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Northwest Africa 16368
Basic information Name: Northwest Africa 16368
     This is an OFFICIAL meteorite name.
Abbreviation: NWA 16368
Observed fall: No
Year found: 2020
Country: (Northwest Africa)
Mass:help 51 g
Classification
  history:
Meteoritical Bulletin:  MB 112  (2024)  LL3-6
Recommended:  LL3-6    [explanation]

This is 1 of 39 approved meteorites classified as LL3-6.   [show all]
Search for other: LL chondrites, LL chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3)
Comments: Approved 3 Jan 2024
Writeuphelp
Writeup from MB 112:

Northwest Africa 16368 (NWA 16368)

(Northwest Africa)

Purchased: Dec 2020

Classification: Ordinary chondrite (LL3-6)

History: Mr. Jasper Spencer purchased a single stone from a Mauritanian dealer in December 2020, who told Mr. Spencer that the stone had been found in Morocco in 2020. Mr. Spencer sent three pieces of the stone, totaling 10.4 g, to Cascadia for classification.

Physical characteristics: Physical Characteristics: One of the three pieces received by Cascadia is partly covered by a dark gray fusion crust. All three samples are friable, with obvious common light gray and rare dark gray clasts set amidst a medium-gray groundmass visible on cut surfaces. Elongate metal grains up to 1.5 mm in length are visible on cut surfaces. Metal abundance is variable across 3 pieces, estimated to average 3-4 area%.

Petrography: (M. Hutson, A. Ruzicka, Cascadia): The thin section sampled groundmass (host) and two large (5 × 3.8 mm and 2.8 × 1.7 mm in exposed area) light clasts. The clasts have a granoblastic texture with coarse feldspar (up to 100 μm across). The main opaque mineral in the clasts is troilite; metal comprises about 2 area % of each clast. The host lithology is composed mainly of small (~300 μm across) fragments and contains only a few well-defined partial chondrules. Fragments comprise a range of petrographic types, with fragments containing coarse feldspar (>50 μm across) adjacent to fragments containing olivine and pyroxene grains set in crystallite-filled mesostases. One fragment contains zoned magnesian olivine grains set in a glassy mesostasis containing small (~7 μm long) Ca-Al-rich pyroxene grains. Host metal is not uniformly distributed, and includes coarse (up to 2 mm long exposed area) vein-like metal. A single 40 μm long grain of ilmenite was observed along the edge of one large metal grain. Approximately 8% of metal in the thin section has been replaced by weathered material.

Geochemistry: Host olivine and pyroxene data show a bimodal distribution in Fe abundance, with a small number of low-Fe grains, suggesting that the host is a mix of two equilibrated materials with a small admixture of unequilibrated material. Average of all host olivine (Fa28.7±4.6, range Fa12.0-33.2, N=44) and low-Ca pyroxene (Fs23.9±2.0Wo1.4±0.4, range Fs20.5-26.9Wo0.7-2.3, N=23) gives a misleading impression as most of the data form two narrow peaks (referred to as host 1 and host 2). Host data was collected from five different areas across the thin section; each area showed a mix of host 1 and host 2 material. All host 1 analyses are of olivine and pyroxene grains that are either in fragments with crystallite-filled mesostases or are single grains, while all host 2 analyses are of olivine and low-Ca pyroxene grains that are either in fragments with coarse feldspar or are single grains. Host 1 olivine (Fa 27.1±1.0, N=20, excluding three analyses with Fa between 12.0 and 19.6) and low-Ca pyroxene (Fs22.5±0.8Wo1.1±0.4, N=14); host 2 olivine (Fa 32.1±0.7, N=20) and low-Ca pyroxene (Fs26.2±0.5Wo1.7±0.2, N=9). Host 2 plagioclase feldspar Ab84.0±0.7An11.1±0.1Or4.9±0.8, N=6. Larger clast: Olivine Fa32.2±0.2, N=8; low-Ca pyroxene Fs26.0±0.2Wo1.8±0.1, N=6; plagioclase feldspar Ab82.4±0.7An11.1±0.1Or6.6±0.6, N=6. The smaller clast has essentially identical mineral compositions to the larger clast: Olivine Fa32.2±0.2, N=3; low-Ca pyroxene Fs26.2±0.1, N=3; plagioclase feldspar Ab83.3±0.6An11.3±0.9Or5.5±1.1, N=3.

Classification: Ordinary chondrite (LL3-6). Chemistry of olivine and low-Ca pyroxene suggests that host lithology is composed of fragments from both Fe-rich and Fe-poor equilibrated LL-chondrite material, with a small admixture of unequilibrated chondritic material. Textures indicate that the Fe-rich material is of petrographic type 6, while the Fe-poor material is at least partly of petrographic type 4.

Specimens: Cascadia holds 9.1 g in two pieces, as well as a polished thin section and material in an epoxy butt; Mr. Jasper Spencer holds the main mass.

Data from:
  MB112
  Table 0
  Line 0:
Place of purchase:FB Messenger
Date:P Dec 2020
Mass (g):51
Pieces:1
Class:LL3-6
Weathering grade:W1
Fayalite (mol%):27.1 (host 1), 32.1 (host 2)
Ferrosilite (mol%):22.5 (host 1), 26.2 (host 2)
Wollastonite (mol%):1.1 (host 1), 1.7 (host 2)
Classifier:M. Hutson and A. Ruzicka, Cascadia
Type spec mass (g):10.4
Type spec location:Cascadia
Main mass:Mr. Jasper Spencer
Comments:Lab number CML 1511; submitted by Melinda Hutson
Institutions
   and collections
Cascadia: Cascadia Meteorite Laboratory, Portland State University, Department of Geology, Room 17 Cramer Hall, 1721 SW Broadway, Portland, OR 97201, United States; Website (institutional address; updated 28 Oct 2011)
Catalogs:
References: Published in Gattacceca J., McCubbin F. M., Grossman J. N., Schrader D. L., Cartier C., Consolmagno G., Goodrich C., Greshake A., Gross J., Joy K. H., Miao B. and Zhang B. (2024) The Meteoritical Bulletin, no. 112. Meteoritics & Planetary Science 59, 1820–1823. ?
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Geography: 
Coordinates:Unknown.

Statistics:
     This is 1 of 9829 approved meteorites from (Northwest Africa) (plus 1851 unapproved names)

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