caa a22 4500 465791158 CHVBK 20180323112025.0 cr unu---uuuuu 170327e19900401xx s 000 0 eng 10.1007/BF00306666 doi (NATIONALLICENCE)springer-10.1007/BF00306666 Single grain argon laser probe dating of phengites from the blueschist to greenschist transition on Sifnos (Cyclades, Greece) [Elektronische Daten] [Jan Wijbrans, Manfred Schliestedt, Derek York] Measurements of 40Ar/39Ar age spectra on single white mica crystals of Tertiary age is a new means of obtaining detailed geochronological information of Alpine blueschists. Internal consistency of the data set, as well as excellent agreement with previous conventional K−Ar results, demonstrates that this new technique can be used with confidence to obtain information on the thermal evolution of young metamorphic belts. As mineral grains can be dated individually with this technique, problems related to multiple generations of mica occurring side in the rock can be addressed, potentially yielding much information which cannot be obtained easily by other dating techniques. Ages decrease from 41.7±0.3 Ma in the fresh blueschists and eclogites in northern Sifnos to ca 30 Ma in the more severely overprinted greenschists of central Sifnos. It is argued that this decreasing trend appears gradual, rather than stepwise. This gradual character of the age trend is taken to indicate that it may be caused by differential uplift and cooling, rather than by tectonic juxtaposition of different rock units. In addition, the rocks of central Sifnos contain mica with a plateau age of 18.9±0.3 Ma. This latter age is younger than previous estimates for the age of greenschist overprinting, and more in line with the age of high temperature metamorphism and granite emplacement elsewhere in the Cyclades. Springer-Verlag, 1990 Wijbrans Jan Geophysics Group, Department of Physics, University of Toronto, M5S 1A7, Toronto, Canada aut Schliestedt Manfred Institut für Mineralogie, Universität Hannover, Welfengarten 1, D-3000, Hannover, Germany aut York Derek Geophysics Group, Department of Physics, University of Toronto, M5S 1A7, Toronto, Canada aut Contributions to Mineralogy and Petrology Springer-Verlag 104/5(1990-04-01), 582-593 0010-7999 104:5<582 1990 104 410 https://doi.org/10.1007/BF00306666 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00306666 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Wijbrans Jan Geophysics Group, Department of Physics, University of Toronto, M5S 1A7, Toronto, Canada aut NATIONALLICENCE 700 1- Schliestedt Manfred Institut für Mineralogie, Universität Hannover, Welfengarten 1, D-3000, Hannover, Germany aut NATIONALLICENCE 700 1- York Derek Geophysics Group, Department of Physics, University of Toronto, M5S 1A7, Toronto, Canada aut NATIONALLICENCE 773 0- Contributions to Mineralogy and Petrology Springer-Verlag 104/5(1990-04-01), 582-593 0010-7999 104:5<582 1990 104 410 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer