Euhedral Tetrataenite in the Jelica Meteorite

Alan E. Rubin
Institute of Geophysics and Planetary Physics, University of California, Los Angeles CA 90024, USA

Abstract: A 65 × 107 µm grain of euhedral tetrataenite (ordered FeNi) attached to a similarly sized grain of troilite occurs within an impact-melt rock clast in the Jelica LL6 chondrite breccia. After impact melting, immiscible metallic Fe-Ni and troilite droplets formed within the silicate melt progenitor of the clast. At ⩾1200°C while the surrounding silicate was still partly molten, euhedral taenite with ∼ 50 wt.% Ni began crystallizing in one of the metal-troilite droplets. Troilite nucleated at one edge of the euhedral taenite grain and began to crystallize at ∼870°C. At 320°C the metal phase underwent an ordering reaction and formed tetrataenite. The unrecrystallized clast-host boundary and the differences in olivine composition and degree of polycrystallinity of troilite between the clast and Jelica host indicate that the clast was incorporated into Jelica during a late-stage brecciation event.

Keywords: tetrataenite • troilite • Jelica meteorite • brecciation

Mineralogical Magazine; June 1994 v. 58; no. 391; p. 215-221; DOI: 10.1180/minmag.1994.058.391.04
© 1994, The Mineralogical Society
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