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Northwest Africa 7680
Basic information Name: Northwest Africa 7680
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 7680
Observed fall: No
Year found: 2011
Country: (Northwest Africa)
Mass:help 123.7 g
Classification
  history:
Meteoritical Bulletin:  MB 102  (2013)  Achondrite-ung
Recommended:  Achondrite-ung    [explanation]

This is 1 of 99 approved meteorites classified as Achondrite-ung.   [show all]
Search for other: Achondrites, Ungrouped achondrites
Comments: Approved 3 Apr 2013
Writeuphelp
Writeup from MB 102:

Northwest Africa 7680 (NWA 7680)

(Northwest Africa)

Purchased: Jan 2011

Classification: Ungrouped achondrite

History: Purchased by David Gregory in Tucson, January 2011.

Physical characteristics: Cutting revealed two distinct regions. One composed of metal and the other largely of silicate grains.

Petrography: Consists of large Fe-Ni-metal pieces with the largest piece being ~1 cm across in the sectioned sample. The remainder of the sample is predominantly olivine (roughly mm scale) with interstitial plagioclase. Chromite is found as stand-alone grains and as inclusions in olivine and plagioclase. Melt inclusions are also found in the olivine and consist of glass, pyroxene and phosphate. Metal and sulfide grains are also present.

Geochemistry: Olivine (Fa44.8; FeO/MnO=73.6), plagioclase (An41.5;Or1.8,N=31), small clinopyroxene grains surrounded by glass have an approximate composition of Fs14Wo47. The glass has nearly albite composition. Chromite has a range in Ti content. Isolated grains tend to have lower concentrations (TiO2=2.17%, N=11) and inclusions have Ti content (TiO2=4.45%, N=7). Metal generally has a Ni content of 6.34% (N=38), however, regions high in Ni are present and can have Ni content up to nearly 50%. Oxygen isotopes (N. Banerjee, I. Jabeen, and A. Ali, WUC): laser fluorination of olivine grain separates (minor plagioclase) and acid-washed bulk powders gave average values of δ17O = 2.65; δ18O = 7.04; Δ17O = -1.03 per mil (N=8).

Classification: Ungrouped achondrite. O isotopes plot on a single trend line near the lodranite-acapulcoite trend line, although the δ18O values are higher than typically seen in this group (see Greenwood et al., 2012). The values are also in the range of ureilites and this connection must be considered. Olivine and plagioclase compositions are more similar to brachinite and brachinite-like meteorites. However, the olivine is more Fe-rich. This meteorite may be related to another ungrouped achondrite, NWA 6962.

Specimens: The specimen currently includes 3 pieces. The type material/largest mass, 1 polished thick section and 1 end cut.

Bibliography:
  • Greenwood R.C., Franchi I.A., Gibson J.M. and Benedix G.K. (2012) Oxygen isotope variation in primitive achondrites: The influence of primordial, asteroidal and terrestrial processes. Geochim. Cosmochim. Acta 94, 146-163. (link)
Data from:
  MB102
  Table 0
  Line 0:
Place of purchase:Tucson, Arizona
Date:P Jan 2011
Mass (g):123.72
Pieces:1
Class:Achondrite-ung
Fayalite (mol%):44.8 (N=72)
Classifier:B. C. Hyde, ROM
Type spec mass (g):20.46
Type spec location:ROM
Main mass:ROM
Comments:Submitted by Brendt C. Hyde, Royal Ontario Museum
Plots: O isotopes:  
Institutions
   and collections
ROM: Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario M5S 2C6, Canada (institutional address; updated 18 Oct 2011)
WUC: Dept. of Earth Sciences, Western University, 1151 Richmond St., London, ON, N6A5B7, Canada (institutional address; updated 3 Apr 2013)
Catalogs:
References: Published in Meteoritical Bulletin, no. 102, MAPS 50, 1662, September 2015
Find references in NASA ADS:
Find references in Google Scholar:
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 7374 approved meteorites from (Northwest Africa) (plus 1957 unapproved names)

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