2/18/2023 0 Comments Kspectra for windows![]() ![]() Freeman 258ppĭeutsch A, Steiger RH (1985) Hornblende K-Ar ages and the climax of tertiary metamorphism in the Lepontine Alps (southcentral Switzerland): An old problem reassessed. J Metamorphic Geol 3:403–415ĭalrymple GB, Lanphere MA (1969) Potassium-Argon Dating: Principles, Techniques and Applications to Geochronology. Jahrb Geol Bundesanstalt Austria 114:121–272Ĭliff RA, Droop GTR, Rex DC (1985) Alpine metamorphism in the south-east Tauern Window, Austria: 2. Contrib Mineral Petrol, submitted for publicationĬliff RA, Norris RJ, Oxburgh ER, Wright RC (1971) Structural, metamorphic and geochronological studies in the Reisseck and southern Ankogel groups, Eastern Alps. Lithos, submitted for publicationīlanckenburg F v, Villa I, Baur H, Morteani G, Steiger RH (1988) Time calibration of a PT-path in the Western Tauern Window, Eastern Alps: The problem of closure temperatures. ![]() Geol Jb 86:835–844īlanckenburg F v, Morteani G (1988) Crystallization and deformation of amphiboles and cummingtonite forming reactions in the garbenschists of the Western Tauern Window (Eastern Alps). Chem Geol 59:43–58īesang Cl, Harre W, Karl F, Kreuzer H, Lenz H, Mueller P, Wendt J (1968) Radiometrische Altersbestimmungen (Rb/Sr und K-Ar) an Gesteinen des Venediger-Gebietes (Hohe Tauern, Österreich). This gives evidence that loss of radiogenic isotopes proceeds by a more complex mechanism than simple volume diffusion through isotropic media.īerry RF, Mc Dougall I (1986) Interpretation of 40Ar/ 39Ar and K-Ar dating evidence from the Ailu Formation, East Timor, Indonesia. In particular those 39Ar- 40Ar release spectra which yield low temperature steps with younger ages than the plateaus are not interpretable in terms of a synchronous closure. This observation leads to a critical evaluation of the closure temperature “constant”, which apparently depends on an incompletely known number of mineralogical and environmental parameters. The retentivity of 40Ar, after correction for excess, shows no correlation with chemistry within the narrow compositional range observed rather, it shows intriguing correlations with irregularities in Ca/K spectra, pointing to a microstructurally controlled mechanism for Ar loss. Ages of 18–20 Ma result for corrected hornblendes. It can be quantified in 4 out of 10 hornblendes by 39Ar- 40Ar stepwise heating experiments. Excess Ar is semiquantitatively corrected for by combining cogenetic hornblende and cummingtonite with K-Ar isochrons. The reason for this scatter is excess Ar, possibly incorporated into amphiboles during healing of fractures, now traceable by trails of fluid inclusions. Two nearly potassiumfree cummingtonites rimming hornblende yield K-Ar ages of 120 Ma, while the 20 tschermakitic hornblendes scatter between 17 and 37 Ma. The post-kinematic amphiboles were produced during the late Alpine prograde metamorphism (6–10 kb and 500–570° C). 22 hornblende K-Ar ages and 10 39Ar- 40Ar spectra were obtained for hornblende garbenschists from the Western Tauern Window. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |