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

Abstract

Multimineral Rb/Sr internal isochrons from eclogite facies rocks of the Eclogite Zone (Tauern Window, Eastern Alps) consistently yield an Early Oligocene age of 31.5±0.7 Ma. This age has been obtained both for late-prograde, dehydration-related eclogitic veins, and for rocks variably deformed and recrystallized under eclogite facies conditions (2.0–2.5 GPa, 600°C). Initial Sr-isotopic equilibria among all phases indicate absence of significant post-eclogitic isotope redistribution processes, therefore the ages date eclogite facies assemblage crystallization. Equilibria also prove that no prolonged pre-eclogite facies history is recorded in the rocks. Instead, subduction, prograde mineral reactions, and eclogitization proceeded rapidly. Fast exhumation immediately after eclogitization, with minimum rates >36 mm/a is inferred from a 31.5±0.5 Ma internal mineral isochron age of a post-eclogitic greenschist facies vein assemblage. Such rates equal typical subduction rates. Late Eocene to Early Oligocene subduction of the European continental margin, with subsequent rapid exhumation of high-pressure nappe complexes has previously been recognized only in the Western Alps. The new data signify synchronous continental collision all along the Alpine belt. Our results demonstrate the unique potential of Rb/Sr assemblage ‘system analysis’ for precise dating of both eclogite facies and post-eclogitic events, thus for precisely constraining exhumation rates of deep-seated rocks, and for straightforward linkage of petrologic evidence with isotopic ages.

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6

References

  1. Arnaud NO, Kelley SP (1995) Evidence for excess argon during high pressure metamorphism in the Dora Maira Massif (western Alps, Italy), using an ultra-violet laser ablation microprobe 40Ar−39Ar technique. Contrib Mineral Petrol 121:1–11

    Article  CAS  Google Scholar 

  2. Barth S, Oberli F, Meier M (1989) U–Th–Pb systematics of morphologically characterized zircon and allanite: a high-resolution isotopic study of the Alpine Rensen pluton (northern Italy). Earth Planet Sci Lett 95:235–254

    Article  CAS  Google Scholar 

  3. von Blanckenburg F, Davies JH (1995) Slab breakoff: A model for syncollisional magmatism and tectonics in the Alps. Tectonics 14(1):120–131

    Article  Google Scholar 

  4. Blichert-Toft J, Frei R (2001) Complex Sm–Nd and Lu–Hf isotope systematics in metamorphic garnets from the Isua supracrustal belt, West Greenland. Geochim Cosmochim Acta 65(18):3177–3189

    Article  CAS  Google Scholar 

  5. Christensen JN, Selverstone J, Rosenfeld JL, DePaolo DJ (1994) Correlation by Rb–Sr geochronology of garnet growth histories from different structural levels within the Tauern Window, Eastern Alps. Contrib Mineral Petrol 118:1–12

    Article  CAS  Google Scholar 

  6. Cliff RA, Meffan-Main S (2003) Evidence from Rb–Sr microsampling geochronology for the timing of Alpine deformation in the Sonnblick Dome, SE Tauern Window, Austria. In: Vance D, Mueller W, Villa IM (eds) Geochronology: linking the isotopic record with petrology and textures. Geol Soc Spec Pub 220:159–172

    CAS  Google Scholar 

  7. Dachs E (1990) Geothermobarometry in metasediments of the southern Grossvenediger area (Tauern Window, Austria). J Metam Geol 8:217–230

    Google Scholar 

  8. Dachs E, Proyer A (2002) Constraints on the duration of high-pressure metamorphism in the Tauern Window from diffusion modelling of discontinuous growth zones in eclogite garnet. J Metam Geol 20:769–780

    Article  CAS  Google Scholar 

  9. Dal Piaz GV, Gosso G (1993) Some remarks on evolution of the Alpine lithosphere. In: Proceedings of symposium “CROP— Central Alps”, Sondrio, pp 93–101

    Google Scholar 

  10. Dodson MH (1973) Closure temperature in cooling geochronological and petrological systems. Contrib Mineral Petrol 40:259–274

    Article  CAS  Google Scholar 

  11. Dodson MH (1979) Theory of cooling ages. In: Jaeger E, Hunziker JC (eds) Lectures in isotope geology. Springer Berlin Heidelberg New York, pp 194–202

    Google Scholar 

  12. Dûchene S, Blichert-Toft J, Luais B, Télouk P, Lardeaux J-M, Albarède F (1997) The Lu-Hf dating of garnets and the ages of the Alpine high-pressure metamorphism. Nature 387(6633):586–589

    Article  Google Scholar 

  13. El-Shazly AK, Bröcker M, Hacker B, Calvert A (2001) Formation and exhumation of blueschists and eclogites from NE Oman: new perspectives from Rb–Sr and 40Ar/39Ar dating. J Metam Geol 19:233–248

    Article  CAS  Google Scholar 

  14. Frisch W, Dunkl I, Kuhlemann J (2000) Post-collisional orogen-parallel large-scale extension in the Eastern Alps. Tectonophysics 327:239–265

    Article  Google Scholar 

  15. Gebauer D (1999) Alpine geochronology of the Central and Western Alps: new constraints for a complex geodynamic evolution. Schweiz Mineral Petrogr Mitt 79:191–208

    CAS  Google Scholar 

  16. Giletti BJ (1991) Rb and Sr diffusion in alkali feldspars, with implications for cooling histories of rocks. Geochim Cosmochim Acta 55:1331–1343

    Article  CAS  Google Scholar 

  17. Glodny J, Austrheim H, Molina JF, Rusin A, Seward D (2003) Rb/Sr record of fluid-rock interaction in eclogites: the Marun-Keu complex, Polar Urals, Russia. Geochim Cosmochim Acta 67(22):4353–4371

    Article  CAS  Google Scholar 

  18. Holland TJB (1979) High water activities in the generation of high pressure kyanite eclogites of the Tauern Window, Austria. J Geol 87(1):1–27

    CAS  Google Scholar 

  19. Hoschek G (2001) Thermobarometry of metasediments and metabasites from the Eclogite Zone of the Hohe Tauern, Eastern Alps, Austria. Lithos 59:127–150

    Article  CAS  Google Scholar 

  20. Hynes A (2002) Encouraging the extrusion of deep-crustal rocks in collision zones. Mineralogical Magazine 66(1):5–24

    Article  CAS  Google Scholar 

  21. Inger S, Cliff RA (1994) Timing of metamorphism in the Tauern Window, Eastern Alps: Rb-Sr ages and fabric formation. J Metam Geol 12:695–707

    CAS  Google Scholar 

  22. Jahn B, Caby R, Monie P (2001) The oldest UHP eclogites of the World: age of UHP metamorphism, nature of protoliths and tectonic implications. Chemical Geol 178:143–158

    Article  CAS  Google Scholar 

  23. Jenkin GRT, Ellam RM, Rogers G, Stuart FM (2001) An investigation of closure temperature of the biotite Rb/Sr system: the importance of cation exchange. Geochim Cosmochim Acta 65(7):1141–1160

    Article  CAS  Google Scholar 

  24. Kelley SP, Wartho JA (2000) Rapid kimberlite ascent and the significance of Ar–Ar ages in xenolith phlogopites. Science 289(5479):609–611

    Article  CAS  PubMed  Google Scholar 

  25. Kretz R (1983) Symbols for rock-forming minerals. Am Mineral 68:277–279

    Google Scholar 

  26. Kühn A, Glodny J, Iden K, Austrheim H (2000) Retention of Precambrian Rb/Sr ages through Caledonian eclogite facies metamorphism, Bergen Arc Complex, W-Norway. Lithos 51:305–330

    Article  Google Scholar 

  27. Kullerud L (1991) On the calculation of isochrons. Chemical Geol 87:115–124

    CAS  Google Scholar 

  28. Kurz W, Neubauer F, Dachs E, (1998) Eclogite meso-and microfabrics: implications for the burial and exhumation history of eclogites in the Tauern window (Eastern Alps) from PTd paths. Tectonophysics 285:183–209

    Article  Google Scholar 

  29. Li S, Wang S, Chen Y, Liu D, Ji Q, Zhou H, Zhang Z (1994) Excess argon in phengite from eclogite; evidence from dating of eclogite minerals by Sm–Nd, Rb–Sr and 40Ar/39Ar methods. Chemical Geol 112(3–4):343–350

    Article  CAS  Google Scholar 

  30. Ludwig KR (1999) Isoplot/Ex Ver 2.06: a geochronological toolkit for Microsoft Excel. Berkeley Geochronology Center Special Publications 1a.

  31. Meffan-Main S, Cliff RA, Barnicoat AC, Lombardo B, Compagnoni R (2004) A Tertiary age for Alpine high-pressure metamorphism in the Gran Paradiso massif, Western Alps: a Rb–Sr microsampling study. J Metam Geol 22(4):267–281

    Article  CAS  Google Scholar 

  32. Miller C (1977) Chemismus und phasenpetrologische Untersuchungen der Gesteine aus der Eklogitzone des Tauernfensters, Österreich. Tschermaks Min Petr Mitt 24:221–277

    Article  CAS  Google Scholar 

  33. Molina JF, Poli S, Austrheim H, Glodny J, Rusin A (2004) Eclogite-facies vein systems in the Marun-Keu complex (Polar Urals, Russia): textural, chemical and thermal constraints for patterns of fluid flow in the lower crust. Contrib Mineral Petrol 147(4):484–504

    Article  CAS  Google Scholar 

  34. Müller W (2003) Strengthening the link between geochronology, textures and petrology. Earth Planet Sci Lett 206:237–251

    Article  Google Scholar 

  35. Müller WF, Franz G (2004) Unusual deformation microstructures in garnet, titanite and clinozoisite from an eclogite of the Lower Schist Cover, Tauern Window, Austria. Eur J Mineral 16:939–944

    Article  Google Scholar 

  36. Raith M, Mehrens C, Thöle W (1980) Gliederung, tektonischer Bau und metamorphe Entwicklung der penninischen Serien im südlichen Venediger-Gebiet, Osttirol. Jahrbuch der Geol Bundesanstalt 123(1):1–37

    Google Scholar 

  37. Ratschbacher L, Dingeldey C, Miller C, Hacker BR, McWilliams MO (2004) Formation, subduction, and exhumation of Penninic oceanic crust in the Eastern Alps: time constraints from 40Ar/39Ar geochronology. Tectonophysics 394:155–170

    Article  CAS  Google Scholar 

  38. Ring U, Reischmann T (2002) The weak and superfast Cretan detachment, Greece: exhumation at subduction rates in extrusion wedges. J Geol Soc London 159:225–228

    CAS  Google Scholar 

  39. Romer RL, Siegesmund S (2003) Why allanite may swindle about its true age. Contrib Mineral Petrol 146:297–307

    Article  CAS  Google Scholar 

  40. Rubatto D, Hermann J (2001) Exhumation as fast as subduction? Geology 29(1):3–6

    Google Scholar 

  41. Selverstone J (1993) Micro- to macroscale interactions between deformational and metamorphic processes, Tauern Window, Eastern Alps. Schweiz Min Pet Mitt 73:229–239

    CAS  Google Scholar 

  42. Selverstone J, Franz G, Thomas S, Getty S (1992) Fluid variability in 2 GPa eclogites as an indicator of fluid behaviour during subduction. Contrib Mineral Petrol 112:341–357

    Article  CAS  Google Scholar 

  43. Spear FS, Franz G (1986) PT evolution of metasediments from the Eclogite Zone, south-central Tauern Window, Austria. Lithos 9:219–234

    Article  Google Scholar 

  44. Stöckhert B, Massonne H-J, Nowlan EU (1997) Low differential stress during high-pressure metamorphism: the microstructural record of a metapelite from the Eclogite Zone, Tauern Window, Eastern Alps. Lithos 41:103–118

    Article  Google Scholar 

  45. Thomas S, Franz G (1988) Kluftminerale und ihre Bildungsbedingungen in Gesteinen der Eklogitzone/Südvenediger-Gebiet (Hohe Tauern, Österreich) Mitteilungen der Österreichischen Geologischen Gesellschaft 81:189–218

    Google Scholar 

  46. Thöni M, Jagoutz E (1992) Some new aspects of dating eclogites in orogenic belts: Sm–Nd, Rb–Sr, and Pb–Pb results from the Austroalpine Saualpe and Koralpe type-locality (Carinthia/Styria, SE Austria). Geochim Cosmochim Acta 56:347–368

    Article  Google Scholar 

  47. Tilton GR, Schreyer W, Schertl H-P (1991) Pb-Sr-Nd isotopic behaviour of deeply subducted crustal rocks from the Dora Maira massif, Western Alps, Italy—II: what is the age of the ultrahigh-pressure metamorphism? Contrib Mineral Petrol 108:22–33

    CAS  Google Scholar 

  48. Vance D, Müller W, Villa IM (eds) (2003) Geochronology: linking the isotopic record with petrology and textures. Geol Soc Lond Spec Publ 220:1–260

    CAS  Google Scholar 

  49. Villa IM (1998) Isotopic closure. Terra Nova 10:42–47

    Article  Google Scholar 

  50. Zimmermann R, Hammerschmidt K, Franz G (1994) Eocene high pressure metamorphism in the Penninic units of the Tauern Window (Eastern Alps): evidence from 40Ar–39Ar dating and petrological investigations. Contrib Mineral Petrol 117:175–186

    Article  CAS  Google Scholar 

Download references

Acknowledgements

This work was supported by the Deutsche Forschungsgemeinschaft (grant RI 538/25 to UR and JG). We thank J. Herwig and V. Kuntz for their help with mineral separation and figure drawing. J. Vervoort and an anonymous referee provided helpful comments on an earlier version of this manuscript. Careful and constructive reviews by M. Bröcker and I.M. Villa are gratefully acknowledged.

Author information

Affiliations

Authors

Corresponding author

Correspondence to Johannes Glodny.

Additional information

Communicated by J. Hoefs

Appendix

Appendix

Sample characterization

EIS5 (47°04.560′N, 12°23.509′E, summit of Weißspitze mountain, 3,290 m). Eclogite facies mobilisate, very coarse-grained, dominated by kyanite+quartz+rutile+white mica. Assemblage: kyanite (cm-sized), phengite (up to several mm thick “books”), paragonite, omphacite (Fe-poor), garnet (few inclusions). Locally apatite megacrysts (up to 1 cm in length). No obvious post-eclogitic alteration phenomena.

352E3 (47°04.301′N, 12°27.071′E, Frosnitztal, 100 m SW of Steinsteg, 2,060 m). Mobilisate in matrix. Mobilisate: coarse-grained, dominated by quartz, kyanite, white mica (books up to 1 cm size), with minor amounts of carbonate, omphacite, garnet, epidote, rutile. Matrix: fine-grained eclogite, slightly foliated, with two different types of omphacite (inclusion-rich vs. inclusion-free). Assemblage: omphacite, garnet (with inclusions), with minor amounts of paragonite (rich in Sr), phengite, rutile, pyrite, zoisite, kyanite, calcite.

EIS1 (47°03.745′N, 12°23.159′E, ~100 m SE of Lake Eissee, 2,720 m). Strongly foliated eclogite, with up to 1 mm sized garnet. Locally (in pressure shadows): crystals of omphacite, epidote, and phengitic white mica up to several 100 μm in size, in an otherwise very fine-grained, omphacite+epidote-dominated matrix. Post-eclogitic alteration restricted to small domains around minute cracks (removed before analysis). Assemblage: garnet, omphacite, epidote, dolomite, apatite (Cl), phengite, paragonite, rutile, kyanite, quartz, zircon, pyrite.

AK5/03 (47°03.745′N, 12°23.159′E, ~100 m SE of Lake Eissee, 2,720 m). Eclogite, with mm-sized garnet. Few major omphacite, and phengitic white mica crystals in otherwise fine-grained, foliated, omphacite-dominated matrix. Assemblage: garnet (with inclusion-rich cores), omphacite (dominant); subordinate amounts of quartz, phengite, paragonite, talc, dolomite, epidote, rutile, ilmenite. apatite, pyrite, kyanite.

291 (47°04.799′N, 12°27.384′E, Frosnitztal, 1,150 m SW of Dabernitzkogel, 2,450 m). Fine-grained eclogite, with weakly developed foliation. Slightly weathered, with some intergranular stainings. Some small alterated domains along cracks (removed before analysis). Assemblage: garnet (with inclusion-rich cores), omphacite, clinozoisite, subordinate amounts of phengite, quartz, carbonate, rutile, epidote, apatite.

EIS9 (47°04.152′N, 12°22.603′E, 800 m SW of Wallhorntörl, 2,877 m). Vein-like, structurally discordant mobilisate, several m long and 20–50 cm wide in outcrop. Mobilisate shows 5–10 cm wide alteration aureole in wallrock, with greenschist facies overprint of eclogites. Vein assemblage: amphibole (actinolite with some Mg-hornblende; radial aggregates with crystals up to 15 cm in length), albitic feldspar megacrysts; minor amounts of muscovite (up to 5 mm diameter), titanite (poor in Fe), apatite, epidote, biotite, ilmenite. Rarity: relic of rutile, with titanite overgrowth.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Glodny, J., Ring, U., Kühn, A. et al. Crystallization and very rapid exhumation of the youngest Alpine eclogites (Tauern Window, Eastern Alps) from Rb/Sr mineral assemblage analysis. Contrib Mineral Petrol 149, 699–712 (2005). https://doi.org/10.1007/s00410-005-0676-5

Download citation

Keywords

  • Eclogite
  • Rb/Sr
  • Geochronology
  • Fluid-rock interaction
  • Exhumation
  • Eastern Alps