Lunar Meteorite: Northwest Africa 4472 & 4485 (paired stones)

Morocco

Two slices of Northwest Africa 4472. Photo credit: Greg Hupé

Two views of Northwest Africa 4485 (188 g). Photo credit: Stefan Ralew and Martin Altmann

Slices of NWA 4472 (left) and NWA 4485 (right). Photo credit: Norbert Classes

NWA 4472 (top) and NWA 4485 (bottom). I acquired samples of the two stones at different times and photographed them under different conditions. Although the slices “look” different, they are almost identical compositionally and together different from any other lunar meteorite. Photo credit: Randy Korotev

Views of two sides of a slice of NWA 4485 with a large clast, which is slightly more feldspathic than the dark matrix. Photo credit: Randy Korotev

from The Meteoritical Bulletin, No. 91

Northwest Africa 4472

Algeria
Find: 2006 July
Mass: 64.3 g

Achondrite (lunar, KREEP-rich breccia)

History: G. Hupé purchased the sample July 2006 from a dealer in Tagounite, Morocco.

Physical characteristics: A single 64.3 g stone with visible pale gray to whitish clasts in a dark gray matrix. Fusion crust is not evident, but the exterior has fractures and thin coatings of desert varnish on exposed surfaces.

Petrography: (A. Irving and S. Kuehner, UWS) Lithic clasts (up to 0.65 cm) are predominantly various types of ophitic to quench-textured basalts (composed of pyroxene(s), plagioclase, olivine, ilmenite, and rare baddeleyite). Granophyre clasts (consisting of “ribbon-like” subparallel intergrowths of silica and K-feldspar with accessory baddeleyite and rare tranquillityite) are present as a minor component, as well as clasts composed mainly of fayalite (with associated glass, silica, K-feldspar, and merrillite) and spherical to ellipsoidal glass objects (up to 60 µm across). Mineral clasts include pyroxenes, olivine, plagioclase, silica, zircon, baddeleyite, merrillite, Ti-chromite, fayalite, ilmenite (with baddeleyite inclusions), metal (both kamacite and taenite), troilite, and schreibersite (Kuehner et al. 2007).

Mineral compositions and geochemistry: Olivine (Fa56.6–64.6; FeO/MnO = 91–101), plagioclase (An86.9–97.5 Or0.2–0.6), orthopyroxene (Fs26.9–29.3Wo3.8–4.1; FeO/MnO = 51–62), subcalcic augite (Fs52.6Wo30.5; FeO/MnO = 72), Al-Cr-rich pigeonite (Fs27.0Wo17.1; FeO/MnO = 51.1, Al = 3.10 wt%, Cr = 1.01 wt%), fayalite (Fa90.3; FeO/MnO = 92), barian K-feldspar intergrown with silica (Or80.9–55.6Ab15.3–30.2 Cn0.6–6.3).

Bulk composition: (R. Korotev, WUSL) INAA on nine ~30 mg subsamples gave a mean composition of: Na = 0.448, Fe = 7.14 (both wt%), Sc = 20.9, La = 44.7, Sm = 19.51, Eu = 1.50, Yb = 13.4, Zr = 438, Hf = 11.1, Ba = 601, Th = 7.49 (all ppm). Although it is possible that there is a minor mare basalt component, this specimen is dominated by materials with KREEP-like compositions and is essentially identical in bulk composition and petrologic characteristics to Northwest Africa 4472. [should read NWA 4485; RLK]

Classification: Achondrite (lunar, KREEP-rich breccia). Type specimen: A total of 12.87 g and 3 polished thick slices are on deposit at UWS. G. Hupé holds the main mass.

from The Meteoritical Bulletin, No. 91

Northwest Africa 4485

Algeria
Find: 2006 September
Mass: 188 g

Achondrite (lunar, KREEP-rich breccia)

History: Stefan Ralew purchased the whole stone in September 2006 from a dealer in Ouarzazate, Morocco. Physical characteristics: A single 188 g spheroidal stone with a brown weathered exterior. The interior consists of pale gray to whitish clasts in a dark gray matrix, and has visible thin veins of terrestrial carbonate.

Petrography: (A. Irving and S. Kuehner, UWS) Lithic clasts (up to 0.5 cm) are predominantly various types of ophitic to quench-textured basalts (composed of pyroxene(s), plagioclase, olivine, ilmenite, and rare baddeleyite). Granophyre clasts (consisting of subparallel to symplectitic intergrowths of silica and K-feldspar with accessory baddeleyite) are present as a minor component, as well as very fine-grained, quench-textured clasts composed of glass and fine plagioclase microlites. Mineral clasts include pyroxenes, olivine, plagioclase, silica, zircon, baddeleyite, merrillite, Ti-chromite, fayalite, ilmenite, metal (both kamacite and taenite), and troilite (Kuehner et al. 2007).

Mineral compositions and geochemistry: Olivine (Fa26.3–63.6; FeO/MnO = 99–121), plagioclase (An88.9–89.7 Or0.3–0.6), orthopyroxene (Fs18.9–19.7Wo4.6–3.7; FeO/MnO = 87–89), pigeonite (Fs37.0Wo10.1; FeO/MnO = 62), subcalcic augite (Fs48.9–49.2Wo26.7–39, FeO/MnO = 59–67), fayalite (Fa90.1, FeO/MnO = 80).

Bulk composition: (R. Korotev, WUSL) INAA on eight ~30 mg subsamples gave a mean composition of: Na = 0.441, Fe = 7.27 (both wt%), Sc = 21.7, La = 31.6, Sm = 14.12, Eu = 1.46, Yb = 11.0, Zr = 443, Hf = 11.4, Ba = 375, Th = 6.37 (all ppm). Although it is possible that there is a minor mare basalt component, this specimen is dominated by materials with KREEP-like compositions, and is essentially identical in bulk composition and petrologic characteristics to Northwest Africa 4472.

Classification: Achondrite (lunar, KREEP-rich breccia).

Type specimen: A total of 20 g and one polished mount are on deposit at UWS. Ralew holds the main mass.

Randy Says…

The Northwest Africa  4472/4485 pair is compositionally  unique in being a subequal mixture of feldspathic material from the highlands, some KREEP lithology, and basalt. It is almost certainly from the nearside of the Moon.

More Information

Meteoritical Bulletin Database

NWA 4472 | 4485

References

Arai T. Misawa K. Tomiyama T. Yoshitake M. Irving A. J. (2009) Constraints on lunar KREEP magmatism: A variety of KREEP basalt derivatives in lunar meteorite NWA 448540th Lunar and Planetary Science Conference, abstract no. 2292.

Arai T., Yoshitake M., Tomiyama T., Niihara T., Yokoyama T., Kaiden H., Misawa K., and Irving A. J. (2010) Support for a prolonged KREEP magmatism: U-Pb age dating of zircon and baddeleyite in lunar meteorite NWA 4485 meteorites41st Lunar and Planetary Science Conference, abstract no. 2379.

Arai T., Yoshitake M., Tomiyama T., Niihara T., Yokoyama T., Kaiden H., Misawa K., Irving A. J. (2010) U-Pb age dating and mineralogy of a KREEP basalt clast in lunar meteorite NWA 4485.  33rd Symposium on Antarctic Meteorites.

Calzada-Diaz A., Joy K. H., Crawford I. A., and Nordheim T. A. (2015) Constraining the source regions of lunar meteorites using orbital geochemical dataMeteoritics & Planetary Science 50, 214-228.

Joy K. H. (2013) Trace elements in lunar plagioclase as indicators of source lithology44th Lunar and Planetary Science Conference, abstract no. 1033.

Joy K. H., Fernandes V. A., Burgess R., Crawford I. A., Irving A. J., Kearsley A.T. (2007) The clast inventory of KREEPy lunar meteorite North West Africa 4472. 70th Annual Meeting of the Meteoritical Society, abstract no. 5223.

Joy K. H., Crawford I. A., Kearsley A. T., Fernandes V. A., Burgess R., and Irving A. J. (2008) The petrography and composition of lunar meteorite Northwest Africa 4472Lunar and Planetary Science XXXIX, abstract no. 1132.

Joy K. H., Burgess R., Hinton R., Fernandes V. A., Crawford I. A., Kearsley A. T., Irving A. J., and EIMF Team (2009) U-Pb and Ar-Ar chronology of lunar meteorite Northwest Africa 447240th Lunar and Planetary Science Conference, abstract no. 1708.

Joy K. H., Burgess R., Hinton R., Fernandes V. A., Crawford I. A., Kearsley A., Irving A., and EIMF (2009) Petrography and chronology of lunar meteorite NWA 4472Geochimica et Cosmochimica Acta Supplement 73, A607.

Korotev R. L. and Zeigler R. A. (2007) Keeping up with the lunar meteoritesLunar and Planetary Science XXXVIII, abstract no. 1340.

Korotev R. L, Zeigler R. A., Jolliff B. L., Irving A. J., and Bunch T. E. (2009) Compositional and lithological diversity among brecciated lunar meteorites of intermediate iron compositionMeteoritics & Planetary Science 44, 1287-1322.

Kuehner S. M., Irving A. J., Korotev R. L., Hupé G. M., and Ralew S. (2007) Zircon-baddeleyite-bearing silica+K-feldspar granophyric clasts in KREEP-rich lunar breccias Northwest Africa 4472 and 4485Lunar and Planetary Science XXXVIII, abstract no. 1516.

Tartese R., Anand M., Joy K. H., Franchi I. A. (2014) H and Cl isotope characteristics of apatite in brecciated lunar meteorites NWA 4472, NWA 773, SaU 169 and Kalahari 009. 77th Annual Meeting of the Meteoritical Society, abstract no. 5085.

Wang N., Tartèse R., Joy K. H., Pernet-Fisher J. F., and Lin Y. T. (2019) Infrared spectroscopic characteristics of zircon in lunar meteorites Northwest Africa 2995 and 4485. 82nd Annual Meeting of the Meteoritical Society, abstract no. 6390.

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