Petrogenesis of KREEP Basalts

KREEP basalts are an oddity. Their trace element signature is evolved, possessing an abundance of incompatible trace elements (KREEP: K, Rare Earth Elements and Phosphorus), and yet they are primitive with regards to their major element composition. A great deal of effort has been spent on understanding how these basalts formed, whether they were impact melts mixing a KREEP-rich lithology with a Mg-rich one. Or as endogenous melts of the lunar interior, owing there KREEPy REE’s to their source, or perhaps to contamination as they travelled to the lunar surface passing through a KREEPy lithology. Based on a combination of crystal size distributions (a quantitative petrographic method), in situ major and trace element analysis, and element mapping, the KREEP basalts were studied. In chapters 2 and 3, I develop and refine methods on two KREEP basalts, one endogenous and one impact. Chapter 4 records the CSD’s that were produced to determine their origin. Chapter 5 combines the data from chapters 2 and 3 and synthesizing these with the major and trace element compositions and calculated equilibrium liquids of pyroxene and plagioclase from additional KREEP basalts.