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Northwest Africa 11115
Basic information Name: Northwest Africa 11115
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 11115
Observed fall: No
Year found: 2016
Country: Morocco
Mass:help 247 g
Recommended:  Martian (shergottite)    [explanation]

This is 1 of 153 approved meteorites (plus 1 unapproved name) classified as Martian (shergottite).   [show all]
Search for other: Martian meteorites
Comments: Approved 25 Feb 2017
Writeup from MB 106:

Northwest Africa 11115 (NWA 11115)


Find: 2016

Classification: Martian meteorite (Shergottite)

History: Purchased by Terry Boudreaux.

Physical characteristics: Completely covered with smooth fusion crust; rounded shape with no regmaglypts.

Petrography: (M. Melwani Daswani, UChi) SEM/EDS analyses of a polished epoxy mount revealed basalt with large (up to 2 mm) olivine phenocrysts. Shock stage is high: all plagioclase has been converted to maskelynite, and some pyroxene + maskelynite melt pockets are visible. Fractures and voids are abundant throughout the sample, especially across olivine grains and along olivine grain boundaries, where spaces are filled by abundant secondary calcite.

Geochemistry: Mineral compositions and geochemistry: SEM/EDS mineral mode (UChicago and FMNH): ~ 9 % olivine, ~ 32 % pyroxene, ~ 56 % maskelynite. Remaining minerals are spinel (mainly chromite), phosphate, silica, and secondary calcite infilling cracks. Mineral composition: olivine Fa51.5±14.2, Fe/Mn=53.2±6.3 (N=56) shows strong zonation from core (Fa29.2) to rim (Fa54.7) in large grains and also compositional differences between large grains and smaller grains. Pyroxenes: low-Ca Wo4.4±0.2Fs25.8±0.3, Fe/Mn=28.8±2.8 (N=8); pigeonite Wo11.1±2.9Fs34.5±6.2, Fe/Mn=30.4±2.8 (N=24); augite Wo24±5.5Fs28.4±3.4, Fe/Mn=28.5±3.2 (N=2); maskelynite An49.3±4.4Ab48.7±3.9Or2.0±0.6 (N=74). LA-ICP-MS whole rock chemistry: four measurements of one glass bead revealed very low K/Th (K/Th=746.6±69.7) compared to other martian meteorites, but bulk Fe/Mn=44.7±0.6 and Rb/K=0.0057±0.0016 are consistent with other shergottites. Oxygen isotopes, laser fluorination (R. Greenwood, OU): analyses on 2 aliquots gave values of δ17O=2.829, 2.817, δ18O=4.821, 4.770, Δ17O=0.322, 0.337 (given), Δ17O=0.302, 0.316 (linearized, all permil).

Classification: Achondrite (Martian basalt), basaltic shergottite with olivine phenocrysts. Large olivine grains show core to rim iron-enrichment trend.

Specimens: 34.2g at FMNH.

Data from:
  Table 0
  Line 0:
Mass (g):246.76
Class:Martian (shergottite)
Shock stage:high
Weathering grade:high
Fayalite (mol%):51.5±14.2 (N=56)
Ferrosilite (mol%):32.1±6.5 (N=34)
Wollastonite (mol%):10.3±5.2 (N=34)
Classifier:M. Melwani Daswani (UChi), P. Heck (UChi and FMNH) and N. Greber (UChi)
Type spec mass (g):34.2 g
Type spec location:FMNH
Main mass:Terry Boudreaux
Comments:Submitted by M. Melwani Daswani, Nicholas Greber, Philipp Heck. Three oxygen isotope analyses by laser-assisteted fluorination mass spectrometry performed by Richard Greenwood at Open University. Initial SEM/EDS data acquired at FMNH by Sara Rastegar. Full sample at FMNH.; submitted by Mohit Melwani Daswani
Plots: O isotopes:  
   and collections
FMNH: Department of Geology The Field Museum of Natural History 1400 South Lake Shore Drive Chicago, IL 60605-2496, USA, United States; Website (institutional address; updated 16 Nov 2011)
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)
UChi: University of Chicago, Chicago, IL 60637, United States (institutional address; updated 28 Feb 2011)
Boudreaux: Terry Boudreaux, Illinois, United States (private address)
References: Published in Meteoritical Bulletin, no. 106, in preparation (2017)
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     This is 1 of 1218 approved meteorites from Morocco (plus 11 unapproved names)

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