THE COASTAL BATHOLITH OF PERU - THE PRODUCT OF RAPID RECYCLING OF NEW CRUST FORMED WITHIN RIFTED CONTINENTAL-MARGIN

The Coastal Batholith of Peru was intruded into 'new' Albian crust of the marginal basin, which formed on major continental rifting. The 'magic switch' from basalt dominated volcanogenic basinal filling to tonalitic Cordilleran type magmatism is part of a magmatic scenario in which the 'new crust' melts on major decompression along megafractures defining the batholith structural lineament. Quantitative modelling of the Icelandic rifting system, which is similar in many respects, indicates basalt melting is likely to produce large amounts of tonalitic to granitic magma. The whole sequence of events leading to batholith formation i.e. extension --> subsidence with basin formation --> spreading --> dyking --> splitting --> basin filling --> gabbro intrusion --> compression with partial inversion --> cratonization --> fracturing and batholith intrusion along the axis of the basin relates to a major cycle of crustal growth.