Geology
The Philippines geology is divided into two separate blocks: the Palawan-Mindoro Continental Block (PCB) and the Philippines Mobile Belt (PMB) (fig. 1).
The PBC is derived from mainland Asia, while the PMB is formed through amalgamation of island arcs and ophiolite complexes. However, both blocks consist of a similar sequence of rocks. Due to the extensive volcanic activity in the island, common rock types are volcanically derived. Both extrusive (basalts to andesites) and intrusive (granodiorite, quartz diorites) rocks are found in the PBC block, along with ultramafic melanges and many ophiolite suites. Sedimentary rocks consist mostly of limestones, sandstones, cherts, shales, slates, mudstones, and conglomerates. Both sediments and volcanics have undergone metamorphic events, resulting in marbles, greenschists, and amphibolites. |
![Picture](/uploads/1/0/0/8/100897130/published/zambales-massifs.png?1491500277)
Zambales Ophiolite Complex.
The Zambales Ophiolite Complex is found in the west shore of Luzon, Philippines. The ophiolite suite is comprised of three segments, the Masinloc, Cabangan and San Antonio massifs (fig. 3). It is an unusually complete and very well preserved ophiolite suite, which is interpreted to have formed in a subduction-related marginal basin (Yumul & Dimalanta, 1997).
Figure 4 shows a cross section across the San Antonio and Cabangan massifs, in which the typical sequence of peridotites (harzburgites and pyroxenites), layered to massive gabbros, sheeted dike complexes, pillow basalts, and sediments is observed (Yumul & Dimalanta, 1997).
The sediments consist of the Aksitero Formation, which overlies the pillow basalts. It consists mostly of limestones and mudstones with interbedded tuff beds, volcanic glass shards, and volcaniclastic turbidites (Scwheller et al., 1983).
The Zambales Ophiolite Complex is found in the west shore of Luzon, Philippines. The ophiolite suite is comprised of three segments, the Masinloc, Cabangan and San Antonio massifs (fig. 3). It is an unusually complete and very well preserved ophiolite suite, which is interpreted to have formed in a subduction-related marginal basin (Yumul & Dimalanta, 1997).
Figure 4 shows a cross section across the San Antonio and Cabangan massifs, in which the typical sequence of peridotites (harzburgites and pyroxenites), layered to massive gabbros, sheeted dike complexes, pillow basalts, and sediments is observed (Yumul & Dimalanta, 1997).
The sediments consist of the Aksitero Formation, which overlies the pillow basalts. It consists mostly of limestones and mudstones with interbedded tuff beds, volcanic glass shards, and volcaniclastic turbidites (Scwheller et al., 1983).
References Cited:
Aurelio, M.A., Pena, R.E., Taguibao, K.J.L (2013). Sculpting the Philippine archipelago since the cretaceous through rifting, oceanic spreading, subduction, obduction, collision, and strike-slip faulting: Contribution to IGMA5000. Journal of Asian Earth Sciences. V. 72. Pp. 102 – 107. Doi: 10.1016/j.jseaes.2012.10.007.
Braxton, D.P., Cooke, D.R., Dunlap, J., Norman, M., Reiners, P., Stein, H., Waters, P. (2012). From crucible to graben in 2.3 Ma: A high-resolution geochronological study of porphyry life cycles, Boyongan-Bayugo copper-gold deposits, Philippines. Geology. V. 40. I. 5. Pp. 471 – 474. Doi: 10.1130/G33125.1.
Schweller, W. J., Karig, D. E., & Bachman, S. B. (1983). Original setting and emplacement history of the Zambales ophiolite, Luzon, Phillipines, from stratigraphic evidence. The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands: Part 2, 124-138.
Yumul, G. P., & Dimalanta, C. B. (1997). Geology of the Southern Zambales Ophiolite Complex,(Philippines): juxtaposed terranes of diverse origin. Journal of Asian Earth Sciences, 15(4), 413-421.