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Erg Atouila 001
Basic information Name: Erg Atouila 001
     This is an OFFICIAL meteorite name.
Abbreviation: EA 001
Observed fall: No
Year found: 2020
Country: Mali
Mass:help 793 g
Classification
  history:
Recommended:  Achondrite-ung    [explanation]

This is 1 of 118 approved meteorites classified as Achondrite-ung.   [show all]
Search for other: Achondrites, Ungrouped achondrites
Comments: Approved 19 Dec 2021
Writeuphelp
Writeup from MB 110:

Erg Atouila 001 (EA 001)        22.489944, -4.551744

Gao, Mali

Find: 2020

Classification: Ungrouped achondrite

History: The first piece of 553 g was found by a nomad in August 2020. A second piece of 240 g was found less than a km from the first piece location in September 2020. Both pieces were purchased by Mohamed Aid.

Physical characteristics: Two similar appearing pieces, 553 and 240 g. Exterior is dominated by a pink to light orange color with some dark gray patches with oxidation halos, and some small green patches are scattered throughout. No fusion crust is present. Several dark-colored shock melt veinlets are visible.

Petrography: (M. Spilde, A. Ross, C. Agee, UNM) Microprobe examination and an SEM survey show that albitic alkali feldspar makes up 95% of the modal abundance of this meteorite. Clinopyroxene makes up approximately 3% of the mode, phases with less than 1% modal abundance include olivine, K-feldspar, fluorapatite, troilite, Fe-metal, ilmenite, and oxidized iron. Small poikiolitic inclusions of olivine and lamellae of K-spar are ubiquitous within the host albite. Clinopyroxene occurs primarily in centimeter-sized nodules along with olivine inclusions and other minor phases.

Geochemistry: (A. Ross, UNM) Albite Ab91.8±0.7Or6.3±1.1An1.9±0.4, n=4; K-feldspar Ab10.2±2.3Or89.3±2.4An0.5±0.1, n=3; high-Ca pyroxene Fs10.0±0.6Wo44.0±0.4, Fe/Mn=9±1, n=10; olivine Fa29.3±0.8, Fe/Mn=20±1, n=3; apatite F=3.2 wt%, Cl=0.13 wt%, iron metal Ni=0.26±0.02 wt%, n=3. Oxygen isotopes (K. Ziegler, UNM): 3 acid-washed fragments analyzed by laser fluorination gave δ18O= 4.789, 4.744, 4.088; δ17O= 1.437, 1.423, 1.074; Δ17O= -1.091, -1.082, -1.084 (linearized, all per mil, TFL slope=0.528).

Classification: Ungrouped achondrite (albitite). This meteorite is an albitite with one of the highest modal feldspar contents ever reported in a meteorite – comparable modal abundance to lunar anorthosite meteorites, however its feldspar is an alkali feldspar solid solution. This albitite meteorite is also unlike other Na-feldspar-rich ungrouped achondrites such as GRA 06128/06129 (Shearer et al., 2008) and Almahata Sitta ALMA-A (Bischoff et al., 2014) which have feldspar as plagioclase solid solutions. When plotted on a total alkali-silica (TAS) diagram the bulk composition of this meteorite falls within the trachyte field. Given the relatively coarse grain size present, syenite or olivine syenite are alternative igneous rock names for this meteorite. The oxygen isotope values plot near the acapulcoite-lodranite field although there is no obvious petrologic link between this meteorite and acapulcoites/lodranites. 

Specimens: 20.5 g on deposit at UNM, Mohamed Aid holds the main mass.

Bibliography:
  • Bischoff A., Horstmann M., Barrat J.-A., Chaussidon M., Pack A., Herwartz D., Ward D., Vollmer C. and Decker S. (2014) Trachyandesitic volcanism in the early Solar System. Proceedings of the National Academy of Sciences 111, 12689–12692. (link)
  • Shearer C. K., Burger P. V., Neal C. R., Sharp Z., Borg L. E., Spivak-Birndorf L., Wadhwa M., Papike J. J., Karner J. M., Gaffney A. M., Shafer J., Weiss B. P., Geissman J. and Fernandes V. A. (2008) A unique glimpse into asteroidal melting processes in the early solar system from the Graves Nunatak 06128/06129 achondrites. American Mineralogist 93, 1937–1940. (link)
Data from:
  MB110
  Table 0
  Line 0:
State/Prov/County:Gao
Place of purchase:Mali
Date:2020
Latitude:22.489944
Longitude:-4.551744
Mass (g):793
Pieces:2
Class:Achondrite-ung
Shock stage:high
Weathering grade:moderate
Fayalite (mol%):29.3±0.8
Ferrosilite (mol%):10.0±0.6
Wollastonite (mol%):44.0±0.4
Classifier:C. Agee, UNM
Type spec mass (g):20.5
Type spec location:UNM
Main mass:Mohamed Aid
Comments:Fieldname AID-235; submitted by C. Agee
Plots: O isotopes:  
Institutions
   and collections
UNM: Institute of Meteoritics MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 USA, United States; Website (institutional address; updated 12 Feb 2015)
Catalogs:
References: Published in Meteoritical Bulletin, no. 110, in preparation (2021)
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Geography:

Mali
Coordinates:
     Recommended::   (22° 29' 24"N, 4° 33' 6"W)

Statistics:
     This is 1 of 11 approved meteorites from Gao, Mali (plus 1 unapproved name)
     This is 1 of 64 approved meteorites from Mali (plus 1 unapproved name)
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