Graciano P. Yumul Jr., Carla B. Dimalanta, Decibel V. Faustino, and Joel V. De Jesus
National Institute of Geological Sciences
College of Science
University of the Philippines, Diliman
doi.org/10.57043/transnastphl.1997.5913
Abstract
The Zambales Ophiolite Complex (ZOC) is a well-studied exposure of upper mantle-crustal sequence in the Philippines. This ophiolite complex is subdivided into three massifs – Masinloc, Cabangan and San Antonio – which are cut by several structures. Reconnaissance gravity and magnetic surveys were conducted in the southern portion of the Zambales Ophiolite Complex to delineate gross structural features. The resulting geophysical anomalies define a major structural feature called the Subic Bay Fault Zone. This confirms the results of earlier field, petrographic and geochemical studies which suggested the presence of a structural boundary between the Cabangan Massif (which represents a mid-ocean ridge mantle suite) and the San Antonio Massif (which represents an arc crust). The results of this work do not only contribute to an understanding of how this ophiolite complex evolved but more importantly identifies a geologic structure which must be taken into consideration in any infrastructure development in this particular area.