Continuous zircon growth during long-lived granulite facies metamorphism: a microtextural, U–Pb, Lu–Hf and trace element study of Caledonian rocks from the Arctic

摘要: Microtextural, U–Pb, trace element and Lu–Hf analyses of zircons from gneisses dredged the Chukchi Borderland indicate a long-lived, Cambrian–Ordovician, granulite facies metamorphism. These results reveal complete prograde, peak cooling history zircon growth during anatexis. Early increasing temperatures caused modification Pb-loss Precambrian by recrystallization dissolution/re-precipitation existing grains. Small variations in initial 176Hf/177Hf (0.282325–0.282042) flat HREE patterns these that they grew presence garnet. Zircons subsequently crystallized partial melt to post-peak metamorphism 530 485 Ma. A broad range ratios (0.282693–0.282050) mineral inclusions within suggest this phase incorporated Zr Hf obtained breakdown Zr-enriched phases. Microtextural evidence along with trace element isotopic data suggests final metamorphic rims on occurred slow crystallization residual melts early Ordovician (485–470 Ma). Younger, late Ordovician–Silurian (420–450 Ma) euhedral, oscillatory-zoned, element-enriched leucocratic veins intrude gneisses. Their age corresponds granitoids dated same dredge. The intrusives provide rifted position near Pearya northwest Svalbard, which represent northern continuation Caledonian orogen. Evidence for earlier Cambrian has not been reported region. here represents earliest deformation Arctic Caledonides.