Detection of alteration zones using hyperspectral remote sensing data from Dapingliang skarn copper deposit and its surrounding area, Shanshan County, Xinjiang Uygur autonomous region, China

Abstract In application of hyperspectral remote sensing, alteration zones are primarily detected by identifying alteration mineral assemblages, but the interpretation of alteration mineral maps is often complicated by surface materials and by minerals not directly associated with alteration. This study was conducted in the Dapingliang skarn copper deposit and its surrounding area, the Shanshan County of the Xinjiang Uygur autonomous region, China. In order to successfully detect alteration zones associated with skarns, this study identified skarns rather than alteration minerals using field spectra of skarn outcrops. In this study, skarn in pixels was identified from spectral overall shape and spectral shapes of absorption-bands; SAM (spectral angle mapper) was applied in the identification. When SAM scores of spectral overall shape were less than 0.022 rad, the identified skarns were mainly distributed in the contact zones of intrusive rocks and carbonates; in particular, the three identified skarns areas (R1, R2 and R3) were consistent with the skarn areas in the geological map of the study area. The field inspection of skarns showed that the identified objects of the three marked targets (A, B and C) were almost consistent with the ground objects. These obtained results demonstrated that using the field spectra, it was possible to identify skarns in the hyperspectral image. To evaluate the identified skarn zones for use in mineral exploration, the end-member spectra extracted from the image were analysed, and alteration zones were detected using these end-member spectra. Compared with these alteration zones, the identified skarn zones were more reliable for mineral exploration of the study area.