The Erguna Massif is located in the southwestern portion of the Great Xing'an Range and is adjacent to the Mongol–Okhotsk suture zone. It has not been determined whether the tectonic evolutionary processes of the Erguna Massif belonged to the Mongol–Okhotsk tectonic regime during the Middle Permian–Mesozoic. In this study, a suite of rocks comprising Mesozoic S-type monzogranite (U–Pb zircon age of 248 ± 1.2 Ma), highly fractionated I-type rhyolite (204 ± 1.1 Ma), gabbro (196 ± 1.9 Ma), A2-type volcanic rocks (190 ± 0.9 Ma), A1-type trachydacite (167 ± 0.8 Ma) and Early Cretaceous A1-type alkaline rhyolite are newly identified and geochemically studied. The rhyolite, gabbro, trachydacite and alkaline rhyolite whole-rock Sr–Nd isotope analyses obtained initial values 87Sr/86Sr ratios ranging from 0.7044 to 0.7058 and εNd(t) values of −0.68 to +2.73. These samples show εHf(t) values ranging from +5.3 to +11.2 and TDM2 ranging from 0.48 to 0.90 Ga. The 248 Ma monzogranites were produced by the partial melting of greywackes. The 204 Ma rhyolites were derived from the partial melting of lower mafic crust. The 196 Ma gabbros originated from the partial melting of an enriched mantle metasomatized by subduction-slab-released fluids. The 190 Ma volcanic rocks, 167 Ma trachydacite and Early Cretaceous alkaline rhyolite were mainly formed by the partial melting of the basaltic rocks. They all show enrichment in the large-ion lithophile elements (e.g. Rb, Ba, and K) and depletion in the high-field-strength elements (e.g. Nb, Ta, and Ti), suggesting they formed in an active continental margin setting. The features of these igneous rocks indicate the southward subduction of the Mongol–Okhotsk oceanic plate. Based on compiled age data, three phases of middle Mesozoic magmatism were identified in the Erguna Massif at c. 275–225, 215–165, and 150–110 Ma. In addition, three similar magmatic phases were found in the Xing'an Massif. However, a hysteresis of c. 15–20 Ma exists between the two massifs. These magmatic rocks may record the three stages of the southward subduction of the Mongol–Okhotsk oceanic plate, and two periods of slab rollback occurred during the Middle Permian to Early Cretaceous.

Supplementary material: Analytical details, radiometric ages and Tables S1–S5 are available at:

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