Spectral Analyses of Aqueous Outcrops at Libya Montes and Their Relationship To Nearby Olivine- and Pyroxene-Bearing Rocks

Libya Montes, situated at the southern edge of the Isidis Basin where olivine- and pyroxene-bearing lithologies were identified with OMEGA[1] and TES/THEMIS[2], contains dense valley networks indicating long-term aqueous processes prevailed here [3, 4]. CRISM data have shown phyllosilicate and carbonate signatures in rocks that exhibit layered textures in HiRISE imagery. We are investigating the mineralogy of these aqueous outcrops using CRISM data and are examining the stratigraphy of the layered units in context with the mafic materials using HiRISE and HRSC DEMs. CRISM spectra of two regions characteristic of aqueous material at Libya Montes are shown in the figure along with mixture spectra [5]. These CRISM spectra are likely mixtures of Fe/Mg-phyllosilicate, carbonate, and olivine. Understanding the nature of the aqueous deposits at Libya Montes has potentially far-reaching applications for the greater Isidis region. Mg-rich carbonates were found at the northwestern edge of Isidis Planitia at Nili Fossae [6]. If similar processes formed phyllosilicates and carbonates at Nili Fossae and Libya Montes then these processes could be widespread. Learning the stratigraphy of the aqueous units at Libya Montes with respect to each other and the olivine-bearing rocks will provide insights into the geochemical history and timeline of the region. [1] Mustard et al. (2007) JGR 112, doi:10.1029/2006JE002834. [2] Tornabene et al. (2008) JGR 113, doi:10.1029/2007JE002988. [3] Crumpler & Tanaka (2003) JGR 108, doi: 8010.1029/2002JE002040. [4] Jaumann et al. (2010) EPSL 294, 272-290. [5] Perry et al. (2011) LPSC #1554. [6] Ehlmann et al. (2008) Science 322, 1828-1832.