Petrography and geochemistry of the chassignite Northwest Africa 2737 (NWA 2737)

Beck, Pierre; Barrat, Jean‐Alix; Gillet, Ph.; Wadhwa, M.; Franchi, I. A.; Greenwood, R. C.; Bohn, Marcel; Cotten, Joseph; Moortèle, Bertrand Van de; Reynard, Bruno

doi:10.1016/j.gca.2006.01.016

Cited by 82 publications

(129 citation statements)

References 38 publications

(55 reference statements)

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“…The chassignite NWA 2737 is also an olivine-spinel cumulate, with a mean olivine composition of Fo 79 (Beck et al 2006). Three pyroxenes (augite, pigeonite, and orthopyroxene), chromite, analbite glass, and apatite are found interstitial to the cumulate phases.…”

Section: Mineral Assemblages Of the Chassignitesmentioning

confidence: 99%

“…b) Compositions of pyroxenes from NWA 2737 (dark gray circles; Beck et al [2006]) and Chassigny (dark gray squares; this work) projected into the pyroxene quadrilateral using the QUILF methodology of Andersen et al (1993). Plotted data from Beck et al (2006) include their reported averaged compositions as well as individual pyroxenes with highest and lowest Ca contents. Light gray squares show specifically melt inclusion pyroxene compositions for the Chassigny (this work).…”

Section: Pyroxenesmentioning

confidence: 99%

“…Black tie lines indicate the computed pyroxene/olivine equilibrium assemblage at 1050 °C and 10 kbar. c) Compositions of pyroxenes from NWA 2737 (light gray circles; Beck et al [2006]) projected into the pyroxene quadrilateral using the QUILF methodology of Andersen et al (1993). Black tie lines link calculated ferromagnesian phases in equilibrium at 1200 °C.…”

Section: Pyroxenesmentioning

confidence: 99%

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Alkalic parental magmas for chassignites?

Nekvasil

Filiberto

McCubbin

et al. 2007

Meteorit & Planetary Scien

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Abstract-Detailed analysis of cumulate and melt inclusion assemblages in the chassignites provide important constraints on the nature of the melt trapped as inclusions in cumulus olivine (and, by extension, parental magma compositions), the pressures of crystallization, and magmatic volatile contents. These mineral assemblages show strong similarities to the experimental fractionation assemblages that produce the sodic silica-saturated alkalic lavas on Earth (e.g., Ascension Island, Azores, the Nandewar volcano of Australia). The experimental assemblages were produced from silica-saturated hawaiite at pressures above 4.3 kbar with dissolved water contents above 0.5 wt%. Such pressures are consistent with Ti:Al ratios of the melt-inclusion pyroxenes in the Chassigny meteorite. Pyroxene compositions suggest early high crystallization temperatures and thus relatively low initial water and F contents. Feldspars indicate that melt evolution proceeded to rhyolite compositions both within the interstices of the cumulate olivine and within the melt inclusions, even though rhyolitic glass is only found within olivine-hosted polyphase melt inclusions. The observed rhyolite glass is compositionally similar to the alkali-rich rhyolite of Ascension Island which is produced experimentally by crystallization of hawaiite. It is proposed that the melt trapped in cumulus olivine of the Chassigny dunite was similar to a terrestrial silica-saturated hawaiite, while that trapped in olivine of the Northwest Africa (NWA) 2727 dunite was less evolved, perhaps mildly alkalic basalt. Melts similar to terrestrial intra-plate tholeiite could be parental to the cumulus minerals and evolve upon crystallization at pressures above 4.3 kbar and water contents abovẽ 0.4 wt% to mildly alkalic basalt, silica-saturated hawaiite, and alkali-rich rhyolite. The melt inclusion assemblages are inconsistent with either crystallization of a low-Al, high-Fe basalt, or lowpressure crystallization of a terrestrial-like tholeiite.

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Section: Mineral Assemblages Of the Chassignitesmentioning

confidence: 99%

Section: Pyroxenesmentioning

confidence: 99%

Section: Pyroxenesmentioning

confidence: 99%

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Alkalic parental magmas for chassignites?

Nekvasil

Filiberto

McCubbin

et al. 2007

Meteorit & Planetary Scien

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“…Shock processes are capable of oxidizing (Bauer 1979;Boslough 1991;McCanta et al 2006) and reducing (Boslough 1991;Beck et al 2006;Van de Moortèle et al 2007) the target material they impact into. The effects of shock on mineral composition and oxidation state are not well understood.…”

Section: Impact-related Shockmentioning

confidence: 99%

“…The effects of shock on mineral composition and oxidation state are not well understood. Olivine in the chassignite NWA 2737 displays nanophase metallic iron indicating a shock reduction episode (Beck et al 2006;Treiman et al 2007), resulting from either the shock event itself or the post-shock thermal pulse. Conversely, experimentally shocked clinopyroxenes show large increases in their Fe 3+ /Fe 2+ ratios indicating a shock oxidation process (McCanta et al 2006).…”

Section: Impact-related Shockmentioning

confidence: 99%

Expanding the application of the Eu‐oxybarometer to the lherzolitic shergottites and nakhlites: Implications for the oxidation state heterogeneity of the Martian interior

McCanta¹,

Elkins-Tanton²,

Rutherford³

2009

Meteorit & Planetary Scien

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Application of the MELTS algorithm to Martian compositions and implications for magma crystallization

Balta

McSween

2013

JGR Planets

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[1] The MELTS algorithm, the most commonly used tool for calculating crystallization of basaltic magmas, uses thermodynamic parameters calibrated by experiments on select compositions, and thus, its use on newly discovered extraterrestrial compositions requires extrapolation across ranges where its applicability has not been evaluated in detail. To apply MELTS to Martian compositions, we undertook a systematic examination of the original MELTS calibration and the pMELTS revision as applied to Martian magmas. We find that the algorithm is effective in predicting the crystallization paths and conditions of Martian magmas, with some issues. The algorithm consistently overestimates the stability of spinel and underestimates pressures of multiple saturation compared to experiments. The pMELTS calibration comes close to fitting multiple-saturation pressures but cannot be used at low pressures. Both calibrations model crystallization temperatures with similar variances to those observed for terrestrial compositions. Both calibrations reproduce important compositional details of crystallizing magmas and coexisting minerals with errors similar to those observed on terrestrial compositions. We calculate several crystallization paths which predict high-FeO, high-density magma compositions that could be a mechanism for cumulate formation. Low-FeO compositions in recent Mars volcanism may be an expression of this density barrier. However, the composition of a high-FeO rock called "Et-Then" discovered by the rover Curiosity is strikingly similar to compositions calculated by the MELTS algorithm and could represent one of these high-FeO volcanic rocks.

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Petrography and geochemistry of the chassignite Northwest Africa 2737 (NWA 2737)

Cited by 82 publications

References 38 publications

Alkalic parental magmas for chassignites?

Alkalic parental magmas for chassignites?

Expanding the application of the Eu‐oxybarometer to the lherzolitic shergottites and nakhlites: Implications for the oxidation state heterogeneity of the Martian interior

Application of the MELTS algorithm to Martian compositions and implications for magma crystallization

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