HR: 0800h
AN: V11A-1416    [Abstracts]
TI: High-pressure Metamorphism in the Evolutionary History of the Earth's Crust in the Urals
AU: * Pystin, A
EM: pystina@geo.komisc.ru
AB: Eclogite ages from the Urals mainly fall within the interval 390 ñ 240 Ma. Grounding on these dates, many researchers limit the time of formation of eclogite-bearing rock associations by the above-mentioned interval, beginning with crystallization of high-pressure parageneses in deep zones and finishing at eclogite exhumation during the collision and post-collision stages of fold-orogenic belt development. At the same time, there are more ancient dates of the objects to be studied. Hence, not denying a theoretical possibility of eclogite formation and exhumation during a single geodynamic cycle, we think that the models, which allow for a significant time interval between the eclogite formation and exhumation of the high-pressure associations out of the deep zones, are more realistic for the Uralian eclogites. On the basis of available geochronological data on the Uralian eclogites, one can single out three time levels of evolution of high-pressure metamorphic rocks: over 1560, 720-550, and 390-240 Ma. At present, most researchers think that conditions for metamorphic eclogite crystallization can be realized only in subduction zones. This could be accepted, however, repeated high-pressure metamorphic manifestations in the same complexes for more than 1000 million years seem unlikely. It appears that only the most ancient eclogite dates (over 1560 Ma) record the time of crystallization of these rocks in subduction zones. Neoproterozoic and Paleozoic ages indicate the time of collision and post-collision processes at later stages of geodynamic development. Movement of eclogite-bearing complexes to the upper layers of the Earth's crust is connected with the processes.
DE: 8102 Continental contractional orogenic belts
DE: 3600 MINERALOGY AND PETROLOGY (replaces
DE: 3660 Metamorphic petrology
DE: 1025 Composition of the mantle
DE: 1020 Composition of the crust
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting