Identification and Description of a Silicic Volcaniclastic Layer in Gale Crater, Mars, Using Active Neutron Interrogation

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  • S. Czarnecki
  • C. Hardgrove
  • Patrick J. Gasda
  • T. S.J. Gabriel
  • M. Starr
  • M. S. Rice
  • Frydenvang, Jens
  • R. C. Wiens
  • W. Rapin
  • S. Nikiforov
  • D. Lisov
  • M. Litvak
  • F. Calef
  • H. Gengl
  • Horton E. Newsom
  • L. Thompson
  • S. Nowicki

The Dynamic Albedo of Neutrons instrument aboard the Mars Science Laboratory rover, Curiosity, has been used to map a stratigraphically conformable layer of high-SiO (Formula presented.) material in Gale crater. Previous work has shown that this material contains tridymite, a high-temperature/low-pressure felsic mineral, interpreted to have a volcanic source rock. We describe several characteristics including orientation, extent, hydration, and geochemistry, consistent with a volcaniclastic material conformably deposited within a lacustrine mudstone succession. Relationships with widely dispersed alteration features and orbital detections of hydrated SiO (Formula presented.) suggest that this high-SiO (Formula presented.) layer extends at least 17 km laterally. Mineralogical abundances previously reported for this high-SiO (Formula presented.) material indicated that hydrous species were restricted to the amorphous (non-crystalline) fraction, which is dominated by SiO (Formula presented.). The low mean bulk hydration of this high-SiO (Formula presented.) layer (1.85 (Formula presented.) 0.13 wt.% water-equivalent hydrogen) is consistent with silicic glass in addition to opal-A and opal-CT. Persistent volcanic glass and tridymite in addition to opal in an ancient sedimentary unit indicates that the conversion to more ordered forms of crystalline SiO (Formula presented.) has not proceeded to completion and that this material has had only limited exposure to water since it originally erupted, despite having been transported in a fluviolacustrine system. Our results, including the conformable nature, large areal extent, and presence of volcanic glass, indicate that this high-SiO (Formula presented.) material is derived from the product of evolved magma on Mars. This is the first identification of a silicic volcaniclastic layer on another planet and has important implications for magma evolution mechanisms on single-plate planets.

Original languageEnglish
Article numbere2019JE006180
JournalJournal of Geophysical Research: Planets
Issue number3
Number of pages20
Publication statusPublished - 1 Mar 2020

    Research areas

  • evolved igneous lithology, Gale crater, Marias Pass, Mars water, neutron spectroscopy, silica

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