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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 99, NO. B2, PAGES 2887–2895, 1994

Quantitative reflectance spectroscopy of buddingtonite from the Cuprite mining district, Nevada

Benjamin Felzer

Center for the Study of Earth from Space, Cooperative Institute for Research in Environmental Sciences, and Department of Geological Sciences, University of Colorado, Boulder


Phoebe Hauff

Center for the Study of Earth from Space, Cooperative Institute for Research in Environmental Sciences, and Department of Geological Sciences, University of Colorado, Boulder


Alexander F. H. Goetz

Center for the Study of Earth from Space, Cooperative Institute for Research in Environmental Sciences, and Department of Geological Sciences, University of Colorado, Boulder


Abstract

Buddingtonite, an ammonium-bearing feldspar diagnostic of volcanic-hosted alteration, can be identified and, in some cases, quantitatively measured using short-wave infrared (SWIR) reflectance spectroscopy. In this study over 200 samples from Cuprite, Nevada, were evaluated by X ray diffraction, chemical analysis, scanning electron microscopy, and SWIR reflectance spectroscopy with the objective of developing a quantitative remote-sensing technique for rapid determination of the amount of ammonium or buddingtonite present, and its distribution across the site. Based upon the Hapke theory of radiative transfer from particulate surfaces, spectra from quantitative, physical mixtures were compared with computed mixture spectra. We hypothesized that the concentration of ammonium in each sample is related to the size and shape of the ammonium absorption bands and tested this hypothesis for samples of relatively pure buddingtonite. We found that the band depth of the 2.12-μm NH4 feature is linearly related to the NH4 concentration for the Cuprite buddingtonite, and that the relationship is approximately exponential for a larger range of NH4 concentrations. Associated minerals such as smectite and jarosite suppress the depth of the 2.12-μm NH4 absorption band. Quantitative reflectance spectroscopy is possible when the effects of these associated minerals are also considered.

Received 4 March 1993; accepted 20 October 1993.

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Citation: Felzer, B., P. Hauff, and A. F. H. Goetz (1994), Quantitative reflectance spectroscopy of buddingtonite from the Cuprite mining district, Nevada, J. Geophys. Res., 99(B2), 2887–2895.