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Elemental Gains/Losses Associated with Alteration Fractures in an Eolian Sandstone, Gale Crater, MarsThe Mars Science Laboratory rover Curiosity has traversed up section through approximately 100 m of sedimentary rocks deposited in fluvial, deltaic, lacustrine, and eolian environments (Bradbury group and overlying Mount Sharp group). The Stimson formation unconformably overlies a lacustrine mudstone at the base of the Mount Sharp group and has been interpreted to be a cross-bedded sandstone of lithified eolian dunes. Unaltered Stimson sandstone has a basaltic composition similar to the average Mars crustal composition, but is more variable and ranges to lower K and higher Al. Fluids passing through alteration "halos" adjacent to fractures have altered the chemistry and mineralogy of the sandstone. Elemental mass gains and losses in the alteration halos were quantified using immobile element concentrations, i.e., Ti (taus). Alteration halos have elemental gains in Si, Ca, S, and P and large losses in Al, Fe, Mn, Mg, Na, K, Ni, and Zn. Mineralogy of the altered Stimson is dominated by Ca-sulfates, Si-rich X-ray amorphous materials along with plagioclase feldspar, magnetite, and pyroxenes. The igneous phases were less abundant in the altered sandstone with a lower pyroxene/plagioclase feldspar. Large elemental losses suggest acidic fluids initially removed these elements (Al mobile under acid conditions). Enrichments in Si, Ca, and S suggest secondary fluids (possibly alkaline) passed through these fractures leaving behind X-ray amorphous Si and Ca-sulfates. The mechanism for the large elemental gains in P is unclear. The geochemistry and mineralogy of the altered sandstone suggests a complicated diagenetic history with multiple episodes of aqueous alteration under a variety of environmental conditions (e.g., acidic, alkaline).
Document ID
20160011487
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Ming, D. W.
(NASA Johnson Space Center Houston, TX, United States)
Yen, A. S.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Gellert, R.
(Guelph Univ. Ontario, Canada)
Sutter, B.
(Jacobs Technology, Inc. Houston, TX, United States)
Berger, J. A.
(University of Western Ontario London, Ontario, Canada)
Thompson, L. M.
(New Brunswick Univ. Fredericton, New Brunswick, Canada)
Schmidt, M. E.
(Brock Univ. Saint Catherines, Ontario, Canada)
Morris, R. V.
(NASA Johnson Space Center Houston, TX, United States)
Treiman, A. H.
(Lunar and Planetary Inst. Houston, TX, United States)
Date Acquired
September 26, 2016
Publication Date
December 12, 2016
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
JSC-CN-37384
Meeting Information
Meeting: AGU Fall Meeting 2016
Location: San Francisco, CA
Country: United States
Start Date: December 12, 2016
End Date: December 16, 2016
Sponsors: American Geophysical Union
Distribution Limits
Public
Copyright
Public Use Permitted.
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