“…It has been argued by some workers that Mg-Suite plutons may form a significant component of the lower lunar crust (Spudis et al, 1999(Spudis et al, , 2000. Remote sensing observations of the lunar surface by the Apollo Gamma-Ray Spectrometer experiment (Adler and Trombka, 1977;Arnold et al, 1977;Metzger et al, 1977;Plate 2.1 of BVSP, 1981) and the Lunar Prospector Gamma-Ray Spectrometer (Lawrence et al, 2002(Lawrence et al, , 2003Prettyman et al, 2006) mapped out the abundances and spatial distribution of Th, Sm and K, which can be used as tracers for surficial outcrops of KREEP-rich material, and MgO, which is a tracer for Mg-Suite deposits (Berezhnoy et al, 2006;Prettyman et al, 2006). These studies revealed that there is an enhancement of KREEP-rich and Mg-rich regoliths concentrated on the nearside of the Moon in the region termed by Jolliff et al (2000) as the Procellarum KREEP Terrane (PKT).…”