Microstructures and crystallographic preferred orientations of omphacite in Alpine eclogites: implications for the exhumation of (ultra-) high-pressure units

Kurz, Walter; Jansen, E.; Hundenborn, Rene; Pleuger, Jan; Schäfer, Wolfgang; Unzog, Wolfgang

doi:10.1016/j.jog.2003.10.001

Cited by 38 publications

(41 citation statements)

References 95 publications

(196 reference statements)

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“…5a); the cores and the rims show jadeite contents of approx. 25 mol% and 30-35 mol%, respectively (Kurz et al 1998a(Kurz et al , 2004. thermobarometric data indicate conditions of 17-20 kbar at approx.…”

Section: Eclogite Microfabricsmentioning

confidence: 94%

“…1-3) and were affected by a multiphase tectonometamorphic evolution (for summary, see Miller 1974;Holland 1979;raith et al 1980;Dachs 1986Dachs , 1990stöckhert et al 1997;Kurz et al 1998aKurz et al , 2004Hoschek 2001;Kurz 2005). the Eclogite Zone is incorporated into a stack of subpenninic nappes, overlain by the ophiolite-bearing Glockner Nappe and is the only tectonic unit entirely metamorphosed under eclogite-facies metamorphic conditions.…”

Section: Geological Settingmentioning

confidence: 99%

“…the microstructural evolution of eclogites from the Eclogite Zone was described in detail by Kurz et al (1998aKurz et al ( , 2004 and Kurz (2005).…”

Section: Eclogite Microfabricsmentioning

confidence: 99%

“…Within finegrained mylonites, many garnets show an elongated shape (Fig. 5c), and a shape preferred orientation parallel to the lineation direction, resulting from preferential growth parallel to the kinematic x-axis (Kurz et al 2004).…”

Section: Eclogite Microfabricsmentioning

confidence: 99%

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Tracing the exhumation of the Eclogite Zone (Tauern Window, Eastern Alps) by 40Ar/39Ar dating of white mica in eclogites

2008

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New radiometric ages from the subpenninic nappes (Eclogite Zone and rote Wand -Modereck Nappe, tauern Window) show that phengites formed under eclogite-facies metamorphic conditions retain their initial isotopic signature, even when associated lithologies were overprinted by greenschist-to amphibolite-facies metamorphism. Different stages of the eclogite-facies evolution can be dated provided 40 Ar/ 39 Ar dating is combined with micro-structural analyses. An age of 39 Ma from the rote Wand -Modereck Nappe is interpreted to be close to the burial age of this unit. Eclogite deformation within the Eclogite Zone started at the pressure peak along distinct shear zones, and prevailed along the exhumation path. An age of ca. 38 Ma is only observed for eclogites not affected by subsequent deformation and is interpreted as maximum age due to the possible influence of homogenously distributed excess argon. During exhumation deformation was localised along distinct mylonitic shear zones. this stage is mainly characterised by the formation of dynamically recrystallized omphacite2 and phengite. Deformation resulted in the resetting of the Ar isotopic system within the recrystallized white mica. Flat argon release spectra showing ages of 32 Ma within mylonites record the timing of cooling along the exhumation path, and the emplacement onto the Venediger Nappe. Ar-release patterns and 36 Ar/ 40 Ar vs. 39 Ar/ 40 Ar isotope correlation analyses indicate no significant 40 Ar-loss after initial closure, and only a negligible incorporation of excess argon. From the pressure peak onwards, eclogitic conditions prevailed for almost 8-10 Ma.tracing the exhumation of the Eclogite Zone (tauern Window, Eastern Alps) by 40 Ar/ 39

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Section: Eclogite Microfabricsmentioning

confidence: 94%

Section: Geological Settingmentioning

confidence: 99%

“…the microstructural evolution of eclogites from the Eclogite Zone was described in detail by Kurz et al (1998aKurz et al ( , 2004 and Kurz (2005).…”

Section: Eclogite Microfabricsmentioning

confidence: 99%

Section: Eclogite Microfabricsmentioning

confidence: 99%

See 2 more Smart Citations

Tracing the exhumation of the Eclogite Zone (Tauern Window, Eastern Alps) by 40Ar/39Ar dating of white mica in eclogites

2008

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“…This deformation is only developed penetratively in the upper structural level of the Venediger Nappe System, parts of the Seidlwinkl-Rote Wand Nappe in the central part of the Tauern Window, and within high-pressure mylonites of the Eclogite Zone (Kurz et al, 1998(Kurz et al, , 2004. During D1 a first penetrative foliation (s1) parallel to the thrust surfaces and a S-to SSEdipping apparent stretching lineation (l1) were developed.…”

Section: Actively-deforming Tectonic Regions/regimes In Western Northmentioning

confidence: 99%

Correlated crustal and mantle deformation in the Tauern Window, Eastern Alps

Qorbani¹,

Kurz²,

Bianchi³

et al. 2015

AJES

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A purely structural restoration of the NFP20‐East cross section and potential tectonic overpressure in the Adula nappe (central Alps)

Pleuger

Podladchikov

2014

Tectonics

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Common extrusion-type models for the high-to ultrahigh-pressure Adula nappe require a major normal fault along the top of this unit which is not conveyed in the structural record. This implies that such a normal fault existed but was completely erased during later deformational stages. However, there is evidence that decompression occurred during top-to-the-foreland thrusting. We performed a new, purely structural kinematic restoration of the central part of the NFP20-East cross section in order to estimate the burial depths of individual units without converting petrological pressure data into depth under the assumption that pressures were lithostatic. The results show that pressures within most of the units were close to but somewhat higher than lithostatic for several stages of the tectono-metamorphic history. Only for the maximum burial stage of the Adula nappe, we estimate local tectonic overpressures of 40 to 80% of the lithostatic pressures. Accepting such an amount of overpressure, which is moderate compared to values theoretically possible, the Adula nappe was probably not subducted to subcrustal depth. We propose that the structural record of the Penninic nappe stack is quite complete and suggest that the decay of tectonic overpressure is a feasible explanation for decompression from eclogite-to amphibolite-facies conditions during thrusting. Consequently, exhumation and convergence rates of the Eocene to Oligocene Alps may be smaller than previously assumed.

show abstract

Microstructures and crystallographic preferred orientations of omphacite in Alpine eclogites: implications for the exhumation of (ultra-) high-pressure units

Cited by 38 publications

References 95 publications

Tracing the exhumation of the Eclogite Zone (Tauern Window, Eastern Alps) by 40Ar/39Ar dating of white mica in eclogites

Tracing the exhumation of the Eclogite Zone (Tauern Window, Eastern Alps) by 40Ar/39Ar dating of white mica in eclogites

Correlated crustal and mantle deformation in the Tauern Window, Eastern Alps

A purely structural restoration of the NFP20‐East cross section and potential tectonic overpressure in the Adula nappe (central Alps)

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