Modeling geochemical anomalies of stream sediment data through a weighted drainage catchment basin method for detecting porphyry Cu-Au mineralization

Abstract

Stream sediment surveying is a geochemical sampling method which is typically applied in the preliminary stages of mineral prospecting. Both continuous and discrete mapping approaches have been proposed to delineate geochemical anomalies at large scales using stream sediment samples. We aim to enhance the efficiency of a recent discrete mapping method called Weighted Drainage Catchment Basin (WDCB) which is independent of sampling sites and density, and has an advantage given that samples may not be uniformly distributed throughout the study area. The Enhanced WDCB (E-WDCB) method can be applied to calculate the weight of each catchment basin using different geochemical parameters such as factor scores. Our study focuses on the factor analysis of three datasets from the Bathurst region, New South Wales, Australia, with different numbers of samples. Different associations of the elements revealed by the factor analysis show that such analyses highly depend on the contributing samples and elements. We propose the Catchment Basin Score (CBS) index to delineate the suitability of sampling in each catchment basin. This index can also be applied to integrate the components resulting from several multivariate analyses on different datasets in a same area. The prediction-area plots show that our proposed method is able to predict a higher percentage of porphyry CuAu occurrences in a smaller area compared to other canonical methods, e.g. the median of factor scores in each catchment basin. We demonstrate that prospective areas for porphyry CuAu mineralization using the proposed discrete mapping method are also well correlated with volcanic and intrusive rocks.