The arc-trench system and the distribution of diorite in the Philippines is mentioned first. And three epochs of diorite intrusion during the Tertiary Era were differentiated. The Paleocene diorites are distributed in the innermost zone of the mobile belt covering the Mindoro-Visaya—northwest Mindanao area. The Eocene—Oligocene diorites are distributed along the eastem coast of Luzon ls. where a collision of microcontinent-island arc is assumed. The middle Miocene to the uppermost Miocene diorites are distributed along the present "two reversely fronting arcs".

Then the geology of ore deposits is outlined by the order of the geologic age from the Permian bedded manganese deposits to the Quatemary native copper bearing basalt.

Conclusively the author distinguished the following mineralization periods: 1) Cretaceous—Paleogene eugeosynclinal basaltic volcanism forming bedded (strata-bound) ore deposits, 2) Paleogene diorite intrusives forming porphyry copper deposits, 3) Paleogene ultramatics forming chromite-nickel deposits, and 4) Eocene-Oligocene diorites forming metasomatic
iron deposits. The above four are the mineralizations prior to the Oligocene orogeny which are not discussed in this paper.

After the Oligocene orogeny, 5) Acidic volcanism under shallow sea environment forming Kuroko (type) ore deposits, 6) Miocene diorite intrusives forming many porphyry copper deposits and skarn type deposits, 7) Pliocene energite—luzonite deposits, and 8) Quaternary native copper bearing basalt are the economically important mineralizations.