Volcanism and sedimentation in a rifting island-arc terrain: an example from Tonga, SW Pacific

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Scientific drilling of narrow sub-basins within the Lau back-arc basin system of the SW Pacific has recovered uppermost Miocene to Recent volcaniclastic sediment and pelagic nannofossil oozes. Pliocene sediment gravity flow and turbidite sands from the western Lau Basin indicate a local source for the sediment, probably intrabasinal seamount volcanoes active during the initial stages of arc rifting. On the basis of the sedimentary, geochemical and seismic data it is suggested that basin rifting involved an initial stage of extension of the original island arc, accompanied by volcanism in the form of major seamount volcanoes within the basin. Basin opening proceeded with a trenchward migration of extension and volcanism with time. This system was disrupted by the southward propagation of the Eastern Lau Spreading Centre into the southern Lau Basin at 1.5-1.0 Ma. This resulted in extension and volcanism being concentrated along the median valley of the spreading centre and a cessation in explosive volcanism of wide composition range. -from Authors

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Volcanism associated with extension at consuming plate margins

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