Chronology of martian breccia NWA 7034 and the formation of the martian crustal dichotomy.

ABSTRACT: Martian meteorite Northwest Africa (NWA) 7034 and its paired stones are the only brecciated regolith samples from Mars with compositions that are representative of the average martian crust. These samples therefore provide a unique opportunity to constrain the processes of metamorphism and alteration in the martian crust, which we have investigated via U-Pu/Xe, ⁴⁰Ar/³⁹Ar, and U-Th-Sm/He chronometry. U-Pu/Xe ages are comparable to previously reported Sm-Nd and U-Pb ages obtained from NWA 7034 and confirm an ancient (>4.3 billion years) age for the source lithology. After almost 3000 million years (Ma) of quiescence, the source terrain experienced several hundred million years of thermal metamorphism recorded by the K-Ar system that appears to have varied both spatially

SUBMITTER: Cassata WS 

PROVIDER: S-EPMC5966191 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature