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Phosphate Stability in Diagenetic Fluids Constrains the Acidic Alteration Model for Lower Mt. Sharp Sedimentary Rocks in Gale Crater, MarsThe Mars rover Curiosity has encountered silica-enriched bedrock (as strata and as veins and associated halos of alteration) in the largely basaltic Murray Fm. of Mt. Sharp in Gale Crater. Alpha Particle X-ray Spectrometer (APXS) investigations of the Murray Fm. revealed decreasing Mg, Ca, Mn, Fe, and Al, and higher S, as silica increased (Fig. 1). A positive correlation between SiO2 and TiO2 (up to 74.4 and 1.7 wt %, respectively) suggests that these two insoluble elements were retained while acidic fluids leached more soluble elements. Other evidence also supports a silica-retaining, acidic alteration model for the Murray Fm., including low trace element abundances consistent with leaching, and the presence of opaline silica and jarosite determined by CheMin. Phosphate stability is a key component of this model because PO4 3- is typically soluble in acidic water and is likely a mobile ion in diagenetic fluids (pH less than 5). However, the Murray rocks are not leached of P; they have variable P2O5 (Fig. 1) ranging from average Mars (0.9 wt%) up to the highest values in Gale Crater (2.5 wt%). Here we evaluate APXS measurements of Murray Fm. bedrock and veins with respect to phosphate stability in acidic fluids as a test of the acidic alteration model for the Lower Mt. Sharp rocks.
Document ID
20160003508
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Berger, J. A. (University of Western Ontario London, Ontario, Canada)
Schmidt, M. E. (Brock Univ. Saint Catherines, Ontario, Canada)
Izawa, M. R. M. (Brock Univ. Saint Catherines, Ontario, Canada)
Gellert, R. (Guelph Univ. Ontario, Canada)
Ming, D. W. (NASA Johnson Space Center Houston, TX, United States)
Rampe, E. B. (NASA Johnson Space Center Houston, TX, United States)
VanBommel, S. J. (Guelph Univ. Ontario, Canada)
McAdam, A. C. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
March 16, 2016
Publication Date
March 21, 2016
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
JSC-CN-35224
Meeting Information
Meeting: Lunar and Planetary Science Conference
Location: The Woodlands, TX
Country: United States
Start Date: March 21, 2016
End Date: March 25, 2016
Sponsors: Lunar and Planetary Inst., Universities Space Research Association
Distribution Limits
Public
Copyright
Public Use Permitted.

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