Paleoproterozoic granite in the Khondalite Belt, northern margin of the North China Craton: Response to the assembly of the Columbia supercontinent

Abstract

Metapelitic gneiss (sillimanite–biotite–garnet gneiss) and S-type granites have been identified in the Khondalite Belt (KB), located in the northeastern margin of the North China Craton (NCC), which has traditionally been considered closely related to the São Francisco–Congo Craton (SFCC). Zircon U–Pb–Hf isotopic experiments on these rocks revealed two distinct late Paleoproterozoic age groups: 2.00–1.95 and 1.93–1.90 Ga. The 2.00–1.95 Ga magmatic zircon cores displayed εHf(t) values ranging from −1.94 to +7.48, with two-stage Hf model ages between 2.28 and 2.71 Ga. The 1.93–1.90 Ga ages obtained from the S-type granites were interpreted as late Paleoproterozoic anatectic magmatism, which coincides with the metamorphism and anatexis ages derived from the metapelitic gneisses. The 1.93–1.90 Ga anatectic zircon rims exhibited significantly lower ¹⁷⁶Lu/¹⁷⁷Hf and ¹⁷⁶Hf/¹⁷⁷Hf values compared to the inherited magmatic zircon cores, indicating that the Lu–Hf isotope compositions were reset during anatexis. A comparative study suggests that the similarities between the khondalite rocks (or granitic rocks in KB) of the NCC and SFCC, such as related mineral paragenesis and reactions, provenance, tectonic setting, depositional age, nearby P–T conditions, and metamorphism age, indicate a potential genetic correlation of these rocks. Therefore, the late Paleoproterozoic metamorphic and anatectic events align with global orogenic events recorded in several continental fragments, suggesting a connection to the Columbia supercontinent.