基于汇水盆地的化探异常识别与评价: 以东昆仑乌拉斯太地区1∶5万水系沉积物地球化学测量为例

水系沉积物地球化学测量是卓有成效的找矿技术方法, 基于汇水盆地的水系沉积物地球化学异常提取有助于追溯异常源头、指明找矿方向。基于SCB法提出了汇水盆地法, 该方法以自然汇水盆地为预测单元, 将各样品点的地球化学属性特征赋予各自所在区域, 预测结果较为符合地形地貌特征, 且对于采样密度较高的1∶5万水系沉积物地球化学测量数据有较好的应用效果。以东昆仑乌拉斯太地区为研究区, 使用高精度DEM划分汇水盆地, 利用该方法对1∶5万水系沉积物Au、Ag、Pb因子得分进行了异常信息提取, 在提取过程中利用多种地貌参数(干流坡度、地形起伏比、汇水盆地面积)作为泥沙输移比进行残差校正计算, 并在此基础上, 利用C-A分形法分离了地球化学背景与异常。异常提取结果表明, 汇水盆地面积参数最适合用作乌拉斯太地区的泥沙输移比参与顺流衰减校正, 使用汇水盆地法可以有效识别和提取该地区地球化学异常信息。使用汇水盆地法提取的化探异常范围与矿床空间位置吻合度高, 可以为进一步找矿工作提供有利的信息。 

Identification of the geochemical anomalies using the catchment basin analysis: A case study of 1∶50000 geochemical survey of stream sediments in Wulasitai region,East Kunlun Orogenic Belt

Geochemical survey of stream sediments is an effective technology for mineral prospecting. The extraction of geochemical anomalies in stream sediments based on catchment basins has always been one of the research hotspots.The catchment basin analysis method is proposed based on Sample Catchment Basin Analysis (SCBA)in this paper, and it is used to identify geochemical anomalies in the Wulasitai region, East Kunlun Orogenic Belt in Qinghai Province.Catchment basins are divided by a high-precision DEM, and the Au, Ag, and Pb factor loadings of 1∶50000 stream sediments are measured by the catchment basin analysis. During the extraction process, a variety of geomorphic parameters such as main stream slope, relief ratio, catchment basin area, are used as the sediment delivery ratios for residual correction calculation, and the geochemical background and anomalies are separated by the C-A fractal modeling. The anomaly extraction results show that the area of the catchment basin is the most suitable parameter as the sediment delivery ratio to participate in the downstream attenuation correction. The catchment basin method can effectively identify and extract geochemical anomaly information.Anomalies correspond well to the spatial location of ore deposits, and can provide beneficial information for the next step of mineral prospecting.