Horizon / Plein textes La base de ressources documentaires de l'IRD

IRD

 

Publications des scientifiques de l'IRD

Ancellin M. A., Vlastelic I., Samaniego Pablo, Nauret F., Gannoun A., Hidalgo S. (2019). Up to 1% Pb isotope disequilibrium between minerals hosted in dacites from the Guagua Pichincha volcano, Ecuador : implication for tracing the source and crustal history of continental arc magmas. Chemical Geology, 525, 177-189. ISSN 0009-2541

Accès réservé (Intranet IRD) Demander le PDF

Lien direct chez l'éditeur doi:10.1016/j.chemgeo.2019.07.016

Titre
Up to 1% Pb isotope disequilibrium between minerals hosted in dacites from the Guagua Pichincha volcano, Ecuador : implication for tracing the source and crustal history of continental arc magmas
Année de publication2019
Type de documentArticle référencé dans le Web of Science WOS:000501715700013
AuteursAncellin M. A., Vlastelic I., Samaniego Pablo, Nauret F., Gannoun A., Hidalgo S.
SourceChemical Geology, 2019, 525, p. 177-189. ISSN 0009-2541
RésuméContinental arc lavas display geochemical signatures that reflect both mantle metasomatism by slab fluids or melts and extensive differentiation of magmas within crustal reservoirs. The relative effect of source and crustal processes are difficult to disentangle based on whole-rock compositions. This issue is critical in Ecuador where volcanism occurs through a thick continental crust (> 50 km). This study reconstructs the history of melts feeding the Guagua Pichincha volcano, Western Cordillera, by analysing the Pb isotope composition and major-trace element content of individual minerals (33 amphiboles, 4 orthopyroxenes and 18 plagioclases) hosted in two dacite samples. It uses a low-blank wet-chemistry method for precise analysis of Pb amounts as low as 150 pg. Early crystallized, high-Al amphiboles with Al2O3 >= 9.8 wt% and Eu/Eu* > 0.7 have the lowest and most heterogeneous Pb-206/Pb-204 (18.816-18.999), whereas plagioclases have the highest and most homogeneous Pb-206/Pb-204 (19.003-19.023). Low-Al amphiboles and orthopyroxenes display intermediate compositions and variability (18.934-19.007). The Pb-206/Pb-204 ratio correlates negatively with Eu/Eu* in amphiboles and orthopyroxenes, which indicates that the Guagua Pichincha magmas assimilate radiogenic Pb within the stability field of plagioclase (i.e. in the upper crust). The radiogenic ankaramites of the Guaranda unit, an accreted ocean terrain making the basement of the Western Cordillera, are the most suitable contaminant. If this is correct, the Pb-206/Pb-204 increase from the two most primitive amphiboles to their respective host rocks requires ca. 20% crustal assimilation, which is higher than previous estimates in the Northern Volcanic Zone but similar to those inferred for Central Andean mafic lavas. The two most primitive amphiboles with no significant Eu anomaly record the composition of melts before plagioclase crystallization. These deep melts have contrasted Pb-206/Pb-204 ratios (18.816-18.879) and contents of fluid mobile elements (Li, Cu, Rb, Pb) that probably reflect the input of different slab components to the mantle wedge. Melts in equilibrium with the two most primitive amphiboles of the Guagua Pichincha volcano are enriched in incompatible elements, but depleted in fluid mobile elements compared to the olivine-hosted melt inclusions of the older Rucu Pichincha volcano. This supports previous inferences based on whole-rock data that the mantle source of the Pichincha Volcanic Complex has changed through time.
Plan de classementGéophysique interne [066]
Descr. géo.EQUATEUR ; GUAGUA PICHINCHA VOLCAN
LocalisationFonds IRD [F B010077439]
Identifiant IRDfdi:010077439
Lien permanenthttp://www.documentation.ird.fr/hor/fdi:010077439

Export des données

Disponibilité des documents

Télechargment fichier PDF téléchargeable

Lien sur le Web lien chez l'éditeur

Accès réservé en accès réservé

HAL en libre accès sur HAL


Accès aux documents originaux :

Le FDI est labellisé CollEx

Accès direct

Bureau du chercheur

Site de la documentation

Espace intranet IST (accès réservé)

Suivi des publications IRD (accès réservé)

Mentions légales

Services Horizon

Poser une question

Consulter l'aide en ligne

Déposer une publication (accès réservé)

S'abonner au flux RSS

Voir les tableaux chronologiques et thématiques

Centres de documentation

Bondy

Montpellier (centre IRD)

Montpellier (MSE)

Cayenne

Nouméa

Papeete

Abidjan

Dakar

Niamey

Ouagadougou

Tunis

La Paz

Quito