Evolution of Eocene to Oligocene arc-related volcanism in the North Patagonian Andes (39–41°S), prior to the break-up of the Farallon plate

Voluminous Paleogene magmatic rocks (44 to 29 Ma) are found in a retroarc position in the Northern Patagonian to Southern Central Andes (~ 39–42°S), whose origin remains controversial. Geochemical data in these Eocene to Oligocene volcanic associations are herein used to unravel their origin and und...

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Detalles Bibliográficos
Autores principales: Iannelli, S.B., Litvak, V.D., Fernández Paz, L., Folguera, A., Ramos, M.E., Ramos, V.A.
Formato: JOUR
Materias:
Arc volcanism
Eocene-Oligocene
Geochemistry
Patagonian Andean margin
Tectonic evolution
Geodynamics
Compositional variation
Geochemical data
Geochemical signatures
Oligocene
Plate configuration
Tectonics
Eocene
geochemistry
magmatism
subduction zone
tectonic evolution
tectonic plate
volcanism
Andes
Patagonia
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_00401951_v696-697_n_p70_Iannelli
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
Descripción
Sumario:Voluminous Paleogene magmatic rocks (44 to 29 Ma) are found in a retroarc position in the Northern Patagonian to Southern Central Andes (~ 39–42°S), whose origin remains controversial. Geochemical data in these Eocene to Oligocene volcanic associations are herein used to unravel their origin and understand changes in subduction parameters. Geochemical signatures indicate arc-related associations and reflect changing geodynamic boundary conditions of the Andean margin through time. In particular, Eocene magmatism (~ 44 Ma; Pilcaniyeu Belt) shows an alkaline-like signature and limited slab influence. Reported contemporaneous within-plate magmatism (~ 47–43 Ma) in an easternmost position reflects a more typical enriched source. Oligocene arc-like volcanism (~ 29 Ma; El Maitén Belt), which developed in an extensional retroarc setting, shows a higher contribution from slab-derived fluids and a calc-alkaline source. A comparison with younger arc-related magmas from the region (~ 26–20 Ma), emplaced in an intra- to retroarc position (Cura Mallín and Abanico basins), indicates a progressive increase in slab-signature, associated with a tholeiitic magma source. We propose that these compositional variations could be directly related to changes in plate configuration before and after the Farallon plate break-up and the initiation of a more orthogonal convergence typical of the present Andean-type subduction zone. © 2016 Elsevier B.V.

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