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The application of the SHRIMP U/Pb dating technique to zircon and monazite of different rock types of the Sierras de Córdoba provides an important insight into the metamorphic history of the basement domains. Additional constraints on the Pampean metamorphic episode were gained by Pb/Pb stepwise leaching (PbSL) experiments on two titanite and garnet separates. Results indicate that the metamorphic history recorded by Crd-free gneisses (M2) started in the latest Neoproterozoic/earliest Cambrian (553 and 543 Ma) followed by the M4 metamorphism at

The Austroalpine basement underwent a multistage Precambrian to Tertiary evolution. Meta-magmatic rocks occur in pre-Early Ordovician and post-Early Ordovician units. Protolith zircon ages and whole-rock trace element data define two magmatic evolution lines. An older trend with Th/Yb typical of subduction-related metamorphism, started by 590 Ma N-MORB-type and 550–530 Ma volcanic arc basalt-type basic suites which mainly involved depleted mantle sources, and was continued by mainly crustal-source 470–450 Ma acid magmatic suites. A presumably younger evolution by tholeiitic MORB-type and 430 Ma alkaline within-plate basalt-type suites is characterized by an intraplate mantle metasomatism and multicomponent sources. These magmatic trends can be related to a Neoproterozoic to Ordovician active margin and a subsequent Palaeo-Tethys passive margin along the north-Gondwanan periphery. During Variscan collision, the Austroalpine basement underwent multiphase deformation and metamorphism. Early deformation involved non-coaxial shearing with formation of sheath folds and calcsilicategneiss bodies in some regions. Syndeformational clockwise P–T paths in lower basement parts passed high-pressure and high-temperature amphibolite-facies stages and are interpreted by a Devonian to Carboniferous crustal stacking. A post-collisional Permian thermal event is documented by pegmatite intrusions, LP-HT assemblages and monazite ages. Ductile overprinting under greenschist-facies conditions during the Cretaceous is indicated by foliated pegmatites and monazite ages in samples with retrogressed garnet. The emplacement of the Oligocene Rieserferner pluton was controlled by sinistral shear zone deformation along the Defereggen–Antholz–Vals line. Shear zone activity ceased at 15 Ma and was superseded by brittle strike-slip movements along NW and SE trending faults.

The Ivrea Zone (southern Alps) is one of the key regions interpreted as exposing a section of the lower continental crust and was the subject of several review-type articles. The Ivrea–Verbano Zone was rotated into an upright position along the Insubric mylonite belt. In the southeast, this unit is in contact with the Strona Ceneri Zone, which is interpreted as upper continental crust crossing the Permian Cossato–Mergozzo–Brissagio Line (CMB Line). The CMB mylonites are locally overprinted by the mylonites and cataclasites of the Pogallo Line, which was active during the Jurassic. In addition, the sinistral, steeply inclined Rosarolo shear zone was active over a long time span from the ductile into the brittle field, i.e. from the Early Permian (high-temperature ultra-mylonites) to the Neo-Alpine basic dykes and pseudotachylites. The high-temperature mylonites accommodated crustal extension and may be related to normal faults generated by magmatic underplating. The reactivation at different crustal levels during exhumation and tilting is documented by strain increments at decreasing P/T conditions. Its present subvertical orientation was attained during the Neo-Alpine deformation. Constraints on its exhumation history are based on new 40Ar/39Ar hornblende ages, K–Ar biotite ages and zircon fission-track data along the NE–SW trending Valstrona section. A re-interpretation of existing U–Pb monazite ages is included, based on a higher closure temperature for monazite. The oldest monazite ages are observed in proximity to the Pogallo Line (c. 292 Ma). Heat input by mafic intrusions was sufficient to reset the U–Pb monazite system, as is evidenced by the youngest ages in the vicinity of the Insubric Line. The re-interpretation favours the hypothesis that the oldest monazite ages are the result of complete resetting by a Permian thermal event. The 40Ar/39Ar hornblende ages and K–Ar biotite ages document the cooling after Permian heating. Roughly parallel age progressions decrease from the Pogallo Line (hornblende: 271 Ma vs. biotite: 227 Ma) towards the Insubric Line (hornblende: 201 Ma vs. biotite: 156 Ma). Zircon fission-track ages run parallel to the biotite ages in the upper part of the profile, whereas towards the Insubric Line a significant deviation from the biotite age progression is attributed to tilting of the basement during the Oligocene. Zircon fission-track ages around 38 Ma are found close to the Insubric Line. No age offset, neither at the CMB nor at the Pogallo Line, is observed. This confirms the hypothesis that the Pogallo Line is an oblique normal fault, and that the CMB Line has accommodated only minor vertical displacement. The capture of the different cooling ages confirms the tilting of the Ivrea–Verbano Zone during the Neo-Alpine deformation and contradicts the tilting of the Ivrea–Verbano Zone during the Permian.

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