|Northwest Africa 11115|
|Basic information||Name: Northwest Africa 11115|
This is an OFFICIAL meteorite name.
Abbreviation: NWA 11115
Observed fall: No
Year found: 2016
Mass: 247 g
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)
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.
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)|
This is 1 of 1212 approved meteorites from Morocco (plus 11 unapproved names)
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