Research Article

Elemental Geochemistry of Sedimentary Rocks at Yellowknife Bay, Gale Crater, Mars

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Science  09 Dec 2013:
1244734
DOI: 10.1126/science.1244734

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Abstract

Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from approximately average Martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved indicating arid, possibly cold, paleoclimates and rapid erosion/deposition. Absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low temperature, circum-neutral pH, rock-dominated aqueous conditions. High spatial resolution analyses of diagenetic features, including concretions, raised ridges and fractures, indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine-rich components, and hydrated calcium-sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. Geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of Mars.

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