PHILCRUST3.0: New constraints in crustal growth rate computations for the Philippine arc

Abstract

A revised crustal thickness map for the Philippine island arc, PHILCRUST3.0, has been generated using new gravity data from the EGM2008. The gravity-derived crustal thickness is compared with crustal thickness estimates obtained using the Sr/Y ratios. PHILCRUST3.0 shows that crustal thickness in the Philippines varies from 13 to 33 km. The Philippine arc appears to be at its thinnest in areas underlain by ophiolites and young magmatic arcs. The resulting crustal thickness values are used to revisit the growth rates of the Philippine arc from magmatic and amagmatic contributions. Arc magmatism contributes more significantly to the growth of Philippine crust with rates from specific volcanoes varying from 5 to 35 km3/km/m.y. Despite being relatively young, magmatism associated with the volcanoes of the East Philippine Arc displayed a higher growth rate (32 km3/km/m.y.) compared to volcanoes belonging to older magmatic arcs in the archipelago. This is attributed to the more hydrated oceanic lithosphere subducting beneath the Philippine Trench. PHILCRUST3.0 provides the most complete crustal thickness map of the Philippines to date. This will enable the computation of crustal growth rate in areas within the Philippines where point gravity or geochemical data is not available.