Grain-size effects on the closure temperature of white mica in a crustal-scale extensional shear zone — Implications of in-situ 40Ar/39Ar laser-ablation of white mica for dating shearing and cooling (Tauern Window, Eastern Alps)

Scharf, Andreas; Handy, Mark R.; Schmid, Stefan M.; Favaro, S.; Sudo, Masafumi; Schuster, Ralf; Hammerschmidt, Konrad

doi:10.1016/j.tecto.2016.02.014

Cited by 27 publications

(23 citation statements)

References 64 publications

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“…12B, C). The finer-grained frac tion pro vides ap prox i mately 8 Ma in creased age; most likely due to re coil ef fect (Sperner et al, 2010;Halama et al, 2014;Scharf et al, 2016). Al though this ef fect was mostly elim i nated dur ing irra di a tion, it is typ i cally ap par ent in very fine-grained mica ag gregates.…”

Section: Discussion -Constraining the Infratatric Evolutionary Stagesmentioning

confidence: 99%

Cretaceous and Eocene tectono-thermal events determined in the Inner Western Carpathians orogenic front Infratatricum

Putiš

Danišík

Siman

et al. 2019

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This pa per re-as sesses the tectono-ther mal evo lu tion of the fron tal Infratatricum part of the In ner West ern Carpathians orogen based on new geo log i cal-pet ro log i cal and zir con fis sion track (ZFT) data and pub lished 40 Ar-39 Ar and K-Ar data. The study area is in the Považský Inovec Mts. in West ern Slovakia, where the Infratatric Inovec Nappe com prises a micaschist-gneiss base ment and Up per Car bon if er ous-Lower Cre ta ceous cover with the Ju ras sic-Lower Cre ta ceous Humienec Suc ces sion; this lat ter is re con structed from olistoliths in the Horné Belice Suc ces sion Up per Cre ta ceous flysch. The Infratatric Inovec Nappe pos te rior part is thrust over its fron tal Humienec tec tonic Slice with infolded Up per Cre ta ceous sed i ments. This nappe ex hib its very low-tem per a ture tectono-ther mal over print ing, and this is doc u mented by elec tron probe microanalysis of meta mor phic phases and P-T es ti mates. The late Early Cre ta ceous age of this D1 stage event at approx i mately 115-95 Ma is re corded by 114 ±2 and 106 ±4 Ma phengitic white mica 40 Ar-39 Ar ages from a Lower Cre ta ceous cherty slate, and by 101 ±3 Ma 40 Ar-39 Ar age and 102 ±4 Ma ZFT age from Perm ian meta-sand stone. The Inovec Nappe was thus de rived from an Albian-Early Cenomanian accretionary wedge. The hemipelagic Up per Turonian to Lower Santonian red marls and up ward syn-orogenic Up per Santonian to Maastrichtian flysch were de pos ited on the fron tal at ten u ated part of the Inovec Nappe-type base ment in the in ferred Pieninic-Váhic (~South-Penninic) zone. This flysch con tains olistolithic to clastogeneous meta mor phosed ma te rial, in clud ing the Lower Cre ta ceous slates, sup plied from the pos te rior part of the Inovec Nappe. The 40 Ar-39 Ar age of 86 ±2 Ma from this nappes' Perm ian meta-sand stone is con sis tent with D2 thrust ing at ap prox i mately 95-85 Ma and Horné Belice fore land flysch ba sin sup ply in the D3 stage at ~85-65 Ma. The Inovec Nappe fron tal Humienec tec tonic Slice with infolded Up per Cre ta ceous sed i ments sug gests for ma tion of a Paleocene-Eocene accretionary wedge at ap prox i mately 65-40 Ma in the D4 stage. This event is con strained by 40 Ar-39 Ar age of 48 ±2 Ma from the Tatricum hang ing wall blastomylonites and whole-rock K-Ar age of 46 ±3 Ma from a Perm ian ba salt olistolith in the footwall Infratatricum Horné Belice flysch. The Infratatricum fi nally be came part of an Eocene accretionary wedge north of the Hrádok-Zlatníky thrust-fault, and re heat ing and ex hu ma tion cool ing is doc u mented by 57-37 Ma ZFT ages. Al though the Infratatricum ex hib its Late Cre ta ceous and Eocene tectono-ther mal im prints, it is a rem nant of the Early Cre ta ceous structure at the In ner West ern Carpathian front. This im poses the Infratatricum as a dis tal con ti nen tal mar gin of the Penninicum.

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Section: Discussion -Constraining the Infratatric Evolutionary Stagesmentioning

confidence: 99%

Cretaceous and Eocene tectono-thermal events determined in the Inner Western Carpathians orogenic front Infratatricum

Putiš

Danišík

Siman

et al. 2019

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“…Based on the slightly older ages of the eastern subdome (Figure a), it was suggested that its unroofing initiated earlier than in the western subdome [ Dunkl et al ., ; Luth and Willingshofer , ; Favaro et al ., ; Scharf et al ., ]. However, as shown by thermal models of folding designed to simulate the western subdome of the Tauern Window [ Bertrand , ], material points exhumed in the hinge of the antiform, which stem from deeper crustal levels compared to those in the limbs, were uplifted at higher rates.…”

Section: Discussionmentioning

confidence: 99%

Exhumation mechanisms of the Tauern Window (Eastern Alps) inferred from apatite and zircon fission track thermochronology

et al. 2017

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Orogen‐parallel extension and orogen‐perpendicular shortening accommodated by folding acted at the same time to exhume the Tauern Window. In order to investigate the relative contribution of upright folding and erosion and of extensional denudation for exhumation, we provide compilations in map view of previous and new zircon and apatite fission track ages. These age maps show that isoage contour lines are subparallel to the axial planes of large‐scale, upright folds. On age versus distance diagrams, along a profile perpendicular to the dome axis, all thermochronometers show bell‐shaped curves with younger ages in the hinge area of the dome and age differences between different chronometers decreasing from the limbs to the hinge area. All these observations suggest that folding synchronous with erosion was largely responsible for exhumation of the Tauern Window. The younger ages and the higher fold amplitudes of the western subdome compared to the eastern one are corroborated by the results of inversion of cooling ages that show higher exhumation rates in the west. These reflect one and the same shortening and folding event that affected the entire Tauern Dome synchronously, but at higher rates than that in the western subdome. Only during Pliocene time were exhumation rates slightly higher along the normal faults bordering the window; hence, extensional unroofing may have dominated exhumation in the Pliocene. The northward displacement of the Dolomites Indenter was associated to a clockwise rotation, which caused increased amounts of shortening westward, hence higher uplift and exhumation rates in the western subdome.

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“…New data on tectonics (Scharf et al, 2013a;Schmid et al, 2013;Schneider et al, 2015;Favaro et al, 2017), deep structure (Behm et al, 2007;Brückl et al, 2007Brückl et al, , 2010Mitterbauer et al, 2011;Spada et al, 2013;Qorbani et al, 2015;Zhao et al, 2016), Barrovian metamorphism (Scharf et al, 2013b;Schneider et al, 2014;Cliff et al, 2015;Favaro et al, 2015), geochronology (Glodny et al, 2008;Wölfler et al, 2008;Nagel et al, 2013;Schneider et al, 2013Schneider et al, , 2015 A C C E P T E D M A N U S C R I P T 10 Bertrand et al, 2015;Cliff et al, 2015;Favaro et al, 2015;Scharf et al, 2016, Heberer et al, 2017, and geodynamics (Wölfler et al, 2011;Favaro et al, 2017;van Gelder et al, 2017) of the Eastern Alps have been published recently. The aim of the present paper is to give an overview, based on these and older works, on the links between kinematics and exhumation during collision in the Eastern Alps, and to discuss first, why the lower part of the orogenic wedge is only exposed within a single area of limited extent (Tauern Window; Fig.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…et al (2015) andScharf et al (2016), based on new and compiled Rb/Sr isochron ages (mainly whole rock-biotite) and 40 Ar/ 39 Ar laser ablation ages of white mica from the southern and northeastern margins of the eastern sub-dome, respectively. Such a trend is in contrast to the fission track data of Bertrand et al(2017; Fig.…”

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confidence: 99%

Relating collisional kinematics to exhumation processes in the Eastern Alps

Rosenberg

Schneider

Scharf

et al. 2018

Earth-Science Reviews

106

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International audienceBased on a review of the surface and deep structure of the Eastern Alps, we link the timing and the inferred displacement fields to exhumation of upper and lower crustal units of the orogenic nappe stack during collision. The discussion focuses mainly on the Tauern Window and its country rocks, the only area of the Eastern Alps where the orogenic wedge, from its uppermost Austroalpine nappes down to its deepest European basement nappes is continuously exposed. We summarize and discuss the long-standing controversy on the mechanisms of exhumation of this nappe stack on the base of a synthesis of structural and geochronological data, and restorations of collisional displacements, both in cross-sections and map views. We conclude that the large amounts of exhumation assessed for the western Eastern Alps resulted from large amounts of thickening and erosion, not observed in the eastern part of the Eastern Alps. Extensional faults, laterally bounding the area of major thickening and exhumation are inferred to nucleate in order to accommodate displacement around the indenter corner in the west, and in order to reduce a large gradient of crustal thickness and surface elevation in the East.Restorations to the pre-indentation stage, document an amount of northward increasing orogen-parallel extension, varying 45 km to 85 km, corresponding to 15% of extension, that is partly accommodated along normal faults. N-S shortening between the Northern Calcareous Alps and the Dolomites Indenter attained 75 km in the west and decreased to 30 km in the east. 55 km out of these 75 were accommodated in the area of the Tauern Window. Our kinematic model shows that lateral extrusion accommodated along conjugate strike-slip faults requires large amounts of north-south shortening in the western part of the Eastern Alps. Such shortening is consistent with the reconstructed upright folding and erosion of the Tauern Window, thus explaining the largest amount of its exhumation. In contrast, the eastern termination of the Eastern Alps represents an area where collisional convergence was barely accommodated by crustal thickening. This transition from a highly shortened, thickened and exhumed wedge in the west, mainly affected by orogen-perpendicular displacements, to a barely shortened and exhumed wedge in the east, mainly characterised by orogen-parallel displacements, spatially coincides with a change in the deep structure of the European slab. Indeed, the inferred continental, European Slab, imaged in the west disappears into a low velocity anomaly, where no slab is detected in the east. An inherited step in the geometry in map view of the European passive margin, causing its crust to enter the subduction zone earlier than the area east of the Tauern Window, may explain the rapid decrease of shortening, of thickening, the different syn-collisional P-T gradients, and the disappearance of the continental slab east of the Katschberg Fault

show abstract

Grain-size effects on the closure temperature of white mica in a crustal-scale extensional shear zone — Implications of in-situ 40Ar/39Ar laser-ablation of white mica for dating shearing and cooling (Tauern Window, Eastern Alps)

Cited by 27 publications

References 64 publications

Cretaceous and Eocene tectono-thermal events determined in the Inner Western Carpathians orogenic front Infratatricum

Cretaceous and Eocene tectono-thermal events determined in the Inner Western Carpathians orogenic front Infratatricum

Exhumation mechanisms of the Tauern Window (Eastern Alps) inferred from apatite and zircon fission track thermochronology

Relating collisional kinematics to exhumation processes in the Eastern Alps

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