GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 295-9
Presentation Time: 3:45 PM


FARRAND, William H., Space Science Institute, 4750 Walnut Street, #205, Boulder, CO 80301

Hyperspectral data can be used to map minerals that display very subtle compositional differences from related minerals based on differences in their respective reflectance spectra. This capability can be used effectively to map surface constituents in mineralized areas, including those that have either acid-generating potential or that can incorporate hazardous trace metals. Both sets of materials have the potential to adversely affect water quality and human health. A cooperative endeavor between NASA and the Indian ISRO agency has allowed for NASA’s Airborne Visible Infrared Imaging Spectrometer – Next Generation (AVIRIS-NG) to be flown over multiple sites in India of interest to several scientific disciplines. Flights of AVIRIS-NG over India took place in both 2016 and 2018. Among the areas for which data were collected were the abandoned Ambaji copper mine in the Indian state of Gujurat, the Zawar zinc mine in Rajasthan and the Gadag schist belt gold mining region in Karnataka.

Endmember detection approaches were applied to subsections of the datasets and, on this basis, mineral mapping was conducted using the Material Identification and Characterization Algorithm (MICA) in the USGS PRISM software. MICA detected the presence of the acid generating mineral jarosite in association with the Ambaji site, a detection later confirmed by field work. The acid-generating potential of jarosite is mitigated in the Ambaji region by generally dry conditions and the presence of acid-neutralizing minerals in the regional country rock. MICA mineral maps of the main drainage from the Zawar zinc mine show potential trace-metal hosting phyllosilicate minerals in that drainage. Work is on-going into whether Al-OH vibrational overtone features associated with the riverbank minerals display any spectral differences from other exposures of similar minerals not in the Zawar drainage. The Gadag schist belt (GSB) is part of the larger Chitradurga schist belt with mining in the area dating back to ancient times. The GSB is formed largely of metavolcanics and metasedimentary rocks. Mapping of the AVIRIS-NG data over the Gadag schist belt site is on-going, but preliminary results indicate the presence of chlorite group minerals and ferric oxides associated with mineralized areas. Work to be presented includes mapping of source regions of trace metals in the AVIRIS-NG coverage and the potential for impacts on local water quality.