Mantle driven cretaceous flare-ups in Cordilleran arcs

Abstract

© 2018 The AuthorsContinental arcs display episodic magmatism characterized by flare-ups and lulls. Models published to explain these patterns invoke (1) upper plate crustal processes driven by internal feedback; (2) episodic mantle melting processes, or (3) external lower plate tectonic events. This study addresses the role of mantle magmas during flare-ups in Mesozoic Cretaceous continental arcs using geochronological and geochemical data for three Cretaceous arc segments: the western Peninsular Ranges Batholith (wPRB), the Peruvian Coastal Batholith (PCB), and the Chilean Coastal Batholith (CCB). In all three arc segments, bedrock zircon age patterns defining a flare-up from ~125 to 90 Ma characterized by gabbro to granite units with Sri < 0.705, ƐNd from 0 to +7.5, 208Pb/204Pb from 38.2 to 38.7, and 206Pb/204Pb from 18.3 to 18.7. These values project well towards a depleted mantle source. Areal measurements show that gabbro forms ~18% (wPRB), ~24% (PCB), and ~10% (CCB) of exposed p