Major and trace-element and Sr, Nd, and Pb isotopic compositions have been determined for Koolau shield lavas and Nuuanu and Wailau landslide deposits, Hawaii. The Koolau shield is composed of older main shield-stage and younger Makapuu-stage lavas. Lavas of the main shield-stage are exposed low in the subaerial Nuuanu Pali and in Nuuanu landslide deposits. Main shield-stage lavas resemble Loa- or Kea-type compositions
they are characterized by lower Ba/Nb, La/Nb, Pb/Nd, Sr/Nb, Nd/Nb, Zr/Nb, and 87Sr/86Sr, and by higher 143Nd/144Nd and 206Pb/204Pb than those of Makapuu-stage lavas (Koolau-type). Sr-Nd-Pb isotope systematics suggest that Koolau shield lavas were generated from at least three endmembers, such as: Enriched Makapuu (EMK), Depleted Makapuu (DMK), and Kea (KEA) components. The proportion of these endmembers successively changed from earlier KEA-dominated to later EMK-dominated. Koolau shield-stage lavas span nearly the entire range of the isotopic compositions reported previously for shield-stage lavas from all Hawaiian islands, and reveal secular changes in the amounts of plume components.