Petrologic constraints on imbrication, metamorphism, and uplift in the SW Tauern Window, eastern Alps

The pressure-temperature-time-deformation (PTtd) history of two tectonic units in the southwest Tauern Window (Austria/Italy) is evaluated from P-T paths of metamorphism and uplift, geochronologic data, and observations on fabric development. Petrologic data indicate burial of the Lower Schieferhulle (LSH) to depths of ≥ 35 km and the adjacent Upper Schieferhulle (USH) to only 24–28 km; the units are now separated by only 2 km of section. Metamorphism was postkinematic in the LSH and synkinematic in the USH. Correlation of P-T path reversals calculated from zoned garnets in the two units, however, indicates that juxtaposition of the LSH and USH occurred prior to metamorphism. Temperature-time and depth-time diagrams for both units show increasing cooling rates and decreasing uplift rates as the rocks approached the surface. Both the petrologic data and the depth-time profiles for the LSH and USH point to a history of differential uplift in the early stages of decompression. Textural features indicate that the LSH behaved as an essentially rigid body during uplift, whereas the USH experienced extensive ductile shearing. The PTtd data for the LSH and USH are incorporated into a model for continental collision in the Eastern Alps. Initial tectonic uplift of the LSH was accompanied by ductile thinning of the USH and overlying Austroalpine units. Final uplift and erosion affected all of the units “en masse”.

[1]  W. Ryan,et al.  Plate Tectonics and the Evolution of the Alpine System , 1973 .

[2]  P. England.  Some thermal considerations of the alpine metamorphism—past, present and future , 1978 .

[3]  P. England,et al.  The influence of erosion upon the mineral fades of rocks from different metamorphic environments , 1977, Journal of the Geological Society.

[4]  Frank S. Spear,et al.  Metamorphic P–T Paths from pelitic schists and greenstones from the south-west Tauern Window, Eastern Alps , 1985 .

[5]  Christine Miller.  Chemismus und phasenpetrologische Untersuchungen der Gesteine aus der Eklogitzone des Tauernfensters, Österreich , 1977 .

[6]  P. England.  Metamorphic pressure estimates and sediment volumes for the Alpine orogeny: an independent control on geobarometers? , 1981 .

[7]  W. Ernst.  Interpretative Synthesis of Metamorphism in the Alps , 1973 .

[8]  G. Hoschek.  Phase relations of a simplified Marly rock system with application to the Western Hohe Tauern (Austria) , 1980 .

[9]  M. Bickle,et al.  Plate tectonics in the Eastern Alps , 1975 .

[10]  D. Rubie.  A Thermal-Tectonic Model for High-Pressure Metamorphism and Deformation in the Sesia Zone, Western Alps , 1984, The Journal of Geology.

[11]  W. Frisch.  Sedimentological response to late Mesozoic subduction in the Penninic windows of the Eastern Alps , 1984 .

[12]  G. Droop.  Alpine metamorphism in the south‐east Tauern Window, Austria: 1. P–T variations in space and time , 1985 .

[13]  C. Hawkesworth.  Rb/Sr geochronology in the Eastern Alps , 1976 .

[14]  W. Frisch.  Tectonic progradation and plate tectonic evolution of the Alps , 1979 .

[15]  R. Nolen-Hoeksema,et al.  The Lepontine Alps as an evolving metamorphic core complex during a-type subduction: Evidence from heat flow, mineral cooling ages, and tectonic modeling , 1985 .

[16]  L. Hollister,et al.  Physical conditions during uplift of metamorphic terranes, as recorded by fluid inclusions , 1979 .

[17]  Alan Bruce Thompson,et al.  Pressure—Temperature—Time Paths of Regional Metamorphism I. Heat Transfer during the Evolution of Regions of Thickened Continental Crust , 1984 .

[18]  Giulio Morteani,et al.  High-Pressure Metamorphism in the SW Tauern Window, Austria: P-T Paths from Hornblende-Kyanite-Staurolite Schists , 1984 .

[19]  V. Dietrich.  Evolution of the Eastern Alps: A plate tectonics working hypothesis , 1976 .

[20]  W. Frisch.  Post-Hercynian formations of the western Tauern window: sedimentological features, depositional environment, and age , 1980 .

[21]  Martin H. Dodson,et al.  Closure temperature in cooling geochronological and petrological systems , 1973 .

[22]  T. Harrison,et al.  Investigations of an intrusive contact, northwest Nelson, New Zealand—I. Thermal, chronological and isotopic constraints , 1980 .

[23]  H. Laubscher.  Plate boundaries and microplates in Alpine history , 1975 .

[24]  P. Baggio,et al.  The Pennine Zone of the Vizze region in the western Tauern Window (Italian Eastern Alps) , 1982 .

[25]  F. Spear,et al.  P-T paths from garnet zoning: A new technique for deciphering tectonic processes in crystalline terranes , 1984 .

[26]  M. Toksöz,et al.  Thermal and mechanical models of continent‐continent convergence zones , 1975 .

[27]  R. Parrish.  Cenozoic thermal evolution and tectonics of the Coast Mountains of British Columbia: 1. Fission track dating, apparent uplift rates, and patterns of uplift , 1983 .

[28]  P. England,et al.  Pressure—Temperature—Time Paths of Regional Metamorphism II. Their Inference and Interpretation using Mineral Assemblages in Metamorphic Rocks , 1984 .

[29]  G. Hoschek.  Alpine metamorphism of calcareous metasediments in the Western Hohe Tauern, tyrol: mineral equilibria in COHS fluids , 1984 .

[30]  B. Burchfiel.  Eastern European Alpine system and the Carpathian orocline as an example of collision tectonics , 1980 .

[31]  L. Royden,et al.  Geologic thermobarometry of retrograded metamorphic rocks: An indication of the uplift trajectory of a portion of the northern Scandinavian caledonides , 1984 .

[32]  T. Holland.  High Water Activities in the Generation of High Pressure Kyanite Eclogites of the Tauern Window, Austria , 1979, The Journal of Geology.

[33]  E. R. Oxburgh,et al.  Thermal gradients and regional metamorphism in overthrust terrains with special reference to the Eastern Alps , 1974 .

[34]  P. England,et al.  A preliminary thermal model for regional metamorphism in the Eastern Alps , 1975 .

[35]  L. Royden,et al.  A technique for analyzing the thermal and uplift histories of eroding orogenic belts: A Scandinavian example , 1984 .

[36]  R. Bone,et al.  Denudation Rates, Thermal Evolution, and Preservation of Blueschist Terrains , 1981, The Journal of Geology.

[37]  P. England,et al.  The Acadian Thermal History of the Merrimack Synclinorium in New Hampshire , 1985, The Journal of Geology.

[38]  F. Spear,et al.  Quantitative P-T paths from zoned minerals: Theory and tectonic applications , 1983 .

[39]  Peter Molnar,et al.  Structure and Tectonics of the Himalaya: Constraints and Implications of Geophysical Data , 1984 .