Tectonic denudation of the Darwin metamorphic core complex in the Andes of Tierra del Fuego, southernmost Chile: Implications for Cordilleran orogenesis

Abstract

Cordillera Darwin in the southernmost Chilean Andes is a tectonically denuded metamorphic similar to those widely developed in the North American Cordillera. Detailed comparison can be drawn with the Shuswap metamorphic in British Columbia and Washington. Analysis of the geotectonic history of the Darwin reinforces the view that the presence of tectonically thickened continental crust is critical for development of most, if not all, known complexes and also suggests that inversion of a marginal basin during a compressional regime is one way of initiating such a crustal welt. The Cordillera Darwin is unique in the Andes and Antarctandes. This indicates that although low-angle normal faulting occurs at high levels in convergent plate settings such as the Central Andes and the Himalayas, extensional denudation of deep crustal levels in active Andean-type orogens may require special tectonic circumstances. Uplift of the Darwin began at about 70 Ma in a localized extensional setting within the developing transform zone between the South American and Antarctic plates. This strike-slip setting is analogous to some metamorphic complexes in North America and possibly to a recently identified core complex in New Zealand. It is likely to be a common one for complexes in convergent orogens.