Early diagenesis at and below Vera Rubin ridge, Gale crater, Mars

Stuart M R Turner , S. P Schwenzer , J. C Bridges , E. B Rampe , C. C Bedford , C. N Achilles , A. C Mcadam , N. Mangold (1) , L. J Hicks , J. Parnell , A. A Fraeman , M. H Reed , Gordon Osinski

1 LPG - Laboratoire de Planétologie et Géodynamique [UMR 6112]

Data returned by NASA’s Mars Science Laboratory Curiosity rover showed evidence for abundant secondary materials, including Fe-oxides, phyllosilicates, and an amorphous component on and below Vera Rubin ridge in the Murray formation. We have used equilibrium thermochemical modeling to test the hypothesis that these altered sediments were deposited predominantly as detrital igneous grains and subsequently underwent diagenetic alteration. Chemical compositions of the altered components were calculated using data returned by the Chemistry and Mineralogy X-ray diffraction instrument and the Alpha Particle X-ray Spectrometer on board Curiosity. Reaction of these alteration compositions with a CO2-poor and oxidizing dilute aqueous solution was modeled at 25 – 100 °C, with varying amounts of Fe3+/Fetot of the host rock. The modeled alteration assemblages contained abundant phyllosilicates and Fe-oxides at >100 water to rock ratios, and were directly comparable to the abundances of hematite and clay minerals observed by Curiosity at 10,000 water to rock at 50 – 100 °C with pH ranging from 7.9 to 9.3. Our modeling results suggest that the hematite-clay mineral assemblage is primarily the result of enhanced groundwater flow compared to the Sheepbed mudstone in the Bradbury Group observed at Yellowknife Bay, and underwent further, localized alteration to produce the mineralogy observed by Curiosity.

Domaines: Planétologie

Stuart M R Turner, S. P Schwenzer, J. C Bridges, E. B Rampe, C. C Bedford, et al.. Early diagenesis at and below Vera Rubin ridge, Gale crater, Mars. Meteoritics and Planetary Science, 2021, ⟨10.1111/maps.13748⟩. ⟨hal-03376533⟩