TY - JOUR
T1 - An insight into a gneiss core of the Orlica-Śnieżnik Dome, NE Bohemian Massif
T2 - New structural and U-Pb zircon data
AU - Redlińska-Marczyńska, Aleksandra
AU - Żlażniewicz, Andrzej
AU - Fanning, C. Mark
N1 - Publisher Copyright:
© 2016, Polish Geological Institute. All rights reserved.
PY - 2016
Y1 - 2016
N2 - The Orlica-Śnieżnik Dome in the Sudetes, the NE Bohemian Mas sif, embraces two formations offelsic gneisses of controversial origin and evolution. Our study shows that despite similar geo chemical signatures, they carry systematic minor differences in mineral, isotope, zircon and geothermobarometric characteristics. Four variants of the Gierałtów gneisses include migmatites and have a longer structural history than the Śnieżnik augen orthogneisses. U-Pb SHRIMP anal y ses yielded U-Pb ages of ~500 Ma for cores and ~498 Ma for wide outer parts of zir con grains in the twice-folded Gierałtów gneisses, and an age of ~500 Ma for a discordant neosome vein. Neoproterozoic meta sediments were among precursors of the lithologically diversified Gierałtów Gneiss Formation. First deformation, meta morphism, and migmatisation of these rocks occurred at 515-475 Ma and over lapped with the development and emplacement of a porphyritic S-type granite precursor to the Śnieżnik Gneiss Formation. Themetagranite (= Śnieżnik augen orthogneiss) embraced migmatitic xe no liths. Zircon grains from such xe no liths revealed distorted and replaced cores which yielded U-Pb ages that dispersed around 507-487 Ma, whilst wide darker poorly zoned out growths yielded ages from ~343 Ma to ~325 Ma (mean ~340 Ma). These out growths were in ter preted as a record of Carboniferous meta morphism assisted by rich Zr- and U-carrying fluids. The Variscan meta morphic over print was heterogeneous, and variously affected rocks of the two gneiss formations.
AB - The Orlica-Śnieżnik Dome in the Sudetes, the NE Bohemian Mas sif, embraces two formations offelsic gneisses of controversial origin and evolution. Our study shows that despite similar geo chemical signatures, they carry systematic minor differences in mineral, isotope, zircon and geothermobarometric characteristics. Four variants of the Gierałtów gneisses include migmatites and have a longer structural history than the Śnieżnik augen orthogneisses. U-Pb SHRIMP anal y ses yielded U-Pb ages of ~500 Ma for cores and ~498 Ma for wide outer parts of zir con grains in the twice-folded Gierałtów gneisses, and an age of ~500 Ma for a discordant neosome vein. Neoproterozoic meta sediments were among precursors of the lithologically diversified Gierałtów Gneiss Formation. First deformation, meta morphism, and migmatisation of these rocks occurred at 515-475 Ma and over lapped with the development and emplacement of a porphyritic S-type granite precursor to the Śnieżnik Gneiss Formation. Themetagranite (= Śnieżnik augen orthogneiss) embraced migmatitic xe no liths. Zircon grains from such xe no liths revealed distorted and replaced cores which yielded U-Pb ages that dispersed around 507-487 Ma, whilst wide darker poorly zoned out growths yielded ages from ~343 Ma to ~325 Ma (mean ~340 Ma). These out growths were in ter preted as a record of Carboniferous meta morphism assisted by rich Zr- and U-carrying fluids. The Variscan meta morphic over print was heterogeneous, and variously affected rocks of the two gneiss formations.
KW - Cambrian
KW - Migmatites
KW - SHRIMP
KW - Sudetes
KW - Variscan orogeny
UR - http://www.scopus.com/inward/record.url?scp=85016325523&partnerID=8YFLogxK
U2 - 10.7306/gq.1287
DO - 10.7306/gq.1287
M3 - Article
SN - 1641-7291
VL - 60
SP - 714
EP - 736
JO - Geological Quarterly
JF - Geological Quarterly
IS - 3
ER -