Heat flow inside the Island Arcs of the northwestern Pacific

A large region of high heat flow has recently been discovered in the northwest Pacific. The area extends from the Sea of Okhotsk in the north to the Philippine Sea in the south and may continue as far as the Fiji plateau. Two possible sources of the extra heat are volcanic intrusion into the crust and dissipative shear heating in the mantle. There are fundamental objections to both explanations, and, therefore, the origin of the high regional heat flow remains unknown. The high temperature gradient is of geological importance, since the crustal temperatures are sufficiently high to cause metamorphism.