¹M. E. Varela,²S.-L. Hwang,³P. Shen,^1,4L. N. Garcia,¹M. Saavedra,⁵T. Maruoka,⁶M. Bose
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14120]
¹Instituto de Ciencias Astronómicas, de la Tierra y del Espacio (ICATE), Universidad Nacional de San Juan, CONICET, San Juan, Argentina
²Department of Materials Science and Engineering, National Dong Hwa University, Hualien, Taiwan, ROC
³Department of Materials and Optoelectronic Science, National Sun Yat-sen University, Kaohsiung, Taiwan, ROC
⁴Instituto de Mecánica Aplicada, Universidad Nacional de San Juan, San Juan, Argentina
⁵Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
⁶School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
Published by arrangement with John Wiley & Sons

The 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.