Provenance and tectonic evolution of Oligocene-Miocene clastic sequences in the Mountain Province, north Luzon, Philippines

Sedimentary geochemistry, particularly whole-rock, trace element, and rare earth element analyses, has proven to be an effective tool for provenance studies, especially in geologically complex regions such as the Philippines. These techniques enhance the delineation of tectonic boundaries and provide critical insights into a region's petrogenesis and tectonic evolution.

In Northern Luzon, Philippines, much of the geological framework of the Central Cordillera Range has been established through field investigations and mineral exploration. While geochemical research has largely concentrated on igneous lithologies, recent studies on sedimentary sequences within the Baguio Mineral District – specifically the Late Oligocene to Early Miocene Zigzag Formation and the Middle to Late Miocene Klondyke Formation – have helped constrain the source rock composition and tectonic setting of these units. This study employs sedimentary geochemical techniques to investigate analogous Oligocene-Miocene clastic successions exposed in southwestern Mountain Province, northwest of the Baguio Mineral District.Geochemical signatures from these clastic units indicate derivation from igneous source rocks and deposition within a sedimentary basin associated with an oceanic island arc system. Paleontological and geochronological data suggests a Middle Miocene unconformity.  This event is likely associated with the transition from a west-verging to an east-verging subduction in Luzon, as suggested by previous studies in the region. These results offer additional constraints into the geodynamic evolution of northern Luzon throughout the Oligocene-Miocene, contributing to a more refined understanding of the region’s tectonic history and its broader implications for the evolution of the Philippine Mobile Belt.