^1,2Yunhua Wu,^1,3Weibiao Hsu(徐伟彪)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.113531]
¹CAS Center for Excellence in Comparative Planetology, Purple Mountain Observatory, Nanjing 210033, China
²University of Chinese Academy of Sciences, Beijing 100049, China
³The State Key Laboratory of Lunar and Planetary Science/Space Science Institute, Macau University of Science and Technology, Taipa, Macau
Copyright Elsevier

Unbrecciated mare basalts are rare in the lunar meteorite collection. Found in 2015, Northwest Africa (NWA) 10597 is a medium-grained low-Ti mare basalt with a subophitic texture. The meteorite consists mostly of mm-sized pyroxene and plagioclase, with minor olivine, spinel, ilmenite, phosphates, silica, and trace Zr-rich minerals, such as baddeleyite, zirconolite and tranquillityite. A portion of plagioclase and silica has been transformed to their high-pressure polymorphs due to shock metamorphism. NWA 10597 has a low TiO₂ content (2.9 wt%) but is relatively enriched in rare earth elements (REE) (La_average = 65 × CI) with an overall unfractionated pattern except for a negative Eu anomaly. Calculated REE concentrations of parent melts in equilibrium with Mg-rich pyroxene and Ca-rich plagioclase suggest no significant assimilation of REE-rich melts after the onset of pyroxene crystallization. In situ UPb analyses of baddeleyite and apatite reveal a mutually consistent age of ~3.0 Ga, which is also in excellent agreement with that of low-Ti mare basalts NWA 4734 and LaPaz Icefield (LAP) 02205 dated with other independent techniques. The concordance suggests no significant thermal disturbance in the UPb isotopic system of NWA 10597 although it was heavily shocked. NWA 10597 closely resembles NWA 4734 in terms of petrographic texture, mineral chemistry and geochronology, indicating a pairing relationship.

^1,2,3Sen Hu,^1,2,3Yangting Lin,^1,2Jianchao Zhang,^1,2Jialong Hao,^4,5Akira Yamaguchi,^1,2Ting Zhang,^1,2Wei Yang,^1,2Hitesh Changela
Earth and Planetary Science Letters (in Press) Link to Article [https://doi.org/10.1016/j.epsl.2019.115902]
¹Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
²Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing 100029, China
³College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
⁴National Institute of Polar Research, Tokyo 190-8518, Japan
⁵Department of Polar Science, School of Multidisciplinary Science, SOKENDAI (The Graduate University for Advanced Studies), Tokyo 190-8518, Japan
Copyright Elsevier

Martian meteorites of various petrogeneses retain a record of volatiles on Mars: from the hydrosphere, crustal water to the mantle. Sputtering of the martian atmosphere by solar wind after the loss of Mars’ magnetic field enriched it in deuterium, which exchanged with martian crustal water. Recent studies show that the hydrogen isotopic composition of the martian crustal water reservoir varies from 3000 to 7000‰ but requires better constraints. Melt inclusion glasses, maskelynite and fusion crust from the depleted olivine-phyric shergotite NWA 6162 were analyzed using NanoSIMS, providing a unique insight into the hydrogen isotopic and volatile elemental content of both the martian crustal water reservoir and the mantle source.

The H₂O, S, and Cl contents of the melt inclusion glasses are ∼0-3137, 14-239, and 16-967 ppm, respectively. δD values vary from −560 to 6137‰. The water content positively correlates with the δD values in both the melt inclusion glasses and maskelynite in a two end-member mixing trend. One end-member is the magmatic water with a δD value of ∼0‰, and the other end member is the martian crustal water with δD ranging from 5000 to 6000‰. NWA 6162, a depleted olivine-phyric shergottite, originated from a different mantle source to the enriched lherzolitic shergottites. However, both types of shergottites exchanged with martian crustal water with the same δD values, indicating a homogeneous martian crustal water hydrogen isotopic composition (5000-6000‰). Most melt inclusion glasses from NWA 6162 have low water content (0-234 ppm) except for two enriched locations as micron-sized bands and dendrites. The low water content in most melt inclusion glasses, the dendritic shaped water enriched areas in melt inclusions, and the martian crustal water diffusion profile recorded in maskelynite collectively suggest short-lived water-rock interactions in the NWA 6162 parent rock that was probably induced by impact. Furthermore, a great contribution (up to 98%) of surface Cl accompanying D-enriched water was recorded in the melt inclusions supported by the positive correlation between Cl and H₂O. The presence of sulfide and S-rich hot spots and low δD end-member of the magmatic water indicate that the degassing during post-entrapment crystallization and ascent of the melt inclusion is negligible. H₂O, S, and Cl contents of the martian mantle reservoir are estimated to be 0.1-3, 0.5-15, and 0.5-4 ppm respectively, after the correction of fractional crystallization of the melt inclusions and contribution from the martian surface reservoir. The martian mantle reservoir estimated from NWA 6162 was water-, S-, and Cl-poorer than the Earth’s interior.