This paper aims to define the geological environment, time of formation, nature and physico-chemical conditions of formation of the porphyry copper deposits in Baguio District, Luzon, Philippines that are relevant to the search for mineral deposits.

***A summary of the author’s dissertation accepted on March 24, 1978 as a partial
requirement for the Degree of Doctor of Science at the Institute of Petrology, Mineral-
ogy and Economic Geology, Faculty of Science, Tohoku University, Sendai, Japan,
(Published with permission of the Director, Philippine Bureau of Mines).