Meteoritical Bulletin: Entry for Northwest Africa 12423

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Northwest Africa 12423

Basic information

Name: Northwest Africa 12423
This is an OFFICIAL meteorite name.
Abbreviation: NWA 12423
Observed fall: No
Year found: 2018
Country: Algeria
Mass: 5.15 kg

Classification
history:

Meteoritical Bulletin:	MB 108	(2020)	Ureilite-an
Recommended:			Ureilite-an [explanation]

This is 1 of 7 approved meteorites classified as Ureilite-an. [show all]
Search for other: Achondrites, Ureilites

Comments:

Approved 9 Feb 2019

Writeup

help

Writeup from MB 108:

Northwest Africa 12423 (NWA 12423)

Algeria

Purchased: 2018 Jul

Classification: Ureilite (anomalous)

History: Found in Algeria and purchased in Morocco in July 2018 by Lhcen Ouabicha and Zaid Sbitti.

Petrography: (A. Irving, UWS and P. Carpenter, WUSL) Aggregate of olivine (~50 vol.%) and low-Ca pyroxene (~50 vol.%) with accessory graphite, Cr-troilite and daubreelite. Some regions have a poikilitic texture, with rounded olivine chadacrysts enclosed in low-Ca pyroxene oikocrysts up to 7 mm across; other regions are composed of olivine exhibitinh triple grain junctions. Olivine grains have partial, more magnesian rims associated with fine grained, blebby Fe metal.

Geochemistry: Olivine (Fa_10.1-10.7, N = 3), low-Ca pyroxene (Fs_9.3-9.5Wo_3.5-4.9, N = 3). Oxygen isotopes (K. Ziegler, UNM) Analyses of acid-washed subsamples by laser fluorination gave, respectively, δ¹⁷O 0.606, 0.669, 0.456; δ¹⁸O 5.643, 5.704, 5.381; Δ¹⁷O -2.374, -2.343, -2.385 per mil.

Classification: Ureilite (anomalous). Although oxygen isotopes are consistent with an affinity to ureilites, this specimen has several anomalous features: (1) much more magnesian mafic silicates than for typical ureilites, (2) a greater proportion of low-Ca pyroxene (opx and Ca-poor pigeonite) compared with typical ureilites, (3) in part a poikilitic texture, (4) daubreelite and Cr-troilite as accessory phases.

Specimens: 24.5 g including one polished thin section at UWB; remainder with Mr. L. Ouabicha and Mr. Z. Sbitti.

Data from:
  MB108
  Table 0
  Line 0:

Place of purchase:	Morocco
Date:	P 2018 Jul
Mass (g):	5150
Pieces:	1
Class:	Ureilite-an
Shock stage:	low
Weathering grade:	low
Fayalite (mol%):	10.1-10.7
Ferrosilite (mol%):	9.3-9.5
Wollastonite (mol%):	3.5-4.9
Classifier:	A. Irving and P. Carpenter, UWS
Type spec mass (g):	24.5
Type spec location:	UWB
Main mass:	L. Ouabicha/Z. Sbitti
Comments:	Work name LO-Ob; submitted by A. Irving

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)
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
WUSL: Washington Univ., One Brookings Drive, St. Louis, MO 63130, United States (institutional address; updated 17 Oct 2011)
UWB: University of Washington, Box 353010 Seattle, WA 98195, United States (institutional address; updated 27 Jul 2012)

Catalogs:

References:

Published in Meteoritical Bulletin, no. 108 (2020) Meteorit. Planet. Sci. 55, 1146-1150

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Geography:

Algeria

Algeria

Coordinates:

Unknown.

Statistics:
This is 1 of 1277 approved meteorites from Algeria (plus 29 unapproved names) (plus 4 impact craters)

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