地球化学块体法在埃塞俄比亚金矿资源评价中的应用

Application of geochemical block method in the evaluation of gold resources in Ethiopia

低密度地球化学填图具有采样水系沉积物级别高,工作覆盖区域面积广阔的特征,适合应用地球化学块体法进行大空间尺度的矿产资源潜力评价,本次研究以埃塞俄比亚1∶100万低密度地球化学填图数据为基础,应用地球化学块体法,以埃塞俄比亚的优势矿种Au为研究对象,结合区域成矿地质背景,对研究区金矿资源潜力进行了评价并划定成矿远景区。数据结果显示:Au元素的异常下限值为1.55 ng/g。在此基础上,分别以1.55 ng/g、1.95 ng/g、2.46 ng/g、3.09 ng/g、3.89 ng/g、4.90 ng/g作为分级间隔,共圈定出地球化学块体6个,区域异常4个。根据研究区已知金矿床储量,计算出Au的成矿率为0.06%。本次以1000 m岩块厚度计算出研究区Au的总供应量565537 t,并估算出研究区内Au的资源量为339.18 t。其中1号地球化学块体、3号地球化学块体所在1∶25万图幅区域可作为进一步详细勘查工作的重点成矿远景区,2号地球化学块体、4号地球化学块体、5号地球化学块体及Ⅲ号区域异常所在的1∶25万图幅区域可作为次重点成矿远景区。

Low density geochemical mapping is characterized of sampling in high level stream and vast covering-area,which is suitable for the application of geochemical block method in the assessment of mineral resource potential in vast region scale.Based on geochemical data obtained from 1∶1000000 stream sediment geochemical survey in Ethiopia and metallogenic geological background,this study investigated the regional gold potential by using geochemical block method and determined the favorable Au prospecting area.The results indicate that the value of geochemical anomaly threshold is 1.55 ng/g.Six geochemical blocks and four regional anomalies are delineated by using 1.55 ng/g,1.95 ng/g,2.46 ng/g,3.09 ng/g,3.89 ng/g and 4.90 ng/g as the grading intervals.The calculated mineralization coefficient is based on the measured resources of the known gold deposit in study area.This study show that the total gold tonnage in these blocks is 565537 t,Au resources in study area(given a 1000 m thickness of every rock mass)is 339.18 t,and the 1∶250000 map sheet in which geochemical blocks No.1 and No.3 spread should be the favorite prospecting area,the 1∶250000 map sheet in which geochemical blocks No.2,No.4,No5 and region anomaliesⅢspread should be the second favorite prospecting area.