Journal
JOURNAL OF SOUTH AMERICAN EARTH SCIENCES
Volume 103, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jsames.2020.102713
Keywords
Continental arc volcanism; Geochemistry; Isotopes; Subduction dynamics; Slab rollback
Categories
Funding
- CONICET [11220150100426C0]
- University of Buenos Aires [UBACYT 20020150100166BA]
- ANPCyT [PICT-2012-1490, PICT-2014-2240, PICT-2017-3259]
- Fondecyt [1151146]
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During Mid-Cenozoic times, voluminous and genetically heterogeneous volcanism took place across North Patagonia in response to a period of plate tectonic reorganization. One of these volcanic associations is represented by the El Maiten Belt, located to the east of the main Andes for over similar to 300 km. This volcanic belt reflects the evolution of a continental arc in an extensional setting with remarkable compositional variations between the late Eocene and the early Miocene. We present new field and isotopic data that, together with lithological, geochronological and geochemical data compilations, suggest significant changes in the nature and location of magmatic sources. This evolution may be summarized in three stages: i) incipient arc magmatism, with a tholeiitic basaltic-basaltic andesitic composition, which evolved to ii) a mature arc, characterized by calcalkaline andesitic-dacitic associations, and a final stage characterized by iii) a late Oligocene-early Miocene juvenile, tholeiitic basaltic volcanism, interpreted as the result of a westward arc migration and extension in the back-arc. Therefore, considering the mid-Cenozoic tectonic configuration given by the eastward subduction of the Farallon and Nazca plates, we evaluate slab dynamics within a petrological framework that can reproduce the geochemical-geochronological characteristics of this belt. In this sense, rollback of the Nazca plate is the most suitable scenario to explain the El Maiten Belt behavior during this protracted extensional regime of Andean evolution.
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