The Solomon Islands comprise three main geologic provinces: The Volcanic province is composed of Pliocene to Holocene volcanic rocks (Coleman and Packham, 1976); the Pacific province is composed of pillow lava and limestone deposited on a segment of a westward-frifting Pacific plate during Late Cretaceous and most of Cenozoic time (Hughes and Turner, 1977); and a Central province is composed of metamorphic rock, lava, and much post-Oligocene sediment, present on many of the major islands (Coleman, 1966). Ultramafic rocks (ophiolite?) are present on Choiseul, Santa Isabel, Florida Group, Guadalcanal, and San Cristobal (Thompson, 1965), and all these ultramafites lie within the Central province of Coleman (1966). Diapiric masses. of ultramafic rocks have been described in the New Hebrides (Mallick and Neef, 1974) and in the Solomons (Stanton, 1961; Stanton and Ramsay, 1975).