VISIBLE AND NEAR INFRARED SPECTRA OF MARBLES AND RELATED ROCKS: IMPLICATIONS FOR MINERAL MAPPING USING FIELD SPECTROSCOPY AND REMOTE SENSING

Visible and near infrared (Vis/NIR, 0.35-2.5 mm) reflectance spectra provide 1) a rapid method for field and laboratory identification of minerals, and 2) the basis for mapping the distribution of minerals using high-spectral-resolution (hyperspectral) remote sensing. This study examines laboratory and field Vis/NIR spectra of 1584 samples of metamorphosed carbonate rocks from over 20 contact and regional settings including notable localities such as Notch Peak and Alta, Utah; Marysville, Montana; and Birch Creek, Ubehebe Peak, and Darwin, California. Emphasis is on diagnostic CO₃ and OH absorption bands at wavelengths between 2.05 and 2.45 mm, because this range is relatively free from atmospheric interferences and, therefore, most applicable in studies that employ hyperspectral remote sensing. Multivariate analysis differentiated spectral end members corresponding to calcite, dolomite, tremolite, phlogopite, serpentine, talc, brucite, humite, epidote, vesuvianite, scapolite, datolite, prehnite(?), zeolite(?), and muscovite. Minerals also present but which lack distinctive absorption features in this wavelength range include quartz, forsterite, diopside, grossular, and wollastonite; however, most of these can be distinguished at shorter Vis/NIR wavelengths. The results underscore the feasibility of mapping the distribution of metamorphic and metasomatic minerals in carbonate rocks using hyperspectral remote sensing methods.