Lunar Meteorite: Northwest Africa (NWA) 4734

Morocco



NWA 4734 stones
(photo courtesy of Albert Jambon)

A 33-g stone, the one nearest the loupe in the top photo. Thanks to Tim Heitz for the sample.
(photo by Randy Korotev)

Note the similarity of the fusion crust to that of the LAP stones
(photo by Randy Korotev)


Chips of basalts LAP 04841 (left) and NWA 4734 (right), same scale (millimeter ticks).
(photos by Randy Korotev)
  


It is an unbrecciated basalt.

At 1.37 kg, it's big.


The meteorite is compositionally and texturally identical to LAP 02205 basalts. Curiously, it has some isotopic characteristics that argue that it cannot be related, however. Stay tuned.
  


from The Meteoritical Bulletin, No. 93, Meteoritics & Planetary Science 43, 571–632 (2007)

Northwest Africa 4734

Rissani, Morocco
Find: October 2006

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 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.



More Information

Meteoritical Bulletin Database

NWA 4734

References

Chennaoui Aoudjehane H. and Jambon A. (2008) First evidence of high pressure silica: Stishovite and seifertite in lunar meteorite Northwest Africa 4734 (abstract). 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 (abstract). In Lunar and Planetary Science XLIII, abstract no. 2648, 43rd Lunar and Planetary Science Conference, Houston.

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 (abstract). In 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. doi: 10.1111/maps.12239

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 (abstract). In Lunar and Planetary Science XL, abstract no. 1045, 40th Lunar and Planetary Science Conference, Houston.

Fernandes V. A. S. M., Fritz J. P., Wünnemann K., and Hornemann U. (2010) K-Ar ages and shock effects in lunar meteorites (abstract). EPSC Abstracts, Vol. 5, EPSC2010-237.

Jambon A. and Devidal J.-L. (2009) Monazite dating of lunar meteorite NWA 4734 (abstract). 72th Annual Meeting of the Meteoritical Society, number 5006.

Korotev R. L., Irving A. J., and Bunch T. E. (2008) Keeping up with the lunar meteorites – 2008 (abstract). In Lunar and Planetary Science XXXIX, abstract no. 1209, 39th Lunar and Planetary Science Conference, Houston.

Korotev R. L., Zeigler R. A., Irving A. J., and Bunch T. E. (2009) Keeping up with the Lunar Meteorites — 2009 (abstract). In Lunar and Planetary Science XL, abstract no. 1137, 40th Lunar and Planetary Science Conference, Houston.

Miyahara M., Kaneko S., Ohtani E., Sakai T., Nagase T., Kayama M., Hishido H., and Hirao N. (2013) High-pressure polymorphs of silica in NWA 4734. Antarctic Meteorites XXXVI, Papers Presented to the Thirty-Sixth Symposium on Antarctic Meteorites, p. 52, Tokyo.

Rochette P., Gattacceca J., Ivanov A. V., Nazarov M. A., and Bezaeva N. S. (2010) Magnetic properties of lunar materials: Meteorites, Luna and Apollo returned samples. Earth Planet. Sci. Lett., doi:10.1016/j.epsl.2010.02.007.

Xu L., Lin Y. T., Hofmann B. A., Gnos E., and Ouyang Z. Y. (2012) The origin of metal particles in lunar meteorites (abstract). 75th Annual Meeting of the Meteoritical Society, abstract no. 5247.

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 (abstract). 73th Annual Meeting of the Meteoritical Society, abstract no. 5024. Lunar and Planetary Institute, Houston.

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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Prepared by:

Randy L. Korotev


Department of Earth and Planetary Sciences
Washington University in St. Louis


Please don't contact me about the meteorite you think you've found until you read this and this.

e-mailkorotev@wustl.edu

Last revised: 04-Mar-2014