Alpine metamorphism in the south-east Tauern Window, Austria; 2, Rates of heating, cooling and uplift

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Authors:Cliff, R. A.; Droop, G. T. R.; Rex, D. C.
Author Affiliations:Primary:
Univ. Leeds, Dep. Earth Sci., Leeds, United Kingdom
Univ. Manchester, Dep. Geol., United Kingdom
Volume Title:Journal of Metamorphic Geology
Source:Journal of Metamorphic Geology, 3(4), p.403-415. Publisher: Blackwell, Oxford, United Kingdom. ISSN: 0263-4929
Publication Date:1985
Note:In English. 26 refs.; illus. incl. 4 tables
Summary:New Rb/Sr, K/Ar and 39Ar/40Ar ages are presented, including a suite of 33 mica ages for a 20 km N-S tunnel section. These and previous geochronological data are discussed in relation to the thermal history from the overthrusting of the Austro-Alpine nappes approx 65 m.y. ago to the present. The earliest metamorphic phase, involving lawsonite crystallization, was associated with emplacement of these nappes; subsequently, T in rocks beneath rose at a mean rate of 3°-6°C/m.y. until the climax of metamorphism. Published data for the age of this climax at high structural levels indicate >35 m.y., but a new 39Ar/40Ar step-heating age of 23.8 + or - 0.8 m.y. on amphibole from near the base of Peripheral Schieferhulle indicates a later climax at deeper structural levels. Following the climax, near-isothermal uplift and erosion reduced P to approx 1 kbar before white mica closure at 19 m.y.; this implies uplift at >3 mm/yr. Along the tunnel, white mica K/Ar ages vary systematically from 24 to 16.5 m.y. with position relative to a late 4 km amplitude dome, whereas biotite Rb/Sr ages are uniform at 16.5 m.y. across the whole profile; doming is thus dated at 16.5 m.y. with transient uplift rates >5 mm/yr. At other times uplift rates were <1 mm/yr. [R.A.H.]
Subjects:Absolute age; Ar-40/Ar-39; Argon; Blueschist facies; Cenozoic; Crystallization; Dates; Facies; Faults; Geochronology; Isotopes; K/Ar; Metamorphic rocks; Metamorphism; Mica group; Mineral assemblages; Noble gases; P-T conditions; Radioactive isotopes; Rb/Sr; Regional metamorphism; Sheet silicates; Silicates; Stable isotopes; Structural geology; Tectonics; Tertiary; Thrust faults; Uplifts; Alps; Austria; Central Europe; Europe; Penninic Zone; Tauern Window; Alpine-type
Abstract Numbers:86M/3917
Record ID:1987035408
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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