DOI: 10.5061/dryad.k3j9kd576
title: Data from: Brine driven destruction of clay minerals in Gale crater, Mars

description: This repository contains files and non-commercial software associated with
 the journal article "Brine Driven Destruction of Clay
 Minerals in Gale Crater, Mars."  The article presents
 mineralogical, geochemical, and sedimentological observations made by the
 Mars Science Laboratory rover Curiosity in an area called Glen
 Torridon, Gale crater, Mars. Rocks exposed in Glen Torridon were
 deposited in a lake that occupied the floor of Gale crater about 3.5
 billion years ago and are stratigraphic and depositional
 equivalents of rocks exposed ~ 400m away on Vera Rubin ridge. The
 mineralogy of rocks in these two areas are different despite
 forming in the same lake at the same time. Glen Torridon rocks
 contain about 30 wt % clay minerals and 2 wt % or less of the mineral
 hematite (an iron oxide). In contrast, Vera Rubin ridge rocks
 contain 5 to 13 wt % clay minerals, with larger quantities
 (between 9 and 16 wt %) of iron oxide and oxyhydroxide minerals.
 The observed differences in mineralogy are attributed to
 preferential post-depositional alteration of Vera Rubin ridge
 rocks by silica-poor brines. These brines are thought to
 have formed during the deposition of sedimentary strata of the
 'sulfate-bearing unit' that overlie Glen Torridon and
 Vera Rubin ridge rocks. Orbital spacecraft have
 detected magnesium sulfates in the sulfate-bearing unit. The
 presence of these highly soluable salts imply that changing
 climate and/or hydrological conditions in Gale crater resulted in the
 formation of dense brines during deposition of the sulfate-bearing unit.
 It is hypothesized that brines infiltrated older
 clay-bearing sediments, converting iron-rich clay minerals to iron oxides
 and oxyhydroxides. Glen Torridon rocks also contain a mineral
 phase not previously identified on the mission. This mineral gives rise to
 a distinctive x-ray diffraction peak represents a interplanar spacing of
 9.22 angstroms. This phase is identified as a mixed-layer serpentine-talc
 and is thought to have been transported into the crater floor by
 rivers. This repository contains: - Files needed to perform mineral search
 and Rietveld refinement of measured x-ray diffraction data using BGMN and
 MDI Jade software.  - A non-commerical
 Excel-based program called FULLPAT, used for mineral and
 x-ray amorphous quantification of x-ray diffraction patterns collected by
 the CheMin instrument aboard Curiosity. - Python code that was
 used to identify the 9.22 angstrom phase through automated search
 the American Mineralogist Crystal Structure Database. -
 Collection times of Alpha Particle X-ray Spectrometer analyses of bulk
 rock geochemical presented in the article that
 can be used to retrieve raw data from NASA's Planetary Data
 system
 (https://pds-geosciences.wustl.edu/msl/msl-m-apxs-4_5-rdr-v1/mslapx_1xxx/extras/) - A compilation of Li abundances across Vera Rubin ridge and Glen Torridon measured by the ChemCam that were presented in the article and used as a proxy for rock clay mineral content.
description: Details of how this dataset was collected can be found in
 Supplementary Materials published with the journal article.
description: The file "APXS_data_Fig.S5_Table_S1.xlxs" is a list of the analysis start times for Alpha Particle X-ray spectrometer data shown in Fig. S5 and Table S1 of the article. Data can be retrieved from: https://pds-geosciences.wustl.edu/msl/msl-m-apxs-4_5-rdr-v1/mslapx_1xxx/extras/ The file "ChemCam_Li_Fig.2.xlsx" is a compiled list of the sol, spacecraft clock identification, and Li abundance of each ChemCam observation point shown in Fig. 2 of the article. All ChemCam spectra utilized to calculate Li abundances in this file can be acquired from: https://pds-geosciences.wustl.edu/msl/msl-m-chemcam-libs-4_5-rdr-v1/mslccm_1xxx/data/ The "FULLPAT" zip folder contains a modified version of the Excel based program FULLPAT used to analyze CheMin instrument XRD data. The folder also contains a copy of the FULLPAT user manual.  The "BGMN files" and "Jade files" zip folders contain: the crystal structure files, measured XRD patterns from the CheMin instrument, and measured XRD patterns of standards used to analyze Mars XRD patterns using BGMN and MDI Jade software. The "Kilmarie-9.22-A-peak-search-master" zip folder contains python code used to search for candidate phases that can account for a peak at 9.22 angstroms observed in the Kilmarie sample.