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Northwest Africa 4590 meteorite (NWA 4590), Er Rachidia Province (Errachidia Province), Drâa-Tafilalet Region, Morocco

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Location is approximate, estimate based on other nearby localities.
Latitude & Longitude (WGS84): 30° North , 4° West (est.)
Margin of Error:~96km
Other regions containing this locality:Anti-Atlas Mountains, Morocco
Atlas Mountains, North Africa
Northwest Africa Meteorites
Köppen climate type:BSh : Hot semi-arid (steppe) climate

Angrite, Cumulate
213 g — in small fragments, minor weathering

In 2006 scattered fragments from an apparently recent fall were found within several meters of each other near the border between Morocco and Algeria. The coarse grained stone is composed of Clinopyroxene (33 vol%), Anorthite (28 vol%), Olivine (14 vol%), Kirschsteinite (5 vol%), Ulvöspinel (18 vol%) with minor accessories accounting for ~ 5 vol%. Exsolution lamellae in several phases plus grain boundary glasses indicate an original mafic or ultramafic rock which was subject to very rapid cooling — perhaps after an unusually violent impact ejection from deep within a very ancient homeworld.

Northwest Africa 4590 (or, NWA 4590) is an angrite — a small class of 21 listed stones (probably representing 13 or 14 separate falls). Angrites are basaltic achondrites — products of differentiating processes on a putative parent body. They are characterized by their low alkali contents, high Ca/Al ratios, and a varying, but distinctive mineral assemblage marked by several Al-Ca-Ti-rich phases which may include Ca-rich olivine with exsolved Kirschsteinite. Angrites have oxygen isotope ratios similar to those of the HED meteorites (likely fragments of asteroid Vesta). At the present time, however, on geochemical grounds any close association between the HED achondrites and the angrites does not seem likely to most meteoriticists.

One thing is agreed upon, however. Angrites are derived from a very ancient homeworld. Formation of the NWA 4590 mineral assemblage occurred approximately 4.558 billion years ago. Several other angrites, including prototype Angra dos Reis, have similar ages (±1-2 million years). Other angrites apparently formed ~5 million years earlier. One hypothesis is that the younger Angrites originated from deeper realms within the putative parent body and cooled more slowly than the older angrites formed near the surface. Eventually, impacts of varying violence ejected both young and old rocks into space where happenstance and gravity have brought a few of them to rest upon the planet earth where an even smaller subset have been viewed by very interested eyes.

Mineral List

9 valid minerals. 1 erroneous literature entry.

Rock Types Recorded

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Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

66 - 145 Ma

ID: 3189694
Mesozoic sedimentary rocks

Age: Cretaceous (66 - 145 Ma)

Lithology: Sedimentary rocks

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Late Cretaceous
66 - 100.5 Ma

ID: 3308996

Age: Late Cretaceous (66 - 100.5 Ma)

Lithology: Sedimentary

Reference: Thiéblemont, D. (ed.). New edition of the 1:10,000,000 geological map of Africa. CGMW-BRGM. [190]

Early Cretaceous
100.5 - 145 Ma

ID: 3133954
Early Cretaceous undifferentiated

Age: Early Cretaceous (100.5 - 145 Ma)

Reference: Asch, K. The 1:5M International Geological Map of Europe and Adjacent Areas: Development and Implementation of a GIS-enabled Concept. Geologisches Jahrbuch, SA 3. [147]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License

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Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Kuehner, S. M. and Irving, A. J. (2007): 38th LPS, Abstract # 1522.
Connolly, Jr., H. C. et al., (2007) Meteoritical Bulletin, no. 92, 2007 September: MAPS 42 (9), 1647-1694. (Sept 2007)
Kuehner, S. M. & Irving, A. J. (2007) Grain Boundary Glasses in the Plutonic Angrite NWA 4590: Evidence for Rapid Decompressive Partial Melting and Cooling on Mercury? Lunar and Planetary Science XXXVIII. LPI Contribution No. 1338, pdf.1522. (March 2007)
Kuehner, S. M. & Irving, A. J. (2007) Primary Ferric Iron-Bearing Rhönite in Plutonic Igneous Angrite NWA 4590: Implications for Redox Conditions on the Angrite Parent Body, American Geophysical Union, Fall Meeting 2007, abs. #P41A-0219. (Dec 2007)
Amelin, Y., Kaltenbach, A. & Stirling, C. H. (2001) The U-Pb Systematics and Cooling Rate of Plutonic Angrite NWA 4590: Lunar and Planetary Science XLII. LPI Contribution No. 1608, pdf.1682. (March 2011)
Mikouchi, T., Sugiyama, K., Satake, W. & Amelin, Y. (2011) Mineralogy and Crystallography of Calcium Silico-Phosphate in Northwest Africa 4590 Angrite. Lunar and Planetary Science XLII. LPI Contribution No. 1608, pdf.2026. (March 2011)
Amelin, Y. & Sapah, M. (2012) Cooling Rates of Plutonic Angrites from Pyroxene-Phosphate U-Pb Chronology: 75th Annual Meeting of the Meteoritical Society. Published in Meteoritics and Planetary Science Supplement, id.5199. (Sept2012)

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