Stream sediment geochemical mapping of the Mount Pinatubo-Dizon Mine area, the Philippines: Implications for mineral exploration and environmental risk

Stream sediments transport elements that are mobilized from adjacent slopes, representing the composition of the upstream watersheds. Thus, the analysis of the stream sediments allows depicting the spatial distribution of geochemical anomalies at the watershed level. In this study, 39 samples of stream sediments were collected in the Zambales Province, in the Philippines, characterized by the presence of the Mount Pinatubo volcano, the abandoned Cu Dizon Mine, small-mining of black sand, agriculture of rice, animal breeding, and fishing. Each sample was digested in aqua regia and was analyzed by ICP-MS to detect the content of 53 elements. This study is focused on elements with an environmental impact or associated to mineralization/ore occurring in the area. Background values for these elements have been evaluated by cumulative frequency curve to identify the occurrence of geochemical anomalies of geogenic or anthropogenic origin, mainly associated to the mining activity. Factor analysis, performed on normalized data with Additive Log Ratio transformation (ALR), allowed identifying three geochemical data associations, and a Geographic Information System (GIS) has been used to define the spatial distribution of the anomalies at the watersheds level. The GIS procedure assigns the value of the element concentration in the sampling location to the upstream watershed by hydrologic analysis of a Digital Elevation Model (DEM) of the study area. The main result of this study is a new type of geochemical mapping of the of the Mount Pinatubo-Dizon Mine area, representing a first approach to the definition of the environmental risk and the assessment of potential mineral resources.