Application of an airborne hyper-spectral survey system CASI/SASI in the gold-silver-lead-zinc ore district of Huaniushan, Gansu, China

Abstract

The airborne hyper-spectral survey system CASI/SASI, which has an integrated system for gathering both image an spectral data, is at the cutting edge developments in the remote-sensing field. It can be used to directly identify surface objects based on diagnostic spectral chara­ cteristics. In this paper, the CASI/SASI were used in the Huaniushan gold-silver-lead-zinc ore district–Gansu to produce a lithologic map, identify altered minerals, and map the mineralized-alteration zones. Radiometric correction, radiometric calibration, atmospheric correction (spectral reconstruction), and geometric corrections were carried out in ENVI to pre-process the measured data. A FieldSpec ® Pro FR portable spectrometer was used to obtain the spectral signatures of all types of rock samples, ore deposits, and mineralized-alteration zones. We extracted and analyzed the spectral characteristics of typical alteration minerals. On the basis of hyper-spectral data, ground-spectral data processing, and comparative analysis of the measured image spectrum, we used the spectral-angle-mapping (SAM) and mixture-tuned matchedfiltering (MTMF) methods to perform hyperspectral­alteration mineral mapping of wall rock and mineralized­alteration­zone hyperspectral identification. Hyperspectral­remote­sensing geological­classification maps were produced as well as distribution maps of all kinds of alteration minerals and mineralized-alteration zones. Based on geological comprehensive analysis and field investigations, the range of mineral alteration was proven to be the same as shown by the remote-sensing imagery. Indications are that airborne hyperspectral-remote-sensing-image CASI/SASI offer good application results and show a promising potential as a tool in geological investigations. The results will provide the basis for hyperspectral remote-sensing prospecting in the same or similar unexplored areas. 2006), thereby offering a high spectral resolution. Many unrecognized substances in wide-band remote sensing can be detected in the hyperspectral data and quantitatively studied (CLARK et al., 2003; TANG et al., 2006; SCHAEPMAN et al., 2009; KRUSE, 2012; VAN DER MEER et al., 2012). Because various minerals and rocks have diagnostic spectral-characteristic-absorption bands in the range of 400–2,500 nm, hyperspectral remote sensing can better capture the characteristics of minerals. Based on these characteristic spectral features, mineral compositional information can be inverted and identified. Thus, classification, mapping of rocks and mineral-resource exploration can be performed (CLARK et al., 2003; GAN & WANG, 2007; ZHANG et al., 2011; WEI et al., 2017). Since the mid-1980s, with the rapid development of key technologies such as data acquisition, radiation calibration, spectral reconstruction, and data processing, many applications of hyperspectral remote-sensing technology to the fields of geology and mineral resources have been performed by researchers around the world, resulting in some noteworthy new achievements (HUNT, 1989; CLARK et al., 1990, 2003; PIETERS & MUSTARD, 1988; KRUSE et al., 1990; CLOUDS, 1996; YESSY et al., 2011; LIU et al., 1999; GAN et al., 2000; WANG et al., 2000; YAN et al., 2004; WANG et al., 2010). At Article history: Manuscript received May 09, 2019 Revised manuscript accepted February 03, 2021 Available online February 28, 2021