The water content and parental magma of the second chassignite NWA 2737: Clues from trapped melt inclusions in olivine

Abstract

Abstract-NWA 2737, the second known chassignite, mainly consists of cumulate olivine crystals of homogeneous composition (Fo = 78.7 AE 0.9). These brown colored olivine grains exhibit two sets of perpendicular planar defects due to shock. Two forms of trapped liquids, interstitial melts and magmatic inclusions, have been examined. Mineral assemblages within the olivine-hosted magmatic inclusions include low-Ca pyroxene, augite, kaersutite, fluorapatite, biotite, chromite, sulfide, and feldspathic glass. The reconstructed parental magma composition (A # ) of the NWA 2737 is basaltic and resembles both the experimentally constrained parental melt composition of chassiginites and the Gusev basalt Humphrey, albeit with lower Al contents. A # also broadly resembles the average of shergottite parent magmas or LAR 06319. However, we suggest that the mantle source for the chassignite parental magmas was distinct from that of the shergottite meteorites, particularly in CaO/Al 2 O 3 ratio. In addition, based on the analysis of the volatile contents of kaersutite, we derived a water content of 0.48-0.67 wt% for the parental melt. Finally, our MELTS calculations suggest that moderate pressure (approximately 6.8 kb) came closest to reproducing the crystallized melt-inclusion assemblages.

Igneous and shock processes affecting chassignite amphibole evaluated using chlorine/water partitioning and hydrogen isotopes

“…The supporting data of He et al. () were used to calculate average amphibole compositions for the melt inclusions analyzed in that study.…”

“…; He et al. ). The chassignites are of particular relevance to studies of the volatile content of Mars’ mantle since they may have crystallized from deep, primitive melts (Johnson et al.…”

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

“…We supplemented these calculations on parental melt crystallization paths with isobaric crystallization calculations on the NWA 2737 chassignite melt inclusion composition [ He et al ., ] to try to fit the mineralogy observed in those inclusions. We also performed a set of isobaric and adiabatic crystallization calculations on the EET‐A composition to fit melt inclusion mineralogy in that meteorite [ Liu et al ., ].…”

The variability of ruthenium in chromite from chassignite and olivine‐phyric shergottite meteorites: New insights into the behavior of PGE and sulfur in Martian magmatic systems

“…; He et al. ). Moreover, ~1–4 ppb Ru broadly overlaps with the calculated Ru inventory (i.e., ~1–10 ppb) of Martian mantle melts undersaturated in sulfide (Righter et al.…”

“…In the chassignites, chromite and olivine presumably accumulated from a variably evolved, incompatible element (e.g., light rare earth elements, LREE) enriched basaltic precursor melt (e.g., Filiberto ; He et al. ). Magma emplacement may have happened as a shallow slow‐cooling magma body or as a stack of thick lava flows (Monkawa et al.…”