FULL-RANGE HYPERSPECTRAL MAPPING IN ALTERED SANDSTONES; IMPLICATIONS FOR WEATHERED VS. DIAGENETIC SYSTEMS ON EARTH AND ON MARS

Authigenic mineral mapping in the diagenetically altered Navajo Sandstone of Grand Staircase Escalante National Monument in Utah is performed with a combination of airborne hyperspectral data from both the VNIR/SWIR HyMap and the LWIR SEBASS. Two sites with very different fluid-rock interaction histories are compared; Mollies Nipple and Kaibab Fault. We found that the secondary diagenetic mineralogy mapped from the imagery at both sites was markedly different from each other in overall spatial patterns dominated by original and secondary fluid-flow conduits (fractures, faults and bedding planes) and in overall mineral assemblage character. Specifically, the Mollies Nipple site possessed hitherto unknown jarosite within the sandstone beds of the Navajo. The presence of this jarosite (as well as other important authigenic minerals including goethite and gypsum) was confirmed with insitu spectroscopy using a portable ASD spectroradiometer. Important spectral features and geometries are reported on as is the ability to scale these fine features down to the spectral sampling level of the imagery. We emphasize the limitations and advantages within both regions of the EM spectrum and assess the need for “full-range” spectroscopy in these types of applications. Ultimately we discuss the implications of this work for hydrocarbon reservoir and ore deposit genesis models as well as for Mars-analog studies. Specifically, the presence of jarosite at Mollies Nipple may indicate direct precipitation from high sulfur, oxidized, low pH, saline waters - not unlike the iron sulfates precipitating out of modern day hypersaline, acid lakes in Western Australia or the diagenesis scenarios postulated for the newly discovered dune-interdune deposits of Mars.