Thermotectonic history of the Marañón Fold–Thrust Belt, Peru: Insights into mineralisation in an evolving orogen

• New thermochronology data constrain evolution of the Marañón Fold–Thrust Belt, Peru.
• Structural evolution involved two discrete intervals of crustal deformation.
• Earlier deformation at ~ 80–20 Ma involved east-vergent thin-skinned tectonics.
• Later deformation at ~ 20–0 Ma involved west-vergent thick-skinned tectonics.
• Thick-skinned contraction coincided with increased focusing of mineralising fluids.

Fold–thrust belts along convergent margins around the world host major ore deposits. The origin of such ore deposits is commonly episodic and so are the temporal and spatial variations in deformation styles in these fold–thrust belts. Here we focus on the Marañón Fold–Thrust Belt (MFTB) of the Peruvian Andes, and demonstrate a link between the spatio-temporal distribution of ore deposits and thick-skinned tectonics. We present low-temperature thermochronology results from the MFTB that document the uplift/exhumation history and timing of thick-skinned tectonics and vergence reversal. Our results suggest that the thermal history of the MFTB involved two discrete intervals of opposed-vergence, large-scale crustal deformation since the Late Cretaceous. An early interval, at ~ 80–20 Ma, was associated with folding and east-vergent thin-skinned tectonics, and was followed by west-vergent thick-skinned deformation at ~ 20–0 Ma. Furthermore, our findings suggest that thick-skinned contraction was coincident with increased focusing of mineralising fluids and ore deposition in the MFTB during the early Miocene, and in the mid-Miocene both mineralisation and deformation were enhanced by subduction of the Nazca Ridge underneath the South American Plate.