基于MRAS证据权重模型的河南老湾地区金矿成矿预测

Metallogenic prediction of gold deposits in Laowan area,Henan Province using the weight of evidence model and MRAS

河南省老湾地区是桐柏—大别有色贵金属成矿带上重要的金成矿区。在综合分析该区成矿因素的基础上,提取构置了地层、韧性剪切域、脆性断束、岩浆岩、与Au有关的蚀变带和Au、As、Sb、Ag水系沉积物单元素异常等9个预测变量,基于MRAS软件,采用证据权重模型对该区金矿进行了成矿远景预测工作。本次采用0.10 km×0.10 km的网格单元进行预测,经过各预测变量的先验概率计算、权重值统计、独立性检验和后验概率的计算等过程,划分出A、B、C三个级别的成矿远景区块,根据预测网格分布特点及该区金矿地质特征,圈出了Ⅰ级找矿远景区4处,Ⅱ级找矿远景区4处。综合分析认为:已知金矿床或矿点多数落入A级或B级成矿远景区块,C级成矿远景区块主要是在A级或B级成矿远景区块的周边,与成矿区带从中心向边缘渐变的特征相符合;圈出的Ⅰ级找矿远景区内均已发现金矿床(点),并且后验概率平均值较高,具有较好的金矿找矿潜力。

The Laowan area in Henan Province is an important gold minerogenetic area in the Tongbai-Dabie noble nonferrous metal metallogenic belt.Based on the comprehensive analysis of the metallogenic factors of the area,the authors extracted and established nine predictive variables,i.e.,strata,ductile shear zones,brittle fault zones,magmatic rocks,gold-related alteration zones,and single-element anomalies of gold,arsenic,antimony,and sliver in stream sediments.Then,the authors predicted metallogenic prospect areas of gold in this area using the weight of evidence model and the MRAS software.Grid cells with a size of 0.10 km×0.10 km were used for prediction,and they were divided into classes A,B,and C in terms of prospecting prediction through the prior probability calculation,weight statistics,independence tests,and posterior probability calculation of each prediction variable.Based on the distribution characteristics of various classes of prediction grid cells and the geological characteristics of gold deposits in the study area,this study delineated four first-and four second-order prospecting target areas.According to comprehensive analysis,most of the known gold deposits or gold ore occurrences fall into the prediction blocks of classes A and B and the prediction blocks of class C lie around the prediction blocks of classes A or B.This analytical result is consistent with the gradual changes of the metallogenic belt from the center to the edges.Gold deposits or ore occurrences have been discovered in all the delineated first-order prospecting target areas,and the posterior probabilities have a high average.Therefore,first-order prospecting target areas have great gold prospecting potential.