0000000000186553
AUTHOR
Alexander Kühn
Diffusion versus recrystallization processes in Rb–Sr geochronology: Isotopic relics in eclogite facies rocks, Western Gneiss Region, Norway
Abstract Rb–Sr and U–Pb isotopic data for granulite facies rocks, forming textural relics with respect to eclogite facies metamorphism in the Western Gneiss Region (WGR) of Norway, highlight the importance of textures and mineral reaction kinetics for the interpretation of geochronological data. Studied rocks from Bardsholmen, southern WGR, were subjected to granulite facies metamorphism at 955 ± 3 Ma (U–Pb, zircon). Later on, they experienced a subduction-related, kinetically stranded eclogitization ( T > 650 °C at ∼20 kbar) at 404 ± 2 Ma (Rb–Sr multimineral internal isochron data), followed by exhumation through amphibolite facies conditions. Full conversion of granulite to eclogite was …
Tectonometamorphic evolution of high-pressure rocks from the island of Amorgos (Central Aegean, Greece)
Structural and metamorphic data from the island of Amorgos (central Aegean Sea) show evidence for the existence of two distinct high-pressure units, the Metabasite Unit and the Basal Conglomerate Unit. These are exposed at the base of a thick marble sequence and overlying flysch deposits. The Metabasite Unit is characterized by a mineral assemblage of blue amphibole, garnet and clinopyroxene, indicating P – T conditions of 500–600 °C and >13 kbar. It is juxtaposed below carpholite-bearing metaconglomerates and quartz-rich micaschists of the Basal Conglomerate Unit, for which metamorphic conditions of 300–450 °C and 10–14 kbar are estimated. The contact between the two units is interpreted a…
Coeval high-pressure metamorphism, thrusting, strike-slip, and extensional shearing in the Tauern Window, Eastern Alps
[1] Recent findings for a young (31.5 ± 0.7 Ma) age of high-pressure metamorphism at ∼90 km depths in the Eclogite Zone of the Tauern Window, Eastern Alps, prompt the question about the timing of the structural development of the Tauern Window and its relation to high-pressure metamorphism. We show that all major structures in the Tauern Window, resulting from strong N-S lithospheric shortening and simultaneous minor E-W extension, began developing coevally with high-pressure metamorphism in the Eclogite Zone. Large-scale strike-slip shear zones started to form at ∼32–30 Ma and facilitated the spatial accommodation of simultaneous shortening and extension. At least some of the strike-slip a…