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Hydrated silica stratigraphy Sulfate stratigraphy Nontronite and doublet stratigraphy

New hydrated spectral phase and stratigraphy of smectites, sulfates, and other hydrated minerals in Ius Chasma, Valles Marineris. L Roach, JF Mustard, S Murchie, RE Milliken, K. Litchenberg, BL Ehlmann, J Bishop, RE Arvidson, and the CRISM Team

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Hydrated silica stratigraphy Sulfate stratigraphy Nontronite and doublet stratigraphy

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  1. New hydrated spectral phase and stratigraphy of smectites, sulfates, and other hydrated minerals in Ius Chasma, Valles Marineris L Roach, JF Mustard, S Murchie, RE Milliken, K. Litchenberg, BL Ehlmann, J Bishop, RE Arvidson, and the CRISM Team Martian Phyllosilicates: Recorders of Aqueous Processes Oct 21, 2008

  2. Hydrated silica stratigraphy • Sulfate stratigraphy • Nontronite and doublet stratigraphy • Identification of doublet mineralogy • Role of Landslides and Faulting

  3. Hydrated silica stratigraphy • Sulfate stratigraphy • Nontronite and doublet stratigraphy • Identification of doublet mineralogy • Role of Landslides and Faulting

  4. Hydrated silica Hydrated silica in multiple fine layers in wallrock at head of Louros Valles and at base. Formed on plateau and washed into trough. Restricted to region near sapping channels. Tyrrhena Mouth Headwall Opal (library)‏ Louros Valles headwall FRT00009998 Louros Valles mouth HRS0000B8EB

  5. Hydrated silica stratigraphy • Sulfate stratigraphy • Nontronite and doublet stratigraphy • Identification of doublet mineralogy • Role of Landslides and Faulting

  6. Sulfates Elevation Contour -4200 m -3500 m Kieserite PHS Doublet Sulfates are within enclosed topographic lows – suggest they were formed by evaporation of a closed basin. First polyhydrated sulfate (PHS), then kieserite as the brine concentrated. Based on shot data, kieserite found below -4175 m, with PHS and doublet at higher elevations (-3700 to -4175 m)‏

  7. FRT00008950 and PSP_005940_1710 Hydrated silica 150 m Sulfate Hydrated silica found overlying PHS, probably sourced from sapping channel Hydrated silica layer < few m thick Thin layer of loose, non-hydrated dark material only partially fills cracks (arrow)‏

  8. Sulfate and hydrated silica

  9. 2 1 • Hydrated silica stratigraphy • Sulfate stratigraphy • Nontronite and doublet stratigraphy • Identification of doublet mineralogy • Role of Landslides and Faulting

  10. Layered Smectite clays Nontronite in thin layers overlain by doublet material. In one case doublet unconformably drapes nontronite. Polygonally fractured but no layering or relief exposed. Doublet material-bearing unit Nontronite-bearing unit Kieserite PHS Doublet 180m across 500m across

  11. HiRISEPSP_006718 colorized with FRT000085A4 (RGB: 2.5, 1.5, 1.08 μm)

  12. Layered Smectite clays Doublet unit is brighter, more fractured, and clearly overlies smectite (smoother layered material). Window into layered smectite through doublet material Doublet unit drapes previously eroded smectite layered unit

  13. Layered Smectite clays Nontronite (green) and doublet (blue)‏ FRTBFE4 FRT9B27 FRTA202 FRT823A

  14. FRT00009B27, looking S Nontronite (green) at higher elevation than doublet. Adjacent obs shows doublet material overlying nontronite.

  15. Doublet spectral type Some variability in relative strength of 2.21 and 2.27 um bands

  16. Doublet spectral type No library spectra are perfect matches

  17. Hydrated silica stratigraphy • Sulfate stratigraphy • Nontronite and doublet stratigraphy • Identification of doublet mineralogy • Role of Landslides and Faulting

  18. Landslides of hydrated material Next slide Multiple landslide events range from “dry” (leftmost, with no mineral signatures) to “wet” (rightmost) and nontronite and doublet material in breccia. Central landslide is not yet determined. Landslides similarly fluidized. Leftmost landslide material overruns doublet breccia material, possibly from earlier landslide Nontronite and doublet material not localized to specific breccia blocks Smectite and Doublet Doublet

  19. Landslides of hydrated material Doublet-only material: located in older landslides or in basement breccia? FRT905B FRT27E2 FRTA396 Distinctive variegated color HiRISE next page

  20. Landslides of hydrated material PSP_006652_1725, overlapping FRTA396 Folds, fractures, and megabreccia blocks. All with 1.4, 1.9, 2.22, and 2.27 μm abs. Images ~250 m across

  21. Interpreted Ius Chasma Stratigraphy • Sulfates form by closed evaporating basin without recharge • Smectite in both breccia and matrix of landslides – Noachian megabreccia altered by hydrothermal processes? Could non-hydrated mineral-bearing landslides be unaltered Hesperian material? • Smectites in layers in local lows – fluvial deposition? Altered ash fall? • Doublet unit unconformably overlies layered smectites, evidence of change in aqueous geochemistry? Need to resolve doublet mineralogy • Doublet also found alone or mixed with smectites in landslides. Perhaps doublet formed by second period of aqueous alteration on trough floor. Would explain both landslides with and without smectite. • Hydrated silica most recent alteration mineral. Transported short distances by sapping channel flow. Sourced from top of wall rock

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