Cenozoic arc-related magmatism in the southern Central and North Patagonian Andes

Abstract

Variable geodynamic contexts have been registered throughout the Cenozoic in the southern Central and North Patagonian Andes. Significantly, these geodynamic changes have controlled the development of arc-related volcanism, as seen in the intensity, volume, extent, location and, primarily, in the geochemical signature of the resulting arc volcanic products. Contrasting and variable patterns are seen in arc-related magmatism developed along the southern Central Andes (~ 29°?38°) and North Patagonian Andes (~ 39°?46°) during the Cenozoic: (i) Paleocene to middle Eocene arc stage was characterized by volumetrically limited arc magmatism, in a context of an oblique subduction setting and extension affecting the upper plate; (ii) during the late Eocene to early Oligocene, arc-relatedvolcanism comprises dispersed and isolated sections through both southern Central and North Patagonian Andes while extensional deformation prevailed; (iii) during the late Oligocene (~ 26?23 Ma), arc magmatism developed with typical tholeiitic to calc-alkaline features in southern Central Andes due toa major change in plate configuration that caused the initiation of an orthogonal subduction; meanwhile in North Patagonian Andes, magmas experienced a change to a mostly tholeiitic composition, associated with the opening of extensional intra-arc and retroarc basins; (iv) finally, during middle Miocene to middle Pliocene (~ 18?4 Ma), arc volcanism prevailed in southern Central Andes linked to a progressive shallow subduction regime that led to its eastward expansion and the development of the present-day Pampean-Chilean flat-slab segment and the late Miocene Payenia shallow subduction segment meanwhile, in North Patagonian Andes, coeval arc magmatism was mainly restricted to the main Andean axis in association with the intra-arc Liquiñe-Ofqui Fault Zone (LOFZ), 1999), experiencing short excursions to the foreland in discrete zones, presumably in association with shallow subduction regimes.