Guangtoushan granites and their enclaves: Implications for Triassic mantle upwelling in the northern margin of the North China Craton

Mineral electron microprobe, bulk rock major, trace elements and Nd isotopes, and zircon U–Pb and Hf isotopic data are reported for granites and dioritic enclaves from the Guangtoushan granitic complex in the northern margin of the North China Craton. The zircon U–Pb dating identifies two stages of magmatism. The early stage enclave and host granite have identical ages (250 ± 2 Ma) and similar bulk rock Nd isotopes (εNd(t) = − 11.5 to − 12.2) as well as similar zircon Hf isotopes (εHf(t) = − 13.3 to − 17.4). However, although the late stage enclave (206 ± 2 Ma), host granite (208 ± 1 Ma) and leucogranite (207 ± 3 Ma) display comparable ages, but exhibit distinct isotopic features: the granite displays moderate bulk rock Nd isotopic value (εNd(t) = − 8.3) and zircon εHf(t) from − 2.6 to − 10.4; the enclave shows least negative bulk rock εNd(t) of − 3.9 and zircon εHf(t) from 0 to − 5.4; and the leucogranite possesses more pronounced negative bulk rock Nd (εNd(t) = − 17.2) and zircon Hf isotopic compositions (εHf(t) = − 6.2 to − 19.0). An integration of field observations, geochronology, geochemistry and zircon Hf isotopic data points to a complex petrogenetic history, where the early stage enclave–granite pair is a product of the early crystallization of felsic magmas that evolved from a mafic magma, whereas the late stage enclave and granite were derived by magma mixing. The late stage leucogranite is considered as a product of remelting of Phanerozoic igneous rocks within this region. The Guangtoushan granitic complex offers robust evidence for a gradual mantle upwelling during Triassic in the northern margin of the North China Craton.

► We report two stages of Triassic magmatism zircon ages of the Guangtoushan complex. ► We report the analytical results of zircon Hf and whole-rock Nd isotopic compositions. ► Mantle-derived and crustal-derived magma mixing occurred in Triassic. ► The time-integrated increasing trend from Carboniferous to Triassic. ► A progressive increase in the mantle component from Carboniferous to Triassic.