Zircon–monazite geochronology and zircon Hf–O isotopes of Ediacaran–Cambrian paragneiss from the Mashan Complex, Jiamusi Block, NE China: implications for sedimentary–metamorphic–tectonic evolution

Intense debate has surrounded the tectonic placement of microcontinents in the eastern Central Asian Orogenic Belt of NE China, with particular focus on the Jiamusi Block. The oldest basement rocks within the Jiamusi Block belong to the Mashan Complex, which preserves evidence of the Late Pan-African granulite-facies metamorphic overprinting. Characterizing this complex is therefore essential for elucidating the tectonic affinity of the Jiamusi Block. Here, we present zircon–monazite U–Pb geochronology, zircon trace-element compositions, and zircon Hf–O isotopic data for paragneisses from the Mashan Complex. Detrital/Inherited zircon ages from five paragneiss samples indicate that the Mashan Complex comprises two distinct supracrustal sequences, whose protoliths were deposited at approximately 1027–895 Ma and 777–757 Ma. Metamorphic zircons recovered from the paragneisses yield a range of concordant ages from 567 to 458 Ma. The few younger analyses down to 458 Ma may represent isolated or mixed ages and are not used to define the principal retrograde interval. The U–Pb ages of metamorphic zircons and monazites, together with zircon Hf–O isotopic compositions, indicate that the paragneisses reached peak granulite-facies metamorphism at 567–563 Ma, followed by retrograde metamorphism between 553 and 476 Ma. CDF and 2D-MDS analyses of detrital zircons support a tectonic affinity of the Jiamusi Block with Northeast India. Based on this and previous studies, it is suggested that the Jiamusi Block underwent a complete Neoproterozoic–Early Palaeozoic tectonothermal evolution corresponding to the Rodinia–Gondwana cycle, including 935–891 Ma arc magmatism and Rodinia peripheral accretion, 825–750 Ma rifting and lithospheric thinning during the break-up of Rodinia, and 567–470 Ma high-grade metamorphism followed by post-orogenic extension associated with the Kuunga–Pinjarra Orogeny.