Devonian tectonothermal activity in the Sowie Góry gneissic block, Sudetes, southwestern Poland: evidence from Rb-Sr and U-Pb isotopic studies
Abstract
Dewońska aktywność tektonometamorficzna w gnejsach bloku Gór Sowich w świetle badań izotopowych Rb-Sr i U-Pb
In widely developed biotite-oligoclase-quartz paragneiss a U-Pb upper intercept age of 1750 ±270 is interpreted as a (possibly mixed) sedimentary provenance age. U-Pb monazite and Rb-Sr biotite ages of 381 ± 2 Ma and ca. 370-360 Ma, respectively, indicate rapid Devonian cooling from upper amphibolite to greenschist facies temperatures. The isotopic data are consistent with stratigraphic evidence for rapid Devonian uplift. U-Pb zircon isotopic data support, but do not prove conclusively, that the metamorphism associated with D2 in the Sowie Góry block was Devonian in age. The Z)4 event has been dated at 370 ± 4 Ma using Rb-Sr in large muscovite books from a pegmatite in an F4 hinge zone. Low-mid-amphibolite facies Ds activity cannot be much younger in view of the biotite cooling ages. The D2-5 tectonothermal activity, rapid cooling and uplift in the Sowie Góry block of the Middle Sudetes pre-date the early Carboniferous granulite facies metamorphism and granitic plutonism further S in the Moldanubian zone of the Hercynides in Czechoslovakia.
Schyłek progresywnego metamorfizmu, aktywność magmową (pegmatyty) i podniesienie kompleksu gnejsów sowiogórskich datowano odpowiednio na 381+2 Ma, 370 + 4 Ma i 370 - 360 Ma. Szybkie stygnięcie kompleksu, wiążące się z inwersją tektoniczną przy końcu dewonu, trwało około 10 - 20 mln lat.
In widely developed biotite-oligoclase-quartz paragneiss a U-Pb upper intercept age of 1750 ±270 is interpreted as a (possibly mixed) sedimentary provenance age. U-Pb monazite and Rb-Sr biotite ages of 381 ± 2 Ma and ca. 370-360 Ma, respectively, indicate rapid Devonian cooling from upper amphibolite to greenschist facies temperatures. The isotopic data are consistent with stratigraphic evidence for rapid Devonian uplift. U-Pb zircon isotopic data support, but do not prove conclusively, that the metamorphism associated with D2 in the Sowie Góry block was Devonian in age. The Z)4 event has been dated at 370 ± 4 Ma using Rb-Sr in large muscovite books from a pegmatite in an F4 hinge zone. Low-mid-amphibolite facies Ds activity cannot be much younger in view of the biotite cooling ages. The D2-5 tectonothermal activity, rapid cooling and uplift in the Sowie Góry block of the Middle Sudetes pre-date the early Carboniferous granulite facies metamorphism and granitic plutonism further S in the Moldanubian zone of the Hercynides in Czechoslovakia.
Schyłek progresywnego metamorfizmu, aktywność magmową (pegmatyty) i podniesienie kompleksu gnejsów sowiogórskich datowano odpowiednio na 381+2 Ma, 370 + 4 Ma i 370 - 360 Ma. Szybkie stygnięcie kompleksu, wiążące się z inwersją tektoniczną przy końcu dewonu, trwało około 10 - 20 mln lat.