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Northwest Africa 11744
Basic information Name: Northwest Africa 11744
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 11744
Observed fall: No
Year found: 2004
Country: (Northwest Africa)
Mass:help 1566 g
Classification
  history:
Recommended:  L5    [explanation]

This is 1 of 6534 approved meteorites (plus 4 unapproved names) classified as L5.   [show all]
Search for other: L chondrites, L chondrites (type 4-7), Ordinary chondrites, and Ordinary chondrites (type 4-7)
Comments: Approved 7 Apr 2018
Writeuphelp
Writeup from MB 107:

Northwest Africa 11744 (NWA 11744)

(Northwest Africa)

Purchased: 2004

Classification: Ordinary chondrite (L5)

History: sample was purchased from a meteorite collector by Dr Mahesh Anand (OU). In July 2016, thin sections of the sample were passed to Craig Walton (UStA) for classification work.

Physical characteristics: A single 1566 g stone. Sample mostly has a dark fusion crust, but in places a light coloured interior is exposed. Sample contains abundant complex shock features, mainly micro-fault shear textures, associated with melt pools.

Petrography: (Craig Walton, UStA) Overall, sample has a chondritic brecciated texture. Main phases are olivine and pyroxene with opaque metal + troilite. Porphyritic olivine, radial pyroxene, barred olivine and porphyritic olivine pyroxene chondrule types are all common, along with rare cryptocrystalline and glassy chondrules. Chondrule average diameter is 370±220 μm (N=27), up to 1 mm. Chondrules comprise ~70 % of the sample. Opaque phases are metal (Fe,Ni in exsolution as kamacite and taenite) and sulfide (troilite). Modal abundances of metal and sulfide are 5.8% and 4.4%, respectively. A recrystallized and shock-darkened matrix of fine-grained lithic fragments comprises ~ 20% of the sample area. Some isolated euhedral olivine grains (up to ~1 mm) occur embedded in this matrix. Olivine contains planar deformation features and has undulose extinction. Planes across which shear displacement has occurred (microfaults) crosscut chondrule and brecciated matrix textures. Fine-grained silicate melt-pools bearing globules of immiscible metal and sulfide are hosted within some sections of these microfaults. Microfault textures crosscut chondrules, matrix and metal, with individual faults running along the length of the slide. Offset on the faults is on the order of 500 μm. ~50 μm-wide shock-melt pools/veins occur within the faults.

Geochemistry: Mineral compositions and geochemistry: (Craig Walton, UStA; Mahesh Anand, Sam Hammond, Richard Greenwood, OU) Microprobe (Cameca SX100 EMPA) (all values given in wt %). Olivine (n=5): MgO = 38.8, CaO = 0.1, MnO = 0.5, FeO = 22.7, SiO = 38.1. TiO = 0.1 Pyroxene (n=2): Na2O = 0.1, MgO = 28.5, K2O = 0.2, CaO = 1.3, MnO = 0.4, FeO = 14.2, Al2O3 = 0.8, Cr2O3 = 0.4, SiO2 = 55.1, TiO2 = 0.1, P2O5 = 0.1. Oxygen Isotopes (Laser fluorination CO2 laser, Thermo Scientific MAT 253 gas source mass spectrometer) δ18O=5.139, δ17O=3.778, Δ17O=1.105 (all in ‰).

Classification: L5 chondrite. Shock stage is S4/5 as evidenced by shear microfault textures, associated shock-melt veins, shock darkening of matrix and undulose extinction and planar deformation features in olivine. Oxygen isotopes are indiscriminate between L and LL, however Fs (Px) and Fa (Ol) data along with metal abundances indicate an L chondrite grouping. Potentially paired with NWA 11745.

Specimens: Main mass at OU

Data from:
  MB107
  Table 0
  Line 0:
Place of purchase:Morocco
Date:P 2004
Mass (g):1566.1
Pieces:1
Class:L5
Shock stage:S4/5
Weathering grade:W1
Fayalite (mol%):24.7±0.5 (N=5)
Ferrosilite (mol%):21.7±1.1 (N=2)
Wollastonite (mol%):2.4±2.5
Classifier:Craig Walton, UStA
Type spec mass (g):1566.1
Type spec location:OU
Main mass:OU
Comments:Work name M13; submitted by Craig Walton
Plots: O isotopes:  
Institutions
   and collections
OU: Planetary and Space Sciences Department of Physical Sciences The Open University Walton Hall Milton Keynes MK7 6AA United Kingdom, United Kingdom (institutional address; updated 8 Dec 2011)
SAM: Department of Mineralogy, South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia; Website (institutional address; updated 18 Oct 2011)
UStA: University of St Andrews College Gate St Andrews KY16 9AJ Fife, Scotland, United Kingdom (institutional address; updated 7 Apr 2018)
Catalogs:
References: Published in Meteoritical Bulletin, no. 107, in preparation (2018)
Find references in NASA ADS:
Find references in Google Scholar:
Photos:
CreditPhotos
Public domain photographs:
Craig Walton   
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 6968 approved meteorites from (Northwest Africa) (plus 2012 unapproved names)

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