Martian Meteorite NWA 13369 - Poikilitic Shergottite (Peridotitic)

Description

NWA 13369
Planetary Achondrite
Martian
Poikilitic Shergottite (Peridotitic)
Specimen is a 2.04g slice
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This meteorite was classified by Anthony love at the Appalachian State University, as a
*
poikilitic
shergottite,
describing it structurally
.
*
Poikilitic
texture refers to igneous rocks where large component crystals contain smaller crystals of other minerals within them. In poikilitic rocks, the contained smaller crystals are termed 'chadacrysts' (here the olivine, the shock darkened crystals) and the larger phenocrysts are termed 'oikocrysts' (here the pyroxene, apple green colored).
The paired meteorites NWA 13250 and NWA 13367 have been described accordingly by their classifier (Carl Agee, University of New Mexico) as
structurally poikilitic indeed, but
he went to submit them to the Nomenclature Comittee of the Meteoritical Societyn as
describing the proposed nature of the rock as well
:
*
peridotitic
*
Peridotite
is a dense, coarse-grained mostly mantelic igneous rock consisting predominatly of the minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium (Mg2+), reflecting the high proportions of magnesium-rich olivine, with appreciable iron. Peridotite is derived from the mantle of a planetary parent body, either as solid blocks and fragments, or as crystals accumulated from magmas that formed in the mantle.
Northwest Africa 13369
Basic information
Name:
Northwest Africa 13369
This is an OFFICIAL meteorite name.
Abbreviation:
NWA 13369
Observed fall:
No
Year found:
2020
Country:
Algeria
Mass:
24.7 g
Classification
history:
Recommended:
Martian (shergottite)
Comments:
Approved 2 Aug 2020
Writeup
Writeup from MB 109:
Northwest Africa 13369
(NWA 13369)
Adrar, Algeria
Purchased: 2020
Classification: Martian meteorite (Shergottite)
History
: The 24.7 g sample was found near Adrar and subsequently purchased in Tindouf. Fabien
Kuntz
purchased the sample in January of 2020.
Physical characteristics
: The 24.7g sample is dark greenish-gray, crystalline and lacks fusion crust. The cut face shows the interior is composed of interlocking green crystals of pyroxene poikilitically enclosing black olivines (shock-darkened).
Petrography
: Description and Classification: (A. Love,
App
) Sample has a poikilitic igneous texture composed of (vol%): 2.23 mm (avg. l.d., n=3) oikocrysts of pyroxene (~21.4) with 317 µm (avg. l.d., n=22) rounded chadacrysts of olivine. Oikocrysts are surrounded by 748µm (avg. l.d., n=20) euhedral prisms of olivine (~42.7); 913µm (avg. l.d., n=23); prismatic, twinned pyroxene (~45.7); and 488 µm (avg. l.d., n=23) lath-shaped maskelynite (~5.3). Additional minerals are merrillite, a Cl-apatite, chromite, ilmenite, titanomagnetite, pyrrhotite and secondary calcite.
Geochemistry
: (A.Patchen-UTK) Olivine (Fa
33.0±3.3
, Mg#67.1±3.3, Fe/Mn=49.2±2.0, n=96); low-Ca pyroxene (Fs
21.3±1.0
Wo
3.3±0.8
, Fe/Mn=30.7±1.2 n=32); pigeonite (Fs
27.9±2.7
Wo
10.2±2.7
, Fe/Mn=28.8±3.4 n=131); subcalcic augite (Fs
18.3±0.9
Wo
28.8±1.1
, Fe/Mn=25.2±1.1, n=8) augite (Fs
16.6±1.2
Wo
34.1±2.3
, Fe/Mn=25.4±1.4 n=51); plagioclase (An
52.0±4.6
Or
1.6±0.5
, n=16).
Classification
: Martian (poikilitic shergottite). Based on mineral compositions (Fs, Wo, Mg# and Fe/Mn) and textures, this sample is a highly shocked (U-S5) poikilitic shergottite.
Specimens
:
Kuntz
holds the main mass. A polished thin section and a sliced fragment weighing 5.71 g are on deposit at
App
.
Data from:
MB109
Table 0
Line 0:
State/Prov/County:
Adrar
Place of purchase:
Tindouf
Date:
P 2020
Mass (g):
24.7
Pieces:
1
Class:
Martian (shergottite)
Shock stage:
U-S5
Weathering grade:
moderate
Fayalite (mol%):
33.0±3.3
Ferrosilite (mol%):
21.3±1.0; 27.9±2.7; 16.6±1.2
Wollastonite (mol%):
3.3±0.8; 10.2±2.7; 34.1±2.3
Magnetic suscept.:
3.7
Classifier:
A. Love, App
Type spec mass (g):
5.71
Type spec location:
App
Main mass:
Kuntz
Comments:
Submitted by Anthony Love
Institutions
and collections
App
: Department of Geology, 572 Rivers St., Appalachian State University, Boone, NC 28608, United States (institutional address; updated 7 Mar 2013)
Kuntz
: Fabien Kuntz, France;
Website
(private address)
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