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IODP Expedition 352 (Izu-Bonin Forearc): Testing the Subduction Initiation Model for the Genesis of Ophiolite Complexes


IPGP - Îlot Cuvier


Séminaires Géosciences Marines

Salle 310

Julian Pearce

Cardiff University

Many of the world's largest ophiolite complexes are now attributed to a brief period of sea-floor spreading that accompanies slab roll-back following initiation of subduction. There are, however, no extant examples where this model can be tested, so drilling was needed to penetrate the best-known analogue: the Eocene rocks of the IBM (Izu-Bonin Mariana) system. IODP Expedition 352 drilled four holes (1200m total) into the inner wall of the Bonin Trench, recovering lavas and dykes from some of the first crust created during the period between subduction initiation and island arc generation. Evidence supporting the subduction initiation model for ophiolites includes the recovery of two lava sequences rooting in dyke swarms and the compositional trend from MORB-like to boninitic in space and time, though our understanding of the roll-back driven spreading process remains far from complete.