ELECTRON MICROSCOPIC STUDY OF GRAPHITE IN THE VACA MUERTA MESOSIDERITE

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

Chicago

Congreso; Annual Meetings of the Meteoritical Society; 2021

Mesosiderites, stony-iron meteorites consisting of silicate clasts and Fe-Ni metal in aboutequal proportions, can have graphite (Gr) occurring as cliftonite grains and aggregates up to 20 mm2 in size,and as 1?10 µm wide veinlets decorating the kamacite-kamacite and kamacite-taenite borders [1-3]. The lowcarbon content (115 ppm) measured in cloudy taenite in the RKP 79015 and Estherville could explain theabsence of graphite in these two mesosiderites [4]. There is still no consensus regarding the processesresponsible for the formation of graphite in the metal phase (e.g., deposition from a mobile vapor phase [3] orsolid-state precipitation of graphite from carbon previously dissolved in the metal [4]). Here scanning electronmicroscopy (SEM) and transmission electron microscopy (TEM) studies coupled with energy dispersive X-ray(EDX) analysis in the Vaca Muerta mesosiderite give some hints about graphite formation