Meteoritical Bulletin: Entry for Northwest Africa 7540

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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: 267 g

Classification
history:

Meteoritical Bulletin:	MB 109	(2020)	LL3
Recommended:			LL3 [explanation]

This is 1 of 487 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

Writeup

help

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 Fa_15.9±8.5(Fa_2.3-31.5; n=21); the mean low-Ca pyroxene composition is Fs_7.9±6.7Wo_0.8±0.7(Fs_1.9-17.8Wo_0.1-2.2; 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)

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Geography:

Coordinates:

Unknown.

Statistics:
This is 1 of 9699 approved meteorites from (Northwest Africa) (plus 1854 unapproved names)

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Revision
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