Tectonics：Cenozoic Evolution of the Sulu Sea Arc-Basin System: An Overview
Abstract The Cenozoic Sulu Sea arc-basin system is situated in the tectonic junction between the South China Sea (SCS), northern Borneo, Palawan Continental Terrane, Philippine Mobile Belt, and Celebes Sea. We compare new/published geochronological and geochemical data from across the circum- Sulu Sea region, and summarize seven major magmatic phases from the Middle Eocene to Pleistocene. The Middle Eocene (42.65 Ma) Sabah ophiolite and Eocene-Oligocene (34-33 Ma) Central Palawan ophiolite have MORB-IAT-transitional features, representing an intraoceanic subduction setting in the Paleogene northern Borneo and central-southern Palawan. After the SCS opening (∼32 Ma) and ridge jump (∼25 Ma), late-stage Proto-SCS subduction (24-21 Ma) may have formed the Panay arc andesite and the BABB magmatism in SW Zamboanga peninsula. Starting of final convergence between the Palawan Continental Terrane and northern Borneo-SW Philippines (∼21 Ma) likely caused regional uplift/ thrusting, forming the Top Crocker Unconformity and triggering the NW-dipping Celebes Sea subduction. The subduction may have formed arc magmatism (21-18 Ma) in the Cagayan ridge and its continuation in Panay and NE Sabah, and opened the NW Sulu Sea back-arc basin through continental crust attenuation. Subduction rollback likely occurred in 17-14 Ma and 13-9 Ma, shifting arc magmatism southeast to the Sulu ridge and opening the SE Sulu Sea back-arc basin. NW-dipping Celebes Sea subduction largely ceased after ∼9 Ma, followed by extension-related uplift/exhumation and 4-0.2 Ma intraplate volcanism in northern Borneo. SE-dipping Sulu Sea subduction likely occurred along the Negros-Sulu trenches, and produced arc volcanism from ∼4 Ma.