Geochronological constraints on the timing of granitoid magmatism, metamorphism and post-metamorphic cooling in the Hercynian crustal cross-section of Calabria

TLDR: In this article, the authors used geochronological results to suggest that the thermal evolution and heat distribution in the Calabrian crust were mainly controlled by advective heat input through magmatic intrusions into all crustal levels during the late Hercynian orogeny.

Abstract: Exposed cross-sections of the continental crust are a unique geological situation for crustal evolution studies, providing the possibility of deciphering the time relationships between magmatic and metamor- phic events at all levels of the crust. In the cross-section of southern and northern Calabria, U-Pb, Rb-Sr and K-Ar mineral ages of granulite facies metapelitic migmatites, peraluminous granites and amphibolite facies upper crustal gneisses provide constraints on the late-Hercynian peak metamorphism and granitoid magmatism as well as on the post-metamorphic cooling. Monazite from upper crustal amphibolite facies paragneisses from southern Calabria yields similar U-Pb ages (295-293±4 Ma) to those of granulite facies metamorphism in the lower crust and of intrusions of calcalkaline and metaluminous granitoids in the middle crust (300±10 Ma). Monazite and xenotime from peraluminous granites in the middle to upper crust of the same crustal section provide slightly older intrusion ages of 303-302±0.6 Ma. Zircon from a mafic to intermediate sill in the lower crust yields a lower concordia intercept age of 290± 2M a, which may be interpreted as the minimum age for metamorphism or intrusion. U-Pb monazite ages from granulite facies migmatites and peraluminous granites of the lower and middle crust from northern Calabria (Sila) also point to a near-synchronism of peak metamorphism and intrusion at 304- 300±0.4 Ma. At the end of the granulite facies metamorphism, the lower crustal rocks were uplifted into mid-crustal levels (10-15 km) followed by nearly isobaric slow cooling (c .3 ° CM a'1) as indicated by muscovite and biotite K-Ar and Rb-Sr data between 210±4 and 123±1 Ma. The thermal history is therefore similar to that of the lower crust of southern Calabria. In combination with previous petrological studies addressing metamorphic textures and P-T conditions of rocks from all crustal levels, the new geochronological results are used to suggest that the thermal evolution and heat distribution in the Calabrian crust were mainly controlled by advective heat input through magmatic intrusions into all crustal levels during the late-Hercynian orogeny.