Evidence of slab tearing on an inherited Mesozoic rift transfer fault in the Betic Cordillera

Abstract

Abstract The Western Mediterranean has undergone complex subduction and collision between the African and Iberian plates, influenced by slab segmentation and melt generation. Despite numerous studies aimed at understanding these connections, the style of subduction remains controversial. Utilizing a compilation of geophysical data and a new map of magmatic suites along the Western Betic Cordillera, along with geochemical and geochronological analyses, this paper presents a 3D reconstruction of a segmented subducting slab beneath the Gibraltar Arc, with a focus on the nature and timing of slab tearing and magmatism. Results suggest that magmatism was coeval with the retreating of subduction and slab tearing along the Antequera Fault Zone, a reactivated Mesozoic rift transfer fault. Slab tearing facilitated asthenospheric upwelling, triggering a localized thermal pulse in the upper plate during the Early Miocene. Zircon U–Pb geochronology witnesses this thermal event with the formation, emplacement, and crystallization of leucogranitic melts at low-pressure conditions, featuring both simple zircons (sometimes with inherited cores) and complex zircons (with rim dissolution and regrowth in host metamorphic units). Our findings demonstrate how inherited rift-related structures can drive slab tearing and asthenospheric upwelling, shaping the spatial and temporal patterns of magmatism and high-temperature metamorphism in complex subduction systems.