>2500-km-Long Contemporaneous Deep Continental Subduction in the West Gondwana Orogen

Thursday, 18 December 2014
Daniela Rubatto1, Carlos E Ganade de Araujo2,3, Joerg Hermann1, Umberto Giuseppe Cordani3, Renaud Caby4 and Miguel A. S. Basei3, (1)Australian National University, Canberra, Australia, (2)Geological Survey of Brazil, Rio de Janeiro, Brazil, (3)Inst Geosciences - USP, São Paulo, Brazil, (4)University of Montpellier II, Geosciences Montpellier, Montpellier Cedex 05, France
The 5000-km-long, deeply eroded West Gondwana Orogen (WGO) is a major continental collision zone that exposes numerous occurrences of deeply subducted rocks (i.e. eclogites) along its strike. The position of these eclogites marks the suture zone between colliding cratons and the age of metamorphism constrains the transition from subduction-dominated tectonics to continental collision and mountain building. We investigated the metamorphic conditions and age of high-pressure (HP) and ultrahigh-pressure (UHP) eclogites from Mali, Togo and NE-Brazil . P-T estimates confirm UHP to HP conditions for all these localities. The U-Pb age and trace element composition of metamorphic zircon domains demonstrate that continental subduction in the WGO occurred within 20 m.y. over at least 2500 km during the Ediacaran period (620-610 Ma). We consider this to be the first record of modern, large-scale deep-continental subduction and the consequent appearance of Himalayan-scale mountains in the geological record. The rise of such mountains in the Late Ediacaran is perfectly timed to deliver by erosion the sediments (nutrients) that have been deemed necessary for life sustainability in the following Earth evolution.