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Jean-alix Barrat - One of the best experts on this subject based on the ideXlab platform.
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Northwest Africa 8694, a ferroan chassignite: Bridging the gap between nakhlites and Chassignites
Geochimica et Cosmochimica Acta, 2020Co-Authors: Roger H. Hewins, Munir Humayun, Jean-alix Barrat, Brigitte Zanda, Jean-pierre Lorand, Sylvain Courrech Du Pont, N. Assayag, P. Cartigny, S. Yang, V. SautterAbstract:Abstract The origin(s) of the Chassignites and nakhlites, closely related martian olivine and augite cumulates, respectively, are much debated. Northwest Africa (NWA) 8694 is the third chassignite to be discovered and the most ferroan, containing 85% olivine (Fo54). Its O-isotope compositions (δ18O ∼ 4.4‰, Δ17O ∼ 0.30‰) are typical of other martian meteorites. It has adcumulate texture and contains cumulus chromite, poikilitic pigeonite (En56Fs37Wo7) and mesostasis (trapped interstitial liquid). The latter contains pyroxene and plagioclase (An23 Ab70 Or8) plus rare K- feldspar (Or74), and has a trachyandesitic to trachytic bulk composition. Melt inclusions in olivine contain a variety of phases including biotite and rare amphibole. Olivine, chromite, and pigeonite compositions are intermediate between those of the other Chassignites and those of the nakhlites. Augite, which appears to mantle pigeonite, has a composition overlapping that in nakhlite NWA 998 and some other nakhlites at (En41-40Wo38-39). The augite lamellae in pigeonite 1–2 μm in apparent width, and the survival of Ca zoning in olivine, suggest a near-surface cooling environment. The bulk-rock REE concentrations in the three Chassignites do not correlate with Mg# but depend on the abundance of trapped liquid. The form of REE patterns calculated for olivine subtraction is very like those of nakhlite mesostases, but the observed concentrations of LREE in NWA 8694 trapped liquid have a very steep slope. This is explained by undersampling of baddeleyite and zirconolite that occur near olivine contacts with mesostasis. Though pyroxene is unzoned, its trace element variations indicate fractional crystallization. The range of olivine compositions in the three Chassignites (Fo79-54) is too large to result from the crystallization sequential growth of olivine from a single magma undergoing fractional crystallization. The Ge/Si ratios show degassing of NWA 8694 which sets this chassignite apart from other Chassignites and nakhlites, implying a unique batch of magma for its genesis. Many potential parent liquids are capable of generating the NWA 8694 olivine composition, though not its alkaline mesostasis. We calculated that Nakhla parent liquid NA01a (Stockstill et al., 2005) with 10% Nakhla core olivine added would produce both olivine crystals and alkaline daughter liquids with compositions matching those of NWA 8694. This meteorite is a chassignite cumulate containing nakhlitic mesostasis, a direct link between the Chassignites and the nakhlites and the association of dunitic to trachytic compositions is reminiscent of terrestrial shield volcanoes. Chassignites and nakhlites were possibly formed when solidification fronts on chamber walls were disrupted, mainly as side eruptions of olivine-charged magmas from the deeper zones, and augite-charged fractionated magmas from nearer the summit of a volcano resembling Piton de la Fournaise on Earth.
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La Réunion Island dunites as analogs of the Martian Chassignites: Tracking trapped melts with incompatible trace elements
Lithos, 2019Co-Authors: Jean-alix Barrat, Patrick BachèleryAbstract:Fractional crystallization of basalts produces a variety of ultramafic cumulates poor in incompatible elements. Inorder to discuss the effect of trapped liquids on the concentrations of incompatible elements in these cumulates,we studied a series of dunites and pyroxenites from the Piton de la Fournaise (La Réunion Island, Indian Ocean).These rocks have a high variability in the abundance of these elements, which is only partially explained by theirproportions of olivines and pyroxenes. Mass balance calculations indicate that≈0.25 to 1 wt% of trapped meltsare required to account for the budget of the highly incompatible element abundances such as U, Rb, Nb orlight Rare Earth Elements (REE). Using our results, we revisited the REE geochemistry of Chassignites, a groupletof Martian meteorites. Chassignites are mineralogically, texturally and chemically very similar to the dunitesfrom La Réunion Island, which can be seen as very close terrestrial analogs. The variations of REE abundancesand ratios in Chassigny, one of the three known Chassignites, can be explained by inhomogeneous distributionof trapped melts in this meteorite at the scale of the size of the fragments (typicallyb1 g) used for the chemicalanalyses. Using these variations, we deduced the shape of the REE pattern and abundances of the Chassigny par-ent melt.
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La Réunion Island dunites as analogs of the Martian Chassignites: Tracking trapped melts with incompatible trace elements
Lithos, 2019Co-Authors: Jean-alix Barrat, Patrick BachèleryAbstract:Abstract Fractional crystallization of basalts produces a variety of ultramafic cumulates poor in incompatible elements. In order to discuss the effect of trapped liquids on the concentrations of incompatible elements in these cumulates, we studied a series of dunites and pyroxenites from the Piton de la Fournaise (La Reunion Island, Indian Ocean). These rocks have a high variability in the abundance of these elements, which is only partially explained by their proportions of olivines and pyroxenes. Mass balance calculations indicate that ≈0.25 to 1 wt% of trapped melts are required to account for the budget of the highly incompatible element abundances such as U, Rb, Nb or light Rare Earth Elements (REE). Using our results, we revisited the REE geochemistry of Chassignites, a grouplet of Martian meteorites. Chassignites are mineralogically, texturally and chemically very similar to the dunites from La Reunion Island, which can be seen as very close terrestrial analogs. The variations of REE abundances and ratios in Chassigny, one of the three known Chassignites, can be explained by inhomogeneous distribution of trapped melts in this meteorite at the scale of the size of the fragments (typically
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Metal‐saturated sulfide assemblages in NWA 2737: Evidence for impact‐related sulfur devolatilization in Martian meteorites
Meteoritics & Planetary Science, 2012Co-Authors: Jean-pierre Lorand, Jean-alix Barrat, Vincent Chevrier, Violaine Sautter, Sylvain Courrech Du PontAbstract:– NWA 2737, a Martian meteorite from the Chassignite subclass, contains minute amounts (0.010 ± 0.005 vol%) of metal-saturated Fe-Ni sulfides. These latter bear evidence of the strong shock effects documented by abundant Fe nanoparticles and planar defects in Northwest Africa (NWA) 2737 olivine. A Ni-poor troilite (Fe/S = 1.0 ± 0.01), sometimes Cr-bearing (up to 1 wt%), coexists with micrometer-sized taenite/tetrataenite-type native Ni-Fe alloys (Ni/Fe = 1) and Fe-Os-Ir-(Ru) alloys a few hundreds of nanometers across. The troilite has exsolved flame-like pentlandite (Fe/Fe + Ni = 0.5–0.6). Chalcopyrite is almost lacking, and no pyrite has been found. As a hot desert find, NWA 2737 shows astonishingly fresh sulfides. The composition of troilite coexisting with Ni-Fe alloys is completely at odds with Chassigny and Nahkla sulfides (pyrite + metal-deficient monoclinic-type pyrrhotite). It indicates strongly reducing crystallization conditions (close to IW), several log units below the fO2 conditions inferred from chromites compositions and accepted for Chassignites (FMQ-1 log unit). It is proposed that reduction in sulfides into base and precious metal alloys is operated via sulfur degassing, which is supported by the highly resorbed and denticulated shape of sulfide blebs and their spongy textures. Shock-related S degassing may be responsible for considerable damages in magmatic sulfide structures and sulfide assemblages, with concomitant loss of magnetic properties as documented in some other Martian meteorites.
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Metal-saturated sulfide assemblages in NWA 2737: Evidence for impact-related sulfur devolatilization in Martian meteorites
Meteoritics and Planetary Science, 2012Co-Authors: Jean-pierre Lorand, Jean-alix Barrat, Vincent Chevrier, Violaine Sautter, Sylvain PontAbstract:NWA 2737, a Martian meteorite from the Chassignite subclass, contains minute amounts (0.010 ± 0.005 vol%) of metal-saturated Fe-Ni sulfides. These latter bear evidence of the strong shock effects documented by abundant Fe nanoparticles and planar defects in Northwest Africa (NWA) 2737 olivine. A Ni-poor troilite (Fe/S = 1.0 ± 0.01), sometimes Cr-bearing (up to 1 wt%), coexists with micrometer-sized taenite/tetrataenite-type native Ni-Fe alloys (Ni/Fe = 1) and Fe-Os-Ir-(Ru) alloys a few hundreds of nanometers across. The troilite has exsolved flame-like pentlandite (Fe/Fe + Ni = 0.5-0.6). Chalcopyrite is almost lacking, and no pyrite has been found. As a hot desert find, NWA 2737 shows astonishingly fresh sulfides. The composition of troilite coexisting with Ni-Fe alloys is completely at odds with Chassigny and Nahkla sulfides (pyrite + metal-deficient monoclinic-type pyrrhotite). It indicates strongly reducing crystallization conditions (close to IW), several log units below the fO2 conditions inferred from chromites compositions and accepted for Chassignites (FMQ-1 log unit). It is proposed that reduction in sulfides into base and precious metal alloys is operated via sulfur degassing, which is supported by the highly resorbed and denticulated shape of sulfide blebs and their spongy textures. Shock-related S degassing may be responsible for considerable damages in magmatic sulfide structures and sulfide assemblages, with concomitant loss of magnetic properties as documented in some other Martian meteorites.
Carl B. Agee - One of the best experts on this subject based on the ideXlab platform.
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The chlorine isotopic composition of Martian meteorites 1: Chlorine isotope composition of Martian mantle and crustal reservoirs and their interactions
Meteoritics & Planetary Science, 2016Co-Authors: J. T. Williams, Francis M. Mccubbin, Charles K. Shearer, Carl B. Agee, Zachary D. Sharp, Paul V. Burger, A. R. Santos, Kevin D. MckeeganAbstract:The Martian meteorites record a wide diversity of environments, processes, and ages. Much work has been done to decipher potential mantle sources for Martian magmas and their interactions with crustal and surface environments. Chlorine isotopes provide a unique opportunity to assess interactions between Martian mantle-derived magmas and the crust. We have measured the Cl-isotopic composition of 17 samples that span the range of known ages, Martian environments, and mantle reservoirs. The 37Cl of the Martian mantle, as represented by the olivine-phyric shergottites, NWA 2737 (chassignite), and Shergotty (basaltic shergottite), has a low value of approximately −3.8‰. This value is lower than that of all other planetary bodies measured thus far. The Martian crust, as represented by regolith breccia NWA 7034, is variably enriched in the heavy isotope of Cl. This enrichment is reflective of preferential loss of 35Cl to space. Most basaltic shergottites (less Shergotty), nakhlites, Chassigny, and Allan Hills 84001 lie on a continuum between the Martian mantle and crust. This intermediate range is explained by mechanical mixing through impact, fluid interaction, and assimilation-fractional crystallization.
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lithium isotope constraints on crust mantle interactions and surface processes on mars
Geochimica et Cosmochimica Acta, 2015Co-Authors: Tomas Magna, James M.d. Day, Klaus Mezger, Manuela A Fehr, Ralf Dohmen, Hasnaa Chennaoui Aoudjehane, Carl B. AgeeAbstract:Abstract Lithium abundances and isotope compositions are reported for a suite of martian meteorites that span the range of petrological and geochemical types recognized to date for Mars. Samples include twenty-one bulk-rock enriched, intermediate and depleted shergottites, six nakhlites, two Chassignites, the orthopyroxenite Allan Hills (ALH) 84001 and the polymict breccia Northwest Africa (NWA) 7034. Shergottites unaffected by terrestrial weathering exhibit a range in δ7Li from 2.1 to 6.2‰, similar to that reported for pristine terrestrial peridotites and unaltered mid-ocean ridge and ocean island basalts. Two Chassignites have δ7Li values (4.0‰) intermediate to the shergottite range, and combined, these meteorites provide the most robust current constraints on δ7Li of the martian mantle. The polymict breccia NWA 7034 has the lowest δ7Li (−0.2‰) of all terrestrially unaltered martian meteorites measured to date and may represent an isotopically light surface end-member. The new data for NWA 7034 imply that martian crustal surface materials had both a lighter Li isotope composition and elevated Li abundance compared with their associated mantle. These findings are supported by Li data for olivine-phyric shergotitte NWA 1068, a black glass phase isolated from the Tissint meteorite fall, and some nakhlites, which all show evidence for assimilation of a low-δ7Li crustal component. The range in δ7Li for nakhlites (1.8 to 5.2‰), and co-variations with chlorine abundance, suggests crustal contamination by Cl-rich brines. The differences in Li isotope composition and abundance between the martian mantle and estimated crust are not as large as the fractionations observed for terrestrial continental crust and mantle, suggesting a difference in the styles of alteration and weathering between water-dominated processes on Earth versus possibly Cl–S-rich brines on Mars. Using high-MgO shergottites (>15 wt.% MgO) it is possible to estimate the δ7Li of Bulk Silicate Mars (BSM) to be 4.2 ± 0.9‰ (2σ). This value is at the higher end of estimates for the Bulk Silicate Earth (BSE; 3.5 ± 1.0‰, 2σ), but overlaps within uncertainty.
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Evidence for a widespread basaltic breccia component in the martian low-albedo regions from the reflectance spectrum of Northwest Africa 7034
Icarus, 2015Co-Authors: Kevin M. Cannon, John F. Mustard, Carl B. AgeeAbstract:Northwest Africa (NWA) 7034 is the first breccia meteorite from Mars, and unlike the shergottite, nakhlite, and chassignite (SNC) martian meteorites, it matches the estimated chemical composition of martian crust. Here we show that the visible-infrared reflectance spectrum of NWA 7034 is unique compared to other SNCs and is more similar than them to remotely sensed data from Mars, suggesting the martian regolith may contain significant brecciated material produced during heavy bombardment of the crust.
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Lithium isotope constraints on crust–mantle interactions and surface processes on Mars
Geochimica et Cosmochimica Acta, 2015Co-Authors: Tomas Magna, James M.d. Day, Klaus Mezger, Manuela A Fehr, Ralf Dohmen, Hasnaa Chennaoui Aoudjehane, Carl B. AgeeAbstract:Abstract Lithium abundances and isotope compositions are reported for a suite of martian meteorites that span the range of petrological and geochemical types recognized to date for Mars. Samples include twenty-one bulk-rock enriched, intermediate and depleted shergottites, six nakhlites, two Chassignites, the orthopyroxenite Allan Hills (ALH) 84001 and the polymict breccia Northwest Africa (NWA) 7034. Shergottites unaffected by terrestrial weathering exhibit a range in δ7Li from 2.1 to 6.2‰, similar to that reported for pristine terrestrial peridotites and unaltered mid-ocean ridge and ocean island basalts. Two Chassignites have δ7Li values (4.0‰) intermediate to the shergottite range, and combined, these meteorites provide the most robust current constraints on δ7Li of the martian mantle. The polymict breccia NWA 7034 has the lowest δ7Li (−0.2‰) of all terrestrially unaltered martian meteorites measured to date and may represent an isotopically light surface end-member. The new data for NWA 7034 imply that martian crustal surface materials had both a lighter Li isotope composition and elevated Li abundance compared with their associated mantle. These findings are supported by Li data for olivine-phyric shergotitte NWA 1068, a black glass phase isolated from the Tissint meteorite fall, and some nakhlites, which all show evidence for assimilation of a low-δ7Li crustal component. The range in δ7Li for nakhlites (1.8 to 5.2‰), and co-variations with chlorine abundance, suggests crustal contamination by Cl-rich brines. The differences in Li isotope composition and abundance between the martian mantle and estimated crust are not as large as the fractionations observed for terrestrial continental crust and mantle, suggesting a difference in the styles of alteration and weathering between water-dominated processes on Earth versus possibly Cl–S-rich brines on Mars. Using high-MgO shergottites (>15 wt.% MgO) it is possible to estimate the δ7Li of Bulk Silicate Mars (BSM) to be 4.2 ± 0.9‰ (2σ). This value is at the higher end of estimates for the Bulk Silicate Earth (BSE; 3.5 ± 1.0‰, 2σ), but overlaps within uncertainty.
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Unique Meteorite from Early Amazonian Mars: Water-Rich Basaltic Breccia Northwest Africa 7034
Science (New York N.Y.), 2013Co-Authors: Carl B. Agee, Francis M. Mccubbin, R. Shaheen, Nicole V. Wilson, Karen Ziegler, Victor J. Polyak, Zachary D. Sharp, Yemane Asmerom, Morgan H. Nunn, Mark H. ThiemensAbstract:We report data on the martian meteorite Northwest Africa (NWA) 7034, which shares some petrologic and geochemical characteristics with known martian meteorites of the SNC (i.e., shergottite, nakhlite, and chassignite) group, but also has some unique characteristics that would exclude it from that group. NWA 7034 is a geochemically enriched crustal rock compositionally similar to basalts and average martian crust measured by recent Rover and Orbiter missions. It formed 2.089 ± 0.081 billion years ago, during the early Amazonian epoch in Mars9 geologic history. NWA 7034 has an order of magnitude more indigenous water than most SNC meteorites, with up to 6000 parts per million extraterrestrial H2O released during stepped heating. It also has bulk oxygen isotope values of Δ17O = 0.58 ± 0.05 per mil and a heat-released water oxygen isotope average value of Δ17O = 0.330 ± 0.011 per mil, suggesting the existence of multiple oxygen reservoirs on Mars.
Francis M. Mccubbin - One of the best experts on this subject based on the ideXlab platform.
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The chlorine isotopic composition of Martian meteorites 1: Chlorine isotope composition of Martian mantle and crustal reservoirs and their interactions
Meteoritics & Planetary Science, 2016Co-Authors: J. T. Williams, Francis M. Mccubbin, Charles K. Shearer, Carl B. Agee, Zachary D. Sharp, Paul V. Burger, A. R. Santos, Kevin D. MckeeganAbstract:The Martian meteorites record a wide diversity of environments, processes, and ages. Much work has been done to decipher potential mantle sources for Martian magmas and their interactions with crustal and surface environments. Chlorine isotopes provide a unique opportunity to assess interactions between Martian mantle-derived magmas and the crust. We have measured the Cl-isotopic composition of 17 samples that span the range of known ages, Martian environments, and mantle reservoirs. The 37Cl of the Martian mantle, as represented by the olivine-phyric shergottites, NWA 2737 (chassignite), and Shergotty (basaltic shergottite), has a low value of approximately −3.8‰. This value is lower than that of all other planetary bodies measured thus far. The Martian crust, as represented by regolith breccia NWA 7034, is variably enriched in the heavy isotope of Cl. This enrichment is reflective of preferential loss of 35Cl to space. Most basaltic shergottites (less Shergotty), nakhlites, Chassigny, and Allan Hills 84001 lie on a continuum between the Martian mantle and crust. This intermediate range is explained by mechanical mixing through impact, fluid interaction, and assimilation-fractional crystallization.
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a petrogenetic model for the comagmatic origin of Chassignites and nakhlites inferences from chlorine rich minerals petrology and geochemistry
Meteoritics & Planetary Science, 2013Co-Authors: Francis M. Mccubbin, Stephen M. Elardo, Charles K. Shearer, Alexander Smirnov, Erik H. Hauri, David S. DraperAbstract:Twelve samples belonging to the chassignite and nakhlite subgroups of Martian meteorites were investigated using a variety of micro-beam analytical techniques to gain insight into the petrogenesis of these two meteorite classes. There are a striking number of geochemical similarities between the Chassignites and nakhlites, including mineralogy and petrology, crystallization age, cosmic-ray exposure age, and radiogenic isotopic compositions. However, there are also geochemical differences, namely in trace element systematics of pyroxenes, that have led some authors to conclude that the nakhlites are comagmatic with each other, but not comagmatic with the Chassignites. On the basis of data presented here, we propose a model in which these differences can be reconciled by the addition of an exogenous Cl-rich fluid to the chassignite-nakhlite magma body shortly after the formation of the cumulate horizon that was sampled by the Chassigny meteorite. This model is supported by the textural and chemical associations of the volatile-bearing minerals apatite, amphibole, and biotite, which record a history starting with the addition of a Cl- and LREE-enriched fluid to the magma body. As the magma continued to crystallize, it eventually reached chloride saturation and degassed a Cl-rich fluid phase. Depending on the provenance of the Cl-rich fluid, this model could explain how the Chassignites and nakhlites originated from an LREE-depleted source, yet all exhibit LREE-enriched bulk-rock patterns. Additionally, the model explains the range in oxygen fugacity that is recorded by the Chassignites and nakhlites because eventual exsolution and loss of Cl-rich fluid phases near the end of crystallization of the nakhlite sequence leads to auto-oxidation of the magma body due to the preferential partitioning of Fe 2+ into the fluid phase.
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A petrogenetic model for the comagmatic origin of Chassignites and nakhlites: Inferences from chlorine‐rich minerals, petrology, and geochemistry
Meteoritics & Planetary Science, 2013Co-Authors: Francis M. Mccubbin, Stephen M. Elardo, Charles K. Shearer, Alexander Smirnov, Erik H. Hauri, David S. DraperAbstract:Twelve samples belonging to the chassignite and nakhlite subgroups of Martian meteorites were investigated using a variety of micro-beam analytical techniques to gain insight into the petrogenesis of these two meteorite classes. There are a striking number of geochemical similarities between the Chassignites and nakhlites, including mineralogy and petrology, crystallization age, cosmic-ray exposure age, and radiogenic isotopic compositions. However, there are also geochemical differences, namely in trace element systematics of pyroxenes, that have led some authors to conclude that the nakhlites are comagmatic with each other, but not comagmatic with the Chassignites. On the basis of data presented here, we propose a model in which these differences can be reconciled by the addition of an exogenous Cl-rich fluid to the chassignite-nakhlite magma body shortly after the formation of the cumulate horizon that was sampled by the Chassigny meteorite. This model is supported by the textural and chemical associations of the volatile-bearing minerals apatite, amphibole, and biotite, which record a history starting with the addition of a Cl- and LREE-enriched fluid to the magma body. As the magma continued to crystallize, it eventually reached chloride saturation and degassed a Cl-rich fluid phase. Depending on the provenance of the Cl-rich fluid, this model could explain how the Chassignites and nakhlites originated from an LREE-depleted source, yet all exhibit LREE-enriched bulk-rock patterns. Additionally, the model explains the range in oxygen fugacity that is recorded by the Chassignites and nakhlites because eventual exsolution and loss of Cl-rich fluid phases near the end of crystallization of the nakhlite sequence leads to auto-oxidation of the magma body due to the preferential partitioning of Fe 2+ into the fluid phase.
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Unique Meteorite from Early Amazonian Mars: Water-Rich Basaltic Breccia Northwest Africa 7034
Science (New York N.Y.), 2013Co-Authors: Carl B. Agee, Francis M. Mccubbin, R. Shaheen, Nicole V. Wilson, Karen Ziegler, Victor J. Polyak, Zachary D. Sharp, Yemane Asmerom, Morgan H. Nunn, Mark H. ThiemensAbstract:We report data on the martian meteorite Northwest Africa (NWA) 7034, which shares some petrologic and geochemical characteristics with known martian meteorites of the SNC (i.e., shergottite, nakhlite, and chassignite) group, but also has some unique characteristics that would exclude it from that group. NWA 7034 is a geochemically enriched crustal rock compositionally similar to basalts and average martian crust measured by recent Rover and Orbiter missions. It formed 2.089 ± 0.081 billion years ago, during the early Amazonian epoch in Mars9 geologic history. NWA 7034 has an order of magnitude more indigenous water than most SNC meteorites, with up to 6000 parts per million extraterrestrial H2O released during stepped heating. It also has bulk oxygen isotope values of Δ17O = 0.58 ± 0.05 per mil and a heat-released water oxygen isotope average value of Δ17O = 0.330 ± 0.011 per mil, suggesting the existence of multiple oxygen reservoirs on Mars.
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Active Igneous and Hydrothermal Activity During the Early-Middle Amazonian: Inferences from the Chassignite and Nakhlite Meteorites and Implications for Astrobiology
2010Co-Authors: Francis M. Mccubbin, M. Glamoclija, Andrew Steele, Alexander SmirnovAbstract:Introduction: The current picture of the present-day martian surface presents a challenge to life [1]. Environmentally-informative mineralogy identified from orbital and in-situ exploration indicates that where water was present during recent times, condi-tions were largely saline, acidic and oxidizing [2]. The martian surface may only have been habitable during the Noachian to early Hesparian, where water was available before it was erased by the emergence of a cold, dry climate that persisted for ~3.5Ga [3]. Below the surface, however, aqueous environments on Mars may be elucidated from the detailed analysis of SNC meteorites; several of which record a magmatic source of water and the potential for young (early-mid Ama-zonian) subsurface hydrothermal activity that could stretch the envelope of martian habitability over both space and time [4-7]. The SNC meteorites represent a direct sampling of igneous processes on Mars, and they are some of the only detailed windows into the martian subsurface that scientists currently have. In recent years, the mineral-ogy of the SNC meteorites has expanded this insight to include subsurface hydrothermal activity on Mars. In particular, the volatile-bearing mineralogy of the Nakhlite and Chassignite meteorites, which includes apatite, amphibole, mica, and jarosite, have recorded both high-temperature and low-temperature interaction with a variety of fluid compositions, including those rich in water, chlorine, sulfur, carbon, iron and alkalis [4-6, 8, 9]. Moreover, many of these fluids were de-rived by magmatic degassing, indicating that the mag-matic source regions were still contributing to the addi-tion of these volatile constituents to the martian surface and subsurface as late as the early-mid Amazonian (the Chassignites and Nakhlites are dated at ~1.3 Ga [10]) [6]. In fact, the recent discovery of methane sources from volcanic provinces on Mars indicates that the same types of processes could even continue today [11]. Areas of young (Amazonian) volcanism have also been identified on Mars from orbital exploration, and several of these locations have been suggested to repre-sent potential source regions for the SNC meteorites [12]. The Chassignites and Nakhlites have been sug-gested to originate from either thick lava flows or shal-low layered intrusions [13], which would likely be as-sociated with Amazonian volcanic provinces. The most prominent young volcanism on Mars is associated with the regions of Tharsis and Elysium. Provinces of Cen-tral Elysium Planitia (southeast of Elysium Mons and Noctic Labyrinthus) and Echus Chasma (east of the Tharsis region) were active until approximately one hundred million years ago [14, 15]. Hydrated light-toned deposits (probably hydrated sulfates or chloride salts) have also been identified in association with these young volcanic features [16]. These deposits are consistent with the presence of aqueous alterations under conditions similar to the cur-rent climate [16]; however, hydrothermal activity can-not be ruled out as a potential source for the deposits. In this contribution, we attempt to synthesize the new findings of evidence for magmatically-derived hydrothermal activity from the Nakhlite and Chassig-nite meteorites with new observations from remote sensing on young Amazonian volcanism on Mars. From this compilation, we are able to make inferences about potential habitable zones at the martian surface and subsurface even after the onset of the cold, dry climate that has existed for much of the Hesparian and Amazonian epochs. Evidence for Hydrothermal Activity from The Nakhlites and Chassignites: At least two types of magmatically-derived hydrothermal fluids have been identified from recent studies of SNC meteorites [4-6, 17]. Both of these fluids were inferred based on the mineral assemblages present within various textural regimes in the meteorites. The water-rich nature of amphibole and mica within olivine-hosted melt inclusions from the Chassigny me-teorite are consistent with magmatically derived fluids that are water-rich. The apatite from these melt inclu-sions indicate that chlorine was also present in the fluid, but it was not the dominant volatile species [5, 6]. These fluids are produced from the magma after reaching fluid-saturation during ascent and crystalliza-tion. At elevated temperatures, these fluids would con-tain primarily silica and un-ionized chlorides of so-dium, potassium, iron, and hydrogen [e.g. 17-21]. Con-tinued crystallization would produce more fluid that would become progressively more dilute (water-rich). At low temperatures, these fluids would be character-ized by neutral to alkaline pH, with moderate-low sa-linity, although some variability could arise from wall-rock interactions. Astrobiology Science Conference 2010 (2010) 5604.pdf
James M.d. Day - One of the best experts on this subject based on the ideXlab platform.
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CHASSIGNITE AND NAKHLITE PARENTAL MELTS DETERMINED FROM MELT INCLUSION ANALYSIS
2020Co-Authors: Amanda Ostwald, Arya Udry, Juliane Gross, James M.d. DayAbstract:Melt inclusion analysis used to constrain and compare parental melt compositions of the nakhlite and chassignite martian meteorites.
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Martian magmatism from plume metasomatized mantle
Nature Communications, 2018Co-Authors: James M.d. Day, Arya Udry, Frédéric Moynier, Yang Liu, Kimberly T. Tait, Clive R. NealAbstract:Direct analysis of the composition of Mars is possible through delivery of meteorites to Earth. Martian meteorites include ∼165 to 2400 Ma shergottites, originating from depleted to enriched mantle sources, and ∼1340 Ma nakhlites and Chassignites, formed by low degree partial melting of a depleted mantle source. To date, no unified model has been proposed to explain the petrogenesis of these distinct rock types, despite their importance for understanding the formation and evolution of Mars. Here we report a coherent geochemical dataset for shergottites, nakhlites and Chassignites revealing fundamental differences in sources. Shergottites have lower Nb/Y at a given Zr/Y than nakhlites or Chassignites, a relationship nearly identical to terrestrial Hawaiian main shield and rejuvenated volcanism. Nakhlite and chassignite compositions are consistent with melting of hydrated and metasomatized depleted mantle lithosphere, whereas shergottite melts originate from deep mantle sources. Generation of martian magmas can be explained by temporally distinct melting episodes within and below dynamically supported and variably metasomatized lithosphere, by long-lived, static mantle plumes. A unified model for the formation of martian rock types is required to understand Mars’s formation and evolution. Here the authors show that nakhlite and chassignite meteorites originate from melting of metasomatized depleted mantle lithosphere, whereas shergottite melts originate from deep plume sources.
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1.34 billion-year-old magmatism on Mars evaluated from the co-genetic nakhlite and chassignite meteorites
Geochimica et Cosmochimica Acta, 2018Co-Authors: Arya Udry, James M.d. DayAbstract:Abstract Nakhlite and chassignite martian meteorites have similar crystallization (1340 ± 40 Ma) and ejection (∼11 Ma) ages, and 87Rb-87Sr and 143Sm-144Nd compositions. Using a near-comprehensive suite of these rocks, we place further constraints on nakhlite and chassignite petrogenesis, utilizing bulk rock and mineral major- and trace-element compositions, and quantitative textural data for 17 samples, including three recent finds (Northwest Africa [NWA] 10153, NWA 10645, and NWA 11013). Bulk rock and mineral compositions indicate that nakhlites and Chassignites originated from
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lithium isotope constraints on crust mantle interactions and surface processes on mars
Geochimica et Cosmochimica Acta, 2015Co-Authors: Tomas Magna, James M.d. Day, Klaus Mezger, Manuela A Fehr, Ralf Dohmen, Hasnaa Chennaoui Aoudjehane, Carl B. AgeeAbstract:Abstract Lithium abundances and isotope compositions are reported for a suite of martian meteorites that span the range of petrological and geochemical types recognized to date for Mars. Samples include twenty-one bulk-rock enriched, intermediate and depleted shergottites, six nakhlites, two Chassignites, the orthopyroxenite Allan Hills (ALH) 84001 and the polymict breccia Northwest Africa (NWA) 7034. Shergottites unaffected by terrestrial weathering exhibit a range in δ7Li from 2.1 to 6.2‰, similar to that reported for pristine terrestrial peridotites and unaltered mid-ocean ridge and ocean island basalts. Two Chassignites have δ7Li values (4.0‰) intermediate to the shergottite range, and combined, these meteorites provide the most robust current constraints on δ7Li of the martian mantle. The polymict breccia NWA 7034 has the lowest δ7Li (−0.2‰) of all terrestrially unaltered martian meteorites measured to date and may represent an isotopically light surface end-member. The new data for NWA 7034 imply that martian crustal surface materials had both a lighter Li isotope composition and elevated Li abundance compared with their associated mantle. These findings are supported by Li data for olivine-phyric shergotitte NWA 1068, a black glass phase isolated from the Tissint meteorite fall, and some nakhlites, which all show evidence for assimilation of a low-δ7Li crustal component. The range in δ7Li for nakhlites (1.8 to 5.2‰), and co-variations with chlorine abundance, suggests crustal contamination by Cl-rich brines. The differences in Li isotope composition and abundance between the martian mantle and estimated crust are not as large as the fractionations observed for terrestrial continental crust and mantle, suggesting a difference in the styles of alteration and weathering between water-dominated processes on Earth versus possibly Cl–S-rich brines on Mars. Using high-MgO shergottites (>15 wt.% MgO) it is possible to estimate the δ7Li of Bulk Silicate Mars (BSM) to be 4.2 ± 0.9‰ (2σ). This value is at the higher end of estimates for the Bulk Silicate Earth (BSE; 3.5 ± 1.0‰, 2σ), but overlaps within uncertainty.
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Lithium isotope constraints on crust–mantle interactions and surface processes on Mars
Geochimica et Cosmochimica Acta, 2015Co-Authors: Tomas Magna, James M.d. Day, Klaus Mezger, Manuela A Fehr, Ralf Dohmen, Hasnaa Chennaoui Aoudjehane, Carl B. AgeeAbstract:Abstract Lithium abundances and isotope compositions are reported for a suite of martian meteorites that span the range of petrological and geochemical types recognized to date for Mars. Samples include twenty-one bulk-rock enriched, intermediate and depleted shergottites, six nakhlites, two Chassignites, the orthopyroxenite Allan Hills (ALH) 84001 and the polymict breccia Northwest Africa (NWA) 7034. Shergottites unaffected by terrestrial weathering exhibit a range in δ7Li from 2.1 to 6.2‰, similar to that reported for pristine terrestrial peridotites and unaltered mid-ocean ridge and ocean island basalts. Two Chassignites have δ7Li values (4.0‰) intermediate to the shergottite range, and combined, these meteorites provide the most robust current constraints on δ7Li of the martian mantle. The polymict breccia NWA 7034 has the lowest δ7Li (−0.2‰) of all terrestrially unaltered martian meteorites measured to date and may represent an isotopically light surface end-member. The new data for NWA 7034 imply that martian crustal surface materials had both a lighter Li isotope composition and elevated Li abundance compared with their associated mantle. These findings are supported by Li data for olivine-phyric shergotitte NWA 1068, a black glass phase isolated from the Tissint meteorite fall, and some nakhlites, which all show evidence for assimilation of a low-δ7Li crustal component. The range in δ7Li for nakhlites (1.8 to 5.2‰), and co-variations with chlorine abundance, suggests crustal contamination by Cl-rich brines. The differences in Li isotope composition and abundance between the martian mantle and estimated crust are not as large as the fractionations observed for terrestrial continental crust and mantle, suggesting a difference in the styles of alteration and weathering between water-dominated processes on Earth versus possibly Cl–S-rich brines on Mars. Using high-MgO shergottites (>15 wt.% MgO) it is possible to estimate the δ7Li of Bulk Silicate Mars (BSM) to be 4.2 ± 0.9‰ (2σ). This value is at the higher end of estimates for the Bulk Silicate Earth (BSE; 3.5 ± 1.0‰, 2σ), but overlaps within uncertainty.
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Northwest Africa 8694, a ferroan chassignite: Bridging the gap between nakhlites and Chassignites
Geochimica et Cosmochimica Acta, 2020Co-Authors: Roger H. Hewins, Munir Humayun, Jean-alix Barrat, Brigitte Zanda, Jean-pierre Lorand, Sylvain Courrech Du Pont, N. Assayag, P. Cartigny, S. Yang, V. SautterAbstract:Abstract The origin(s) of the Chassignites and nakhlites, closely related martian olivine and augite cumulates, respectively, are much debated. Northwest Africa (NWA) 8694 is the third chassignite to be discovered and the most ferroan, containing 85% olivine (Fo54). Its O-isotope compositions (δ18O ∼ 4.4‰, Δ17O ∼ 0.30‰) are typical of other martian meteorites. It has adcumulate texture and contains cumulus chromite, poikilitic pigeonite (En56Fs37Wo7) and mesostasis (trapped interstitial liquid). The latter contains pyroxene and plagioclase (An23 Ab70 Or8) plus rare K- feldspar (Or74), and has a trachyandesitic to trachytic bulk composition. Melt inclusions in olivine contain a variety of phases including biotite and rare amphibole. Olivine, chromite, and pigeonite compositions are intermediate between those of the other Chassignites and those of the nakhlites. Augite, which appears to mantle pigeonite, has a composition overlapping that in nakhlite NWA 998 and some other nakhlites at (En41-40Wo38-39). The augite lamellae in pigeonite 1–2 μm in apparent width, and the survival of Ca zoning in olivine, suggest a near-surface cooling environment. The bulk-rock REE concentrations in the three Chassignites do not correlate with Mg# but depend on the abundance of trapped liquid. The form of REE patterns calculated for olivine subtraction is very like those of nakhlite mesostases, but the observed concentrations of LREE in NWA 8694 trapped liquid have a very steep slope. This is explained by undersampling of baddeleyite and zirconolite that occur near olivine contacts with mesostasis. Though pyroxene is unzoned, its trace element variations indicate fractional crystallization. The range of olivine compositions in the three Chassignites (Fo79-54) is too large to result from the crystallization sequential growth of olivine from a single magma undergoing fractional crystallization. The Ge/Si ratios show degassing of NWA 8694 which sets this chassignite apart from other Chassignites and nakhlites, implying a unique batch of magma for its genesis. Many potential parent liquids are capable of generating the NWA 8694 olivine composition, though not its alkaline mesostasis. We calculated that Nakhla parent liquid NA01a (Stockstill et al., 2005) with 10% Nakhla core olivine added would produce both olivine crystals and alkaline daughter liquids with compositions matching those of NWA 8694. This meteorite is a chassignite cumulate containing nakhlitic mesostasis, a direct link between the Chassignites and the nakhlites and the association of dunitic to trachytic compositions is reminiscent of terrestrial shield volcanoes. Chassignites and nakhlites were possibly formed when solidification fronts on chamber walls were disrupted, mainly as side eruptions of olivine-charged magmas from the deeper zones, and augite-charged fractionated magmas from nearer the summit of a volcano resembling Piton de la Fournaise on Earth.
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Metal‐saturated sulfide assemblages in NWA 2737: Evidence for impact‐related sulfur devolatilization in Martian meteorites
Meteoritics & Planetary Science, 2012Co-Authors: Jean-pierre Lorand, Jean-alix Barrat, Vincent Chevrier, Violaine Sautter, Sylvain Courrech Du PontAbstract:– NWA 2737, a Martian meteorite from the Chassignite subclass, contains minute amounts (0.010 ± 0.005 vol%) of metal-saturated Fe-Ni sulfides. These latter bear evidence of the strong shock effects documented by abundant Fe nanoparticles and planar defects in Northwest Africa (NWA) 2737 olivine. A Ni-poor troilite (Fe/S = 1.0 ± 0.01), sometimes Cr-bearing (up to 1 wt%), coexists with micrometer-sized taenite/tetrataenite-type native Ni-Fe alloys (Ni/Fe = 1) and Fe-Os-Ir-(Ru) alloys a few hundreds of nanometers across. The troilite has exsolved flame-like pentlandite (Fe/Fe + Ni = 0.5–0.6). Chalcopyrite is almost lacking, and no pyrite has been found. As a hot desert find, NWA 2737 shows astonishingly fresh sulfides. The composition of troilite coexisting with Ni-Fe alloys is completely at odds with Chassigny and Nahkla sulfides (pyrite + metal-deficient monoclinic-type pyrrhotite). It indicates strongly reducing crystallization conditions (close to IW), several log units below the fO2 conditions inferred from chromites compositions and accepted for Chassignites (FMQ-1 log unit). It is proposed that reduction in sulfides into base and precious metal alloys is operated via sulfur degassing, which is supported by the highly resorbed and denticulated shape of sulfide blebs and their spongy textures. Shock-related S degassing may be responsible for considerable damages in magmatic sulfide structures and sulfide assemblages, with concomitant loss of magnetic properties as documented in some other Martian meteorites.
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Metal-saturated sulfide assemblages in NWA 2737: Evidence for impact-related sulfur devolatilization in Martian meteorites
Meteoritics and Planetary Science, 2012Co-Authors: Jean-pierre Lorand, Jean-alix Barrat, Vincent Chevrier, Violaine Sautter, Sylvain PontAbstract:NWA 2737, a Martian meteorite from the Chassignite subclass, contains minute amounts (0.010 ± 0.005 vol%) of metal-saturated Fe-Ni sulfides. These latter bear evidence of the strong shock effects documented by abundant Fe nanoparticles and planar defects in Northwest Africa (NWA) 2737 olivine. A Ni-poor troilite (Fe/S = 1.0 ± 0.01), sometimes Cr-bearing (up to 1 wt%), coexists with micrometer-sized taenite/tetrataenite-type native Ni-Fe alloys (Ni/Fe = 1) and Fe-Os-Ir-(Ru) alloys a few hundreds of nanometers across. The troilite has exsolved flame-like pentlandite (Fe/Fe + Ni = 0.5-0.6). Chalcopyrite is almost lacking, and no pyrite has been found. As a hot desert find, NWA 2737 shows astonishingly fresh sulfides. The composition of troilite coexisting with Ni-Fe alloys is completely at odds with Chassigny and Nahkla sulfides (pyrite + metal-deficient monoclinic-type pyrrhotite). It indicates strongly reducing crystallization conditions (close to IW), several log units below the fO2 conditions inferred from chromites compositions and accepted for Chassignites (FMQ-1 log unit). It is proposed that reduction in sulfides into base and precious metal alloys is operated via sulfur degassing, which is supported by the highly resorbed and denticulated shape of sulfide blebs and their spongy textures. Shock-related S degassing may be responsible for considerable damages in magmatic sulfide structures and sulfide assemblages, with concomitant loss of magnetic properties as documented in some other Martian meteorites.