Zambales Ophiolite Complex (Philippines) Transition-Zone Dunites: Restite, Cumulate, or Replacive Products?

摘要

The transition-zone dunites in the Coto and Acoje blocks of the Zambales Ophiolite Complex are host to chromitites, nickel sulfides, and platinum-group minerals. The dunites are intercalated with harzburgites-lhetzolites, layered ultramafic cumulate rocks, and layered gabbros. Chromitite pods are rimmed by dunite aureoles. Based on field and geochemical evidence, transition-zone dunites of the Zambales Ophiolite Complex were formed predominantly by crystallization processes. Limited partial melting and melt-mantle interaction can explain the formation and occurrence of the other dunite types, especially the aureoles around chromitites. The geophysical and petrological Moho in the Zambales Ophiolite Complex are located in two distinct horizons.