Northwest Africa 4734 (NWA 4734)
History: Two pieces were purchased from nomads in Erfoud, Morocco in October 2006 and February 2007.
Physical characteristics: A. Habibi purchased two pieces, with a total mass of 477 g, in Rissani, Morocco, and several other pieces of the same stone totaling 895 g are with M. Oumama in Rissani, Morocco. Dull black/brown fusion crust nearly complete and inside slightly tarnished where absent. It is a gray, coarse grained, pristine magmatic rock consisting of millimeter-sized phenocrysts, mainly of pyroxene and plagioclase.
Petrography: (A. Jambon, O. Boudouma and D. Badia, UPVI). The texture is best described as shergottite-like. Pyroxene grains are highly fractured while plagioclase laths, partly transformed to maskelynite, are only affected by a small number of fractures. Silica and silica-feldspar glass are minor components. A few patches of impact melt are also observed. Ilmenite, baddeleyite, zirconolite, tranquilityite, pyrrhotite and metal. Fayalite associated with silica probably results from the dissociation of iron rich pyroxene. Modal mineralogy (vol %): Cpx 50, Plagioclase + Kspar 32, silica + glass 7.5, opaques (ilmenite, Ti-magnetite, pyrrhotite) + fayalite 7, voids + fractures 3.
Geochemistry: Mineralogy by EMP and SEM. (Trace and major element analyses ICP-MS and ICP-AES, J-A Barrat, UBO). Pyroxene grains are complexly zoned (En65Fs21Wo13 to En2Fs83Wo15; FeO/MnO = 78 [average]). A few compositions correspond to pyroxferroite. Plagioclase is normally zoned from An75-91 (average An89) with minor olivine (Fa80-95). Chondrite normalized REE pattern with an enrichment of 53 (La) to 40 (Yb). Trace element pattern with negative anomalies of Sr and Eu. Interstitial glass is high in silica (75 wt%) and contains microcrysts of K-feldspar with a significant celsian component. The chemistry, major and trace elements, is identical to NWA 032-479-773 and LAP 02205-02224-02226-02234-02436-03632. The texture is very similar to that of the LAP specimens. The very low abundance of olivine and the relative abundance of silica in NWA 4734 are the main differences beside the grain size and the slightly different composition of the major phases.
Classification: Achondrite (lunar); extensive shock.
Type specimens: A total of 20 g of sample and one polished section is on deposit at UPVI. Mbarek Ait Elkaid hold the main masses.
Northwest Africa 10597 (NWA 10597)
Classification: Lunar meteorite (basalt)
History: Purchased by Ke Zuokai in Feb. 2016 at Tucson mineral show from an anonymous Moroccan dealer.
Physical characteristics: A single stone with a complete fresh fusion crust.
Petrography: The meteorite is a medium-grained unbrecciated basalt composed of elongate, zoned pyroxene (up to 1 mm) grains and plagioclase (up to 1.2 mm) laths. Olivine phenocrysts are up to 350 µm, and commonly have inclusions of hercynite, Ti-Al-rich chromite, pigeonite or rarely augite with intergrowth of Na-rich glass. Most pyroxene grains are pigeonite with a minor amount of augite. A few pigeonite grains have augite rims. Plagioclase is partly converted to maskelynite. Late-stage mesostasis is composed of silica, Fe-rich olivine, Fe-rich pyroxene, K-rich glass, ilmenite, pyrrhotite, baddeleyite, and elongate, skeletal apatite and merrillite. Other opaque phases include chromite, Ti-rich chromite, troilite, ulvöspinel, tranquillityite, zirconolite and a few FeNi metal. Shock veins and impact melt pockets are present. Mineral modes (vol%): olivine = 6, pyroxene =52, plagioclase = 32, silica=3, ilmenite = 4, mesostasis + impact melt = 3.
Geochemistry: Plagioclase, An85.1±2.3Or0.4±0.3 (An78.5-87.8Or0.2-0.8, n=20); olivine zoned from Fo58.2-49.9 (cores) to Fo36.6-40.7 (rims) (Fa46.5-93.1, n=13; FeO/MnO = 81.9-106.8, average: 91±7); zoned pigeonite, core En57.7-51.6Wo8.9-16.8, rim En7.2-22Wo20.2-31.5 (Fs28.5-79.6Wo10.1-25.5, n=23), and augite, Fs21.3-52.5Wo28.4-39.3 (Wo32.9-36.2 En11.9-38.8, n=9), with pyroxene FeO/MnO = 30.8-81.9, average: 60±10; mesostasis olivine and pyroxene, Fo2.3-13.5 and En1-3Wo14-17. Chemical compositions (wt.%) of fusion crust: MgO 7.0, FeO 23.5, Al2O3 7.9, SiO2 47.4, CaO 10.6, TiO2 3.5.
NWA 10597 may be one of the “several other pieces of the same stone [NWA 4734] totaling 895 g…” in the NWA 4734 write-up above.
NWA 4734/10597 is is compositionally and texturally identical to LAP basalts from Antarctica and likely launch paired.
Meteoritical Bulletin Database
Chen J., Wang A., Jolliff B. L., Korotev R. L., Ling Z. C., Fu X. H., and. Ni Y. H (2018) Petrogenetic and shock history of mare basaltic lunar meteorite Northwest Africa 4734. 49th Lunar and Planetary Science Conference, abstract no. 2976.
Chen J., Jolliff B. L., Wang A., Korotev R. L., Wang K., Carpenter P. K., Chen H., Ling Z., Fu X., Ni Y., Cao H., and Huang Y. (2019) Petrogenesis and shock metamorphism of basaltic lunar meteorites Northwest Africa 4734 and 10597. Journal of Geophysical Research: Planets, 2583-2598.
Chennaoui Aoudjehane H. and Jambon A. (2008) First evidence of high pressure silica: Stishovite and seifertite in lunar meteorite Northwest Africa 4734. 71st Annual Meeting of the Meteoritical Society, abstract no. 5058, Meteoritics & Planetary Science 43, A32.
Elardo S. M., Shearer C. K. Jr., Fagan A. L., Neal C. R., Burger P. V., and Borg L. E. (2012) Diversity in low-Ti mare magmatism and mantle sources: A Perspective from lunar meteorites NWA 4734, NWA 032, and LAP 02205. 43rd Lunar and Planetary Science Conference, abstract no. 2648.
Elardo S. M., Shearer C. K., Fagan A. L., Borg L. E., Gaffney A. M., Burger P. V., Neal C. R., and McCubbin F. M. (2013) The origin of young mare basalts inferred from lunar meteorites NWA 4734, NWA 032, and LAP 02205. 44th Lunar and Planetary Science Conference, abstract no. 2762.
Elardo S. M., Shearer C. K. Jr., Fagan A. L., Borg L. E., Gaffney A. M., Burger P. V., Neal C. R., Fernandes V. A., and McCubbin F. M. (2013) The origin of young mare basalts inferred from lunar meteorites Northwest Africa 4734, 032, and LaPaz Icefield 02205. Meteoritics & Planetary Science 49, 261–291.
Fernandes V. A., Korotev R. L., and Renne P. R. (2009) 40Ar-39Ar ages and chemical composition for lunar mare basalts: NWA 4734 and NWA 4898. 40th Lunar and Planetary Science Conference, abstract no. 1045.
Fernandes V. A. S. M., Fritz J. P., Wünnemann K., and Hornemann U. (2010) K-Ar ages and shock effects in lunar meteorites. EPSC Abstracts, Vol. 5, EPSC2010-237.
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Wang Y. and Hsu W. (2010) SIMS Pb/Pb dating of Zr-rich minerals from NWA 4734 and LAP 02205/02224: Evidence for the same crater on the Moon. 73rd Annual Meeting of the Meteoritical Society, abstract no. 5024.
Wang Y. and Hsu W. (2016) Shock-induced metamorphism in the lunar meteorite Northwest Africa 4734. 79th Annual Meeting of the Meteoritical Society, abstract no. 6337.
Wang Y. and Hsu W. (2017) SIMS Pb-Pb dating of phosphates in the lunar meteorite Northwest Africa 4734. 80th Annual Meeting of the Meteoritical Society, abstract no. 6187.
Wang Y., Hsu W., Guan Y., Li X., Li Q., Liu Y., and Tang G. (2012) Petrogenesis of the Northwest Africa 4734 basaltic lunar meteorite. Geochimica et Cosmochimica Acta 92, 329-344.
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