Uncertainty about timing and location of the initiation of convergence in the western and south western Pacific greatly hinders accurate plate tectonic reconstructions of subduction systems in that area. The chemistry and age of dikes intruding mantle peridotite in the ophiolite of New Caledonia infer that subduction-related magmatism began prior to 53 Ma. These new results infer that obduction in the Southwest Pacific is unrelated to the reorientation of the Pacific plate motion that occurred at ca. 43 Ma and confirm new interpretations showing that changes in mantle flow, hotspot and plate motion may have occurred as soon as late Paleocene or early Eocene.
