Crystallization and very rapid exhumation of the youngest Alpine eclogites (Tauern Window, Eastern Alps) from Rb/Sr mineral assemblage analysis

Diffusion versus recrystallization processes in Rb–Sr geochronology: Isotopic relics in eclogite facies rocks, Western Gneiss Region, Norway

“…6), with a weighted mean age of 404 ± 2 Ma. It has been shown that initial Sr-isotopic equilibria among all eclogite facies phases, together with absence of a positive correlation between apparent age and grain size for mica, are sufficient criteria to interpret such multimineral isochron data as eclogitization ages (Glodny et al, 2002;Glodny et al, 2005). Grain size vs. age correlations for phengite are not observed in the dataset from the eclogites (Fig.…”

“…Among the most prominent examples is the survival of Ar-isotopic microscale disequilibria in polygenetic white mica through metamorphic temperatures exceeding 600°C (Giorgis et al, 2000;Di Vincenzo et al, 2001). The persistence of Rb-Sr biotite signatures in ultramafic rocks through eclogite facies metamorphism (Kühn et al, 2000) and the unaltered preservation of Rb-Sr phengite signatures set at >600°C in eclogites (Glodny et al, 2003(Glodny et al, , 2005 can be explained by modally controlled closed system behaviour (see discussion in Glodny et al, 2003). Shielding is another mechanism that can prevent isotopic systems from being reset even at extreme temperatures (Montel et al, 2000).…”

Crystallographic preferred orientations of exhumed subduction channel rocks from the Eclogite Zone of the Tauern Window (Eastern Alps, Austria), and implications on rock elastic anisotropies at great depths

“…The rocks were subjected to PT conditions of 2.0-2.5 GPa and 600 +/-30°C (Dachs, 1990, Stöckert et al, 1997Hoschek, 2001;2004). Rb-Sr dating by Glodny et al (2005) and LuHf dating by Nagel et al (2013) indicate an Oligocene age for the peak PT conditions, and a fast exhumation thereafter within 1-2 Ma. Because of the fast exhumation from great depths, only part of the rocks suite was severely affected by retrograde metamorphism.…”

No need for lithospheric extension for exhuming (U)HP rocks by normal faulting

“…For the three examples of extrusion wedges we provide a brief summary here; details have been published elsewhere (Glodny et al 2005(Glodny et al , 2008Ring et al 2007a,b). To plausibly argue for the existence of an extrusion wedge, it is critical to demonstrate that thrust-related mylonitic deformation in the footwall fault zone occurred contemporaneously with normal shearing in the hanging-wall fault zone.…”

“…The Eclogite Zone in the Tauern Window of the Eastern Alps (Fig. 3a) was metamorphosed at 31.5 ± 0.7 Ma (2σ errors) (Glodny et al 2005) in the course of initial collision between the Adriatic and European continental plates. Peak metamorphic pressures were c. 2.5 -2.7 GPa (Fig.…”