RUI: Collaborative Research: Metamorphism and Deformation Associated with Late Cenozoic Strike-Slip Faulting in the Philippines

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The Philippine Fault, an active, left-lateral strike-slip fault, transects almost the entire length of the Philippine Archipelago. It is one of several major strike-slip fault systems worldwide that occur at obliquely converging intra-oceanic plate boundaries. This and a collaborative project (EAR87-07951) will study the genesis and emplacement of metamorphic rocks that occur along the fault. Some of these metamorphic rocks-- greenschist-facies metavolcanics, amphibolites and serpentinites-- may be created at convergent suture zones, but we will test the hypothesis that at least some of them were generated entirely as a result of strike-slip related processes. We will use structural, geochronological and geochemical techniques to determine if the deformational and metamorphic history of metamorphic rocks is consistent with their creation along the Philippine Fault, rather than by collisional process. The common occurrence of major strick-slip faults at modern obliquely converging margins suggest that similar structures should occur as terrane boundaries in ancient active margin assemblages, but few such structures have been recognized. This may be because many petrologic and structural associations common to both convergent and strike-slip "sutures" are generally believed to be associated only with the former. By studying the origin of metamorphic rocks along an active strike-slip fault that also acts to juxtapose disparate terranes in the Philippines, we hope to establish a framework for recognizing such structures in old arc terranes.