Bulletin of the Geological Society of Malaysia, Volume 43, Dec. 1999, pp. 537 – 543
1Rushurgent Working Group, National Institute of Geological Sciences, College of Science, University of the Philippines, Diliman, Quezon City, Philippines
2Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo 164-8639, Japan
Abstract: Ophiolites are rock associations representing crust-mantle sequences. Interest in these rock suites is reflected in the extensive geological, geochemical and petrological studies that have been carried out. It is only recently, however, that geophysical tools have found application in the study of these sequences. In the Philippines, the southern Zambales area was the subject of one of the few geophysical investigations applied on ophiolite complexes. The magnetic and gravity surveys conducted in the southern portion of the Zambales Ophiolite Complex defined a northwest-southeast linear feature which is believed to correspond to the Subic Bay Fault Zone. The fault zone was delineated on the basis of the steep gradients displayed by the magnetic anomalies and from inflections noted in the gravity contours. This structure is believed to be the tectonic contact between the central (Cabangan) and southern (San Antonio) massifs of this ophiolite complex. Recognition of the fault zone is consistent with a model which suggests that the San Antonio massif was a rifted unit from the Acoje block of the Masinloc Massif. The translation southward of this massif may have occurred along the Subic Bay Fault Zone.