Northwest Africa 7611 (NWA 7611)

Morocco

Found: May 2012

Classification: Lunar meteorite

History: Reportedly found near the Moroccan/Algerian border in May 2012. Purchased from a Moroccan meteorite dealer in 2012.

Physical characteristics: Single 916 g stone, no fusion crust, smooth exterior with numerous light- and dark-colored clasts, saw cuts reveal brecciated texture with white feldspar and green-brown pyroxene and olivine grains (up to 3 mm) set in a darker gray-green matrix; scattered gabbroic and dark clasts up to 1 cm.

Petrography: (C. Agee, UNM; A. Irving, UWS) Microprobe examination of a polished 7 × 2 cm sawn slice and a separate polished mount shows a fragmental breccia of plagioclase, pyroxene, and olivine grains in a wide range of grain sizes. A prominent ~1-cm pyroxene-plagioclase gabbroic clast was observed as well as several smaller gabbroic fragments. One small clast consists of intergrown hedenbergite+fayalite+silica (after pyroxferroite). The groundmass is variable with some domains showing a uniform fine-grained subophitic plagioclase-pyroxene texture, while other domains show densely packed mineral clasts ranging from 10-300 μm. There are several sharp boundaries between the various textural domains, with at least two compositionally distinct olivine populations, and a wide range of pyroxene compositions, indicating multiple lithologies of a mingled fragmental breccia. Accessory ilmenite, silica polymorph, minor zircon, troilite, Ti-bearing chromite, Ni-free iron metal and kamacite are present.

Geochemistry: (C. Agee and M. Spilde, UNM; A. Irving and S. Kuehner, UWS). Fayalitic olivine Fa_90.6±5.7, Fe/Mn=90±4, n=15; forsteritic olivine Fa_31.6±11.1, Fe/Mn=93±9, n=3; pyroxene Fs_43.6±13.3Wo_20.2±8.5, Fe/Mn=67±8, n=37; pyroxene in gabbroic clast Fs_45.3±13.1 Wo_15.4±5.3, Fe/Mn=69±7, n=12; plagioclase An_93.5±1.5Ab_6.0±1.4Or_0.5±0.5, n=13. Bulk composition (R. Korotev, WUSL). INAA on 4 subsamples gave the following mean values: Na₂O=0.405, CaO=14.8, FeO=11.27 (wt%); Sc=25.1, Cr=1692, Co=37.6, Ni=181, La=6.38, Nd=8.9, Sm=3.07, Eu=0.891, Lu=0.321, Hf=2.12, Ir=0.0044, Au=0.0036, Th=0.97, U=0.36 (ppm). Oxygen Isotopes, laser fluorination (K.Ziegler, UNM), 6 analyses on 3 acid-washed aliquots gave mean values δ¹⁷O=3.161±0.080, δ¹⁸O=5.931±0.031, Δ¹⁷O=0.030±0.075 (linearized, all permil).

Classification: Achondrite (lunar, mingled breccia), high bulk FeO and Sc, and fayalitic olivines suggest the presence of a mare basalt component.

Specimens: A total of 20 g is on deposit at UNM. The remainder is divided between Jay Piatek, Matt Morgan, Mike Hankey, and Haag; Jay Piatek holds the main mass.