The use of unmixing technique in stream sediment geochemical exploration

Abstract

This research has aimed at employing unmixing method as a sediment tracing technique and its use in stream sediment geochemical exploration. Sediment tracing could be applied to determine the relative contributions of source units (Cij) to the metal contents of stream sediment samples. This is the first attempt to use the “fingerprinting” technique for estimating the background values of stream sediment samples.In catchment basin analysis of stream sediment data, the relative area sizes of lithological units (Xij) were used as the proxies for their contributions to the metal contents of stream sediment samples. The Hughes mixing model was solved using the particle swarm optimization (PSO) method to assign the contributions of 7 lithological units to 69 sample catchment basins. The results revealed some similarities between the estimated Cij values and the relative area sizes of lithological units (Xij) in all catchment basins, demonstrating the representativeness of area sizes as the proxies for the relative contributions of upstream sources to the metal content of stream sediments. The background values at the basin outlet were estimated using both Xij and Cij values. The results, therefore, revealed the superiority of the mixing model in estimating the background values at the basin outlet for most of the elements. The mixing model accurately estimated the elemental concentrations of Fe, Mo, Sb, Th, Ti, Y, and Yb; however, the unmixing approach failed to accurately predict the metal contents of elements such as Cr, Ni, Pb, Li, and Zn.