Geologic Evidence and Implications of Multiple Collision – Suturing in Central Philippines: Insights from Palawan, Mindoro, Romblon and Panay Islands

G.P. Yumul,Jr.^1,2, C.B. Dimalanta², R.A. Tamayo, Jr.², F.T. Jumawan³, V.B. Maglambayan⁴, E.J. Marquez⁵, K.L. Queaño^6,12, L.R. Zamoras⁴, N.T. Ramos⁷, T.A. Tam III⁸, E.G.L. Ramos², M.G. Asio-Montes², J.A. Gabo², L.T. Armada², D.V. Faustino-Eslava⁹, L.O. Suerte¹⁰, E.S. Andal⁴ and B.D. Payot¹¹

¹Department of Science and Technology, Bicutan, Taguig, Metro Manila
²National Institute of Geological Sciences, University of the Philippines, Diliman
³Jumawan and Associates, Cebu City
⁴Philex Mining Corporation, Pasig City
⁵Department of Physical Sciences and Mathematics, University of the Philippines - Manila
⁶Mines and Geosciences Bureau, North Avenue, Quezon City
⁷Department of Geophysics, Kyoto University, Japan
⁸CGG Veritas, Houston, Texas, USA
⁹Department of Earth Sciences, University of Hong Kong
¹⁰Mines and Geosciences Bureau-Region VI, Iloilo City
¹¹Faculty of Science, Kanazawa University, Japan
¹²Earth and Materials Science and Engineering Department, Mapua Institute of Technology

Abstract

The collision of the aseismic Palawan microcontinental block (PCB) with the seismically-active Philippine mobile block (PMB) has long been recognized. Evidence for this collision are exposed specifically along the leading edge of the Palawan group of islands and in the islands of Mindoro, Romblon island group and Panay. Detailed surface and subsurface studies involving field geological, geochemical and geophysical data and information had revealed the different facets of the collision. The Calamian group of islands, specifically Busuanga in Palawan revealed Permian to Mesozoic oceanic plate stratigraphy within an ancient accretionary prism. The Mindoro island, with three ophiolite belts, the Eocene Lubang-Puerto Galera, the Cretaceous Mangyan and the mid-Oligocene Amnay Ophiolite Complex, exposes oceanic lithosphere emplacement mechanisms that range from subduction upwedging through strike-slip faulting to onramping. Models vary on where the collision boundary is placed: from southwest Mindoro through central Mindoro to offshore east Mindoro. For the Romblon island group, the geology of the three major islands (Tablas, Romblon, Sibuyan) suggest that this is part of the leading edge of the PCB. The back-thrusted Sibuyan Ophiolite Complex over the metamorphic rock basement is believed to be related to the collision event of the PMB and PCB. Lastly, The Buruanga Peninsula in NW Panay is found to mimic the geology of Busuanga island in the Calamian group of islands, Palawan. Instead of the predominance of metamorphic rocks, the Buruanga Peninsula has intercalated chert – clastic sediments similar to that of Busuanga island. The boundary with the Antique Ophiolite Complex appears to be fault-related. A collation of all of these information shows that the typical signatures (e.g. cusping, emplaced ophiolites, raised terraces, volcanic arc gap, rifting on the back arc side, steep subducted slab) of a collision zone are present. Although new geological information have been generated in the region, there are still a lot of data and information that have to be generated to further understand the evolution of central Philippines.

Funding, logistic, field and monitoring support have been extended by the Department of Science and Technology (DOST), the DOST-Philippine Council for Industry and Energy Research and Development (DOST-PCIERD), the DOST-Philippine Council for Advanced Science and Technology Research and Development (DOST-PCASTRD), UP-National Institute of Geological Sciences and Mines and Geosciences Bureau Region 6. Laboratory support and machine time have been extended by the University of Okayama, University of Hong Kong, University of Bretagne Occidentale, University of Tokyo and University of Paul Sabatier.