Abstract
The dynamic effects of spreading ridge subduction on the geology of the overriding plate have been used to account for changes in upper-plate topography, erosion rates and patterns, and regional stress regimes in Cordilleran systems. This study used an orogen-scale thermochronological modeling data set of 55 samples in the southern Patagonian Andes (47°S–54°S) to derive the spatio-temporal patterns of rock cooling relative to Miocene–present ridge subduction and slab window emplacement. These results identify a northward-migrating record of rock cooling and interpreted uplift from 20 Ma to 5 Ma throughout the arc batholith and retroarc that predate the subduction of the Chile Ridge spreading center by 2–5 m.y. We interpret this signal as the first orogen-scale evidence from Patagonia that rock uplift and erosion in ridge subduction settings are primarily driven by the generation of a thickened crustal welt along the leading edge of the obliquely subducting ridge. This signal is uniform across tectonic domains >160 km from the trench, indicating that ridge subduction does not trigger concentrated deformation only in the retroarc fold-and-thrust belt, as has been suggested. Moreover, rock cooling ceases within 10–20 m.y. of slab window emplacement, suggesting that asthenospheric upwelling and heating do not produce measurable thermal resetting in the upper crust above the slab window. Multiple thermochronometers are required to model the time-temperature histories that capture northward-migrating uplift and rock cooling associated with subduction of the Chile Ridge, a signal that is not evident from thermochronometric ages alone.
