UNIGE document Scientific Article
previous document  unige:19353  next document
add to browser collection
Title

Origin of Early Carboniferous pseudo-adakites in northern Brittany (France) through massive amphibole fractionation from hydrous basalt

Authors
Barboni, Mélanie
Published in Terra Nova. 2011, vol. 23, no. 1, p. 1-10
Abstract The first Variscan pseudo-adakites were identified in close association with the Saint-Jean-du-Doigt (SJDD) mafic intrusion (Brittany, France) in a geodynamic context unrelated to subduction. These rocks are trondhjemites emplaced 347 ± 4 Ma ago as 2–3 km2 bodies and dykes. Trace-element concen- trations and Sr–Nd–Pb isotope ratios indicate that the SJDD pseudo-adakites probably resulted from extreme differentiation of an SJDD-type hydrous basaltic magma in a lower continental crust of normal thickness (0.8 GPa). Modelling shows that garnet is not a required phase, which was commonly believedto be the case for continental arc-derived adakite-like rocks. A massive fractionation of amphibole fits the data much better and does not require high pressures, in agreement with the inferred extensional tectonic regime at the time of pluton emplacement. Alternatively, the SJDD pseudo-adakites could have resulted from the melting of newly underplated SJDD mafic precursors, but thermal considerations lead us to believe that this was not the case.
Identifiers
Full text
Structures
Research groups Isotope Geochemistry, Geochronology and Thermochronology
Mineral Resources and Geofluids
Citation
(ISO format)
BARBONI, Mélanie, BUSSY, François, CHIARADIA, Massimo. Origin of Early Carboniferous pseudo-adakites in northern Brittany (France) through massive amphibole fractionation from hydrous basalt. In: Terra Nova, 2011, vol. 23, n° 1, p. 1-10. https://archive-ouverte.unige.ch/unige:19353

200 hits

0 download

Update

Deposited on : 2012-04-02

Export document
Format :
Citation style :