The isotopic record of lunar volcanism

Lunar cryptomaria: Mineralogy and composition of ancient volcanic deposits

“…The density of KREEP and high-Al mare basalts is similar to the latest estimates of the average crustal density (Wieczorek et al, 2013), which would allow these mantle melts to propagate and erupt onto the surface if located within hydrostatically favorable locations, such as impact basins (Solomon, 1975). The high aluminum content of the KREEP and high-Al mare basalts and their occurrence in Apollo 14 Fra Mauro breccias argues for a similar geologic provenance (Nyquist and Shih, 1992). The identification of in situ troctoliterich lithologies is confined to crater central peaks Tompkins and Pieters, 1999).…”

“…The primary lunar crust is dominated by ferroan anorthosites (Smith et al, 1970;Wood et al, 1970), while extrusive KREEP basalts and intrusive Mg-suite rocks are derived from melts of the lunar mantle (Warren and Wasson, 1977). The few dated samples of Mg-suite rocks and KREEP basalts indicate ancient ages 43.8 Ga, immediately after the Imbrium formation event (Nyquist et al, 1975;Papanastassiou and Wasserburg, 1976;Ryder and Spudis, 1980;Nyquist and Shih, 1992;Stöffler et al, 2006). There is no indication that these lithologies continued to be produced after 3.8 Ga.…”

“…Returned samples tell the story of a much more compositionally and temporally diverse volcanic history compared to the mare basalt deposits. During the first $ 500 My, the Moon was simultaneously producing mare basalts, KREEP basalts, and Mg-suite rocks (Ryder and Spudis, 1980;Taylor et al, 1983;Nyquist and Shih, 1992;Stöffler et al, 2006;Terada et al, 2007). Soon afterwards, around 3.8 Ga, there was either a substantial increase in the eruption of mare basalts or a decrease in the production of parental melts for KREEP basalts and Mg-suite rocks, or both processes occurred simultaneously.…”

Chemical variation of the large Apollo 15 olivine‐normative mare basalt rock samples

“…While they were both extruded at -3.3 +/-0.1 Ga [Nyquist and Shih, 1992], these mare basalt groups were quickly recognized as representing at least two distinct lava flows [e.g., Apollo 15 Preliminary Examination Team, 1972]. Stratigraphic considerations indicate that the quartz-normative mare basalts underlie the olivine-normative mare basalts at the With continued study, both the conclusion that the A15 olivine-normative mare basalt samples are related by simple olivine fractionation and that they even compose a single group have been questioned, with varied complexities added to the petrogenesis.…”

A Rb–Sr and Sm–Nd isotope geochronology and trace element study of lunar meteorite LaPaz Icefield 02205

“…The 87 Sr/ 86 Sr and 143 Nd/ 144 Nd isotopic evolution of the lunar mantle source regions of the LAP parent magma, Apollo 12 and 15 olivine basalts, and KREEP are modeled assuming two-stage models ( Figure 8A and B) with the mixing parameters listed in Table 3 (data from this study, Borg et al, 2004;Gnos et al, 2004;Jolliff et al, 2003;Neal, 2001;Nyquist and Shih, 1992;Nyquist et al, 1995;Rankenburg et al, 2006;Snyder et al, 1997). Because the trace element abundances in the SaU 169 impact melt breccia are the highest among the KREEP-rich samples, it probably represents a relatively 'pure' KREEP composition, and the REE and Sr concentrations of SaU 169 (Gnos et al, 2004) are therefore used in the mixing calculations.…”