Silicic volcanism on Mars evidenced by tridymite in high-SiO2 sedimentary rock at Gale crater.
Tridymite, a low-pressure, high-temperature (>870 °C) SiO2 polymorph, was detected in a drill sample of laminated mudstone (Buckskin) at Marias Pass in Gale crater, Mars, by the Chemistry and Mineralogy X-ray diffraction instrument onboard the Mars Science Laboratory rover Curiosity The tridymitic mudstone has ∼40 wt.% crystalline and ∼60 wt.% X-ray amorphous material and a bulk composition with ∼74 wt.% SiO2 (Alpha Particle X-Ray Spectrometer analysis). Plagioclase (∼17 wt.% of bulk sample), tridymite (∼14 wt.%), sanidine (∼3 wt.%), cation-deficient magnetite (∼3 wt.%), cristobalite (∼2 wt.%), and anhydrite (∼1 wt.%) are the mudstone crystalline minerals. Amorphous material is silica-rich (∼39 wt.% opal-A and/or high-SiO2 glass and opal-CT), volatile-bearing (16 wt.% mixed cation sulfates, phosphates, and chlorides-perchlorates-chlorates), and has minor TiO2 and Fe2O3T oxides (∼5 wt.%). Rietveld refinement yielded a monoclinic structural model for a well-crystalline tridymite, consistent with high formation temperatures. Terrestrial tridymite is commonly associated with silicic volcanism, and detritus from such volcanism in a "Lake Gale" catchment environment can account for Buckskin's tridymite, cristobalite, feldspar, and any residual high-SiO2 glass. These cogenetic detrital phases are possibly sourced from the Gale crater wall/rim/central peak. Opaline silica could form during diagenesis from high-SiO2 glass, as amorphous precipitated silica, or as a residue of acidic leaching in the sediment source region or at Marias Pass. The amorphous mixed-cation salts and oxides and possibly the crystalline magnetite (otherwise detrital) are primary precipitates and/or their diagenesis products derived from multiple infiltrations of aqueous solutions having variable compositions, temperatures, and acidities. Anhydrite is post lithification fracture/vein fill.
NASA Johnson Space Center, Houston, TX 77058; grotz@gps.caltech.edu richard.v.morris@nasa.gov.
Richard V
RV
Morris
Planetary Science Institute, Tucson, AZ 85719;
David T
DT
Vaniman
NASA Ames Research Center, Moffitt Field, CA 94035;
David F
DF
Blake
Department of Physics, University of Guelph, Guelph, ON, Canada N1G 2W1;
Ralf
R
Gellert
Chesapeake Energy, Oklahoma City, OK 73118;
Steve J
SJ
Chipera
Aerodyne Industries, Houston, TX 77058;
Elizabeth B
EB
Rampe
NASA Johnson Space Center, Houston, TX 77058;
Douglas W
DW
Ming
Department of Geosciences, University of Arizona, Tucson, AZ 85721;
Shaunna M
SM
Morrison
Department of Geosciences, University of Arizona, Tucson, AZ 85721;
Robert T
RT
Downs
Lunar and Planetary Institute, Houston, TX 77058;
Allan H
AH
Treiman
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109;
Albert S
AS
Yen
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125; grotz@gps.caltech.edu richard.v.morris@nasa.gov.
John P
JP
Grotzinger
Department of Geosciences, University of Arizona, Tucson, AZ 85721;
Cherie N
CN
Achilles
NASA Ames Research Center, Moffitt Field, CA 94035;
Thomas F
TF
Bristow
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109;
Joy A
JA
Crisp
NASA Ames Research Center, Moffitt Field, CA 94035;
David J
DJ
Des Marais
School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287;
Jack D
JD
Farmer
Department of Geosciences, University of Arizona, Tucson, AZ 85721;
Kim V
KV
Fendrich
Los Alamos National Laboratory, Los Alamos, NM 87545; Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark;
Jens
0000-0001-9294-1227
J
Frydenvang
Jacobs, Houston, TX 77058;
Trevor G
TG
Graff
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109;
John-Michael
JM
Morookian
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125;
Edward M
EM
Stolper
Lunar and Planetary Institute, Houston, TX 77058; Department of Environment, Earth and Ecosystems, The Open University, Milton Keynes MK7 6AA, United Kingdom.
Susanne P
SP
Schwenzer
Gale crater; Mars; lake; tridymite; volcanism