Refining the granite, gneiss and schist interrelationships within the Lusatian–Izera Massif, West Sudetes, using SHRIMP U-Pb zircon analyses and new geologic data

摘要: The eastern part of the Lusatian–Izera Massif, West Sudetes, comprises different types gneissose rocks, collectively known as Izera gneisses, with a subordinate component petrographically varied mica schists. Coarse-grained gneisses and their protoliths have been dated at 515–480 Ma, but lack age data for other rocks has impeded accounts mutual relationships and, thus, region’s geological evolution. This paper reports new sensitive high-mass resolution ion microprobe (SHRIMP) U-Pb zircon data, some field petrographic observations, three representative rock types: 1) Zlotniki schist (a fine-grained quartz–albite–chlorite–sericite–biotite schist); 2) gneiss that grades to ‘porphyroblastic’ granite which occurs on slopes Mt. Stog Izerski; 3) leucogranite found just south village Kotlina. A volcanogenic intercalation in Lubanskie schists developed 560 Ma contained xenocrystic zircons grew source 620 600–580 Ma. are interpreted metamorphosed equivalent Lusatian greywackes, were derived from dissected arc deposited convergent-margin basin along northern peri-Gondwana. yielded four groups: 515 ± 7 500 12 487 13 471 8 Similar groups can also be coarse-grained metagranites. Rifting Gondwana during mid-Cambrian–early Ordovician was protracted thermal event lasting ~30–45 m.y., episodic attenuation mainland crust every ~5–10 m.y. before continental fragments finally became separated. Each episode successively promoted an increased heat flux mantle facilitated melting crust, causing metamorphism fusion Precambrian basement final phase S-type felsic magmatism. sample two groups, 508 5 483.1 3.6 low Th/U ratios, is product anatectic deeper crustal levels. These leucogranites close spatial relation belts schist, could mean these granites used rheologically weak zones introduced into pluton where large country trapped within ~500 granites.