New England Meteoritical Services

Reprinted from the proceedings of the Meteoritical Society, July 1996

DRUSY VUGS IN THE ALBION IRON METEORITE: MINERALOGY AND TEXTURES. U.B. Marvin1, M.I. Petaev1, and R. Kempton2, 1Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA, 2New England Meteoritical Services, Mendon MA 01756, USA.

Albion (name submitted to the Nomenclature Committee of the Meteoritical Society), a IVA fine octahedrite, is unique in having vugs scattered throughout the otherwise orderly Widmanstätten structure, The most prominent vugs are open cavities, up to ~5 x 9 mm, partially filled with drusy spheroidal masses. The final growth phase was the deposition of a thin rim chiefly of kamacite on all exposed surfaces. Such vugs are surrounded by thin zones, (less than or equal to) 2 mm wide, of granulated kamacite. A second type of vug lining, observed by Buchwald [1] consists of masses of cubic Fe crystals with (less than or equal to) 0.5 wt% Ni. Still other vugs occur as narrow voids, (less than or equal) to 2 mm long, and as minute vacuoles a few micrometers across, along the kamacite-taenite grain boundaries of the Widmanstätten patterns.

The spheroidal masses consist mainly of irregular kamacite grains. 1-35 (micrometers) across, containing 2-3.5 wt% Ni, plus a few rounded segregations of Ni-rich tetrataenite with 55.6 wt% Ni. Enmeshed in both metals are thin, branching films of troilite that appears to have invaded and corroded them. Scattered throughout the spheroids are blocky, euhedral grains of daubreelite (FeCr2S4), and scarcer ones of euhedral schreibersite [(Ni0.54Fe0.46)3P].

The Ni content of kamacites rises steadily from 2-3.5 wt% in the spheroids to ~5.3 wt% in the granulated nectar zone to 7.1 wt% Ni in the Widmanstätten patterns. Along the same traverses, the content of Ni in the tetrataenite grains drops precipitously from ~55 wt% Ni in the spheroids and granulated zone to an average of 33.7 wt% Ni in the taenite of the main mass. We have observed no evidence of shock metamorphism in the meteorite. Clearly, the Albion iron has been subject to the passage of reactive fluid phases during one or more episodes of its history. Possibilities, will be discussed in our companion paper [2].

References-. [I] Buchwald V.F. (1991) Meteoriter, 226, [2]Petaev M.I. and Marvin U. B. this volume.

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