Zircon U–Th–Pb–Hf isotopes of the basement rocks in northeastern Cathaysia block, South China: Implications for Phanerozoic multiple metamorphic reworking of a Paleoproterozoic terrane

摘要: Abstract The Cathaysia block records a complex tectonic history, the understanding of which is central to debate on evolution South China Block and its position in various supercontinent assemblies. Here we investigate two key formations from this block, Mayuan Group northern Fujian Province, northeastern equivalent Badu southwestern Zhejiang Province. Previous studies traced Paleoproterozoic whereas Neoproterozoic age was proposed for Group. rocks sampled study both groups show similar mineral assemblages garnet + sillimanite + biotite + plagioclase + quartz ± K-feldspar ± muscovite ± graphite as well high contents SiO2 Al2O3, typical amphibolite- granulite-facies metapelitic rocks. Zircon U–Pb data yield discordia intercept ages ~ 1990 Ma ~ 2450 Ma one sample ~ 3.5 Ga, 2.5 Ga, 1.86 Ga 233 Ma another Zircons samples group 1859 Ma 249 Ma ~ 2.6 Ga, 1.87 Ga, 257 Ma weighted mean 206Pb/238U 248 Ma other. ca. 1.86–1.87 Ga 230–250 Ma are interpreted represent time metamorphic reworking because zircon grains these tend have low Th/U ratios, flat HREE patterns unzoned internal texture revealed by cathodoluminescene (CL) images. These results confirm that lithostratigraphic unit also suggest at least part, if not all, Paleoproterozoic. Evidence Paleozoic considered affected whole study; contrast our clearly obvious Mesozoic 230–250 Ma. ɛHf(t) values range − 19 + 11 with peak − 5.5 TDMC(Hf) ranging 1.9 4.1 Ga 2.7–3.0 Ga suggesting major crustal growth took place during time. This interpretation consistent previously suggested peaks ~ 2.7 Ga ~ 2.9Ga. A synthesis reliable geochronological gathered so far Phanerozoic reveals imprints tectonothermal events differently distributed different zones. Rocks metamorphosed event dominantly occur western zone those reworked high-grade metamorphism mainly outcrop eastern zone. Our alerts previous notion uniform distribution all across provides new insights Block.