Lunar polymict breccia 14321: a compositional study of its principal components

Osmium isotope and highly siderophile element systematics of lunar impact melt breccias: Implications for the late accretion history of the Moon and Earth

“…No clasts of granulitic breccia have been described from 14321. Duncan et al (1975) favored the interpretation that microbreccias 2 and 3 formed in the Imbrium impact. If this interpretation is correct, the HSE in these microbreccias are derived from the Imbrium impactor.…”

“…Sample 14321 was described by Grieve et al (1975), Duncan et al (1975), and Shervais et al (1984). The rock is a breccia consisting of rounded clasts of dark aphanitic impact melt breccias (termed microbreccia 3) and clasts of mare basalt, olivine vitrophyre, and feldspathic highland rocks in a light-colored matrix; the matrix consists mostly of finely comminuted, sintered mare basalt (Fig.…”

“…The microbreccia 3 clasts themselves contain clasts of finegrained noritic impact melts (termed microbreccia 1), feldspathic highland rocks, and accretionary lapilli of aphanitic impact melt breccias (termed microbreccia 2). Microbreccias 2 and 3 are interpreted as having formed sequentially in the same impact event (Duncan et al, 1975). Lithic clasts >1 mm across make up about 30% of the rock; microbreccia 3 makes up about 50% of these clasts and mare basalts about 35%.…”

Oxygen isotopic signature of 4.4–3.9Ga zircons as a monitor of differentiation processes on the Moon

“…The oldest lithic component that has been recognised by these authors, called microbreccia-1, is represented by KREEP-rich norite and fragments of crystalline norite and microgranite. Duncan et al (1975b) combined these fragments into one chronological group. Other components that appear to be similar to this group in age, but preserve their igneous textures, include fragments of anorthosite, olivine breccia, mare basalt, and rhyolite glass.…”

“…Other components that appear to be similar to this group in age, but preserve their igneous textures, include fragments of anorthosite, olivine breccia, mare basalt, and rhyolite glass. This compositional variety of fragments forms clasts in texturally later microbreccia-2 and 3 (Duncan et al, 1975b). Microbreccias 2 and 3 together with anorthosite clasts and fragments of basalt, which are compositionally different from the basalts included in microbreccia-1, bind with the matrix to form sample 14321.…”