Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4691815 | Tectonophysics | 2014 | 12 Pages |
Abstract
High-precision SIMS U-Pb zircon age determinations are conducted in this study on migmatites and Mg-K magmatic suites from the Variscan orogen of Corsica (France). Zircons from leucosomes of four migmatites yield consistent crystallization ages of ca. 345Â Ma. Four Mg-K granitoid rocks and one monzogabbro enclave from the Calvi-IIe Rousse pluton of NW Corsica yield indistinguishable U-Pb zircon ages of ca. 330Â Ma. These new SIMS zircon U-Pb dating results indicate that the regional crustal anatexis under amphibolite-facies condition occurred synchronously at ca. 345Â Ma throughout the Corsican Variscan chain. There is a ca. 15Â m.y. time interval between anatexis of the thickened crust and partial melting of the metasomatized mantle and overlying crust to form the Mg-K rock suites. In combination with the previous dating results for the high-temperature and high-pressure granulite-facies metamorphism, three major discrete tectonothermal events at ca. 360Â Ma, ca. 345Â Ma, and ca. 330Â Ma are acknowledged. We argue for a slab break-off model accounting for thermal and mechanical evolution of the crust within the Variscan orogen of Corsica. A tearing of the subducting oceanic lithosphere initiates the asthenosphere rise to fill the void and causes the granulite-facies metamorphism of the overlying continental crust at ca. 360Â Ma. Final breaking of the subducting oceanic lithosphere results in exhumation of the subducted crust to the thickened lower to middle crustal-level. Internal radiogenic heating causes crust-scale migmatization at ca. 345Â Ma. Slab break-off and foundering enhance the rise of hot asthenosphere, resulting in conducted thermal perturbation that leads to melting of the metasomatised enriched mantle lithosphere to form Mg-K mafic-granitoid magmatism at ca. 330Â Ma.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Earth-Surface Processes
Authors
Xian-Hua Li, Michel Faure, Wei Lin,