Petrogenesis and tectonic implications of the Xiachehe granite porphyries in the Wutai-Hengshan area (North China Craton): Constraints from geochemistry, zircon U-Pb geochronology and Hf isotopes

Abstract The Wutai-Hengshan area located in the Trans-North China Orogen (TNCO) is a classic example of the geological evolution in the North China Craton (NCC) and carries varied Mesozoic magmatism associated with lithospheric destruction. In this paper, we provide zircon U-Pb geochronology, whole-rock chemistry, and zircon Lu-Hf isotopic data of the Xiachehe granite porphyries to discuss their petrogenesis and tectonic implications. According to the results of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), Xiachehe granite porphyries yield zircon U-Pb ages of 135.1 ± 0.8 Ma, representing age in the Early Cretaceous. The Xiachehe granite porphyries are high-K calc-alkaline and peraluminous. These rocks have REE and trace element patterns, characterized by enrichment in large-ion lithophile elements (LILE) and light rare-earth elements (LREE), and depletion in high-field-strength elements (HFSE), heavy rare-earth elements (HREE), with negative Eu anomalies. Therefore, They are classified as I-type granites with adakitic features. The Xiachehe granite porphyries have homogeneous zircon Hf isotopic compositions. Their zircons have negative εHf(t) values (-20.7 to -19.3) and two-stage Hf model ages of 2417–2501 Ma, indicating that the studied rocks were derived from partial melting of Neoarchean-Paleoproterozoic crustal materials with mantle-derived inputs. Therefore, it is suggested that the Xiachehe granite porphyries formed in a back-arc extensional setting likely associated with the ancient Pacific Plate subduction and retreat beneath the Eurasian continent. The TNCO was influenced by the subduction and retreat of the ancient Pacific Plate in the Early Cretaceous.