SPECTRAL ANALYSIS OF EXPLOSIVE AND EFFUSIVE VOLCANISM IN THE MARIUS HILLS VOLCANIC COMPLEX

The Marius Hills Volcanic Complex (MHVC; 13.3ºN, 47.5ºW) is a 35,000 km² plateau that extends 100-200 m above the surrounding plains of Oceanus Procellarum and contains a wide assortment and unusual concentration of volcanic features. These volcanic features include volcanic domes, lava flows, sinuous rilles, and volcanic cones. The volcanic cones in the MHVC were identified initially using visible imagery based on morphologies similar to cinder cones on Earth. Lawrence et al. (2013) completed a morphological survey of the cinder cones of the MHVC, identifying 93 possible cinder cones and 55 ambiguous circular structures. A definitive designation of a cinder cone would require evidence that the volcanic edifice was constructed of ballistic glass-rich pyroclasts from an explosive, volatile-rich eruption. A previous analysis using Moon Mineralogy Mapper (M³) orbital visible/near-infrared (VNIR) spectra was not able to spectrally distinguish the volcanic cones from the underlying domes; however, new techniques for detecting glass in VNIR spectra have since been developed. This research will answer the question: Is glass present in the MHVC, and can glass signatures be used to confirm the distribution and explosive origin of the MHVC cones?

Using the M³ data, we show that the volcanic cones within the MHVC exhibit spectra that are distinct from the underlying domes that are consistent with the presence of significant glass. Mapping glass in the region reveals that the shape and orientation of the volcanic cones in M³ maps mirror the visible imagery. The matching shapes indicate that the volcanic cones are glass-rich, as expected in an explosive eruption resulting in cinders. In response to the success to finding glass spectral signatures in known volcanic cones, we have applied the method to the 55 ambiguous circular structures to confirm or deny cone designation.

Spectral analysis of the MHVC can increase the known amount and the extent of volcanic cones, which require a higher volatile contribution for formation than the other volcanic features in the region. When all the cone locations are mapped, a trend in the distribution of the features may indicate the presence of rift zones, help track the past movement of magma through the region, and give insight to the volcanic and volatile history of the volcanic complex.