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A unique, (almost) unaltered spinel‐rich fine‐grained inclusion in Kainsaz
Author(s) -
Holmberg B. B.,
Hashimoto A.
Publication year - 1992
Publication title -
meteoritics
Language(s) - English
Resource type - Journals
eISSN - 1945-5100
pISSN - 0026-1114
DOI - 10.1111/j.1945-5100.1992.tb00742.x
Subject(s) - melilite , allende meteorite , spinel , inclusion (mineral) , mineralogy , geology , pyroxene , geochemistry , carbonaceous chondrite , mineral , chondrite , meteorite , materials science , olivine , astrobiology , metallurgy , paleontology , physics
We report a unique, spinel‐rich, extremely porous fine‐grained inclusion in the Kainsaz (CO3) meteorite. This inclusion is the least altered fine‐grained inclusion yet discovered, having escaped almost entirely the secondary alterations experienced by Allende fine‐grained inclusions. The inclusion is comprised of loosely packed 5–30 μm spinel grains mantled by thin layers of melilite, anorthite, and diopsidic pyroxene. The inclusion, which has over 30 vol% void space, is one of the most spinel‐rich, most porous fine‐grained inclusions seen to date. The mineralogy of the inclusion matches that which has been predicted for a precursor of the altered mineral assemblages of Allende fine‐grained inclusions, though a lack of interstitial material in the Kainsaz inclusion reduces the likelihood of a direct genetic relationship between the two (Allende fine‐grained inclusions contain abundant interstitial material). Its mineralogical composition confirms that the precursors of other, more altered, fine‐grained inclusions were assemblages of refractory minerals exclusively.