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Lunar Meteorite

Northwest Africa 4819

northwestern Africa

 

A sawn slice of Northwest Africa 4819. Click on image for enlargement. Millimeter ticks for scale.
(photo credit: Randy Korotev)

 

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

Northwest Africa 4819

Northwest Africa
Find: 2007
Mass: 234 g

Achondrite (lunar, feldspathic breccia)

History and physical characteristics: A single 234 g crusted stone was purchased in Rissani, Morocco in 2007. The crust is fresh, dark gray to black crusted areas and vermillion to light brown in abraded to weathered areas, some areas show melt bubbles and flow. A network of thin fractures is filled with weathering products.

Petrography (T. Bunch and J. Wittke, NAU; A. Irving, UWS): This stone is very dark, well indurated, and is fine-grained with few clasts that exceed one mm in diameter. No evidence of flow orientation was observed. NWA 4819 is a regolith breccia and has two unusual characteristics for a lunar sample: (1) a relatively large amount of homogeneously distributed fine-grained metallic nickel-iron (2 wt. %) and troilite (1.5 wt. %) and (2) a large population of pyroxene fragments. Most lithic clasts follow the ferroan anorthositic trend and include anorthosites, fine-grained anorthositic norites, gabbros, and troctolites, in addition to shock melt clast. K-rich glass, and spherules. No intact basaltic clasts were observed and all clasts are crushed to some extent.

Mineral compositions and geochemistry: Host orthopyroxene (Fs48.9 – 67.5Wo2.2 – 4.3; FeO/MnO = 56), exsolution lamellae (Fs24.4 – 41.4Wo12.3 – 32.9; FeO/MnO = 60). Anorthositic norite: orthopyroxene (Fs35.4Wo4.3) and plagioclase (An96.5). Anorthositic troctolite olivine (Fa28.1; FeO/ MnO = 105), pigeonite (Fs26.9Wo5.9; FeO/MnO = 54), plagioclase (An97) and chromite (cr# = 80). Kamacite (mean Ni = 6.2, Co = 0.77 (both wt%) and taenite (Ni - 8.2 - 23.6 wt%).

Bulk composition (R. Korotev, WUSL): FeO = 7.0%, Ni = 290 ppm, Sm = 3.4 ppm, Th = 1.5 ppm, Ir = 12 ppb.

Classification: Achondrite (lunar, feldspathic breccia).

Type specimen: A total of 20.3 g is on deposit at NAU. The main mass holder is anonymous.

 

Randy Says…

It is more mafic (richer in iron and magnesium) than most feldspathic regolith breccias that do not contain mare basalt

 

More Information

Meteoritical Bulletin Database

NWA 4819

References

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.

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 composition. Meteoritics & Planetary Science 44, 1287-1322.

 

 

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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-mail
korotev@wustl.edu

Last revised: 14-Oct-2015