¹Benjamin J. Farcy, ^2,3Juliane Gross, ⁴Paul Carpenter, ¹Jacob Hicks, ¹Justin Filiberto
¹Carbondale, Parkinson Lab, Geology Department, Southern Illinois University, Carbondale, Illinois, USA
²Department of Earth and Planetary Sciences, Rutgers University, Piscataway, New Jersey, USA
³Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, USA
⁴Department of Earth and Planetary Sciences, Washington University, St. Louis, Missouri, USA

Martian magmas are thought to be rich in chlorine compared with their terrestrial counterparts. Here, we experimentally investigate the effect of chlorine on liquidus depression and near-liquidus crystallization of olivine-phyric shergottite NWA 6234 and compare these results with previous experimental results on the effect of chlorine on near-liquidus crystallization of the surface basalts Humphrey and Fastball. Previous experimental results showed that the change in liquidus temperature is dependent on the bulk composition of the basalt. The effect of chlorine on liquidus depression is greater for lower SiO2 and higher Al2O3 magmas than for higher SiO2 and lower Al2O3 magmas. The bulk composition for this study has lower Al2O3 and higher FeO contents than previous work; therefore, we provide additional constraints on the effect of the bulk composition on the influence of chlorine on near-liquidus crystallization. High pressure and temperature crystallization experiments were performed at 1 GPa on a synthetic basalt, of the bulk composition of NWA 6234, with 0–4 wt% Cl added to the sample as AgCl. The results are consistent with previous notions that with increasing wt% Cl in the melt, the crystallization temperature decreases. Importantly, our results have a liquidus depression ∆T (°C) from added chlorine that is consistent with the difference in bulk composition and suggest a dependence on both the bulk Al2O3 and FeO content. Our results suggest that the addition of chlorine to the Martian mantle may lower magma genesis temperatures and potentially aid in the petrogenesis of Martian magmas.

Reference
Farcy BJ, Gross J, Carpenter P, Hicks J, Filiberto J (2016) Effect of chlorine on near-liquidus crystallization of olivine-phyric shergottite NWA 6234 at 1 GPa: Implication for volatile-induced melting of the Martian mantle. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12662]
Published by arrangement with John Wiley & Sons

¹First E, ¹Hammer J
¹Department of Geology & Geophysics, University of Hawai‘i at Mānoa, 1680 East-West Road, POST 606A, Honolulu, Hawai‘i, USA

Dynamic crystallization experiments were performed on a liquid having the bulk composition of olivine-phyric shergottite Yamato 980459, to constrain the igneous thermal history of this meteorite. Key characteristics of the meteorite’s mineralogy and texture, including several morphologically distinct olivine and pyroxene crystal populations and a glassy mesostasis devoid of plagioclase, were replicated upon cooling from 1435 to 909 °C at 1 atmosphere under reducing conditions. Three sequential cooling ramps are required to produce synthetic samples with textures and compositions matching Yamato 980459. Olivine phenocrysts formed at

Reference
First E, Hammer J (2016) Igneous cooling history of olivine-phyric shergottite Yamato 980459 constrained by dynamic crystallization experiments. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12659]
Published by arrangement with John Wiley & Sons

¹Antoine S. G. Roth, ²Knut Metzler, ³Lukas P. Baumgartner, ¹Ingo Leya
¹Institute of Physics, University of Bern, Bern, Switzerland
²Institute for Planetology, University of Münster, Münster, Germany
³Institute of Earth Sciences, University of Lausanne, Lausanne, Switzerland

If chondrules were exposed to cosmic rays prior to meteorite compaction, they should retain an excess of cosmogenic noble gases. Beyersdorf-Kuis et al. (2015) showed that such excesses can be detected provided that the chemical composition of each individual chondrule is precisely known. However, their study was limited to a few samples as they had to be irradiated in a nuclear reactor for instrumental neutron activation analysis. We developed a novel analytical protocol that combines the measurements of He and Ne isotopic concentrations with a fast method to correct for differences in chemical composition using micro X-ray computed tomography. Our main idea is to combine noble gas, nuclear track, and petrography data for numerous chondrules to understand the precompaction exposure history of the chondrite parent bodies. Here, we report our results for a total of 77 chondrules and four matrix samples from NWA 8276 (L3.00), NWA 8007 (L3.2), and Bjurböle (L/LL4). All chondrules from the same meteorite have within uncertainty identical 21Ne exposure ages, and all chondrules from Bjurböle have within uncertainty identical 3He exposure ages. However, most chondrules from NWA 8276 and a few from NWA 8007 show small but resolvable differences in 3He exposure age that we attribute to matrix contamination and/or gas loss. The finding that none of the chondrules has noble gas excesses is consistent with the uniform track density found for each meteorite. We conclude that the studied chondrules did not experience a precompaction exposure longer than a few Ma assuming present-day flux of galactic cosmic rays. A majority of chondrules from L and LL chondrites thus rapidly accreted and/or was efficiently shielded from cosmic rays in the solar nebula.

Reference
Roth ASG, Metzler K,Baumgartner LP, Leya I (2016) Cosmic-ray exposure ages of chondrules. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12658]
Published by arrangement with John Wiley & Sons

¹Katrina D. van Drongelen, ²Douglas Rumble III,³Kimberly T. Tait
¹Department of Earth Sciences, University of Toronto, Toronto, Ontario, Canada
²Geophysical Laboratory, Carnegie Institution of Washington, Washington, District of Columbia, USA
³Royal Ontario Museum, Department of Natural History, Toronto, Ontario, Canada

Northwest Africa (NWA) 5232, an 18.5 kg polymict eucrite, comprises eucritic and exogenic CM carbonaceous chondrite clasts within a clastic matrix. Basaltic clasts are the most abundant eucritic clast type and show a range of textures and grain size, from subophitic to granoblastic. Other eucritic clast types present include cumulate (high-En pyroxene), pyroxene-lath, olivine rich with symplectite intergrowths as a break-down product of a quickly cooled Fe-rich metastable pyroxferroite, and breccia (fragments of a previously consolidated breccia) clasts. A variable cooling rate and degree of thermal metamorphism, followed by a complex brecciation history, can be inferred for the clasts based on clast rounding, crystallization (and recrystallization) textures, pyroxene major and minor element compositions, and pyroxene exsolution. The range in δ18O of clasts and matrix of NWA 5232 reflects its origin as a breccia of mixed clasts dominated by eucritic lithologies. The oxygen isotopic compositions of the carbonaceous chondrite clasts identify them as belonging to CM group and indicate that these clasts experienced a low degree of aqueous alteration while part of their parent body. The complex evolutionary history of NWA 5232 implies that large-scale impact excavation and mixing was an active process on the surface of the HED parent body, likely 4 Vesta.

Reference
van Drongelen KD, Rumble III D, Tait KT (2016) Petrology and oxygen isotopic compositions of clasts in HED polymict breccia NWA 5232. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12651]
Published by arrangement with John Wiley & Sons

^1,2Andrew Glikson, ³Arthur Hickman, ⁴Noreen J. Evans, ^4,5Christopher L. Kirkland, ^7,8Jung-Woo Park, ⁷Robert Rapp, ^3,6Sandra Romano
¹Geoscience Australia, P.O. Box 378, Canberra, A.C.T. 2601, Australia
²Planetary Science Institute, Australian National University, Acton, Australian Capital Territory, Australia
³Geological Survey of Western Australia, 100 Plain Street, East Perth, W.A. 6004, Australia
⁴Applied Geology, John de Laeter Centre, TIGeR, Curtin University, Bentley, WA 6102, Australia
⁵Centre for Exploration Targeting, Curtin Node, Department of Applied Geology, Western Australian School of Mines, Curtin University, WA 6102, Australia
⁶Centre for Exploration Targeting, School of Earth and Environment, The University of Western Australia, 35 Stirling Highway, Crawley, W.A. 6004, Australia
⁷Research School of Earth Sciences, Australian National University, Acton, Canberra 2601, Australia
⁸School of Earth and Environmental Sciences & Research Institute of Oceanography, Seoul National University, Seoul 151-747, South Korea

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Reference
Glikson A, Hickman A,Evans NJ, Kirkland CL, Park J-W, Rapp R, Romano S (2016) A new ∼3.46 Ga asteroid impact ejecta unit at Marble Bar, Pilbara Craton, Western Australia: A petrological, microprobe and laser ablation ICPMS study. Precambrian Research 279, 103–122
Link to Article [doi:10.1016/j.precamres.2016.04.003]

¹Shaolin Li, ^1,2Weibiao Hsu, ³Yunbin Guan, ⁴Linyan Wang, ¹Ying Wang
¹Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, China
²Institute of Space Sciences, Macau University of Science and Technology, Macau, China
³Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
⁴Faculty of Earth Sciences, China University of Geosciences, Wuhan, China

Northwest Africa (NWA) 4898 is the only low-Ti, high-Al basaltic lunar meteorite yet recognized. It predominantly consists of pyroxene (53.8 vol%) and plagioclase (38.6 vol%). Pyroxene has a wide range of compositions (En12–62Fs25–62Wo11–36), which display a continuous trend from Mg-rich cores toward Ca-rich mantles and then to Fe-rich rims. Plagioclase has relatively restricted compositions (An87–96Or0–1Ab4–13), and was transformed to maskelynite. The REE zoning of all silicate minerals was not significantly modified by shock metamorphism and weathering. Relatively large (up to 1 mm) olivine phenocrysts have homogenous inner parts with Fo ~74 and sharply decrease to 64 within the thin out rims (~30 μm in width). Four types of inclusions with a variety of textures and modal mineralogy were identified in olivine phenocrysts. The contrasting morphologies of these inclusions and the chemical zoning of olivine phenocrysts suggest NWA 4898 underwent at least two stages of crystallization. The aluminous chromite in NWA 4898 reveals that its high alumina character was inherited from the parental magma, rather than by fractional crystallization. The mineral chemistry and major element compositions of NWA 4898 are different from those of 12038 and Luna 16 basalts, but resemble those of Apollo 14 high-Al basalts. However, the trace element compositions demonstrate that NWA 4898 and Apollo 14 high-Al basalts could not have been derived from the same mantle source. REE compositions of its parental magma indicate that NWA 4898 probably originated from a unique depleted mantle source that has not been sampled yet. Unlike Apollo 14 high-Al basalts, which assimilated KREEPy materials during their formation, NWA 4898 could have formed by closed-system fractional crystallization.

Reference
Li S, Hsu W, Guan Y, Wang L, Wang Y (2016) Petrogenesis of the Northwest Africa 4898 high-Al mare basalt. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12663]
Published by arrangement with John Wiley and Sons

¹Andrew G. Tomkins, ¹Lara Bowlt, ^2,3Matthew Genge, ¹Siobhan A. Wilson, ⁴Helen E. A. Brand, ^1,4,5Jeremy L. Wykes

¹School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria 3800, Australia
²Impact and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College London, Exhibition Road, London SW7 2AZ, UK
³Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 2BT, UK
⁴Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3168, Australia
⁵¹Department of Earth and Planetary Sciences, Macquarie University, North Ryde, New South Wales 2113, Australia

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Reference
Tomkins AG, Bowlt L, Genge M, Wilson SA, Brand HEA, Wykes JL (2016) Ancient micrometeorites suggestive of an oxygen-rich Archaean upper atmosphere. Nature 533, 235–238
Link to Article [doi:10.1038/nature17678]

^1,2J. T. Williams, ^1,3C. K. Shearer, ^1,2Z. D. Sharp, ^1,3P. V. Burger, ^3,4F. M. McCubbin, ^1,3A. R. Santos, ^1,3C. B. Agee, ⁵K. D. McKeegan
¹Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, USA
²Center for Stable Isotopes, University of New Mexico, Albuquerque, New Mexico, USA
³Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, USA
⁴NASA Johnson Space Center, Mailcode XI2, Houston, Texas, USA
⁵Department of Earth, Planetary, and Space Sciences, UCLA, Los Angeles, California, USA

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.

Williams JT, Shearer CK, Sharp ZD, Burger PV, McCubbin FM, Santos AR, Agee CB, McKeegan KD (2016) The chlorine isotopic composition of Martian meteorites 1: Chlorine isotope composition of Martian mantle and crustal reservoirs and their interactions. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12647]
Published by arrangement with John Wiley & Sons

¹Dennis Harries,²Michael E. Zolensky
¹Institute of Geosciences, Friedrich Schiller University Jena, Jena, Germany
²Astromaterial Research and Exploration Science—NASA Johnson Space Center, Houston, Texas, USA

The polymict Kaidun microbreccia contains lithologies of C-type chondrites with euhedral iron sulfide crystals of hydrothermal origin. Our FIB-TEM study reveals that acicular sulfides in a CM1 lithology are composed of Fe-rich pyrrhotite with nonintegral vacancy superstructures (NC-pyrrhotite), troilite, and pentlandite, all showing distinct exsolution textures. Based on phase relations in the Fe-Ni-S system, we constrain the temperature of formation of the originally homogeneous monosulfide solid solution to the range of 100–300 °C. In some crystals the exsolution of pentlandite and the microtextural equilibration was incomplete, probably due to rapid cooling. We use thermodynamic modeling to constrain the physicochemical conditions of the extreme hydrothermal alteration in this lithology. Unless the CM1 lithology was sourced from a large depth in the parent body (internal pressure >85 bar) or the temperatures were in the lower range of the interval determined, the water was likely present as vapor. Previously described light δ34S compositions of sulfides in Kaidun’s CM1 lithology are likely due to the loss of 34S-enriched H2S during boiling. Platy sulfide crystals in an adjacent, intensely altered CI1 lithology are composed of Fe-poor, monoclinic 4C-pyrrhotite and NC-pyrrhotite and probably formed at lower temperatures and higher fS2 relative to the CM1 lithology. However, a better understanding of the stability of Fe-poor pyrrhotites at temperatures below 300 °C is required to better constrain these conditions.

Reference
Harries D, Zolensky ME (2016) Mineralogy of iron sulfides in CM1 and CI1 lithologies of the Kaidun breccia: Records of extreme to intense hydrothermal alteration. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12648]
Published by arrangement with John Wiley & Sons

¹Pietrek, A., ¹Kenkmann, T.
¹Institute of Earth and Environmental Sciences—Geology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany

We reassessed two drill cores of the Bunte Breccia deposits of the Ries crater, Germany. The objectives of our study were the documentation of evidence for water in the Bunte Breccia, the evaluation of how that water influenced the emplacement processes, and from which preimpact water reservoir it was derived. The Bunte Breccia in both cores can be structured into a basal layer composed mainly of local substrate material, overlain by texturally and compositionally diverse, crater-derived breccia units. The basal layer is composed of the youngest sediments (Tertiary clays and Upper Jurassic limestone) and has a razor-sharp boundary to the upper breccia units, which are composed of older rocks of Upper Jurassic to Upper Triassic age. Sparse material exchange occurred between the basal layer and the rest of the Bunte Breccia. Fluids predominantly came from the Tertiary and the Upper Triassic sandstone formation. In the basal layer, Tertiary clays were subjected to intense, ductile deformation, indicating saturation with water. This suggests that water was mixed into the matrix, creating a fluidized basal layer with a strong shear localization. In the upper units, Upper Triassic sandstones are intensely deformed by granular flow. The texture requires that the rocks were disaggregated into granular sand. Vaporization of pore water probably aided fragmentation of these rocks. In the Otting core, hot suevite (T > 600 °C) covered the Bunte Breccia shortly after its emplacement. Vertically oriented gas escape pipes in suevite partly emanate directly at the contact to the Bunte Breccia. They indicate that the Bunte Breccia contained a substantial amount of water in the upper part that was vaporized and escaped through these vents.

Reference
Pietrek A, Kenkmann T (2016) Ries Bunte Breccia revisited: Indications for the presence of water in Itzing and Otting drill cores and implications for the emplacement process. Meteoritics & Planetary Science (in Press)
Link to Article [doi: 10.1111/maps.12656]
Published by arrangement with John Wiley & Sons