A transmision electron microscopy study of the olivine coronas in the Vaca Muerta mesosiderite.

HWANG S.L.; SAAVEDRA M.; SHEN, POUYAN; MARIA EUGENIA VARELA; CHU, H-T; YUI T.F.

Chicago

Congreso; Annual Meetings of the Meteoritical Society; 2021

Mesosiderites are breccias usually composed of approximately equal amounts of Fe-Ni metal andsilicates. The latter contains mineral and lithic clasts in a fine-grained matrix [e.g., 1-3]. Based on silicate textures,mesosiderites are subdivided into four subtypes (1 to 4), which are considered to reflect an increasing degree in metamorphism [4]. Coronas in olivine, a mineral always present in scares amounts (~2 vol%), are considered the resultof thermal metamorphism formed by the reaction of olivine with a mesosiderite-like matrix assemblage [4-7|. Coronasconsist mainly of orthopyroxene with abundant chromite and merrillite and minor plagioclase, clinopyroxene andilmenite [5]. Although the coronas are texturally similar, they can be divided in different mineralogical distinct zoneswith variable development even within the same mesosiderite. Here, a transmission electron microscopy (TEM) coupled with energy dispersive X-ray (EDX) analysis was performed to shed light on the main process under which theVaca Muerta coronas were formed.