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Northwest Africa 12455
Basic information Name: Northwest Africa 12455
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 12455
Observed fall: No
Year found: 2018
Country: (Northwest Africa)
Mass:help 611 g
Classification
  history:
Recommended:  CR7    [explanation]

This is 1 of 2 approved meteorites classified as CR7.   [show all]
Search for other: Carbonaceous chondrites, Carbonaceous chondrites (equilibrated) , CR chondrites, and CR chondrites (equilibrated)
Comments: Approved 18 Jun 2019
Writeuphelp
Writeup from MB 108:

Northwest Africa 12455 (NWA 12455)

(Northwest Africa)

Purchased: 2018 Nov

Classification: Carbonaceous chondrite (CR7)

History: Purchased by Ben Hoefnagels in November 2018 from a dealer in Agadir, Morocco.

Petrography: (A. Irving and S. Kuehner, UWS; P. Carpenter, WUSL) This specimen has a triple grain junction texture (grainsize 0.3-1.5 mm) completely devoid of chondrules, and is composed of olivine, orthopyroxene, intermediate plagioclase, chromite, altered kamacite, taenite, troilite, pentlandite, and minor secondary calcite. Modal metal content is ~5 vol.%; troilite is much less abundant, as small blebs, ~0.5 vol.%.

Geochemistry: Olivine (Fa35.0-35.3, FeO/MnO = 83-94, N = 4), orthopyroxene (Fs27.8-28.0Wo3.5-4.0, FeO/MnO = 51-56, N = 4), plagioclase (An48.2-48.9Or1.1, N = 2), kamacite (Ni = 7.2 wt.%), taenite (Ni = 16.4 wt.%). Oxygen isotopes (K. Ziegler, UNM): analysis of acid-washed subsamples by laser fluorination gave, respectively: δ17O 0.661, 0.470, 0.296, 0.359, 0.375, 0.303; δ18O 4.314, 4.021, 3.637, 3.840, 3.939, 3.761; Δ17O -1.617, -1.653, -1.625, -1.668, -1.705, -1.683 per mil. Chromium isotopes (M. Sanborn and Q. Yin, UCD): 54Cr is the same within analytical uncertainty as that for CR2 chondrite Renazzo reported by Sanborn et al. (2019).

Classification: Carbonaceous chondrite (CR7). This specimen exhibits a completely recrystallized texture with no evidence of remnant chondrules, and has oxygen isotopic compositions which plot on the established trend for CR chondrites.

Specimens: 22.3 g including two polished thin sections at UWB; remainder with Mr. B. Hoefnagels.

Bibliography:
  • Sanborn M.E., Wimpenny J., Williams C.D., Yamakawa A., Amelin Y., Irving A.J., and Yin Q.-Z. (2019) Carbonaceous achondrites Northwest Africa 6704/6693: New milestones for early Solar System chronology and geneaology. Geochim, Cosmochim. Acta 245, 577-596 . (link)
Data from:
  MB108
  Table 0
  Line 0:
Place of purchase:Mauritania
Date:P 2018 Nov
Mass (g):611
Pieces:1
Class:CR7
Shock stage:low
Weathering grade:low
Fayalite (mol%):35.0-35.3
Ferrosilite (mol%):27.8-28.0
Wollastonite (mol%):3.5-4.0
Magnetic suscept.:4.28
Classifier:A. Irving and P. Carpenter, UWS
Type spec mass (g):22.3
Type spec location:UWB
Main mass:B. Hoefnagels
Comments:Work name BH173; submitted by A. Irving
Plots: O isotopes:  
Institutions
   and collections
UNM: Institute of Meteoritics MSC03 2050 University of New Mexico Albuquerque NM 87131-1126 USA, United States; Website (institutional address; updated 12 Feb 2015)
UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
WUSL: Washington Univ., One Brookings Drive, St. Louis, MO 63130, United States (institutional address; updated 17 Oct 2011)
UWB: University of Washington, Box 353010 Seattle, WA 98195, United States (institutional address; updated 27 Jul 2012)
UCD: University of California Dept Earth and Planetary Sciences 2119 Earth and Physical Sciences One Shields Avenue Davis, CA 95616, United States (institutional address; updated 18 Nov 2014)
Catalogs:
References: Published in Meteoritical Bulletin, no. 108, in preparation (2019)
Find references in NASA ADS:
Find references in Google Scholar:
Photos:
CreditPhotos
Public domain photographs:
A. Irving         
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 7035 approved meteorites from (Northwest Africa) (plus 2000 unapproved names)

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