Petrogenesis of the western highlands of the moon - Evidence from a diverse group of whitlockite-rich rocks from the Fra Mauro formation

A group of KREEPy basalts has been discovered in Apollo 14 soils. These samples exhibit similarities to both HA and VHK basalts, albeit with much higher REE abundances, and contain up to 2 vol pct whitlockite and can be explained by assimilation of a K-, REE- and P-rich fluids by an original HA or VHK basalt. This KREEP component could have been produced late in the evolution of the lunar magma ocean and is similar in composition to QMD at Apollo 14. Two rocks have trace element compositions that are representative of actual KREEP. One of the samples appears to be petrographically pristine and could represent an actual KREEP basalt rock. Five subophitic high-Al basalts represent sampling of either a slowly cooled impact melt sheet or, more likely, the same basalt flow. Two 'quasi-pristine' highland rocks confirm the postulate of a connection between KREEP and the alkali suite. A newly discovered alkali anorthosite is a plagioclase cumulate with about 15 percent trapped KREEPy liquid.