INVESTIGADORES
VARELA Maria Eugenia
congresos y reuniones científicas
Título:
FeS GRAINS WITH ABUNDANT Fe1-xO-Fe3O4 CORE-SHELL CRYSTALS IN THE ANGRITE D´ORBIGNY.
Autor/es:
HWANG S.L.; SHEN P; CHU, H-T; YUI T.F.; IIZUKA Y.; VARELA M.E.
Lugar:
Houston
Reunión:
Conferencia; Lunar and Planetary Science Conference; 2015
Institución organizadora:
NASA
Resumen:
Introduction: The angrites are rocks as old as the solar system [1] with unusual petrological and geo-chemical characteristics. Notwithstanding their contro-versial genesis, they are considered to be igneous rocks of basaltic composition [e.g., 2 and references therein]. D´Orbigny is by far the largest (16.55 kg) angrite known and is peculiar in several respects. Its bulk chemical composition, mineralogical composition, mineral chemistry, rare gas contents and O isotope abundances are in line with other members of this me-teorite class. However, the shape of D?Orbigny, its structure with highly porous lithologies alternating with compact ones and its mineralogical heterogeneity strongly suggest that the rock was not formed by sim-ple crystallization of a basaltic melt [3, 4]. Although the source of angritic melts remains unknown, melts chemically resembling those of bulk angrites were produced by partial melting of Allende under very high oxygen fugacity conditions (IW+2) [5]. Albeit none of the experimentally produced melts match angritic melts in all parameters, these rocks are believed to have been formed under oxidizing conditions (e.g., [2 and references therein]). A previous chemical and petrological study of D'Orbigny suggests formation of this rock under redox changing conditions, ranging from reducing to highly oxidizing [3, 4]. Our study of high Ni-bearing metal and sulfides phases hosted by anorthite or anorthite and olivine in the groundmass of this rock strongly indicates that redox conditions in angrites need to be revised [6]. As another contribution towards this revision, we report in this abstract the presence of FeS grains with abundant Fe1-xO-Fe3O4 core shell crystals in the angrite D´Orbginy.