The mantle, crust and atmosphere of Mars as illuminated by the light element geochemistry of NWA 7034

Grady, M. M.; Schwenzer, S. P. and Verchovsky, A. B. (2014). The mantle, crust and atmosphere of Mars as illuminated by the light element geochemistry of NWA 7034. In: 45th Lunar and Planetary Science Conference, 17-21 Mar 2014, The Woodlands, TX, USA.



The martian meteorite NWA 7034 (and its paired siblings NWA 7475, 7533, 7906, 7907 and 8114) is classified as a basaltic breccia. More
detailed studies describe the sample as either a monomict or polymict breccia consisting of multiple igneous-textured clasts, including impact melt rocks and phenocrysts set in a fine-grained clastic matrix. The breccia may be the product of its volcanic history or regolith processes. The first report of noble gases in NWA 7034 deduced a CRE age of between 5 and 11 Ma, depending on the assumed chemistry of the meteorite. NWA 7034 differs from other martian meteorites not just in its petrology, but also in its chronological evolution: it contains ancient zircons (~ 4.4 Ga; ref. 3), but has a Rb-Sr crystallization age of ~ 2.1 Ga, implying a later disturbance. A difference in the volatile inventory might help to distinguish between the former and the latter origins, since one might hope to detect a component related to the surface exposure history of the meteorite in regolith material, which might be otherwise absent in a volcanic breccia. Determination of the light element (C, N, noble gases) chemistry of brecciated meteorites (asteroidal and lunar) has enabled inferences to be drawn concerning the history of material at a parent body surface, as well as the evolutionary history of the parent prior to exposure. NWA 7034 offers the first opportunity to apply the lessons learnt from asteroid and lunar breccias to be applied to Mars.

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