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Northwest Africa 7540
Basic information Name: Northwest Africa 7540
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 7540
Observed fall: No
Year found: 2011
Country: (Northwest Africa)
Mass:help 267 g
Classification
  history:
Recommended:  LL3    [explanation]

This is 1 of 365 approved meteorites classified as LL3.   [show all]
Search for other: LL chondrites, LL chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3)
Comments: Approved 12 Dec 2020
Writeuphelp
Writeup from MB 109:

Northwest Africa 7540 (NWA 7540)

(Northwest Africa)

Purchased: 2011 Oct 26

Classification: Ordinary chondrite (LL3)

History: Purchased from a Moroccan mineral dealer at the mineral show in Hamburg, Germany

Petrography: (K. Metzler, IfP) Shock-darkened ordinary chondrite of very low petrologic type, consisting of closely packed chondrules (up to 2.9 mm), chondrule fragments, troilite, and very low amounts of Fe-Ni metal. Small amounts of fine-grained interchondrule matrix. The mean apparent chondrule size is 570 µm (n=45).The mean value of Cr2O3 (wt.%) in ferroan olivine and the 1-sigma standard deviation is is 0.23±0.08 (n=13), similar to Y-791558.

Geochemistry: Mineral compositions and geochemistry: The mean olivine composition is Fa15.9±8.5 (Fa2.3-31.5; n=21); the mean low-Ca pyroxene composition is Fs7.9±6.7Wo0.8±0.7 (Fs1.9-17.8Wo0.1-2.2; n=7).

Classification: LL chondrite, based on mean chondrule size and very low metal content. Estimated petrologic subtype 3.15 based on the mean value and standard deviation of Cr2O3 in ferroan olivine (Grossman and Brearley, 2005).

Bibliography:
  • Grossman J.N. and Brearley A.J. (2005) The onset of metamorphism in ordinary and carbonaceous chondrites. Meteorit. Planet. Sci. 40, 87-122. (link)
Data from:
  MB109
  Table 0
  Line 0:
Place of purchase:Munich, Germany
Date:P 2011 Oct 26
Mass (g):267
Pieces:1
Class:LL3
Shock stage:C-S3
Weathering grade:W2
Fayalite (mol%):15.9±8.5
Ferrosilite (mol%):7.9±6.7
Wollastonite (mol%):0.8±0.7
Classifier:K. Metzler, IfP
Type spec mass (g):20
Type spec location:IfP
Main mass:anonymous
Comments:Submitted by K. Metzler, IfP
Institutions
   and collections
IfP: Institut für Planetologie, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany (institutional address; updated 23 Jan 2012)
Catalogs:
References: Published in Meteoritical Bulletin, no. 109, in preparation (2020)
Find references in NASA ADS:
Find references in Google Scholar:
Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 7655 approved meteorites from (Northwest Africa) (plus 1972 unapproved names)

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