(Primitive achondrite-ung in MetBull 98)
Found March 2008
no coordinates recorded
Nine small stones having a combined weight of 130 g were found near Alargoug, Morocco and then sold in June 2008 to meteorite dealer G. Hupé. A sample was submitted for analysis and classification to the University of Washington in Seattle (A. Irving and S. Kuehner), and NWA 5297 was determined to be a completely metamorphosed chondrite (metachondrite) with similarities to the LL chondrite group.
The initial type specimen analysis of NWA 5297 determined that it is composed of olivine, orthopyroxene, and very sodic plagioclase, along with minor taenite and Ni-bearing troilite. Accessory phases found by Dunlap et al. (2015 #2570) include chromite and merrillite. It is a texturally evolved meteorite that exhibits a poikiloblastic structure (finer-grained inclusions of one mineral embedded within larger crystals of another mineral) and lacks any relict chondrules.
The O-isotopic composition of NWA 5297 was evaluated at the Carnegie Institute in Washington D.C. by D. Rumble III, and again by Greenwood et al. (2017). The meteorite was shown to have affinities to the LL-chondrite group (see diagram below).
Diagram credit: Greenwood et al., Chemie der ErdeGeochemistry, vol. 77, p. 24 (2017, open access link)
'Melting and differentiation of early-formed asteroids: The perspective from high precision oxygen isotope studies'
Despite its O isotope similarity, NWA 5297 has a greater abundance (~10 vol%) of FeNi-metal than would be expected for an LL-chondrite parent body which had experienced a high degree of metamorphism. Furthermore, it was determined that the the olivine composition of NWA 5297 lies outside the range for equilibrated LL chondrites, and the meteorite was recognized by Dunlap et al. (2015 #2570) as being similar to the brachinites. They also found that silicates in NWA 5297 plot in the brachinite field on an Fe/Mn vs. Fe/Mg coupled diagram.
Based on AlMg systematics, Dunlap et al. (2015 #5317) calculated an upper limit of <4.5679 b.y. ago for the timing of Al/Mg fractionation during differentiation on the NWA 5297 parent body. When all of these data are considered together, NWA 5297 could be considered to be an ungrouped achondrite, but it may be related to the brachinites. The specimen of NWA 5297 shown above is a 2.78 g partial slice.