|Basic information||Name: Tafassasset|
This is an OFFICIAL meteorite name.
Abbreviation: There is no official abbreviation for this meteorite.
Observed fall: No
Year found: 2000
Mass: 114 kg
This is 1 of 11 approved meteorites classified as Achondrite-prim. [show all]
Search for other: Primitive achondrites
|Comments:||Revised 16 Jan 2016: Reclassification|
Writeup from MB 86:
undisclosed location until 2005 February 14
Tenere desert, Niger
Found 2000 February 14
Carbonaceous chondrite (equilibrated CR-like meteorite) or primitive achondrite
Twenty-six pieces with a total weight of ~110 kg were found by Bernard Dejonghe on an ancient alluvial plain. The two largest weigh ~30 kg each. Twenty stones were found on a trip in early 2000, and six more in 2001 March. The geographic coordinates of these meteorites are being withheld by the finder for three years. Classification (M. Bourot-Denise, MNHNP): Fa29.3, pyroxene Fs24.3; ~30 vol% millimeter-sized relic chondrules are clearly visible in backscattered electron images. Textures and relative abundances of the phases vary considerably. The dominant lithology has a coarse grain size. It consists of olivine (poikilitically enclosed within pyroxenes in the relic chondrules), a small amount of plagioclase, 10% metal in rounded or oval-shaped grains often edged by chromite, and minor sulphides in small grains. The interchondrule matrix consists of subhedral crystals of olivine embedded in plagioclase and within anhedral crystals of chromite and phosphate that are up to 1 mm in size. Two distinct plagioclase compositions are present: An46.4Or2.2 in the matrix and An26.6Or5.2 in chondrule relics. A second lithology is finer grained and porous, without large metal grains but with fairly abundant sulphide grains. The large metal grains are composed of kamacite (6% Ni, 0.6% Co) and martensite (12% Ni, 0.4% Co). Some smaller metal grains associated with sulphides are made up of taenite (up to 36% Ni, 0.2% Co) with martensite cores. The sulphide is troilite (Cr 0.02–0.08%), with some grains containing inclusions of Cu-bearing pentlandite. See also Bourot-Denise et al. (2002). Bulk chemistry (J. Zipfel and B. Spettel, MPI; H. Palme, Köln): refractory lithophiles fractionated compared to a typical CR composition, leading to possible classification as a primitive achondrite (Zipfel et al., 2002). Oxygen isotopes (M. Javoy, IPGP): δ17O = +0.18 ± 0.08‰, δ18O = +2.94 ± 0.2‰. Weathering grade, W0/1; shock stage, unknown. Specimens: type specimen, 396 g plus five polished sections, MNHNP; main mass partly left in Niger, partly with the finder.
A 3.61 kg stone, labeled "Te-1", was found in 2000 March, probably on the same expedition noted above, and is reported by J. Otto (Frei) to have been found in the Tenere Desert at 20°45.8' N, 10°26.5' E. Classification (J. Otto and A. Ruh, Frei): a primitive achondrite; partly covered with black fusion crust; shows a recrystallization texture with abundant 120° triple junctions dominated by olivine (56 vol%, 100–700 µm, Fa28.7, 0.06 wt% CaO) and poikilitic orthopyroxene (23 vol%, up to 3 mm, Fs25.4Wo3.6) with exsolved clinopyroxene (Fs12.7Wo39.7); Fe-Ni metal is irregulary distributed (~10 vol%, up to 5 mm); poikilitic plagioclase occurs in interstices (6.5 vol%, An38.5Or3.7); troilite (~3.5 vol%, 0.01 wt% Ni); chromite (~1 vol%, Fe/(Fe + Mg) = 0.817, Cr/(Cr + Al) = 0.818). Oxygen isotopes (R. Clayton and T. Mayeda, UChi): δ17O = -0.85‰, δ18O = +1.70‰, different from other achondrites. Noble gases (L. Schultz, MPI): data compatible with those of brachinites; exposure age is ~45 Ma. Shock stage, S1/2; weathering grade, W0. Specimens: main mass with Christian Stehlin, Basel; type specimen, 30.2 g and thin section, Frei.
Writeup from MB 105:
Classification: Primitive achondrite
History: A comparison of the overall petrography, modal mineralogy, mineral compositions, oxidation state, and bulk composition of Tafassasset with the CR chondrites, the brachinites, and two anomalous achondrites indicates that Tafassasset is not a thermally metamorphosed CR chondrite. For example, the bulk Fe content of Tafassasset samples range from 23 to 40 wt.% (Gardner-Vandy et al., 2012), whereas the mean Fe content of CR chondrites is 24 wt.% Fe (Kallemeyn et al., 1994).
Frei: Universität Freiburg, Mineralogisch-Petrographisches Institut, Albertstrasse 23b, D-79104 Freiburg, Germany (institutional address)
MNHNP: Museum National d'Histoire Naturelle, 61 Rue Buffon, LMCM-CP52, 75005 Paris, France, France; Website (institutional address; updated 8 Nov 2012)
UChi: University of Chicago, Chicago, IL 60637, United States (institutional address; updated 28 Feb 2011)
IPGP: Institute de Physique du Globe de Paris, 1 rue Jussieu, 75252 Paris, Cedex 05, France (institutional address; updated 3 Nov 2014)
Killgore: Marvin and Kitty Killgore, Southwest Meteorite Laboratory, P.O. Box 95, Payson, AZ 85547, United States; Website (private address)
MPI: Max-Planck-Institut für Chemie, Abteilung Kosmochemie, Postfach 3060, D-55020 Mainz, Germany; Website (institutional address; updated 7 Nov 2015)
|References:||Published in Meteoritical Bulletin, no. 86, MAPS 37, A157-A184 (2002)|
Published in Meteoritical Bulletin, no. 105, in preparation (2016)
This is 1 of 30 approved meteorites from Agadez, Niger
This is 1 of 39 approved meteorites from Niger (plus 1 unapproved name)
Te-1 (In NHM Cat)|
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