Tectonic setting of a composite terrane: A review of the Philippine island arc system

Abstract

Features resulting from the interplay of arc magmatism, ophiolite accretion, ocean basin closure and other subsequent tectonic processes are preserved in the Philippine island arc system. Subduction of ocean floor along the trenches surrounding the Philippines is a major factor in shaping the geologic history of this island arc system. Stress-strain relationships, as manifest in both the regional and local setting of the archipelago, are derived from the interaction of at least four major plates: Sundaland, Philippine Mobile Belt, Philippine Sea and, to a certain extent, the Indo-Australian plate. Collision zones in this island arc system are characterized by the involvement of oceanic bathymetric highs (seamounts, spreading ridge, submerged continental fragment). A major strike-slip fault, the Philippine Fault Zone, with compressional and extensional components, traverses the whole archipelago where all excess stress not accommodated by the surrounding trenches is taken up. Tholeiitic through adakitic to calc-alkaline rock suites characterize the different magmatic arcs. Exposed oceanic lithospheric fragments exhibit transitional mid-ocean ridge, back arc basin to island arc geochemical characteristics. The observed crustal thickness in the Philippines resulted from combined magmatic (volcanism) and amagmatic (ophiolite accretion) processes, with the former being the dominant factor.

Philippine Island Arc System Tectonic Features Inferred from Magnetic Data Analysis

“…In the Philippine archipelago positive magnetization is distributed mainly along the islands of Luzon, Samar, Leyte, and the south portion of Mindanao. These locations are similar to the magmatic arcs identified by Yumul et al (2008). Visayas Province is a specific area with high free-air gravity anomaly but low magnetization.…”

“…Based on magnetic data analysis, the main conclusions in this study are: (1) The positive magnetization distribution coincides closely with the magmatic arcs related to subduction identified by Yumul et al (2008). The Philippine fault occurs roughly along the boundary of high/low magnetization.…”

“…After collision with the Palawan-Mindoro continental block, continued motion along the Manila trench north of Mindoro has ruptured the central Philippines along the Sibuyan Sea fault branch of the Philippine fault (Bischke et al 1990). Mindanao presents another left-lateral fault, the NW -SE trending Sindangan-Cotabato-Daguma Lineament (also called Cotabato Fault), the northern extension of which connects with the Siayan-Sindangan Suture Zone (Yumul et al 2008).…”

Origin and diversification of Philippine bulbuls

“…Thus, Luzon harbors three species, Panay, two and small oceanic islands like Tablas, Camiguin (Heaney, 1986;Voris, 2000) and these temporary links may have provided opportunities for vicariant events and back-colonizations between islands. An alternative hypothesis is that these three species arose in allopatry prior to the midMiocene when the Zamboanga peninsula, central Mindanao and eastern Mindanao were distinct islands (Yumul et al, 2008). This explanation is unlikely because it would require several additional long-distance dispersal events and molecular divergences between the taxa do not seem high enough for such an ancient scenario.…”

“…The Philippine archipelago has had a complex geological history but the major stages are now fairly well understood as summarized in Hall (2002) and Yumul et al (2008). The western islands of Palawan and Mindoro are composed of continental crust that rifted from the margins of southern China and rafted to their current position.…”