Origin of metallic Fe-Ni in Renazzo and related chondrites
1992; Elsevier BV; Volume: 56; Issue: 6 Linguagem: Inglês
10.1016/0016-7037(92)90206-x
ISSN1872-9533
AutoresMin Sung Lee, Alan E. Rubin, J. T. Wasson,
Tópico(s)Stellar, planetary, and galactic studies
ResumoThe “anomalous” positive Co-Ni correlation among metal grains from the Renazzo and Al Rais chondrites reported in previous studies has two components: (1) a chondrule trend that extends up to 120–145 mg/g Ni probably reflects the mixing of Fe-rich and Fe-poor nebular metal; and (2) a weak extrachondrule trend that spans a Ni range from 40–70 mg/g reflects Fe introduction during mild metamorphism. We interpret the low Co and Ni contents at the edges of grains in chondrule margins to reflect dilution by Fe produced by FeO reduction. The reduction seems not to have occurred in the nebula but rather during a brief period of parent-body metamorphism; reduction of fine-grained FeO produced metallic Fe that plated onto nearby metal grains. Although diffusive exchange between pentlandite and metal could produce the observed Ni gradient, it is doubtful that it could produce the similar gradient of Co. Metal from chondrule interiors was inaccessible during the reduction event and'retained the flat profiles established during chondrule formation.
Referência(s)