Late Cretaceous felsic intrusions in oceanic ...
Document type :
Article dans une revue scientifique: Article original
Title :
Late Cretaceous felsic intrusions in oceanic plateau basalts in SW Ecuador: Markers of subduction initiation?
Author(s) :
Seyler, M. [Auteur]
Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 [LOG]
Witt, C. [Auteur correspondant]
Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 [LOG]
Omaña, B. [Auteur]
Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 [LOG]
Durand, C. [Auteur]
Laboratoire de Génie Civil et Géo-Environnement (LGCgE) - ULR 4515 [LGCgE]
Chiaradia, M. [Auteur]
Villagomez, D. [Auteur]
Poujol, Marc [Auteur]
Géosciences Rennes [GR]
Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 [LOG]
Witt, C. [Auteur correspondant]
Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 [LOG]
Omaña, B. [Auteur]
Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 [LOG]
Durand, C. [Auteur]
Laboratoire de Génie Civil et Géo-Environnement (LGCgE) - ULR 4515 [LGCgE]
Chiaradia, M. [Auteur]
Villagomez, D. [Auteur]
Poujol, Marc [Auteur]
Géosciences Rennes [GR]
Journal title :
Journal of South American Earth Sciences
Pages :
103348
Publisher :
Elsevier
Publication date :
2021-10
ISSN :
0895-9811
English keyword(s) :
Caribbean oceanic plateau
Tonalite
Subduction initiation
SW Ecuador
Tonalite
Subduction initiation
SW Ecuador
HAL domain(s) :
Planète et Univers [physics]/Sciences de la Terre/Géochimie
English abstract : [en]
Felsic magmatic rocks (tonalites and trondhjemites) with calc-alkaline affinity were emplaced in SW Ecuador (Pascuales area; North Guayaquil) at ~87–89 Ma intruding the top of the basalts of the Caribean Large Igneous ...
Show more >Felsic magmatic rocks (tonalites and trondhjemites) with calc-alkaline affinity were emplaced in SW Ecuador (Pascuales area; North Guayaquil) at ~87–89 Ma intruding the top of the basalts of the Caribean Large Igneous Province (CLIP), prior to the development of typical well-known island arcs from ~85 to 80 Ma onwards. A clear depletion of REE distinguishes the Pascuales felsic rocks from the more differentiated lavas of the Rio Cala Arc in Ecuador and from other Late Cretaceous arc-like felsic intrusives emplaced within the CLIP in Colombia and the Antilles. In addition, the Pascuales tonalites have very low K2O (<0.4 wt%), TiO2 (<0.4 wt%) and P2O5 (<0.15 wt%) contents compared to dacitic rocks of the Rio Cala Arc. In contrast, their geochemistry and their similar age suggest that the Pascuales tonalites are an equivalent of the Las Orquideas dacitic volcanic rocks. The Pascuales felsic rocks have the less radiogenic Nd compositions of the whole spectrum of Ecuadorian oceanic plateau rocks, nevertheless shearing similarities with some Totoras amphibolites. The geochemical characteristics of the Pascuales intrusives and Las Orquideas dacites are similar to those formed by hydrous partial melting of mafic protoliths. The dacitic magmas must have been in equilibrium with residual mineral assemblages largely dominated by amphibole + Fe–Ti oxides (no garnet). This requires two conditions: 1) low-pressure melting under high water content and 2) a source rock extremely depleted in minor incompatible elements (K, Ti, P, Y) and REE. These conditions are fulfilled by partial melting of mafic-ultramafic cumulates undergoing high temperature and shear deformation at the base of the oceanic plateau triggered by new basaltic intrusions. The Pascuales felsic rocks emplaced at the SW border of the oceanic plateau during its final stage of building; they can thus be related to asthenopheric upwelling during the initial stage of island arc magmatism.Show less >
Show more >Felsic magmatic rocks (tonalites and trondhjemites) with calc-alkaline affinity were emplaced in SW Ecuador (Pascuales area; North Guayaquil) at ~87–89 Ma intruding the top of the basalts of the Caribean Large Igneous Province (CLIP), prior to the development of typical well-known island arcs from ~85 to 80 Ma onwards. A clear depletion of REE distinguishes the Pascuales felsic rocks from the more differentiated lavas of the Rio Cala Arc in Ecuador and from other Late Cretaceous arc-like felsic intrusives emplaced within the CLIP in Colombia and the Antilles. In addition, the Pascuales tonalites have very low K2O (<0.4 wt%), TiO2 (<0.4 wt%) and P2O5 (<0.15 wt%) contents compared to dacitic rocks of the Rio Cala Arc. In contrast, their geochemistry and their similar age suggest that the Pascuales tonalites are an equivalent of the Las Orquideas dacitic volcanic rocks. The Pascuales felsic rocks have the less radiogenic Nd compositions of the whole spectrum of Ecuadorian oceanic plateau rocks, nevertheless shearing similarities with some Totoras amphibolites. The geochemical characteristics of the Pascuales intrusives and Las Orquideas dacites are similar to those formed by hydrous partial melting of mafic protoliths. The dacitic magmas must have been in equilibrium with residual mineral assemblages largely dominated by amphibole + Fe–Ti oxides (no garnet). This requires two conditions: 1) low-pressure melting under high water content and 2) a source rock extremely depleted in minor incompatible elements (K, Ti, P, Y) and REE. These conditions are fulfilled by partial melting of mafic-ultramafic cumulates undergoing high temperature and shear deformation at the base of the oceanic plateau triggered by new basaltic intrusions. The Pascuales felsic rocks emplaced at the SW border of the oceanic plateau during its final stage of building; they can thus be related to asthenopheric upwelling during the initial stage of island arc magmatism.Show less >
Language :
Anglais
Peer reviewed article :
Oui
Audience :
Internationale
Popular science :
Non
Source :
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