An 807–763 Ma continental arc records crust-mantle interaction in the Erguna Block during the breakup of Rodinia

Circum-Rodinia subduction-related magmatism provides important insights into the evolution of orogens that formed at the margins of the Rodinia supercontinent. However, the nature of the magma sources and geodynamic processes remain enigmatic. In this paper, we present a systematic study of the petrology, whole-rock geochemistry and geochronology of Neoproterozoic potassium-rich mafic and granitic intrusions from the Erguna Block in northeast China. The granitic intrusions include quartz monzonite and monzogranite and belong to the high-K calc-alkaline to shoshonite series. The quartz monzonite has a zircon U-Pb age of 807 ± 3 Ma with εHf_(t) values of −0.50 to + 4.06 and was derived from low degree partial melting of amphibolites. The monzogranite has a zircon U-Pb age of 792 ± 3 Ma with εHf_(t) values of + 0.82 to + 4.64 and was generated from fractional crystallization of high-K calc-alkaline gabbroic magma. The mafic intrusions are hornblende gabbros with a zircon U-Pb age of 763 ± 6 Ma, εHf_(t) values of −9.19 to + 9.18, and an enriched mantle source. Together with existing data, we identify two stages of potassium-rich mafic magmatism at 792 Ma and 763 Ma, whose primary melts were produced by partial melting of mélange diapirs formed by the subducted sediments mixed with a pyroxenite source at depths of 79–72 km and a peridotite source at 71–66 km, respectively. The 807–763 Ma potassium-rich magmatic rocks in the Erguna Block suggest the presence of a mature continental arc. Oceanic subduction supported an orogen along the northwest margin of Rodinia during its breakup, and was responsible for significant mantle heterogeneity, juvenile crustal accretion and reworking of ancient crust.