The igneous end member compositions preserved in Gale Crater sediments

The sedimentary outcrop and float rocks in Gale Crater contain evidence of a mixture of igneous protoliths: basaltic, trachybasaltic, SiO2-rich, and alkali-rich. The fine grain size of many of the sediments offers the possibility of estimating accurate bulk compositions of igneous protoliths. However, the sediments also have undergone extensive diagenesis, veining and silica-rich alteration zones. Here we test a hypothesis that end member igneous compositions are recorded within the Gale Crater sediments, compare to other martian datasets, and distinguish alteration trends from the igneous detrital input sourced in the ancient highlands. We analyse this data from the first 1500 sols of Mars Science Laboratory operations using the Gale stratigraphic column. With over 400,000 ChemCam LIBS spectra, 198 APXS analyses and 19 CheMin analyses, the MSL results provide a unique compositional and stratigraphic sampling of the martian crust. The use of density contours with the large ChemCam dataset allows us to distinguish the key compositional end members from fractionation based on mineral density during deposition, or localised remobilisation during post depositional alteration.