NORTHWEST AFRICA 8671


Eucrite-anomalous
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Purchased May 2014
no coordinates recorded

A single 164.2 g stone without fusion crust was found near Foum El Hisn, Morocco and subsequently sold to Ali and Mohammed Hmani. A sample was sent for analysis and classification to the University of Washington in Seattle (A. Irving and S. Kuehner), and NWA 8671 was classified as an anomalous eucrite with a unique texture (Irving et al. (2018, MetBull 107).

The meteorite is composed of polygranular calcic plagioclase (An91.493.0) embayed within recystallized clinopyroxene plus fayalite, along with accessory silica polymorph, Al-bearing chromite, and troilite (Irving et al., 2018). Within the interstitial clinopyroxene are small regions composed of ferropigeonite having two distinct Ca compositions. The unique texture of NWA 8671 is attributed by Irving et al. (2018) to shock-generated partial melting which differentially affected the original rock, considered to have been a coarse-grained gabbroic eucrite. An oxygen isotope analysis conducted at the University of New Mexico (K. Ziegler) demonstrates that NWA 8671 has more negative Δ17O values than all other eucrites with the exception of the anomalous eucrite NWA 13355 (672 g), which was classified in 2020 and has similar Δ17O values but more variable δ18O values (see diagrams below).

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Diagrams from the Meteoritical Bulletin Oxygen Isotope Plots—The Meteoritical Society

standby for nwa 8671  o-isotopic diagram
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Diagram credit: Irving et al., 49th LPSC, #2247 (2018)

Further information about the anomalous eucrite-like meteorites and their proposed origin from multiple distinct parent bodies can be found on the Pasamonte page. The specimen of NWA 8671 shown above is a 0.52 g partial slice, while two excellent thin section photomicrographs are shown below.

Thin Section of NWA 8671 (XPL, FoV 11 × 11 mm)
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Image credit: Irving et al., 49th LPSC, #2247 (2018)

Thin Section of NWA 8671 (XPL, FoV 17 × 19 mm)
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Image credit: Peter Marmet