Geological, geochemical and induced polarization surveys yielded favorable results in the search for copper-molybdenum minerals in Larap area. The deposits which are being exploited by Philippine Iron Mines, Inc. are of the igneous contact metamorphic and porphyry types. Control of mineralization is mainly structural and stratigraphic and, to a minor extent chemically controlled. The ore deposits occur peripheral to andesite-diorite stocks.

Calcareous sediments metamorphosed to skarn, and metamorphosed andesitic volcanics acted as host rocks to metamorphic mineralization. Porphyry mineralization is associated with the intrusive andesite—diorite and metamorphic andesitic volcanics.

Alteration minerals consist mostly of sericite, biotite, quartz and clays, Although not a common alteration mineral, K-Feldspar occurs in several areas.