NWA 13446 - Ungrouped Olivine-Dominated Igneous Achondrite

Description

NWA 13446
NWA 13446
Found Sahara, 2020
Ungrouped Achondrite
Specimen is a 0.86g slice
The specimen has an igneous cumulate texture and consists predominantly of zoned olivine (~90 vol.%) with intercumulus assemblages composed of low-Ca pyroxene (mostly pigeonite)
Northwest Africa 13446
Basic information
Name:
Northwest Africa 13446
This is an OFFICIAL meteorite name.
Abbreviation:
NWA 13446
Observed fall:
No
Year found:
2020
Country:
Algeria
Classification
history:
Recommended:
Achondrite-ung
This is 1 of 101 approved meteorites classified as Achondrite-ung.
[show all]
Comments:
Approved 1 Nov 2020
Writeup
Writeup from MB 109:
Northwest Africa 13446
(NWA 13446)
Algeria
Purchased: 2020 Jun
Classification: Ungrouped achondrite
History
: Purportedly found in Algeria and purchased by Habib Naji in June 2020 from a dealer in Adrar, Algeria.
Petrography
: (A. Irving,
UWS
and P. Carpenter,
WUSL
) The specimen has an igneous cumulate texture and consists predominantly of zoned olivine (~90 vol.%) with intercumulus assemblages composed of low-Ca pyroxene (mostly pigeonite), subcalcic augite and sodic plagioclase-like glass with accessory chromite, troilite and very rare spherical grains of metal (kamacite and taenite).
Geochemistry
: Olivine (Fa
19.8±3.7
, range Fa
15.8-27.9
, FeO/MnO = 47-54, N = 11), low-Ca pyroxene (Fs
28.8
Wo
4.6
, FeO/MnO = 26), pigeonite (Fs
26.6±4.4
Wo
10.4±4.7
, range Fs
18.3-30.6
Wo
6.5-18.9
, FeO/MnO = 26-30, N = 6), subcalcic augite (Fs
34.2±6.7
Wo
27.2±5.0
, range Fs
27.3-43.3
Wo
23.0-34.2
, FeO/MnO = 27-35, N = 4), plagioclase-like glass (Ab
65.4-86.0
An
15.7-5.8
Or
18.9-8.2
, N = 4), kamacite (Ni = 1.6 wt.%), taenite (Ni = 36.4 wt.%). Oxygen isotopes (K. Ziegler,
UNM
): analyses of acid-washed subsamples by laser fluorination gave, respectively, δ
17
O 3.638. 3.614, 3.623; δ
18
O 4.887, 4.859, 4.947; Δ
17
O 1.058, 1.049, 1.012 per mil (all data linearized).
Classification
: Achondrite (igneous, ultramafic, ungrouped). This specimen is an almost metal-free, olivine-dominated igneous achondrite with oxygen isotope affinities to L chondrites. Olivine exhibits compositional zoning from core values typical of H chondrites to rim values more typical of L chondrites, and intercumulus pyroxene also exhibits zoning from pigeonite cores to subcalcic augite rims.
Specimens
: 54 g including one polished thin section at
UWB
; remainder with Mr. H. Naji.
Data from:
MB109
Table 0
Line 0:
Place of purchase:
Adrar
Date:
P 2020 Jun
Mass (g):
6484
Pieces:
several
Class:
Achondrite-ung
Shock stage:
low
Weathering grade:
low
Fayalite (mol%):
19.8±3.7
Ferrosilite (mol%):
28.8; 26.6±4.4; 34.2±6.7
Wollastonite (mol%):
4.6; 10.4±4.7; 27.2±5.0
Classifier:
A. Irving, UWS, and P. Carpenter, WUSL
Type spec mass (g):
54.0
Type spec location:
UWB
Main mass:
H. Naji
Comments:
Work name HN 630; submitted by A. Irving
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)
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