Sediment-hosted Abra Pb-Zn-Cu-Au

Hyper and multispectral mineral footprints surrounding the 1.59 Ga Abra Pb-Zn-Cu-Au deposit were investigated in a PhD study between 2014 and 2018 as a part of the broader Capricorn Distal Footprints project. Before, it was known that the top of the sulfide mineralisation at Abra lied at ~250 m depth from the surface, and that the sulfide deposit was enveloped by chlorite-siderite halo of unknown extent. The deposit and surrounding rocks were intersected by several drill holes with hyperspectral data and weathered bedrock in the Edmund basin is only about 50% under transported cover. Therefore there was a good chance that any mineral signature surviving through the weathering detected from the drill core hyperspectral data could be delineated from the CSIRO’s continental scale ASTER mineral product maps.

The Abra deposit drill hole hyperspectral data investigation revealed that the phengitic signature in white micas, which was discovered to be a distal expression of the mineral footprint above the Abra deposit, indeed survived to the surface (Lampinen et al. 2019).

Lampinen et al. (2017) hyperspectral study identified the distal phengitic white mica alteration from the in-situ polymictic lag overlying the weathered rocks above the Abra deposit. The findings from field and regolith sample reflectance spectra enabled delineation of a broader surface expression of this distal alteration using the multispectral ASTER AlOH composition mineral product map together with potassium radiometric grid data.