Geology of central Libya Montes, Mars: Aqueous alteration history from mineralogical and morphological mapping

1D. Tirsch, 2,3J.L. Bishop, 1J. Yoigt, 4L.L. Tornabene, 5G. Erkeling, 1,6R. Jaumann
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.05.006]
1Institute of Planetary Research, German Aerospace Center (DLR), Rutherfordstrasse 2, 12489 Berlin, Germany
2Carl Sagan Center, The SETI Institute, Mountain View, CA 94043, USA
3Exobiology Branch, NASA-Ames Research Center, Moffett Field, CA 94035, USA
4University of Western Ontario, London, ON, Canada
5German National Library of Science and Technology (TIB), Leibniz Information Centre for Science and Technology, Hannover, Germany
6Institute of Geological Sciences, Freie Universitaet Berlin, 12249 Berlin, Germany
Copyright Elsevier

We analyze the emplacement chronology and aqueous alteration history of distinctive mineral assemblages and related geomorphic units near Hashir and Bradbury impact craters located within the Libya Montes, which are part of the southern rim of the Isidis Basin on Mars. We derive our results from a spectro-morphological mapping project that combines spectral detections from CRISM near-infrared imagery with geomorphology and topography from HRSC, CTX, and HiRISE imagery. Through this combination of data sets, we were able to use the morphology associated with specific mineral detections to extrapolate the possible extent of the units hosting these compositions. We characterize multiple units consistent with formation through volcanic, impact, hydrothermal, lacustrine and evaporative processes. Altered pyroxene-bearing basement rocks are unconformably overlain by an olivine-rich unit, which is in turn covered by a pyroxene-bearing capping unit. Aqueously altered outcrops identified here include nontronite, saponite, beidellite, opal, and dolomite. The diversity of mineral assemblages suggests that the nature of aqueous alteration at Libya Montes varied in space and time. This mineralogy together with geologic features shows a transition from Noachian aged impact-induced hydrothermal alteration and the alteration of Noachian bedrock by neutral to slightly basic waters via Hesperian aged volcanic emplacements and evaporative processes in lacustrine environments followed by Amazonian resurfacing in the form of aeolian erosion.

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