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Mreïra
Basic information Name: Mreïra
     This is an OFFICIAL meteorite name.
Abbreviation: There is no official abbreviation for this meteorite.
Observed fall: Yes, probable fall
Year of probable fall: 2012
Country: Mauritania
Mass:help 6 kg
Classification
  history:
Meteoritical Bulletin:  MB 102  (2013)  L6
Recommended:  L6    [explanation]

This is 1 of 10989 approved meteorites (plus 6 unapproved names) classified as L6.   [show all]
Search for other: L chondrites, L chondrites (type 4-7), Ordinary chondrites, and Ordinary chondrites (type 4-7)
Comments: Approved 27 Jul 2013
Revised 26 Feb 2015: Change in fall status
Writeuphelp
Writeup from MB 102:

Mreïra        25°57.550’N, 10°57.615’W

Tiris Zemmour, Mauritania

Found:  Dec 2012

Classification: Ordinary chondrite (L6)

History: According to Ait Hiba Abdelhad, a fireball was seen in the afternoon sky on December 16, 2012, several school children saw the fireball explode and detonations were heard near the village of Mehaires, Western Sahara. Pieces were recovered approximately 40 miles south of Mehaires, near Mreïra, Mauritania, only a few days after the event. The strewn field is in the area called "Stailt Omgrain", which is a local nomadic name. This is south of Mehaires and north of the mountain "Galbe lahmar". Therefore this is a possible fall associated with the fireball of December 16, 2012.

Physical characteristics: The largest single piece weighed 602 grams and was completely covered with fresh fusion crust. A total of approximately 6 kg of freshly crusted stones were recovered.

Petrography: (C. Agee, UNM) Microprobe examination of two polished surfaces shows brecciation and numerous fractured silicate grains, scattered equilibrated chondrules, shock-melt pockets, kamacite, troilite, and merrillite. Fresh, vesiculated fusion crust ~200 μm thick.

Geochemistry: (C. Agee and L. Burkemper, UNM) Olivine Fa24.4±0.2, Fe/Mn= 47±3, n=8; low-Ca pyroxene Fs20.3±0.1Wo1.5±0.1, Fe/Mn= 28±1, n=7; plagioclase Ab82.7±2.0An10.4±0.6Or6.8±1.4, n=4.

Classification: Ordinary chondrite (L6), weathering grade (W0), shock grade (S6)

Specimens: 91.2 g including a fusion-crusted complete stone and a microprobe mount on deposit at UNM, MtMorgan holds the 602 g main mass and another 400 g of complete stones, Gary Fujihara holds 335 g of fusion crusted individuals, the largest being 104 g.


Writeup from MB 104:

Mreïra, change in fall status


New data on the Mreïra L6 chondrite support a change in its status to "Probable fall." It had been listed as a find in MetBull 102.  Magnetic susceptibility is log χ = 4.76 (χ in 10-9 Am2/kg).  Gamma activity analysis by A. Jambon (UPVI) and P. Weber (Bern): the presence of 22Na and 54Mn (half-lives of 2.6 and 0.85 a, respectively) indicates a recent fall. The 22Na/54Mn and 22Na/26Al ratios of 0.61 and 1.4, respectively, are consistent with a fall date of December 16, 2012.

Data from:
  MB102
  Table 0
  Line 0:
State/Prov/County:Tiris Zemmour
Date:16 Dec 2012
Latitude:25°57.550'N
Longitude:10°57.615'W
Mass (g):6000
Pieces:several
Class:L6
Shock stage:S6
Weathering grade:W0
Fayalite (mol%):24.4±0.2
Ferrosilite (mol%):20.3±0.1
Wollastonite (mol%):1.5±0.1
Classifier:C. Agee, UNM
Type spec mass (g):91.2
Type spec location:UNM
Main mass:MtMorgan
Comments:Submitted by C. Agee
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)
UPVI: Université Pierre et Marie Curie (Paris VI),Case 110, 4 Place Jussieu, 75005 Paris, France (institutional address; updated 5 Oct 2014)
Bern: University of Bern, University of Bern, Hochschulstrasse 4, CH-3012 Bern, Switzerland (institutional address)
MtMorgan: Matt Morgan, Mile High Meteorites, P.O. Box 151293, Lakewood, CO 80215-9293, United States; Website (private address)
Catalogs:
References: Published in Meteoritical Bulletin, no. 102, MAPS 50, 1662, September 2015
Published in Meteoritical Bulletin, no. 104, MAPS 52, 2284, Octover 2017, http://onlinelibrary.wiley.com/doi/10.1111/maps.12930/full
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Photos:
CreditPhotos
Photos uploaded by members of the Encyclopedia of Meteorites.
    (Caution, these are of unknown reliability)
Denis gourgues   
Franco Vignato   
Michael S. Scherman   
Robert Zdancewicz   
Runar Sandnes   
Woreczko Jan & Wadi         
Public domain photographs:
Gary Fujihara         
Geography:

Mauritania
Coordinates:
     Recommended::   (25° 57' 33"N, 10° 57' 37"W)

Statistics:
     This is 1 of 9 approved meteorites from Tiris Zemmour, Mauritania (plus 1 impact crater)
     This is 1 of 103 approved meteorites from Mauritania (plus 1 unapproved name) (plus 2 impact craters)
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