Figure F4. Location map of the northern Izu-Bonin-Mariana (IBM) arc system. White star = primary proposed Site IBM-3C. Four tectonic settings of magmatism are referenced during this project: the volcanic front, which includes the named volcanoes; active rifts, which are located just behind and between the volcanic front volcanoes; a 100 km wide extensional zone that extends westward from the active rifts; and rear-arc seamount chains including Enpo and Manji that start in the Shikoku (back arc) Basin west of the arc and continue into the extensional zone. We refer to magmatism in the active rifts and extensional zone as “rift-type” and magmatism in the rear-arc seamount chains as “rear-arc type.”
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