Demouy S., Paquette J. L., de Saint Blanquat M., Benoit M., Belousova E. A., O'Reilly S. Y., Garcia F., Tejada L. C., Gallegos R., Sempéré Thierry. (2012). Spatial and temporal evolution of Liassic to Paleocene arc activity in southern Peru unraveled by zircon U-Pb and Hf in-situ data on plutonic rocks. Lithos, 155, p. 183-200. ISSN 0024-4937.
Titre du document
Spatial and temporal evolution of Liassic to Paleocene arc activity in southern Peru unraveled by zircon U-Pb and Hf in-situ data on plutonic rocks
Demouy S., Paquette J. L., de Saint Blanquat M., Benoit M., Belousova E. A., O'Reilly S. Y., Garcia F., Tejada L. C., Gallegos R., Sempéré Thierry
Source
Lithos, 2012,
155, p. 183-200 ISSN 0024-4937
Cordilleran-type batholiths are built by prolonged arc activity along active continental margins and provide detailed magmatic records of the subduction system evolution. They complement the stratigraphic record from the associated forearcs and backarcs. We performed in-situ U-Pb geochronology and Hf isotope measurements on zircon grains from a large set of plutonic rocks from the Coastal Batholith in southern Peru. This batholith emplaced into the Precambrian basement and the Mesozoic sedimentary cover. We identify two major periods of voluminous arc activity, during the Jurassic (200-175 Ma) and the Late Cretaceous-Paleocene (90-60 Ma). Jurassic arc magmatism mainly resulted in the emplacement of a dominantly mafic suite with epsilon(Hf) values ranging from -9.5 to +0.1. Published ages south of the Arequipa area suggest that the arc migrated southwestward out of the study area during the Middle Jurassic. After a magmatic gap of 85 Ma, arc activity abruptly resumed 90 Ma ago in Arequipa. Intrusive bodies emplaced into both basement and older Jurassic intrusions and strata. This activity culminated between 70 and 60 Ma with the emplacement of very large volumes of dominantly quartz-dioritic magmas. This last episode may be considered as a flare-up event, characterized by intense magmatic transfers into the crust and rapid relief creation. The Late Cretaceous-Paleocene initial EH( are shifted toward positive values (up to +3.3 and +2.6) compared to the Jurassic ones, indicating either a larger input of juvenile magmas, a lesser interaction with the ancient crust, or an increase of re-melting of young mantle-derived mafic lower crust. These magmatic fluxes with juvenile component are coeval with the onset of the crustal thickening at 90 Ma and represent a significant ontribution to the formation of the continental crust in this area.
Plan de classement
Géologie et formations superficielles [064]
;
Géophysique interne [066]
