Resumen de Low Temperature Thermochronology and Tectonics in the Chiloe Region, Southern Chilean Andes (41°-43°S; 72°-74°W)
Fission track (FT) dating o f zircon and apatite combined with microfabric analyses on deformed rocks are applied to determine the low-temperature thermal history and uplift/erosion rates o f the north Patagonian Andes, in relation to the latest movements o f the Liquihe-Ofqui Fault Zone (LOFZ). FT Time-temperature profiles are obtained from collected samples across the main lineaments of the LOFZ within the Chiloe Region (41 °-43°S; 72°-74°W), and compared with available Rb-Sr,K-Ar and Ar-Ar ages. In the Reloncavi sector o f the LOFZ (4I°21 ’-42°S), apatite FT ages range up to 3.3 +/- 1.2 M.a within the fault zone, whereas outside older ages are registered. Increasing cooling rates from west to east on the western block o f the fault are shown by the apatite track length distribution, whereas along the fault zone itselfvery rapid cooling rates are implied. Microstructural studies on deformed tonalites from the Isla Llancahue-Cholgo demostrate ductile deformation under high strain /low temperature conditions (low temperature plasticity regime fo r quartz).
Together with the FT data this evidence is compatible with high rates o f uplift/ erosion due to late Cenozoic tectonics along the LOFZ.
