APXS‐derived compositional characteristics of Vera Rubin Ridge and Murray formation, Gale crater, Mars: Geochemical implications for the origin of the ridge

1L.M.Thompson et al. (>10)
Journal of Geophysical Research (Planets) Link to Article [https://doi.org/10.1029/2019JE006319]
1Planetary and Space Science Centre, University of New Brunswick, Canada
Published by arrangement with John Wiley & Sons

The resistant ~50 m thick Vera Rubin ridge (VRR) situated near the base of Mount Sharp, Gale crater, Mars has been deemed a high priority science target for the Mars Science Laboratory mission. This is because of 1) its position at the base of the 5 km layered strata of Mount Sharp, and 2) the detection of hematite from orbit, indicating that it could be the site of enhanced oxidation. The compositional data acquired by the Alpha Particle X‐ray spectrometer (APXS) during Curiosity’s exploration of VRR helps to elucidate questions pertaining to the formation of the ridge. APXS analyses indicate that VRR falls within the compositional range of underlying lacustrine mudstones, consistent with a continuation of that depositional environment and derivation from a similar provenance. Lower Fe concentrations for VRR compared to the underlying strata discounts the addition of large amounts of hematite to the strata, either as cement or as detrital input. Compositional trends associated with VRR cross‐cut stratigraphy, indicating post‐depositional processes. Higher Si and Al, and lower Ti, Fe and Mn than the underlying mudstone, particularly within distinct patches of gray/blue bedrock are consistent with the addition of Si and Al. Lateral and vertical compositional variations, suggest enhanced element mobility and fluid flow (possibly via multiple events) through VRR, increasing towards the top of the ridge, consistent with the action of warm (~50‐100 °C), locally acidic saline fluids as inferred from the mineralogy of drilled samples.


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