Geochemistry and 40Ar-39Ar geochronology of impact-melt clasts in feldspathic lunar meteorites: Implications for lunar bombardment history

Barbara Anne Cohen, Timothy Swindle, David A. Kring

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39 Citations (Scopus)

Abstract

We studied 42 impact-melt clasts from lunar feldspathic regolith breccias MacAlpine Hills (MAC) 88105, Queen Alexandra Range (QUE) 93069, Dar al Gani (DaG) 262, and DaG 400 for texture, chemical composition, and/or chronology. Although the textures are similar to the impact-melt clasts identified in mafic Apollo and Luna samples, the meteorite clasts are chemically distinct from them, having lower Fe, Ti, K, and P, thus representing previously unsampled impacts. The 40Ar- 39Ar ages on 31 of the impact melts, the first ages on impact-melt samples from outside the region of the Apollo and Luna sampling sites, range from ∼4 to ∼2.5 Ga. We interpret these samples to have been created in at least six, and possibly nine or more, different impact events. One inferred impact event may be consistent with the Apollo impact-melt rock age cluster at 3.9 Ga. but the meteorite impact-melt clasts with this age are different in chemistry from the Apollo samples, suggesting that the mechanism responsible for the 3.9 Ga peak in lunar impact-melt clast ages is a lunar-wide phenomenon. No meteorite impact melts have ages more than 1 σ older than 4.0 Ga. This observation is consistent with, but does not require, a lunar cataclysm.

Original languageEnglish (US)
Pages (from-to)755-777
Number of pages23
JournalMeteoritics and Planetary Science
Volume40
Issue number5
StatePublished - May 2005

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lunar meteorite
impact melts
geochronology
meteorites
geochemistry
clast
bombardment
histories
melt
history
meteorite collisions
meteorite
textures
texture
regolith
chronology
chemical composition
sampling
rocks
chemistry

ASJC Scopus subject areas

  • Geophysics

Cite this

Geochemistry and 40Ar-39Ar geochronology of impact-melt clasts in feldspathic lunar meteorites : Implications for lunar bombardment history. / Cohen, Barbara Anne; Swindle, Timothy; Kring, David A.

In: Meteoritics and Planetary Science, Vol. 40, No. 5, 05.2005, p. 755-777.

Research output: Contribution to journalArticle

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