川西北金矿的证据权模型及其预测应用

Application of Evidence Weight Model for Prediction of Gold Mineralization in the Northwestern Sichuan Province

在深入理解川西北地区金矿成矿特征的基础上 ,建立了该区的地质、物探、化探、遥感和金矿床 (点 )数据库 ,优选了 10个致矿证据层。应用证据权模型对该区进行成矿分析 ,认为本区共有NW、NE、SN、EW四个方向上的金矿成矿区 ,同时分析了四个成矿区的分布特征和空间耦合关系。在此基础上 ,根据该区成矿概率分布进行了有利成矿远景区的预测 。

Geographic information system (GIS) is a new technique successfully applied to geological research. It is advantageous in processing data with spatial distribution. The evidence weight model is a mathematical model combined with GIS technique. Based on the spatial relation of elemental data, it synthesizes various favorable ore forming factors (evidence layers) and can be used in mineralization prognosis and evaluation efficiently. The northwest of Sichuan Province is an important micro fine disseminated gold resource base in China. In this sense, it is significant to have a metallogenic analysis of the region and to search for the areas favorable for gold mineralization. This paper is an empirical example for application of evidence weight model in the northwestern Sichuan Province. Based on the comprehensive analysis of features of gold mineralization in this region, five databases have been created: geology database, geophysics database, geochemistry database, remote sensing database, and ore deposits (occurrences) database. According to the analysis of the ore controlling factors in this region, we selected 10 ore producing evidence layers, which include the stratigraphic lithological assemblage, linear faults, minor plutons, joints of structure from remote sensing, geochemical anomalies of Au, As, Sb, Ag, and the gravity and magnetic anomalies deduced to different elevations. Extracting the data from the above mentioned five databases, the authors calculated the evidence weight values and the correlation degrees between the particular evidence layers and ore deposits (occurrences), created an evidence weight model of gold mineralization in the northwestern Sichuan Province. Using the evidence weight model in this paper, the authors analyzed the features of gold mineralization in this region, indicated existence of four main gold mineralization zones in four different directions: the NW directed gold mineralization zone controlled by Maqu Lueyang structure belt, the NE directed gold mineralization zone controlled by Qingchuan Pingwu structure belt, the SN directed gold mineralization zone controlled by Minjiang structure belt, and the EW directed gold mineralization zone controlled by Xueshan structure belt. Based on the analysis of distribution characteristics of gold mineralization zones and spatial coupling relationships among them, the favourable areas have been predicted in three levels according to the ore formation probability values. Finally, some suggestions related to application of GIS in metallogenic prognosis are also proposed.