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

Exposed cross-sections of the continental crust are a unique geological sit uation for crustal evolution studies, providing the possibility of decipher ing the time relationships between magmatic and metamorphic events at all l evels 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 migmatit es, peraluminous granites and amphibolite facies upper crustal gneisses pro vide constraints on the late-Hercynian peak metamorphism and granitoid magm atism as well as on the post-metamorphic cooling. Monazite from upper crust al 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 peraluminou s 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 t o intermediate sill in the lower crust yields a lower concordia intercept a ge of 290 +/- 2 Ma, which may be interpreted as the minimum age for metamor phism 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, th e lower crustal rocks were uplifted into mid-crustal levels (10-15 km) foll owed by nearly isobaric slow cooling (c. 3 degrees C Ma(-1)) as indicated b y 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 addre ssing metamorphic textures and P-T conditions of rocks from all crustal lev els, the new geochronological results are used to suggest that the thermal evolution and heat distribution in the Calabrian crust were mainly controll ed by advective heat input through magmatic intrusions into all crustal lev els during the late-Hercynian orogeny.