Trench retreat recorded by a subduction zone metamorphic history

Abstract Upper amphibolite-facies metamorphism in subduction zone rocks may occur under exceptional tectonic settings. Differentiating competing mechanisms for its occurrence requires carefully integrated, high-resolution thermobarometric and geochronologic studies of mélange with well-defined field relationships. We present new pressure, temperature, age data from the classic Cretaceous Catalina Schist southern California (USA) that allow us to establish a plausible model high-temperature metamorphic history. Our results indicate garnet-amphibolite blocks structurally highest preserve evidence three stages evolution: (1) prograde lawsonite eclogite-facies peaked at 2.4–2.7 GPa temperatures >580 °C during fixed-trench (120–115 Ma); (2) post-peak epidote followed by 1.4–1.3 740–790 trench retreat (115–105 (3) isothermal decompression (1.3 <1.0 ~780 °C) cooling advance slab-flattening (ca. 105–100 Ma). implies presence continuous Cordilleran system Cretaceous, which had varying regimes through episodes retreat/advance slab shallowing/steepening that, turn, dictated development arc system.