IDEAN   23403
INSTITUTO DE ESTUDIOS ANDINOS "DON PABLO GROEBER"
Unidad Ejecutora - UE
artículos
Título:
Early andean tectonomagmatic stages in North Patagonia: Insights from field and geochemical data
Autor/es:
OLIVEROS, VERÓNICA; CREIXELL, CHRISTIAN; FOLGUERA, ANDRÉS; LUCASSEN, FRIEDRICH; ECHAURREN, ANDRÉS; IBARRA, FEDERICO
Revista:
JOURNAL OF THE GEOLOGICAL SOCIETY
Editorial:
GEOLOGICAL SOC PUBL HOUSE
Referencias:
Lugar: Londres; Año: 2017 vol. 174 p. 405 - 421
ISSN:
0016-7649
Resumen:
The Andes in northern Patagonia are mainly formed by Mesozoic magmatic units: the mostly Jurassic-Cretaceous North Patagonian Batholith and volcanism of the Jurassic Lago La Plata (Ibáñez) Formation as well as the mid-Cretaceous Divisadero Group. These rocks represent the development of a magmatic belt through Jurassic-mid-Cretaceous time, during a switch of the tectonic regime from extension to compression. To study arc evolution during this transition, we carried out fieldwork and geochemical sampling at c. 43°S, clarifying structural relationships and characterizing the magmatic sources. Multi-element diagrams for both volcanic units suggest a slab-derived signature, whereas isotopic ratios (Sr-Nd-Pb) indicate parental melts sourced from the subduction-modified asthenospheric mantle interacting with crustal sources during their emplacement. An angular unconformity is identified between the synextensional Jurassic volcanic rocks and Lower Cretaceous sedimentary rocks beneath the mid-Cretaceous sequences. Although this deformational event was simultaneous with generalized overriding plate compression, geochemical ratios indicate an immature Aptian-Albian arc with no associated crustal thickening. Late Jurassic to mid-Cretaceous arc settlement after a trenchward retraction of magmatism from the foreland between c. 41 and 45°S, with an associated increase in slab dip angle, may have provoked crustal softening facilitating the subsequent initial fold-thrust belt growth.