Lunar Meteorite: Northwest Africa 4734 & 10597

from The Meteoritical Bulletin, No. 93

Northwest Africa 4734 (NWA 4734)

Rissani, Morocco
Find: October 2006
Mass: 477 g (“2” pieces)

Achondrite (lunar)

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 An_75-91 (average An₈₉) with minor olivine (Fa_80-95). 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.

from The Meteoritical Bulletin, No. 105

Northwest Africa 10597 (NWA 10597)

Morocco
Purchased: 2016 Feb
Mass: 350 g (1 piece)

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, An_85.1±2.3Or_0.4±0.3 (An_78.5-87.8Or_0.2-0.8, n=20); olivine zoned from Fo_58.2-49.9 (cores) to Fo_36.6-40.7 (rims) (Fa_46.5-93.1, n=13; FeO/MnO = 81.9-106.8, average: 91±7); zoned pigeonite, core En_57.7-51.6Wo_8.9-16.8, rim En_7.2-22Wo_20.2-31.5 (Fs_28.5-79.6Wo_10.1-25.5, n=23), and augite, Fs_21.3-52.5Wo_28.4-39.3 (Wo_32.9-36.2 En_11.9-38.8, n=9), with pyroxene FeO/MnO = 30.8-81.9, average: 60±10; mesostasis olivine and pyroxene, Fo_2.3-13.5 and En_1-3Wo_14-17. Chemical compositions (wt.%) of fusion crust: MgO 7.0, FeO 23.5, Al₂O₃ 7.9, SiO₂ 47.4, CaO 10.6, TiO₂ 3.5.

Randy Says…

More Information

Meteoritical Bulletin Database

NWA 4734 | 10597

References

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