Lunar bulk sample trace element contents and KREEP.

The geochemical coherence of KREEP-related labile (Cl) and refractory (F, K, P, and REE) elements in lunar soils is shown to provide some insights into the evolution of the lunar samples studied. Thus, this coherence may help define the physical conditions under which the samples evolved. These conditions range from high temperatures and relatively open systems for mare basalts to moderate temperatures and closed systems for KREEP-related material. The water leachable Cl may be the residuum of the Cl-containing phase with which mare and KREEP source material equilibrated.