REVISITING THE ACCRETIONARY HISTORY AND MAGMA SOURCES IN THE SOUTHERN ANDES: TIME VARIATION OF THE “TYPICAL ANDEAN” GRANITES.

RAPELA, C.W.; PANKHURST, R.J.; BALDO, E.; DAHLQUIST, J.A.; CASQUET , C.; GALINDO, C.

Nice, Francia.

Simposio; 7th International Symposium on Andean Geodynamics (ISAG-2008).; 2008

Institut de Recherche pour le Développement (IRD) and the University of Nice - Sophia Antipolis.

Subduction associated with pre-Andean episodes was related to Wilson cycles of ocean opening and closing, where the final event is either a continent-continent collision or large-scale back-arc closure. At 30º-34ºS, three main episodes of pre-Andean plate convergence are well established: (1) Pampean: 540-528 Ma subduction, followed by oblique continent-continent collision at 528-515 Ma. The supercontinent grew westwards by lateral accretion of the Western Sierras Pampeanas Grenvillian block (Rapela et al., 2007), including the Precordillera (Fig.2). (2) Famatinian: 484-463 Ma convergent episode associated with the opening and closing of a large backarc basin in Early to Mid Ordovician times (Pankhurst et al., 2000; Dahlquist et al., 2008) (Fig.2). (3) Gondwanan: 320-190 Ma. After the intrusion of Devonian and Early Carboniferous (c. 380 and 340 Ma) intraplate A-type granites in the Sierras Pampeanas, a new subduction regime started along the palaeo-Pacific margin in Late Carboniferous times (c. 320 Ma), which included younger pulses (Parada et al., 1999). At 33ºS the Late Palaeozoic batholiths occur both in the coast range of Chile and in the Frontal Cordillera, suggesting that no major continental accretion took place after the collision of the Western Sierras Pampeanas and associated Grenvillian blocks.et al., 2007), including the Precordillera (Fig.2). (2) Famatinian: 484-463 Ma convergent episode associated with the opening and closing of a large backarc basin in Early to Mid Ordovician times (Pankhurst et al., 2000; Dahlquist et al., 2008) (Fig.2). (3) Gondwanan: 320-190 Ma. After the intrusion of Devonian and Early Carboniferous (c. 380 and 340 Ma) intraplate A-type granites in the Sierras Pampeanas, a new subduction regime started along the palaeo-Pacific margin in Late Carboniferous times (c. 320 Ma), which included younger pulses (Parada et al., 1999). At 33ºS the Late Palaeozoic batholiths occur both in the coast range of Chile and in the Frontal Cordillera, suggesting that no major continental accretion took place after the collision of the Western Sierras Pampeanas and associated Grenvillian blocks.