Reassessing long-term exhumation rates in magmatic terranes

Frances Cooper , Byron Adams, Simon Dahlström, Todd Ehlers, Matthijs van Soest, Kip Hodges, Brian Jicha, Brad Singer , Jaime Cortes Yañez, Rebecca Perkins

Crustal exhumation is central to mountain building, weathering, and sediment production processes, which significantly influence the composition and behavior of Earth’s oceans and atmosphere. It also controls the formation, enrichment, and preservation of porphyry copper deposits, which are a vital source of metals for the clean energy technologies underpinning the global green energy transition. Exhumation rates are typically determined from rock cooling histories combined with a geothermal model. However, in magmatically active regions, models can overpredict exhumation rates because the elevated heat signature is mistakenly attributed to advection driven by rapid exhumation. We present a method to accurately constrain exhumation histories in magmatic terranes that combines thermokinematic modeling of thermochronometric cooling histories with independent geobarometric constraints on the total exhumed crustal thickness. Focusing on the Central Andes, which has a prolonged history of magmatic and magmatic-hydrothermal activity, we find that accounting for this additional source of heat results in exhumed crustal thicknesses within error of the independent constraints, whereas ignoring it results in exhumed thicknesses up to four times greater than geologically plausible.