Meteorite Picture of the Day (10 photos): Arguin 002
from The Meteoritical Bulletin, No. 112
Lunar meteorite (norite)
History: Two pieces of this meteorite (342 g and 127 g) were purchased by Bachir Salek in December 2021 from a dealer in Nouadhibou, Mauritania, who said that he had found them at 20.649°N, 15.141°W near Tijirit, Mauritania about 37 km east of the well-known Tasiast gold mine. Some of this material was subsequently purchased by Jay Piatek. On March 25, 2022, additional material (two larger pieces weighing 500 g and 100 g plus many small fragments) was recovered by a shepherd at the same location. 100.2 g of this material was purchased by Ziyao Wang in June 2022 from a dealer in Laayoune, Morocco, who sold the remainder to Luc Labenne.
Physical Characteristics: The material has an overall beige color with clear glassy maskelynite grains and some thin, dark glassy shock veinlets visible. The very fresh fusion crust is consistent with this meteorite being a very recent fall.
Petrography: (A. Irving, UWS and P. Carpenter, WUSL; A. Ross, and C. Agee, UNM) Relatively coarse grained igneous assemblage (grainsize up to ~1.2 mm) of predominantly orthopyroxene (exhibiting undulose extinction) and anorthite (completely converted to maskelynite) in approximately equal proportions. Orthopyroxene grains contain very small, rounded to irregular-shaped blebs of augite, which do not form continuous, crystallographically-rational exsolution lamellae. The overall amount of augite is only a few vol.% and olivine is absent. Accessory phases include troilite and kamacite (each as discrete grains and in composite grains), taenite, low-Ti chromite (associated with troilite), REE-bearing merrillite (associated with chromite in veinlets), chlorapatite, Ni-poor Fe metal and rare zircon. Shock glass analyzed with a 20 micrometer defocused beam gave a bulk composition consistent with that of a mixture of orthopyroxene+anorthite.
Geochemistry: Orthopyroxene (Fs33.2-34.5Wo3.8-3.2, FeO/MnO = 62-73, N = 13), augite (Fs14.4-15.7Wo44.2-42.6, FeO/MnO = 47-65, N = 11), pigeonite bleb within augite (Fs33.7Wo8.8, FeO/MnO = 67), maskelynite (An91.2-92.6Or0.8-0.6, N = 13), shock glass (in wt.%, SiO2 47.8±1.0, TiO2 0.23±0.03, Al2O3 22.8±0.7, Cr2O3 0.18±0.03, MgO 7.3±0.5, FeO 7.0±0.6, MnO 0.09±0.02, CaO 12.0±0.8, Na2O 0.45±0.05, K2O 0.08±0.01.
Classification: Lunar (unbrecciated norite). Although much more heavily shocked than most others, this specimen has textural and mineralogical counterparts especially among the returned magnesian plutonic igneous samples from the Apollo 14, 16 and 17 landed lunar missions (e.g., Papike et al., 1998).
Specimens: 20.l g including a polished mount and one polished thin section at UWB; 30 g including a polished mount at UNM; 557 g with Labenne; 317 g with Mr. B. Salek; 122 g with Mr. J. Piatek; 100.2 g with WangZ.
I have not studied Arguin 002. It would be nice to have a whole-rock composition and some geochronolgical data on this one.
Meteoritical Bulletin Database