The Vaca Muerta mesosiderite: The path under which Fe‐Ni alloy ±C phases could have formed

Abstract

AbstractThe combined SEM and TEM studies on the metal (Fe‐Ni alloy ±C) portion of the Vaca Muerta mesosiderite reveal structural and compositional evidence at micro to nanoscale, which sheds light on the solidification of taenite + graphite as a cement, and later solid‐state precipitation process for the kamacite formation as grain boundary allotriomorph. Besides, it is proposed that the graphite veinlets formed through a complex partial melting process followed by a solidification toward the final eutectic transient coupled with the solid‐state precipitation and later decomposition ordering of taenite. The presence of defects and taenite in graphite signal formation in a liquid environment. The δ13C values of graphite in the graphite‐rich areas (e.g., ranging from −0.8 ± 1.7‰ to +15.3 ± 2.5‰) suggest a short‐circuit diffusion path for C isotope fractionation.