eEarth Discussions www.electronic-earth-discuss.net 1815-3836 1815-3844 2 1 2007 10.5194/eed-2-1-2007 http://www.electronic-earth-discuss.net/2/1/2007/ http://www.electronic-earth-discuss.net/2/1/2007/eed-2-1-2007.html http://www.electronic-earth-discuss.net/2/1/2007/eed-2-1-2007.pdf 1 35 2007-01-18 Exhumation of metamorphic rocks in N Aegean: the path from shortening to extension and extrusion R. Lacassin lacassin@ipgp.jussieu.fr N. Arnaud P. H. Leloup R. Armijo B. Meyer Institut de Physique du Globe de Paris, UMR7174 CNRS, Paris, France Lab. Dynamique de la Lithosphère, UMR 5573 CNRS, USTL, Montpellier, France Lab. Sciences de la Terre, UMR5570 CNRS, UCB Lyon, France Lab. Tectonique, UMR7072 CNRS, Univ. P. et M. Curie, Paris, France The Olympos-Ossa-Pelion (OOP) ranges, in NW Aegean, encompass Greece highest summit and are located near the extremity of the North Anatolian Fault (NAF). Structural and thermochronological data gathered in the OOP ranges show that the main exhumation of metamorphic nappes occurred in the Eocene, at ca. 43–39 Ma. This early exhumation, associated with ductile, then brittle-ductile normal faulting with northeastward transport, is nearly coeval with orogenic shortening in the close area. Cooling rates, and likely exhumation, have been low between ~40 Ma and ~20 Ma. ⁴⁰Ar/³⁹Ar crystallization ages (between 20 and 15 Ma) appears related to brittle-ductile normal faulting and likely associated with the onset of Aegean back-arc extension. The dating of a diabase dyke, and the geometry of associated brittle jointing, of onshore and offshore active normal faults imply a shift in extension direction after 4 Ma. Such a shift is probably related the propagation of the NAF in northern Aegean known to have occurred around 5 Ma. Armijo, R., Meyer, B., King, G. C. P., Rigo, A., and Papanastassiou, D.: Quaternary evolution of the Corinth Rift and its implications for the late Cenozoic evolution of the Aegean, Geophys. J. Int., 126, 11–53, 1996. Armijo, R., Meyer, B., Hubert, A., and Barka, A.: Westward propagation of the North Anatolian Fault into the northern Aegean; timing and kinematics, Geology (Boulder), 27, 267–270, 1999. Armijo, R., Flerit, F., King, G., and Meyer, B.: Linear elastic fracture mechanics explains the past and present evolution of the Aegean, Earth Planet. Sci. Lett., 217(1–2), 85–95, 2004. Avigad, D. and Garfunkel, Z.: Uplift and exhumation of high-pressure metamorphic terrains: the example of the cycladic blueschist belt (Aegean Sea), Tectonophysics, 188, 357–372, 1991. Berger, G. W. and York, D.: Geothermometry from $^40$Ar/$^39$Ar dating experiments, Geochem. Cosmochem. Acta, 45, 795–811, 1981. Brun, J. P., Sokoutis, D., and Van den Driessche, J.: Analogue modeling of detachment fault systems and core complexes, Geology, 22, 319–322, 1994. Brunel, M., Arnaud, N., Tapponnier, P., Pan, Y., and Wang, Y.: Kongur Shan normal fault: type example of mountain building assisted by extension (Karakoram fault, eastern Pamir), Geology, 22, 707–710, 1994. Buick, I. S.: The late alpine evolution of an extensional shear zone, Naxos, Greece, J. Geol. Soc. London, 148, 93–103, 1991. Celet, P. and Ferrière, J.: Les Hellénides internes: le Pélagonien: Eclogae Geologicae Helveticae, 71, 467–495, 1978. Dalrymple, G. B. and Lanphere, M. A.: $^40$Ar/$^39$Ar age spectra of some undisturbed terrestrial samples, Geochim. Cosmochim. Acta, 38, 715–738, 1974. Fleury, J. J. and Godfriaux, I.: Arguments pour l'attribution de la série de la fenêtre de l'Olympe (Grèce) à la zone de Gavrovo Tripolitza: présence de fossiles du Maastrichtien et de l'Eocène inférieur (et moyen ?), Annales de la Société Géologique du Nord, 94, 149–156, 1974. Gautier, P. and Brun, J. P.: Ductile crust exhumation and extensional detachments in the central Aegean (Cyclades and Evvia Islands), Geodinamica Acta, 7, 57–85, 1994. Gautier, P., Brun, J.-P., Moriceau, R., Sokoutis, D., Martinod, J., and Jolivet, L.: Timing, kinematics and cause of Aegean extension: a scenario based on a comparison with simple analogue experiments, Tectonophysics, 315, 31–72, 1999. Goldsworthy, M., Jackson, J., and Haines, J.: The continuity of active fault systems in Greece, Geophys. J. Int., 148, 596–618, 2002. Harrison, T. M., Lovera, O. M., and Heizler, M. T.: $^40$Ar/$^39$Ar results for alkali feldpsars containing diffusion domains with differing activation energy, Geochim. Cosmochim. Acta, 55, 1435–1448, 1991. Hatzfeld, D., Ziazia, M., Kementzetzidou, D., Hatzidimitriou, P., Panagiotopoulos, D., Makropoulos, K., Papadimitriou, P., and Deschamps, A.: Microseismicity and focal mechanisms at the western termination of the North Anatolian Fault and their implications for continental tectonics, Geophys. J. Int., 137, 891–908, 1999. Hodges, K. V., Parrish, R. R., Housh, T. B., Lux, D. R., Burchfiel, B. C., Royden, L. H., and Chen, Z.: Simultaneous Miocene extension and shortening in the Himalayan orogen, Science, 258, 1466–1470, 1992. Jolivet, L., Brun, J. P., Gautier, P., Lallemant, S., and Patriat, M.: 3D-kinematics of extension in the Aegean region from the early Miocene to the present; insights from the ductile crust, Bull. Soc. Geol. Fr., 165, 195–209, 1994. Jolivet, L. and Patriat, M.: Ductile extension and the formation of the Aegean Sea, in: The Mediterranean basins: Tertiary extension within the Alpine orogen, edited by: Durand, B., Jolivet, L., Horvath, F., and Séranne, M., Geol. Soc. Spec. Publ., London, 156, 427–456, 1999. Jolivet, L., Faccenna, C., Goffé, B., Burov, E., and Agard, P.: Subduction tectonics and exhumation of high-pressure metamorphic rocks in the Mediterranean orogens, Am. J. Sci., 303, 353–409, 2003. Laigle, M., Hirn, A., Sachpazi, M., and Roussos, N.: North Aegean crustal deformation: An active fault imaged to 10 km depth by reflection seismic data, Geology, 28, 71–74, 2000. Le Pichon, X. and Angelier, J.: The Aegean sea, Phil. Trans. R. Soc. Lond., A, 300, 357–372, 1981. Lister, G. S., Banga, G., and Feenstra, A.: Metamorphic core complexes of cordilleran type in the Cyclades, Aegean Sea, Greece, Geology, 12, 221–225, 1984. Lips, A. L. W., White, S. H., and Wijbrans, J. R.: 40Ar/39 Ar laserprobe direct dating of discrete deformational events; a continuous record of early Alpine tectonics in the Pelagonian Zone, NW Aegean area, Greece, Tectonophysics, 298, 133–153, 1998. Lips, A. L. W., Wijbrans, J. R., and White, S. H.: New insights from $^40$Ar/$^39$Ar laserprobe dating of white mica fabrics from the Pelion Massif, Pelagonian Zone, internal Hellenides, Greece; implications for the timing of metamorphic episodes and tectonic events in the Aegean region, in: The Mediterranean basins, Tertiary extension within the Alpine Orogen, edited by: Durand, B., Jolivet, L., Horvath, F., and Séranne, M., Geol. Soc. Spec. Publ., London, 156, 457–474, 1999. Lovera, O. M., Richter, F. M., and Harrison, T. M.: The $^40$Ar/$^39$Ar thermochronometry for slowly cooled samples having a distribution of diffusion domain sizes, J. Geophys. Res., 94, 17 917–17 935, 1989. Lovera, O. M., Richter, F. M., and Harrison, T. M.: Diffusion domains determined by 39Ar released during step heating, J. Geophys. Res., 96, 2057–2069, 1991. Mascle, G. and Martin, L.: Shallow structure and recent evolution of the Aegean sea: a synthesis based on continuous reflection profiles, Marine Geol., 94, 271–299, 1990. McKenzie, D. P.: Active tectonics of the alpine-himalayan belt: the Aegean sea and surrounding region, Geophys. J. Roy. Astr. Soc., 30, 109–185, 1978. McNeil, L. C., Mille, A., Minshull, T. A., Bull, J. M., Kenyon, N. H., and Ivanov, M.: Extension of the North Anatolian Fault into the North Aegean trough: Evidence for transtension, strain partitioning, and analogues for Sea of Marmara basin models, Tectonics, 23, TC2016, doi:10.1029/2002TC001490, 2004. Mercier, J. L., Sorel, D., Vergely, P., and Simeakis, K.: Extensional tectonic regimes in the Aegean basin during the Cenozoic, Basin Res., 2, 49–71, 1989. Papanikolaou, D., Alexandri, M., Nomikou, P., and Ballas, D.: Morphotectonic structure of the western part of the North Aegean Basin based on swath bathymetry, Mar. Geology, 190, 465–492, 2002. Passchier, C. W. and Trouw, R. A. J.: Microtectonics, Springer, Berlin, 289 pp., 1998. Roddick, J. C.: The application of isochron diagrams in (super 40) Ar - (super 39) Ar dating, a discussion, Earth Planet. Sci. Lett., 41, 233–244, 1978. Roddick, J. C., Cliff, R. A., and Rex, D. C.: The evolution of excess argon in alpine biotites, Earth Planet. Sci. Lett., 48, 185–208, 1980. Schermer, E.: Geometry and kinematics of continental basement deformation during the Alpine Orogeny, Mt. Olympos region, Greece, J. Struct. Geol., 15, 571–591, 1993. Schermer, E. R., Lux, D. R., and Burchfiel, B. C.: Temperature-time history of subducted continental crust, Mount Olympos region, Greece, Tectonics, 9, 1165–1195, 1990. Shaked, Y., Avigad, D., and Garfunkel, Z.: Alpine high-pressure metamorphism at the Almyropotamos window (Soutern Evia, Greece), Geol. Mag., 137, 367–380, 2000. Schmitz, M. D. and Bowring, S. A.: U-Pb zircon and titanite systematics of the Fish Canyon Tuff: an assessment of high-precision U-Pb geochronology and its application to young volcanic rocks, Geochim. Cosmochim. Acta, 65, 2571–2587, 2001. Schmitz, M. D., Bowring, S. A., Ludwig, K. R., and Renne, P. R.: Comment on "Precise K-Ar, 40Ar-39Ar, Rb-Sr and U-Pb mineral ages from the 27.5 Ma Fish Canyon Tuff reference standard" by M. A. Lanphere and H. Baadsgaard, Chemical Geology, 199, 277–280, 2003. Vergely, P. and Mercier, J. L.: La fenêtre métamorphique de l'Olympe (Macédonie, Grèce): compression et extension cénozoique, Bull. Soc. Geol. Fr., 6, 819–829, 1990. Walcott, C. R.: The alpine evolution of Thessaly (NW Greece) and late Tertiary Aegean kinematics, Geologica Ultraiectina, Utrecht University, 162, 176 pp., 1998. York, D.: Least squarefitting o a straight line with correlated errors, Earth Planet. Sci. Lett., 5, 320–324, 1969.