Quantitative compositional analysis of martian mafic regions using the MEx/OMEGA reflectance data

Abstract

The primary objectives of this paper are to determine the modal mineralogy of selected low albedo terrains of different ages ranging from Noachian to Amazonian exposed on the surface of Mars. This analysis is conducted using the spectral modeling of the Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) reflectance data. Results from this work are consistent with the major results of previous spectroscopic studies: plagioclase (40-60% in volume) and high calcium pyroxene (20-40%, HCP) are the dominant minerals of the most regions. Low calcium pyroxene (10-15%, LCP) and minor amounts of olivine are also present. The oldest terrains are characterized by the largest amount of LCP and the lowest concentration of plagioclase. These overall compositions are consistent with two-pyroxene basalts. The particle sizes are in the range of a few hundreds of micrometers, which is in good agreement with the thermal inertia of the martian low albedo regions. In the region around the Nili Fossae, localized concentrations of olivine up to 40% with millimeter particle size similar to picritic basalts observed in situ by the Spirit rover in the Gusev crater are inferred. Chemical compositions are calculated for the first time from OMEGA spectra. They are quite consistent with Gusev rocks and shergottite compositions but they appear to be significantly SiO 2 -poorer than Thermal Emission Spectrometer data. A decreasing low calcium pyroxene abundance with the decreasing age of the low albedo regions is reported. This may be indicative of decreasing degree of partial melting as thermal flux decreases with time. We propose that the ancient Noachian-aged, LCP-rich terrains could have been formed from H 2 O-bearing melts. Then, dry, basaltic volcanism occurred leading to decreasing LCP abundance with time due to decreasing degree of partial melting. The olivine-bearing material modeled in Nili Fossae resembles the composition of ALH77005 and Chassigny meteorites consistent with prior studies. Implications on the formation of the basaltic Shergottites are discussed.

Modal mineralogy of planetary surfaces from visible and near-infrared spectral data

“…This modal mineralogy is typical of mafic magmatic rocks, which could be classified as gabbro-norites with minor amount of olivine for plutonic rocks; the volcanic equivalent nomenclature is two-pyroxene basalt. A decrease of the Low Calcium Pyroxene abundance through time is also observed [15]. The modal mineralogy of areas analyzed here clearly indicates an affinity with some of the basaltic Martian meteorites; they have young crystallization ages, suggesting that they are samples of young (dust-covered) volcanic centers such as Tharsis or Elysium.…”

“…The derivation of the modal mineralogy of unaltered mafic-rich regions allows to evaluate constraints on the chemistry and petrology of the ancient crust, and to explore how crustal components might have arisen on Mars. OMEGA modal derived analyses [15] indicate a basaltic composition for all of the low albedo extended regions (Fig. 3).…”

The effects of mantle composition on the peridotite solidus: Implications for the magmatic history of Mars

“…The martian meteorites appear to be depleted in aluminum (or plagioclase), sodium, potassium, and thorium relative to both in-situ measurements of rocks and soils of materials at the Gusev, Meridiani, Gale, and Mars Pathfinder landing sites and with orbital gamma ray spectrometer and near-infrared spectroscopy observations (McSween et al, 2009;Poulet et al, 2009;Treiman and Filiberto, 2015). These differences in magma composition may reflect temporal changes in the water content, oxidation state, or temperature of the mantle over time (Balta and McSween, 2013;Baratoux et al, 2013;Tuff et al, 2013;Filiberto and Dasgupta, 2015).…”

Characterization and Calibration of the CheMin Mineralogical Instrument on Mars Science Laboratory

“…In this section, analyses of a suite of ultramafic rocks similar to those identified on Mars (Poulet et al 2009;Ehlmann et al 2009) are shown. We evaluated the ability of the Terra Fig.…”