Northwest Africa 773

Lunar origin and iron-enrichment trend

Timothy Jay Fagan, G. J. Taylor, K. Keil, T. L. Hicks, M. Killgore, T. E. Bunch, J. H. Wittke, D. W. Mittlefehldt, R. N. Clayton, T. K. Mayeda, O. Eugster, S. Lorenzetti, M. D. Norman

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

The meteorite Northwest Africa 773 (NWA 773) is a lunar sample with implications for the evolution of mafic magmas on the moon. A combination of key parameters including whole-rock oxygen isotopic composition, Fe/Mn ratios in mafic silicates, noble gas concentrations, a KREEP-like rare earth element pattern, and the presence of regolith agglutinate fragments indicate a lunar origin for NWA 773. Partial maskelynitization of feldspar and occasional twinning of pyroxene are attributed to shock deformation. Terrestrial weathering has caused fracturing and precipitation of Carich carbonates and sulfates in the fractures, but lunar minerals appear fresh and unoxidized. The meteorite is composed of two distinct lithologics: a two-pyroxene olivine gabbro with cumulate texture, and a polymict, fragmental regolith breccia. The olivine gabbro is dominated by cumulate olivine with pigeonite, augite, and interstitial plagioclase feldspar. The breccia consists of several types of clasts but is dominated by clasts from the gabbro and more FeO-rich derivatives. Variations in clast mineral assemblage and pyroxene Mg/(Mg + Fe) and Ti/(Ti + Cr) record an igneous Fe-enrichment trend that culminated in crystallization of fayalite + silica + hedenbergite-bearing symplectites. The Fe-enrichment trend and cumulate textures observed in NWA 773 are similar to features of terrestrial ponded lava flows and shallow-level mafic intrusives, indicating that NWA 773 may be from a layered mafic intrusion or a thick, differentiated lava flow. NWA 773 and several other mafic lunar meteorites have LREE-enriched patters distinct from Apollo and Luna mare basalts, which tend to be LREE-depleted. This is somewhat surprising in light of remote sensing data that indicates that the Apollo and Luna missions sampled a portion of the moon that was enriched in incompatible heat-producing elements.

Original languageEnglish
Pages (from-to)529-554
Number of pages26
JournalMeteoritics and Planetary Science
Volume38
Issue number4
Publication statusPublished - 2003 Apr
Externally publishedYes

Fingerprint

gabbro
trends
iron
meteorites
cumulate
olivine
clast
pyroxene
breccia
regolith
natural satellites
lava
lava flow
meteorite
Moon
feldspar
textures
texture
minerals
lunar meteorite

ASJC Scopus subject areas

  • Geophysics

Cite this

Fagan, T. J., Taylor, G. J., Keil, K., Hicks, T. L., Killgore, M., Bunch, T. E., ... Norman, M. D. (2003). Northwest Africa 773: Lunar origin and iron-enrichment trend. Meteoritics and Planetary Science, 38(4), 529-554.

Northwest Africa 773 : Lunar origin and iron-enrichment trend. / Fagan, Timothy Jay; Taylor, G. J.; Keil, K.; Hicks, T. L.; Killgore, M.; Bunch, T. E.; Wittke, J. H.; Mittlefehldt, D. W.; Clayton, R. N.; Mayeda, T. K.; Eugster, O.; Lorenzetti, S.; Norman, M. D.

In: Meteoritics and Planetary Science, Vol. 38, No. 4, 04.2003, p. 529-554.

Research output: Contribution to journalArticle

Fagan, TJ, Taylor, GJ, Keil, K, Hicks, TL, Killgore, M, Bunch, TE, Wittke, JH, Mittlefehldt, DW, Clayton, RN, Mayeda, TK, Eugster, O, Lorenzetti, S & Norman, MD 2003, 'Northwest Africa 773: Lunar origin and iron-enrichment trend', Meteoritics and Planetary Science, vol. 38, no. 4, pp. 529-554.
Fagan TJ, Taylor GJ, Keil K, Hicks TL, Killgore M, Bunch TE et al. Northwest Africa 773: Lunar origin and iron-enrichment trend. Meteoritics and Planetary Science. 2003 Apr;38(4):529-554.
Fagan, Timothy Jay ; Taylor, G. J. ; Keil, K. ; Hicks, T. L. ; Killgore, M. ; Bunch, T. E. ; Wittke, J. H. ; Mittlefehldt, D. W. ; Clayton, R. N. ; Mayeda, T. K. ; Eugster, O. ; Lorenzetti, S. ; Norman, M. D. / Northwest Africa 773 : Lunar origin and iron-enrichment trend. In: Meteoritics and Planetary Science. 2003 ; Vol. 38, No. 4. pp. 529-554.
@article{2c081ecb8edc4aa9a878d8bf501895dc,
title = "Northwest Africa 773: Lunar origin and iron-enrichment trend",
abstract = "The meteorite Northwest Africa 773 (NWA 773) is a lunar sample with implications for the evolution of mafic magmas on the moon. A combination of key parameters including whole-rock oxygen isotopic composition, Fe/Mn ratios in mafic silicates, noble gas concentrations, a KREEP-like rare earth element pattern, and the presence of regolith agglutinate fragments indicate a lunar origin for NWA 773. Partial maskelynitization of feldspar and occasional twinning of pyroxene are attributed to shock deformation. Terrestrial weathering has caused fracturing and precipitation of Carich carbonates and sulfates in the fractures, but lunar minerals appear fresh and unoxidized. The meteorite is composed of two distinct lithologics: a two-pyroxene olivine gabbro with cumulate texture, and a polymict, fragmental regolith breccia. The olivine gabbro is dominated by cumulate olivine with pigeonite, augite, and interstitial plagioclase feldspar. The breccia consists of several types of clasts but is dominated by clasts from the gabbro and more FeO-rich derivatives. Variations in clast mineral assemblage and pyroxene Mg/(Mg + Fe) and Ti/(Ti + Cr) record an igneous Fe-enrichment trend that culminated in crystallization of fayalite + silica + hedenbergite-bearing symplectites. The Fe-enrichment trend and cumulate textures observed in NWA 773 are similar to features of terrestrial ponded lava flows and shallow-level mafic intrusives, indicating that NWA 773 may be from a layered mafic intrusion or a thick, differentiated lava flow. NWA 773 and several other mafic lunar meteorites have LREE-enriched patters distinct from Apollo and Luna mare basalts, which tend to be LREE-depleted. This is somewhat surprising in light of remote sensing data that indicates that the Apollo and Luna missions sampled a portion of the moon that was enriched in incompatible heat-producing elements.",
author = "Fagan, {Timothy Jay} and Taylor, {G. J.} and K. Keil and Hicks, {T. L.} and M. Killgore and Bunch, {T. E.} and Wittke, {J. H.} and Mittlefehldt, {D. W.} and Clayton, {R. N.} and Mayeda, {T. K.} and O. Eugster and S. Lorenzetti and Norman, {M. D.}",
year = "2003",
month = "4",
language = "English",
volume = "38",
pages = "529--554",
journal = "Meteoritics and Planetary Science",
issn = "1086-9379",
publisher = "The University of Arkansas Press",
number = "4",

}

TY - JOUR

T1 - Northwest Africa 773

T2 - Lunar origin and iron-enrichment trend

AU - Fagan, Timothy Jay

AU - Taylor, G. J.

AU - Keil, K.

AU - Hicks, T. L.

AU - Killgore, M.

AU - Bunch, T. E.

AU - Wittke, J. H.

AU - Mittlefehldt, D. W.

AU - Clayton, R. N.

AU - Mayeda, T. K.

AU - Eugster, O.

AU - Lorenzetti, S.

AU - Norman, M. D.

PY - 2003/4

Y1 - 2003/4

N2 - The meteorite Northwest Africa 773 (NWA 773) is a lunar sample with implications for the evolution of mafic magmas on the moon. A combination of key parameters including whole-rock oxygen isotopic composition, Fe/Mn ratios in mafic silicates, noble gas concentrations, a KREEP-like rare earth element pattern, and the presence of regolith agglutinate fragments indicate a lunar origin for NWA 773. Partial maskelynitization of feldspar and occasional twinning of pyroxene are attributed to shock deformation. Terrestrial weathering has caused fracturing and precipitation of Carich carbonates and sulfates in the fractures, but lunar minerals appear fresh and unoxidized. The meteorite is composed of two distinct lithologics: a two-pyroxene olivine gabbro with cumulate texture, and a polymict, fragmental regolith breccia. The olivine gabbro is dominated by cumulate olivine with pigeonite, augite, and interstitial plagioclase feldspar. The breccia consists of several types of clasts but is dominated by clasts from the gabbro and more FeO-rich derivatives. Variations in clast mineral assemblage and pyroxene Mg/(Mg + Fe) and Ti/(Ti + Cr) record an igneous Fe-enrichment trend that culminated in crystallization of fayalite + silica + hedenbergite-bearing symplectites. The Fe-enrichment trend and cumulate textures observed in NWA 773 are similar to features of terrestrial ponded lava flows and shallow-level mafic intrusives, indicating that NWA 773 may be from a layered mafic intrusion or a thick, differentiated lava flow. NWA 773 and several other mafic lunar meteorites have LREE-enriched patters distinct from Apollo and Luna mare basalts, which tend to be LREE-depleted. This is somewhat surprising in light of remote sensing data that indicates that the Apollo and Luna missions sampled a portion of the moon that was enriched in incompatible heat-producing elements.

AB - The meteorite Northwest Africa 773 (NWA 773) is a lunar sample with implications for the evolution of mafic magmas on the moon. A combination of key parameters including whole-rock oxygen isotopic composition, Fe/Mn ratios in mafic silicates, noble gas concentrations, a KREEP-like rare earth element pattern, and the presence of regolith agglutinate fragments indicate a lunar origin for NWA 773. Partial maskelynitization of feldspar and occasional twinning of pyroxene are attributed to shock deformation. Terrestrial weathering has caused fracturing and precipitation of Carich carbonates and sulfates in the fractures, but lunar minerals appear fresh and unoxidized. The meteorite is composed of two distinct lithologics: a two-pyroxene olivine gabbro with cumulate texture, and a polymict, fragmental regolith breccia. The olivine gabbro is dominated by cumulate olivine with pigeonite, augite, and interstitial plagioclase feldspar. The breccia consists of several types of clasts but is dominated by clasts from the gabbro and more FeO-rich derivatives. Variations in clast mineral assemblage and pyroxene Mg/(Mg + Fe) and Ti/(Ti + Cr) record an igneous Fe-enrichment trend that culminated in crystallization of fayalite + silica + hedenbergite-bearing symplectites. The Fe-enrichment trend and cumulate textures observed in NWA 773 are similar to features of terrestrial ponded lava flows and shallow-level mafic intrusives, indicating that NWA 773 may be from a layered mafic intrusion or a thick, differentiated lava flow. NWA 773 and several other mafic lunar meteorites have LREE-enriched patters distinct from Apollo and Luna mare basalts, which tend to be LREE-depleted. This is somewhat surprising in light of remote sensing data that indicates that the Apollo and Luna missions sampled a portion of the moon that was enriched in incompatible heat-producing elements.

UR - http://www.scopus.com/inward/record.url?scp=0141611996&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0141611996&partnerID=8YFLogxK

M3 - Article

VL - 38

SP - 529

EP - 554

JO - Meteoritics and Planetary Science

JF - Meteoritics and Planetary Science

SN - 1086-9379

IS - 4

ER -