Miocene Collision-related Strike-slip Origin of Some Metamorphic Basement in Luzon, Philippines
Abstract
The basement of the northern Philippines consists of ophiolitic rocks, arc magmatic rocks, and scattered foliated metamorphic rock of uncertain age and origin. The Dalupirip Schist in northern Luzon, an epidote, chlorite, actinolite schist, was once thought be part of old (i.e., pre-Tertiary) basement material in the northern Philippines and later was assigned a variety of origins including thrust-related metamorphism at the base of an ophiolite and contact metamorphism adjacent to arc intrusions. This study shows that the Dalupirip Schist metamorphism is, at least in part, Middle Miocene in age (based on 40-Ar/39-Ar dating) and was formed by wrench faulting and metamorphism of arc pluton and volcanic protoliths. The metamorphic fabric of the Dalupirip Schist is broadly parallel to the active Philippine Fault. The Philippine Fault is recognized as one of the great active strike slip faults on Earth. It had been suggested that the Philippines has been subject to wrench faulting since as early as the Cretaceous. Subsequent work has shown, however, that the present Philippine Fault initiated fairly recently (Pliocene). The Dalupirip schist therefore provides evidence for strike slip faulting, sub-parallel to the Philippine Fault, but prior to the initiation of the current Philippine Fault system. The amount of displacement along the Dalupirip shear zone is unknown. Formation of the Dalupirip Schist shear zone was probably associated with the collision of the Luzon arc (eastern Philippines) with the rifted continental margin of China (North Palawan Continental Terrane; western Philippines) in the Miocene. Other "basement" metamorphic rocks elsewhere in Luzon may have a similar collision-related origin.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T53B..06E
- Keywords:
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- 8104 Continental margins: convergent;
- TECTONOPHYSICS;
- 8105 Continental margins: divergent;
- TECTONOPHYSICS;
- 8157 Plate motions: past;
- TECTONOPHYSICS;
- 8185 Volcanic arcs;
- TECTONOPHYSICS