By PhD candidate MSc Heta Lampinen and supervisors; Dr Carsten Laukamp (CSIRO), Dr Sandra Occhipinti, Prof Campbell McCuaig and Prof Marco Fiorentini (CET/UWA) as part of the 2015 Students in Mining & Energy TerraSpec Instrument Program.
The project aims to discover how reflectance spectra measured from the surface of the earth can be utilised in finding mineral footprints of hydrothermal ore deposits concealed by the regolith. The scope is to identify the mineral assemblages at the study area that are characteristic for four schematic domains: 1) unweathered, unaltered bedrock, 2) unweathered altered bedrock, 3) regolith atop unaltered bedrock, and 4) regolith atop altered bedrock.
Prior to fieldwork, reflectance spectra measurements were collected in a laboratory setting (Figure 1) using FieldSpec® 3 spectrometer from 552 surface regolith samples, archived by the Geological Survey of Western Australia (GSWA) and the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The acquired VNIR-SWIR reflectance spectra were processed in The Spectral Geologist (TSG®) software using the Multiple Feature Extraction Method MFEM; (Cudahy et al. 2008 and Laukamp et al. 2010) for characterisation of mineral assemblages. This work was carried out to establish the regional and deposit scale variation in the surface mineralogy in general, but also to compare the hyperspectrally derived mineralogy with geochemical analyses undertaken by GSWA to effectively target the fieldwork areas of interest.
The TerraSpec® 4 Hi-Res mineral spectrometer was used during three weeks of fieldwork from April 20th to May 10th 2015 in the Edmund basin of the Proterozoic Capricorn Orogen in Western Australia. The study area of 60*110 km in size is located 900 km north from Perth, west of the Collier Range National Park and roughly 170 km west from the Great Northern Highway. The study area is designed around the sediment hosted stratiform Pb-Cu-Zn-Ba deposit Abra, discovered at roughly 200 m depth in 1981 by drilling into a magnetic bulls-eye anomaly. Geochemical sampling efforts have so far failed to a find mineralisation footprint around the Abra deposit. Other known base metal mineralisation occurs within the same structural corridor, along the crustal-scale Quartzite Well Fault.