Mincy mesosiderite metallic nodules analyzed by EBSD: An approach to understanding their thermal history

GARCÍA, LAURA NOEL; VARELA, EUGENIA; HWANG, SHYH-LUNG ; SHEN, POUYAN; BOLMARO, RAÚL; AVALOS, MARTINA

METEORITICS & PLANETARY SCIENCE

METEORITICAL SOC

Año: 2022

1086-9379

Meteorites carry information about the most common processes that have been active in the early solar system. In particular, mesosiderites are meteorites with a structure considered to be composed of equal parts of iron-nickel metal and silicates. Systems of such complexity require an interdisciplinary effort. A natural delimitation in the mesosiderites study is the discrimination of the phases in iron-nickel metallic and silicate domains. In this work, we focus on the metallic phases of the Mincy mesosiderite, a specimen available at the ICATE repository. In Mincy, the metallic phases are Fe-Ni-C alloys that are distributed forming metallic lumps or pebbles (referred to as metallic nodules in the manuscript) in which kamacite and taenite are present, and taenite is found both at the kamacite/silicate interface and surrounded by kamacite, that is, isolated from the silicates. We made use of the EBSD technique to determine the crystallographic orientation relationships along the taenite/kamacite boundaries as well as for characterizing the (hkl)-specific grain boundaries regarding the underlying tilt, twist, or twinning mechanism to assist the interpretation of the phase transformations and mechanisms that could explain the formation of these metallic nodules. From the results, each of the metallic nodules has a unique temperature-pressure history and kinetics to undergo phase transformations (mainly partial melting, heterogeneous nucleation controlled solidification and possible evaporation-condensation) as well as liquid-phase sintering and recrystallization in its own way.