Petrology of contact metamorphic metapelites from the southern rim of the Permian Brixen Granodiorite (South Tyrol, italy)

Wyhlidal, Stefan; Thöny, Werner F.; Tropper, Peter; Kaindl, Reinhard; Hauzenberger, Christoph; Mair, Volkmar

doi:10.1007/s00710-012-0240-8

Cited by 6 publications

(1 citation statement)

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“…The superimposition of such an elevated thermal state in the pre-Alpine basement suggests that the thermal softening of the continental lithosphere at the end of the Variscan convergence may have led to the localization of Permian-Triassic weakened zones in the Alpine area. The inferred evolution makes unique this portion of the Southalpine basement with respect to the other units, where the thermal record of the late-collisional evolution is instead registered at deeper crustal levels, as testified by sillimanite and/or cordierite with andalusite [42,44,49,103,104]. This contribution indicates that the high thermal regime affecting Southalpine basement rocks during pre-Alpine times may also result from late-Variscan orogenic collapse and not only by Permian-Triassic lithospheric thinning.…”

Section: Discussionmentioning

confidence: 99%

Cld-St-And-Bearing Assemblages in the Central Southalpine Basement: Markers of an Evolving Thermal Regime during Variscan Convergence

et al. 2021

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Multiscale structural analysis was carried out to explore the sequence of superposed pre-Alpine chloritoid–staurolite–andalusite metamorphic assemblages in the polydeformed Variscan basement of the upper Val Camonica, in the central Southalpine domain. The dominant fabric in the upper Val Camonica basement is the late-Variscan S2 foliation, marked by greenschist facies minerals and truncated by the base of Permian siliciclastic sequences. The intersection with the sedimentary strata defines a Permianage limit on the pre-Alpine tectonometamorphic evolution and exhumation of the Variscan basement. The detailed structural survey revealed that the older S1 foliation was locally preserved in low-strained domains. S1 is a composite fabric resulting from combining S1a and S1b: in the metapelites, S1a was supported by chloritoid, garnet, and biotite and developed before S1b, which was marked by staurolite, garnet, and biotite. S1a and S1b developed at intermediate pressure amphibolite facies conditions during the Variscan convergence, S1a at T = 520–550 °C and P ≃ 0.8 GPa, S1b at T = 550–650 °C and P = 0.4–0.7 GPa. The special feature of the upper Val Camonica metapelites is andalusite, which formed between the late D1b and early D2 tectonic events. Andalusite developed at T = 520–580 °C and P = 0.2–0.4 GPa in pre-Permian times, after the peak of the Variscan collision and before the exhumation of the Variscan basement and the subsequent deposition of the Permian covers. It follows that the upper Val Camonica andalusite has a different age and tectonic significance as compared to that of other pre-Alpine andalusite occurrences in the Alps, where andalusite mostly developed during exhumation of high-temperature basement rocks in Permian–Triassic times.

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Section: Discussionmentioning

confidence: 99%