Journal
METEORITICS & PLANETARY SCIENCE
Volume 57, Issue 11, Pages 2017-2041Publisher
WILEY
DOI: 10.1111/maps.13917
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Funding
- Dr. Rolf M. Schwiete-Stiftung
- Wilhelm and Else Heraeus Foundation
- Deutsche Forschungsgemeinschaft (DFG) [INST 161/921-1 FUGG, INST 161/923-1 FUGG]
- Projekt DEAL
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This study focuses on the analysis of the Si-rich mesostasis in Martian shergottite NWA 6963 using laser ablation multicollector inductively coupled plasma mass spectrometry U-Pb measurements. The results indicate that the Si-rich mesostasis represents a late-stage differentiated melt produced in the final phase of the magmatic history, rather than a shock melt.
Enriched shergottites contain interstitial Si-rich mesostasis; however, it is unclear whether such mesostasis is formed by impact or magmatic processes. We use laser ablation multicollector inductively coupled plasma mass spectrometry U-Pb measurements of minerals within the interstitial Si-rich mesostasis and of merrillite within the coarse-grained groundmass of Martian-enriched gabbroic shergottite Northwest Africa (NWA) 6963. The date derived of tranquillityite, Cl-apatite, baddeleyite, and feldspar from the Si-rich mesostasis is 172.4 +/- 6.1 Ma, and the derived merrillite date is 178.3 +/- 10.6 Ma. We conclude, based on textural observation, that merrillite is a late magmatic phase in NWA 6963, that it was not produced by shock, and that its U-Pb-system was not reset by shock. The indistinguishable dates of the gabbroic merrillite and the minerals within the Si-rich mesostasis in NWA 6963 indicate that the Si-rich mesostasis represents a late-stage differentiated melt produced in the final phase of the magmatic history of the gabbroic rock and not a shock melt. This can likely be transferred to similar Si-rich mesostases in other enriched shergottites and opens the possibility for investigations of Si-rich mesostasis in enriched shergottites to access their magmatic evolution. Our results also provide a crystallization age of 174 +/- 6 Ma (weighted average) for NWA 6963.
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