Meteoritical Bulletin: Entry for Northwest Africa 12997

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Northwest Africa 12997

Basic information

Name: Northwest Africa 12997
This is an OFFICIAL meteorite name.
Abbreviation: NWA 12997
Observed fall: No
Year found: 2015
Country: (Northwest Africa)
Mass: 60 g

Classification
history:

Meteoritical Bulletin:	MB 108	(2020)	Lunar (troct)
Recommended:			Lunar (troct) [explanation]

This is 1 of 3 approved meteorites classified as Lunar (troct). [show all]
Search for other: Lunar meteorites

Comments:

Approved 23 Dec 2019

Writeup

help

Writeup from MB 108:

Northwest Africa 12997 (NWA 12997)

(Northwest Africa)

Purchased: 2015

Classification: Lunar (troct)

History: Found by unknown nomads (date and location unconfirmed). Purchased in 2015 in Morocco by Graham Ensor.

Physical characteristics: Light grey sandblasted exterior, with visible dark melt veins visible on exterior and interior of rock. No fusion crust. Cumulus olivine and plagioclase.

Petrography: (T. S. Hayden, M. Anand, T. J. Barrett, OU). The meteorite is a cumulate troctolite mainly comprising olivine and plagioclase crystals, with minor pyroxene. Accessory phases include ilmenite, spinel, merrillite and chromite.

Geochemistry: Mineral Composition and Geochemistry: (T. S. Hayden, M. Anand, T. J. Barrett, OU) Feldspar (An_96.6±1.0Ab_3.4±1.0, N = 13), Pigeonite (Fs_22.3±8.2Wo_9.7±5.4, Fe/Mn = 46.7±8.7, N=6), Augite (Fs_11.3±1.2Wo_37.0±1.7, Fe/Mn = 28.0±3.5, N=3), Clinoenstatite (Fs_19.3±1.3Wo_3.5±0.8, Fe/Mn = 47.4±4.2, N=8), Olivine (Fa_22.9±1.2, Fe/Mn = 88.1±5.9, N=21). O isotopes (measured at OU): Repetition 1: δ¹⁷O = 3.092‰, δ¹⁸O = 5.916‰, Δ¹⁷O = -0.008‰, Repetition 2: δ¹⁷O = 3.057‰, δ¹⁸O = 5.844‰, Δ¹⁷O = -0.005‰. Mean: δ¹⁷O = 3.0745±0.025‰ (1-sigma), δ¹⁸O = 5.880±0.051‰ (1-sigma), Δ¹⁷O = -0.006±0.002‰ (1-sigma) (linearized using a slope of 0.5247 (of Miller (2002)).

Classification: Lunar troctolite. Thought to be paired with NWA 5744 clan based on textural and mineralogical similarities.

Specimens: Specimen: 16.8 g specimen held at OU. Graham Ensor holds the main mass (two stones weighing 60 g).

Bibliography:

Miller M.F. (2002) Isotopic fractionation and the quantification of 17O anomalies in the three oxygen isotope system: an appraisal and geochemical significance. Geochim. Cosmochim. Acta 66, 1881-1889 (link)

Data from:
  MB108
  Table 0
  Line 0:

Place of purchase:	Morocco
Date:	P 2015
Mass (g):	60
Pieces:	Many
Class:	Lunar (troct)
Fayalite (mol%):	22.9±1.2 (N =21)
Ferrosilite (mol%):	18.9±6.1 (N=17)
Wollastonite (mol%):	11.6±12.8 (N=17)
Classifier:	T. S. Hayden, M. Anand, T. J. Barrett, R. C. Greenwood, OU
Type spec mass (g):	16.8
Type spec location:	OU
Main mass:	Graham Ensor
Finder:	Nomads
Comments:	Field name prior to submission: VERA-1; submitted by T. S. Hayden (OU)

Plots:

O isotopes:

Institutions
and collections

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)

Catalogs:

References:

Published in Meteoritical Bulletin, no. 108 (2020) Meteorit. Planet. Sci. 55, 1146-1150

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Geography:

Coordinates:

Unknown.

Statistics:
This is 1 of 9344 approved meteorites from (Northwest Africa) (plus 1872 unapproved names)

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