evidence Method In Mineral Resource Assessments In The Middle-south Part Of The Da Higgnan Mountains

The middle-south part of the Da Higgnan Mountains covering 400000km2 located at the Inner Mongolia Autonomous Region, is an ore-forming area superimposed by both the Paleo-Asian mega-metallogenic province and the Western Pacific Marginal mega metallogenic province, and thus has great ore-prospecting potential. The ore-finding targets are Pb-Zn-Ag polymetallic deposits. In this book the characters of geological background and the mineral distribution are analyzed. This paper quantitatively analyzes the spatial relationship among various kinds of forming information (ore-controlling factors) from geological and geochemical data with the help of the "weights-of-evidence method" on the basis of GIS. The best evidence layers such as the combined strata entropy, the favorable rock, one kilometer buffering zone of linear structure, and geochemical anomalous associations Ag-Pb-Zn-Mo-W, and copper anomaly are chosen as the variables for mineral resource assessments. They are used for calculating the posterior ore-forming probability of each unit. Eventually ore-finding target areas are quantitatively delineated and evaluated according to their posterior probabilities. Three targets among 31 ore-finding targets belong to the grade A, 23 ones belong to the grade B, and 5 ones belong to the grade of C. In general the targets are controlled by the crossing areas between NW and EW trend of faults. Most known deposits are located at the target areas, which show the liability of ore-forming prediction. This study provides ore-finding targets for prospecting works next step in the ore-forming zone. This case study has illustrated that on the GIS platform, the favorable mineralized areas can be effectively distinguished the favorable ones from the unfavorable ones by the "weights-of-evidence method" with ore-finding information so that the goal of fast quantitative delineation and assessments of the ore-finding target areas may achieved with the help of MORPAS3.0. The "weights-of-evidence method" can be used to model the spatial relationships between ore deposits and ore-controlling factors, which is different from traditional statistical methods. The advantages of the method are as follows: (a) the geological interpretation of the weights is relatively straight; (b) modeling processes can independently be realized; and (c) It is easy for the prediction results to produce repeatability.