TY - JOUR
T1 - Late- orogenic magmatism in the Central European Variscides
T2 - SHRIMP U-Pb zircon age constraints from the żeleźniak intrusion, Kaczawa Mountains, West Sudetes
AU - MacHowiak, Katarzyna
AU - Armstrong, Richard
AU - Kryza, Ryszard
AU - Muszyński, Andrzej
PY - 2008
Y1 - 2008
N2 - We present new U-Pb isotope data obtained using the sensitive high mass- resolution ion microprobe (SHRIMP) technique on zircon crystals from the Żeleźniak subvolcanic intrusion in the Kaczawa Mountains, West Sudetes, SW Poland. The intrusion comprises shallow- level unmetamorphosed and undeformed fine- grained rhyolites, rhyodacites, and trachy andesites and deep- level medium- grained monzogranites and granodiorites. The surrounding country rocks, thought to be fragments of a Varis can accretionary prism, are blueschist- to subsequent greenschist facies metavolcanic and metasedimentary rocks of the Kaczawa Complex. The Żeleźniak intrusion has been correlated with other late- to post- tectonic Varis can volcanic and plutonic bodies in the region, such as the Karkonosze Granite, but the scarcity and often problematic quality of age constraints and of geochemical data have made such correlations speculative. Our new SHRIMP zircon ages of ∼315-316 Ma from the Żeleźniak in trusion probably corresponds to the main magmatic stage. However, a younger age of ∼269 Ma, derived from some zircon rims, is more difficult to interpret but might reflect either a much younger igneous event or a hydrothermal episode. The new date of ∼315-316 Ma for the undeformed Żeleźniak intrusion also provides an upper age limit for deeper- level tectonic and metamorphic processes in the Kaczawa accretionary prism. Furthermore, the new SHRIMP zircon ages are among the oldest obtained from the volcanic rocks within the Variscan Belt in Central Europe and may correspond to the final stages of the exhumation of the blueschist facies rocks in this part of the orogen.
AB - We present new U-Pb isotope data obtained using the sensitive high mass- resolution ion microprobe (SHRIMP) technique on zircon crystals from the Żeleźniak subvolcanic intrusion in the Kaczawa Mountains, West Sudetes, SW Poland. The intrusion comprises shallow- level unmetamorphosed and undeformed fine- grained rhyolites, rhyodacites, and trachy andesites and deep- level medium- grained monzogranites and granodiorites. The surrounding country rocks, thought to be fragments of a Varis can accretionary prism, are blueschist- to subsequent greenschist facies metavolcanic and metasedimentary rocks of the Kaczawa Complex. The Żeleźniak intrusion has been correlated with other late- to post- tectonic Varis can volcanic and plutonic bodies in the region, such as the Karkonosze Granite, but the scarcity and often problematic quality of age constraints and of geochemical data have made such correlations speculative. Our new SHRIMP zircon ages of ∼315-316 Ma from the Żeleźniak in trusion probably corresponds to the main magmatic stage. However, a younger age of ∼269 Ma, derived from some zircon rims, is more difficult to interpret but might reflect either a much younger igneous event or a hydrothermal episode. The new date of ∼315-316 Ma for the undeformed Żeleźniak intrusion also provides an upper age limit for deeper- level tectonic and metamorphic processes in the Kaczawa accretionary prism. Furthermore, the new SHRIMP zircon ages are among the oldest obtained from the volcanic rocks within the Variscan Belt in Central Europe and may correspond to the final stages of the exhumation of the blueschist facies rocks in this part of the orogen.
KW - Geochemistry
KW - Variscan igneous activity
KW - West Sudetes
KW - Zircon geochronology
KW - Żeleźniak intrusion
UR - http://www.scopus.com/inward/record.url?scp=76149139479&partnerID=8YFLogxK
M3 - Article
SN - 0072-100X
VL - 40
SP - 1
EP - 18
JO - Geologia Sudetica
JF - Geologia Sudetica
ER -