An outline of the Geology of New Caledonia; from Permian-Mesozoic Southeast Gondwanaland active margin to Cenozoic obduction and supergene evolution
Résumé
The geological evolution of New Caledonia may be divided into three phases. The Gondwanan phase (Permian-Early Cretaceous), is marked by subduction along the SE Gondwaland margin. At that time, proto-New Caledonia was located in afore-arc region in which volcanic-arc detritus accumulated; whilst accretion and subduction of oceanic and terrigenous material formed an accretionary complex metamorphosed into the blueschist facies. During the Late Cretaceous-Eocene, marginal rifting isolated New Caledonia, and after a short period of shallow water terrigenous sedimentation associated with minor volcanic activity, only pelagic sediments accumulated. A new NE-dipping subduction appeared to the E of New Caledonia at the Paleocene-Eocene boundary, it generated the eclogite-blueschist complex of northern New Caledonia, consumed the eastern Australian Plate, and eventually ended with Late Eocene obduction when the Norfolk Ridge blocked the subduction zone. Finally, during the post-Eocene phase, New Caledonia definitively emerged; this episode mainly corresponds to prominent regolith development and minor tectonic events that lead to the present morphology and to the development of supergene nickel ores.