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Diagenesis and clay mineral formation at Gale Crater, Mars.

Bridges JC, Schwenzer SP, Leveille R, Westall F, Wiens RC, Mangold N, Bristow T, Edwards P, Berger G - J Geophys Res Planets (2015)

Bottom Line: On the basis of the observed host rock and alteration minerals, we present results of equilibrium thermochemical modeling of the Sheepbed mudstones of Yellowknife Bay in order to constrain the formation conditions of its secondary mineral assemblage.The modeling shows that the mineral assemblage formed by the reaction of a CO2-poor and oxidizing, dilute aqueous solution (Gale Portage Water) in an open system with the Fe-rich basaltic-composition sedimentary rocks at 10-50°C and water/rock ratio (mass of rock reacted with the starting fluid) of 100-1000, pH of ∽7.5-12.We therefore deduce a dissolving composition of approximately 70% amorphous material, with 20% olivine, and 10% whole rock component.

View Article: PubMed Central - PubMed

Affiliation: Space Research Centre, Department of Physics and Astronomy, University of Leicester Leicester, UK.

ABSTRACT

The Mars Science Laboratory rover Curiosity found host rocks of basaltic composition and alteration assemblages containing clay minerals at Yellowknife Bay, Gale Crater. On the basis of the observed host rock and alteration minerals, we present results of equilibrium thermochemical modeling of the Sheepbed mudstones of Yellowknife Bay in order to constrain the formation conditions of its secondary mineral assemblage. Building on conclusions from sedimentary observations by the Mars Science Laboratory team, we assume diagenetic, in situ alteration. The modeling shows that the mineral assemblage formed by the reaction of a CO2-poor and oxidizing, dilute aqueous solution (Gale Portage Water) in an open system with the Fe-rich basaltic-composition sedimentary rocks at 10-50°C and water/rock ratio (mass of rock reacted with the starting fluid) of 100-1000, pH of ∽7.5-12. Model alteration assemblages predominantly contain phyllosilicates (Fe-smectite, chlorite), the bulk composition of a mixture of which is close to that of saponite inferred from Chemistry and Mineralogy data and to that of saponite observed in the nakhlite Martian meteorites and terrestrial analogues. To match the observed clay mineral chemistry, inhomogeneous dissolution dominated by the amorphous phase and olivine is required. We therefore deduce a dissolving composition of approximately 70% amorphous material, with 20% olivine, and 10% whole rock component.

No MeSH data available.


Related in: MedlinePlus

Clay Compositions on Mg-Al-Fetot. The starting compositions are the Portage, Cumberland, and John_Klein amorphous compositions [Vaniman et al., 2014; Morris et al., 2014[ and the analogue comparison clays. Saponite and saponitic gel and serpentine from the nakhlites [Hicks et al., 2014[ and griffithite [Treiman et al., 2014[ are also plotted. For the run compositions, we have plotted a range of mixtures of amorphous, olivine, plagioclase, and whole rock, reacted with GPW fluid at W/R of 1000 (purple color), 100 (green color), and 10 (brown color). The Portage whole rock reacted with CO2-bearing GPW is also plotted, and the results of clays from runs of Portage whole rock reacted with GPW at Fe3+/Fetot from 10 to 75% (Figure 4). The Portage 70% amorphous, 20% olivine, and 10% whole rock reactions at W/R 1000 and 100 have compositions close to the saponite from the nakhlites. The Portage 70% olivine, 15% augite, and 15% plagioclase run at W/R 1000 and 100 are closer to Mg-rich serpentine, and this type of olivine-rich run may be analogous to the formation of Mg-rich ridges at Yellowknife Bay. W/R is the ratio of incoming fluid with reacted rock.
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fig08: Clay Compositions on Mg-Al-Fetot. The starting compositions are the Portage, Cumberland, and John_Klein amorphous compositions [Vaniman et al., 2014; Morris et al., 2014[ and the analogue comparison clays. Saponite and saponitic gel and serpentine from the nakhlites [Hicks et al., 2014[ and griffithite [Treiman et al., 2014[ are also plotted. For the run compositions, we have plotted a range of mixtures of amorphous, olivine, plagioclase, and whole rock, reacted with GPW fluid at W/R of 1000 (purple color), 100 (green color), and 10 (brown color). The Portage whole rock reacted with CO2-bearing GPW is also plotted, and the results of clays from runs of Portage whole rock reacted with GPW at Fe3+/Fetot from 10 to 75% (Figure 4). The Portage 70% amorphous, 20% olivine, and 10% whole rock reactions at W/R 1000 and 100 have compositions close to the saponite from the nakhlites. The Portage 70% olivine, 15% augite, and 15% plagioclase run at W/R 1000 and 100 are closer to Mg-rich serpentine, and this type of olivine-rich run may be analogous to the formation of Mg-rich ridges at Yellowknife Bay. W/R is the ratio of incoming fluid with reacted rock.

Mentions: Three different amorphous components (a) Portage [Morris et al., 2014[, (b) Cumberland, and (c) John Klein, reacted with GPW at 10°C. For compositional details, see Table 2. The results of these runs are also plotted on the clay ternary (Figure 8). The Fe oxide in Figure 5c is goethite. W/R is the ratio of incoming fluid with reacted rock.


Diagenesis and clay mineral formation at Gale Crater, Mars.

Bridges JC, Schwenzer SP, Leveille R, Westall F, Wiens RC, Mangold N, Bristow T, Edwards P, Berger G - J Geophys Res Planets (2015)

Clay Compositions on Mg-Al-Fetot. The starting compositions are the Portage, Cumberland, and John_Klein amorphous compositions [Vaniman et al., 2014; Morris et al., 2014[ and the analogue comparison clays. Saponite and saponitic gel and serpentine from the nakhlites [Hicks et al., 2014[ and griffithite [Treiman et al., 2014[ are also plotted. For the run compositions, we have plotted a range of mixtures of amorphous, olivine, plagioclase, and whole rock, reacted with GPW fluid at W/R of 1000 (purple color), 100 (green color), and 10 (brown color). The Portage whole rock reacted with CO2-bearing GPW is also plotted, and the results of clays from runs of Portage whole rock reacted with GPW at Fe3+/Fetot from 10 to 75% (Figure 4). The Portage 70% amorphous, 20% olivine, and 10% whole rock reactions at W/R 1000 and 100 have compositions close to the saponite from the nakhlites. The Portage 70% olivine, 15% augite, and 15% plagioclase run at W/R 1000 and 100 are closer to Mg-rich serpentine, and this type of olivine-rich run may be analogous to the formation of Mg-rich ridges at Yellowknife Bay. W/R is the ratio of incoming fluid with reacted rock.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508961&req=5

fig08: Clay Compositions on Mg-Al-Fetot. The starting compositions are the Portage, Cumberland, and John_Klein amorphous compositions [Vaniman et al., 2014; Morris et al., 2014[ and the analogue comparison clays. Saponite and saponitic gel and serpentine from the nakhlites [Hicks et al., 2014[ and griffithite [Treiman et al., 2014[ are also plotted. For the run compositions, we have plotted a range of mixtures of amorphous, olivine, plagioclase, and whole rock, reacted with GPW fluid at W/R of 1000 (purple color), 100 (green color), and 10 (brown color). The Portage whole rock reacted with CO2-bearing GPW is also plotted, and the results of clays from runs of Portage whole rock reacted with GPW at Fe3+/Fetot from 10 to 75% (Figure 4). The Portage 70% amorphous, 20% olivine, and 10% whole rock reactions at W/R 1000 and 100 have compositions close to the saponite from the nakhlites. The Portage 70% olivine, 15% augite, and 15% plagioclase run at W/R 1000 and 100 are closer to Mg-rich serpentine, and this type of olivine-rich run may be analogous to the formation of Mg-rich ridges at Yellowknife Bay. W/R is the ratio of incoming fluid with reacted rock.
Mentions: Three different amorphous components (a) Portage [Morris et al., 2014[, (b) Cumberland, and (c) John Klein, reacted with GPW at 10°C. For compositional details, see Table 2. The results of these runs are also plotted on the clay ternary (Figure 8). The Fe oxide in Figure 5c is goethite. W/R is the ratio of incoming fluid with reacted rock.

Bottom Line: On the basis of the observed host rock and alteration minerals, we present results of equilibrium thermochemical modeling of the Sheepbed mudstones of Yellowknife Bay in order to constrain the formation conditions of its secondary mineral assemblage.The modeling shows that the mineral assemblage formed by the reaction of a CO2-poor and oxidizing, dilute aqueous solution (Gale Portage Water) in an open system with the Fe-rich basaltic-composition sedimentary rocks at 10-50°C and water/rock ratio (mass of rock reacted with the starting fluid) of 100-1000, pH of ∽7.5-12.We therefore deduce a dissolving composition of approximately 70% amorphous material, with 20% olivine, and 10% whole rock component.

View Article: PubMed Central - PubMed

Affiliation: Space Research Centre, Department of Physics and Astronomy, University of Leicester Leicester, UK.

ABSTRACT

The Mars Science Laboratory rover Curiosity found host rocks of basaltic composition and alteration assemblages containing clay minerals at Yellowknife Bay, Gale Crater. On the basis of the observed host rock and alteration minerals, we present results of equilibrium thermochemical modeling of the Sheepbed mudstones of Yellowknife Bay in order to constrain the formation conditions of its secondary mineral assemblage. Building on conclusions from sedimentary observations by the Mars Science Laboratory team, we assume diagenetic, in situ alteration. The modeling shows that the mineral assemblage formed by the reaction of a CO2-poor and oxidizing, dilute aqueous solution (Gale Portage Water) in an open system with the Fe-rich basaltic-composition sedimentary rocks at 10-50°C and water/rock ratio (mass of rock reacted with the starting fluid) of 100-1000, pH of ∽7.5-12. Model alteration assemblages predominantly contain phyllosilicates (Fe-smectite, chlorite), the bulk composition of a mixture of which is close to that of saponite inferred from Chemistry and Mineralogy data and to that of saponite observed in the nakhlite Martian meteorites and terrestrial analogues. To match the observed clay mineral chemistry, inhomogeneous dissolution dominated by the amorphous phase and olivine is required. We therefore deduce a dissolving composition of approximately 70% amorphous material, with 20% olivine, and 10% whole rock component.

No MeSH data available.


Related in: MedlinePlus