Determination of metamorphic grade in siliceous muscovite-bearing rocks in Madagascar using reflectance spectroscopy

• Published in: Terra nova (Oxford, England) Vol. 12; no. 1; pp. 21 - 27
• Main Authors: Longhi, Mazzoli, Sgavetti
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.02.2000
• ISSN: 0954-4879; 1365-3121
• DOI: 10.1046/j.1365-3121.2000.00264.x

Visible short‐wave infrared laboratory reflectance spectra of quartzites and micaschists from the Precambrian basement of central‐western Madagascar are dominated by the muscovite spectrum. The spectra were measured from rock samples collected along an E–W traverse across a metamorphic sequence recording progressively higher metamorphic grades. The wavelength of the Al–OH band around 2200 nm decreased westward and was inversely correlated with AlVI content of muscovite in rocks showing the same nonlimiting assemblage. This shift is correlated also with an increase of band intensity, which is attributed to the progressive increase of metamorphic grade. All of these variations in rock spectral properties can be detected by the high spectral resolution MIVIS and AVIRIS sensors, as well as by the lower resolution TM sensor.