Paleoproterozoic ultrahigh-temperature pelitic granulites in the northern Sulu orogen: Constraints from petrology and geochronology

•1.82–1.85 Ga pelitic granulites are reported firstly in the north Sulu UHP metamorphic belt.•These granulites underwent UHT metamorphism with peak P–T conditions of 11–13 kbar and >900 °C.•The UHT metamorphism possibly related to the assembly of the supercontinent Columbia.

Ultrahigh-temperature (UHT) pelitic granulites are reported firstly in Weihai area, the northern segment of Sulu ultrahigh-pressure (UHP) metamorphic belt. The pelitic granulites, together with other metamorphic supracrustal rocks, including gneisses, marbles, quarzites and calc-silicates, occur as blocks within the orthogneisses which formed at Neoproterozoic but underwent Triassic UHP metamorphism. The pelitic granulites have a peak mineral assemblage of garnet + sillimanite + K-feldspar + plagioclase (antiperthite) + quartz + rutile + ilmenite ± biotite. The P–T pseudosection and mineral isopleths thermobarometry modeled in the MnNCFKMASHTO system constrain P–T conditions of 11–13 kbar and >900 °C for the peak stage. In situ LA–ICPMS U–Pb dating and trace element analyses show that zircons from the two granulites have low Th/U ratios, flat HREE patterns with negative Eu anomalies, typical of granulite-facies metamorphic zircon. These zircons yielded 207Pb/206Pb ages of 1818 ± 10 Ma to 1854 ± 9 Ma, representing the time of the UHT granulite-facies metamorphism. Our result, together with previous investigations, indicates that the Mid-Paleoproterozoic tectonothermal event was widespread in the northern margin of the South China Craton. The Paleoproterozoic UHT granulite-facies metamorphism and associated anatexis, and coeval magmatism possibly derived from accretionary orogeny during the assembly of the supercontinent Columbia.