Santo Tomas II Group

Porphyry copper (Cu-Au) deposit in Benguet, Philippines

Names and other identifiers

Alternate names Santo Tomas II, Philex, Padcal Expansion Project
Tract name Luzon Arc (Central Cordillera segment) (142pCu7301b)
Included sites Padcal, Macawilli
Site status deposit

Geographic location

Country Philippines
State or province Benguet
Geographic location 120.6225, 16.263055555
Geologic map unit 120.6225, 16.263055555
Nearby data

Geologic information

Deposit type Porphyry copper
Deposit subtype Cu-Au
Age (Ma) 1.5Ma
Age determination method K-Ar whole rock
Age range 1.5 ±0.4 Ma
Age reference Imai (2001); Imai (2002)
Minerals actinolite, altaite, anhydrite/gypsum, apatite, azurite/malachite, biotite, bornite, calcite, chalcocite/digenite, chalcopyrite, chlorite, chrysocolla, covellite, electrum, epidote, galena, gold, hematite/specularite, hessite, magnetite, merenskyite, molybdenite, moncheite, petzite, pyrite, pyrophyllite, sericite, silver, sphalerite
Associated rocks andesite porphyry, breccia, dacite porphyry, diorite porphyry, quartz diorite, basalt flow, limestone, clastic sediments, andesite, metavolcanic rocks, conglomerate, dacite, diorite, gabbro, siltstone
Tectonic setting island arc
Stratigraphic age Pleistocene

Commodity and development information

Development status Prospect
Major commodities Cu, Mo, Au
Tonnage (Mt) 449Mt
Cu grade (%) 0.38%
Mo grade (%) 0.0005%
Au grade (g/t) 0.7g/t
Ag grade (g/t) 1.5g/t
Contained copper 1,700,000t
Gold-Moly ratio 1000

Reference information

Comments Mined by open-pit until 2004. In ore: 0.045 g/t Pt, 0.032 g/t Pd. Exposed.
Study area name East and Southeast Asia
References Apostol (1974); Bryner (1969); Imai (2001); Imai (2002); Imai and others (1992); MMAJ-JICA (1977); Motegi (1977); Philippines Mines and Geosciences Bureau (1986); Sillitoe (1997); Takenouchi (1980); Tarkian and Koopmann (1995); Singer and others (2008); Philippines Mines and Geosciences Bureau (2005)
Site reference Hammarstrom and others (2014)
Apostol, E.L., 1974, Porphyry copper deposits in Baguio district, Luzon, Philippines: Geological Society of the Philippines Journal, v. 28, no. 2, p. 32–43.
Bryner, Leonid, 1969, Ore deposits of the Philippines—An introduction to their geology: Economic Geology, v. 64, p. 644–666. (Also available at, Akira, 2001, Generation and evolution of ore fluids for porphyry Cu-Au mineralization of the Santo Tomas II (Philex) deposit, Philippines: Resource Geology, v. 51, no. 2, p. 71–96. (Also available at, Akira, 2002, Metallogenesis of porphyry Cu deposits of the Western Luzon arc, Philippines—K-Ar ages, SO3 contents of microphenocrystic apatite and significance of intrusive rocks: Resource Geology, v. 52, no. 2, p. 147–161. (Also available at 10.1111/j.1751-3928.2002.tb00127.x.)
Imai, A., Muyco, J.D., Domingo, E.G., Almeda, R.L., Villones, R.I., Yumul, G.P., Jr., Damasco, F.V., Baluda, R.I., Malihan, T.D., Datuin, R.T., Punongbayan, R.S., Listanco, E.L., and Santos, R.A., 1992, Porphyry copper and gold mineralization in the Philippines, in Kojima, Satoru, and Hase, Hirokazu, eds., Mineral deposits of Japan and the Philippines: Nagoya, Japan, Society of Resource Geology, 29th IGC Field Trip Guide Book, v. 6, p. C36-1–C36-30.
MMAJ-JICA, 1977, Report on geological survey of northeastern Luzon, Phase III: Metal Mining Agency of Japan (MMAJ) and Japan International Cooperation Agency (JICA), Tokyo, 280 p.
Motegi, M., 1977, Porphyry copper deposits in Philippines—Their tectonic setting and present status of development: Mining Geology, v. 27, p. 221–230.
[Philippines] Mines and Geosciences Bureau, 1986, Geology and mineral resources of the Philippines, v. 2—Mineral resources: Manila, [Philippines] Mines and Geosciences Bureau, 446 p.
[Philippines] Mines and Geosciences Bureau, 2005, Copper: [Philippines] Mines and Geosciences Bureau Mineral Resource Information Series No. 5, 23 p.
Sillitoe, R.H., 1997, Characteristics and controls of the largest porphyry copper-gold and epithermal gold deposits in the circum-Pacific region: Australian Journal of Earth Sciences, v. 44, p. 373–388. (Also available at, D.A., Berger, V.I., and Moring, B.C., 2008, Porphyry copper deposits of the world—Database and grade and tonnage models, 2008: U.S. Geological Survey Open-File Report 2008-1155, [45] p. and digital data, accessed December 31, 2013, at
Takenouchi, S., 1980, Preliminary studies on fluid inclusions of the Santo Tomas II (Philex) and Tapian (Marcopper) porphyry copper deposits in the Philippines: Mining Geology Special Issue, no. 8, p. 141–150.
Tarkian, M., and Koopmann, G., 1995, Platinum-group minerals in the Santo Tomas II (Philex) porphyry copper-gold deposit, Luzon Island, Philippines: Mineralium Deposita, v. 30, p. 39–47. (Also available at