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Northwest Africa 13440
Basic information Name: Northwest Africa 13440
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 13440
Observed fall: No
Year found: 2018
Country: Algeria
Mass:help 310 g
Recommended:  Martian (shergottite)    [explanation]

This is 1 of 298 approved meteorites (plus 2 unapproved names) classified as Martian (shergottite).   [show all]
Search for other: Martian meteorites
Comments: Approved 2 Nov 2020
Writeup from MB 109:

Northwest Africa 13440 (NWA 13440)


Find: 2018

Classification: Martian meteorite (Shergottite)

History: 4 stones weighing a total of 309.95 g were found in an area known as Laricha by a meteorite prospector in May of 2018. Dave Lehman and a partner obtained the specimens in 2020.

Physical characteristics: Samples are crusted and uncrusted. Where preserved, fusion crusted samples show broad, shallow regmaglypts. and flow-lines. The exterior and interior of all samples have an igneous texture composed of fractured coarse-grained, dark green, lath-shaped and blocky crystals enclosing smaller patches of irregular-shaped light grey translucent crystals. This assemblage is crosscut by sporadic dark-colored, vesicular melt pockets.

Petrography: (A. Love, App) Sample has an ophitic texture composed of (vol%): coarse-grained (laths up to 8.5mm), euhedral laths of twinned clinopyroxene (64) enclosing lath-shaped to subhedral regions of maskelynite (33), merrillite (1), mesostasis (1) and opaques (1). Pigeonite contains blebs of augite and is zoned to more ferroan rims. Pyroxene lacks the complex zoning present in other basaltic shergottites. Pyroxenes laths contain thin exsolution lamellae and show preferred orientation. Additional minerals are: elongate rods of merrillite, Ti-magnetite with µm-sized exsolution lamellae of ilmenite, chromite, pyrrhotite and rare baddeleyite.

Geochemistry: (A. Patchen, UTenn) Pigeonite Cores (Fs38.4±4.3Wo11.8±1.7, Fe/Mn=31.1±1.9, Mg#56.4±5.3, n=90); Augite (Fs27.5±2.7Wo32.8±1.9, Fe/Mn=31.1±1.8, Mg#59.2±1.8, n=17); Pigeonite rims (Fs58.8±7.2Wo15.2±4.7, Fe/Mn=36.3±1.5, Mg#30.8±6.7, n=68); Maskelynite (An50.3±5.1Or2.0±01.0, n=66).

Classification: (Martian) gabbroic shergottite. Based on coarse-grained size of sample, mineralogy, compositions and shock features, this sample is a gabbroic shergottite M-S5, low weathering.

Specimens: Dave Lehman and his partner hold the main masses. 4 slices and many small fragments totaling 21.77 g comprise the type specimen. The type specimen and 2 polished thin sections are on deposit at App.

Data from:
  Table 0
  Line 0:
Mass (g):309.95
Class:Martian (shergottite)
Shock stage:high
Weathering grade:low
Ferrosilite (mol%):38.4±4.3; 27.5±2.7; 58.8±7.2
Wollastonite (mol%):11.8±1.7; 32.8±1.9; 15.2±4.7
Magnetic suscept.:3.13
Classifier:A. Love, App
Type spec mass (g):21.77
Type spec location:App
Main mass:Dave Lehman
Comments:Submitted by Anthony Love
   and collections
UTenn: Planetary Geosciences Institute, Department of Earth and Planetary Sciences, University of Tennessee, 1412 Circle Drive, Knoxville, TN 37996-1410, United States (institutional address; updated 1 Nov 2011)
App: Department of Geology, 572 Rivers St., Appalachian State University, Boone, NC 28608, United States (institutional address; updated 7 Mar 2013)
References: Published in Meteoritical Bulletin, no. 109, in preparation (2020)
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     This is 1 of 1294 approved meteorites from Algeria (plus 30 unapproved names) (plus 4 impact craters)

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