Mineralogical mapping of southern Namibia by application of continuum-removal MSAM method to the HyMap data

• Published in: International journal of remote sensing Vol. 34; no. 15; pp. 5282 - 5295
• Main Authors: Oshigami, Shoko, Yamaguchi, Yasushi, Uezato, Tatsumi, Momose, Atsushi, Arvelyna, Yessy, Kawakami, Yuu, Yajima, Taro, Miyatake, Shuichi, Nguno, Anna
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 2013
• Subjects: Airborne sensing; Alterations; Animal, plant and microbial ecology; Applied geophysics; Biological and medical sciences; CUPRITE; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General aspects. Techniques; Internal geophysics; Mapping; MINERALS; PORPHYRY ORES; Remote sensing; Rock; SPECTRA; Teledetection and vegetation maps; Southern Africa; Namibia; Africa; short period waves; X-ray diffraction; mineralogy; remote sensing; cartography; distribution; samples; Spectral data; Hyperspectral imaging sensor; hydrothermal alteration; Hyperspectral characteristic; Spectroscopical observation; methodology; Reflectance
• ISSN: 0143-1161; 1366-5901
• DOI: 10.1080/01431161.2013.789147

We applied the Modified Spectral Angle Mapper (MSAM) and continuum-removal methods to reflectance data obtained in the shortwave infrared regions by the airborne hyperspectral sensor, HyMap, to delineate distribution of the minerals related to hydrothermal alteration and pegmatite. The combination of these two methods was applied to remotely sensed hyperspectral data for the first time in this study. The effectiveness of this method, 'continuum-removal MSAM', was confirmed by comparing our mineral index maps with existing mineral maps of the Cuprite region, Nevada, USA. We then produced mineral index maps of southern Namibia using newly observed hyperspectral data. The existence of many pegmatite- and porphyry-type deposits is reported in this study area, where detailed mineralogical mapping based on remote-sensing data has not previously been conducted. Our mineral index maps are consistent with our field survey results, and also with X-ray diffraction analyses and spectral measurements of rock samples. In this study, the continuum-removal MSAM method successfully discriminated hydrothermal alteration minerals such as kaolinite and pyrophyllite, and pegmatite-related minerals such as high-aluminium muscovite and lepidolite in southern Namibia for the first time. The main advantages of our classification method are simplicity and high-precision identification of alteration minerals.