In situ U-Pb dating of zircons from five samples of Calabrian augen gneisses shows that their protoliths are Latest Precambrian to Early Cambrian in age (562 ± 15, 547 ± 7, 540 ± 4, 539 ± 16 and 526 ± 10 Ma), and contain Archaean (3.1 Ga), Palaeoproterozoic (1.7-2.4 Ga) and Neoproterozoic (0.6-0.9 Ga) inheritance. Geochemical signature of augen gneisses is typical of high-K calc-alkaline post-collisional magmatism. Their Sr-Nd isotopic compositions [0.7093 < ( 87 Sr/ 86 Sr) i < 0.7139; -3.2 < e Nd(t) < -5.4; 1.5 < T DM < 1.7 Ga] indicate the involvement of a crustal component in significant proportions. The Calabrian augen gneisses have, therefore, to be distinguished from the orthogneisses of Sardinia and northern Algeria, and from the porphyroids of Sicily, which are Middle Ordovician. By contrast, the Calabrian augen gneisses show a close similarity to the Pan-African post-collisional granitoids of the northern edge of the West African craton (e.g. the Moroccan Anti-Atlas). This suggests a periGondwana origin and corroborates previous palaeogeodynamic reconstructions attributing the Alboran microplate to the northern margin of the West African craton.

The lower crust of the Serre massif (Calabria,\ud southern Italy) provides a window into the mid- to lower\ud crust of the south European Variscan orogenic belt.\ud Previously, zircon U-Pb ages were employed to date\ud high-temperature processes affecting this portion of the\ud Variscan crust. The present paper reports new LAICP-\ud MS U-Pb data on the zircon of a deformed quartzmonzodiorite\ud dike and of three mafic granulites sampled\ud at the base of the lower crust section. Determination of\ud trace elements on zircon, including rare earth elements\ud (REE), has been also performed. The end of the Variscan\ud exhumation, dated by anatectic zircon from migmatitic\ud metapelites, and the growth-modification of zircon with\ud respect to the growth of Variscan metamorphic garnet\ud have been assumed as “time markers”. The concordant\ud zircon ages of the metamorphic basic rocks cover a\ud range from 744±20 Ma to 231±10 Ma with high age\ud density from 357±11 Ma to 279±10 Ma, a few ages\ud comprised between 418±14 Ma and 483±12 Ma and\ud between 505±11 Ma and 593±14 Ma. Zircon from the\ud deformed quartz-monzodiorite dike evidences a minimum age of emplacement of 323±5 Ma. Most of the analysed\ud zircon domains dated between 357±11 Ma to 279±10 Ma\ud from garnet-bearing metabasic rocks show flat patterns of\ud heavy rare earth elements (HREE), as expected in the case\ud of their simultaneous growth with garnet. This allows to\ud consider (1) zircon domains giving Variscan ages as\ud “metamorphic” with specific geological significance,\ud and (2) zircon domains with ages ranging from 564±17\ud Ma to 593±14 Ma as dating the emplacement of the\ud magmatic protoliths as shown by internal microtextures,\ud fractionated patterns of HREE and Th/U ratios (0.16–\ud 0.19). The Variscan zircon ages (357–279 Ma) reflect\ud effects of crustal thickening, peak metamorphism and\ud subsequent multistage Variscan decompression documented\ud by the statistically significant clusters of ages\ud around 347–340 Ma, 323–318 Ma, 300–294 Ma and\ud 279 Ma. The U-Pb zircon ages of the metabasic rocks\ud suggest a period of about 60–70 Ma for granulite facies\ud metamorphism and anatectic conditions. Literature data\ud indicate that the migmatitic metapelites of the upper part\ud of the Serre crust section also underwent a long period,\ud about 40 Ma, of granulite facies metamorphism and anatectic\ud conditions. A diachronism emerges through the time comparison\ud of the Variscan evolution between the upper and the\ud lower portions of the Serre deep crust. The duration of the\ud Variscan processes defined in Calabria is comparable to that of\ud other south European Variscan blocks

The paper presents the metamorphic trajectory recorded by metapelitic migmatites of\ud the upper part of the Hercynian lower continental crust of the Serre (southern Calabria, Italy). The\ud relict minerals, reaction textures and phase equilibria define a clockwise P–T path. The prograde\ud metamorphism from temperature of about 500 ◦C and pressure of 4–5 kbar to T<700 ◦C and\ud P∼8 kbar stabilized the assemblage Grt+Ky+Bt+Ms(Si/11ox=3.26–3.29) in the uppermost\ud metapelites of the profile. Progressive heating led to H2O-fluxed and dehydration melting first of\ud Ms, then of Bt at T<700 ◦C in the stability field of sillimanite. This process was followed by nearly\ud isothermal decompression producing additional melt with a transition from Grt to a Grt+Crd stability\ud field. Further decompression caused the formation of Crd-corona around garnet. Nearly isobaric\ud cooling led to rehydration and retrogression across the stability field of andalusite up to the stability\ud field of kyanite. The lowermost metapelites of the studied profile have lost most of the memory of\ud the prograde P–T path; they record decompression and cooling. High-temperature mylonites occur in\ud which boudinage, elongation and pull-aparts characterize the porphyroclasts. The pull-aparts in the\ud high-T mylonites are filled with low-P minerals (Crd+Spl). The Hercynian metamorphic trajectory\ud and the microtextures are consistent with crustal thickening and subsequent extensional regime. During\ud extension, an important tectonic denudation probably caused the isothermal decompression. Extension\ud also occurred in post-Hercynian times as documented by pull-aparts in sillimanite porphyroclasts filled\ud with chloritoid within a low-grade mylonite

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