Isotopic analysis of basaltic fragments from lunar breccia 14321: Chronology and petrogenesis of pre-Imbrium mare volcanism

Timing and duration of mare volcanism in the central region of the northern farside of the Moon

“…Previous studies of dark haloed craters and light plains revealed the presence of cryptomaria (i.e., maria that were buried by ejecta from large craters or basins) and interpreted them as evidence for ancient mare volcanism (e.g., Spudis, 1978, 1983;Hawke and Bell, 1981;Bell and Hawke, 1984;Antonenko et al, 1995). Such ancient mare volcanism has been supported by radiometric analyses of rock samples returned from the lunar nearside (e.g., Taylor et al, 1983;Dasch et al, 1987;Nyquist et al, 2001) and lunar meteorites (Terada et al, 2007), which indicate ages of 4.2-4.35 Gyr for their basalt clasts. In the central northern region of the farside, the onset of mare volcanism is not well understood, even though our results indicate that mare volcanism began at least as early as 3.9 Gyr ago, for a total duration of ∼1.3 Gyr.…”

Early crustal building processes on the moon: Models for the petrogenesis of the magnesian suite

“…The KREEP basalts are younger, having crystallization ages of 3.85 to 4.10 Ga (Nyquist and Shih, 1992). The high-Al basalt clasts from the A-14 site have crystallization ages that range from 3.95 to 4.3 Ga (Papanastassiou and Wasserburg, 1971;Dasch et al, 1987;Nyquist and Shih, 1992). The A-14 pyroclastic glasses have not been dated.…”

Geochemistry, petrology and ages of the lunar meteorites Kalahari 008 and 009: New constraints on early lunar evolution

“…However, Taylor et al (1983) found ancient mare basalt clasts in the Fra Mauro breccias and proposed that mare volcanism began in the Apollo 14 region at least as early as 4.2 Ga ago. Additionally, Dasch et al (1987) reported Rb-Sr isochron ages for Apollo 14 mare basalts ranging from 3.96 up to 4.33 ± 0.13 Ga, also indicating pre-4.1 Ga (pre-Nectarian) mare basalt volcanism. Remote sensing and photo-geologic evidence also indicates the onset of mare volcanism prior to the termination of late heavy bombardment (Hartmann et al, 1981).…”