摘要：Above subduction zones, magma production rate and crustal generation can increase by an order of magnitude during narrow time intervals known as magmatic flare-ups. However, the consequences of these events in the deep arc environment remain poorly understood. Here we use petrological and in-situ zircon dating techniques to investigate the root of a continental arc within the collisional West Gondwana Orogen that is now exposed in the Kaby Massif, Togo. We show that gabbros intruded 670 million years ago at 20-25 km depth were transformed to eclogites by 620 million years ago at 65-70 km depth. This was coeval with extensive magmatism at 20-40 km depth, indicative of a flare-up event which peaked just prior to the subduction of the continental margin. We propose that increased H2O flux from subduction of serpentinized mantle in the hyper-extended margin of the approaching continent was responsible for the increased magma productivity and crustal thickening. Dehydration of serpentinised mantle during subduction of the hyper-extended margin of an approaching continent drove a magmatic flare-up which caused crustal thickening recorded in the Kaby Massif, Togo, according to petrological and geochronological analyses.
