Age and petrogenesis of ore-bearing porphyry from the Houyu Mo-polymetallic deposit, central North China Craton

Abstract

Porphyry-related molybdenum deposits formed within the plate's interior are unique, yet the understanding of the magmatic hydrothermal Mo system remains limited. Houyu is a typical porphyry-related Mo-polymetallic deposit situated in the inner region of the North China Craton (NCC). The ore bodies are found in Archean biotite plagioclase gneiss and diorite, followed by Early Cretaceous quartz porphyry, granite porphyry, and brecciated porphyry. Zircon U-Pb dating reveals that the biotite plagioclase gneiss, quartz porphyry, and granite porphyry were formed at 2499.2 ± 7.8 Ma, 135.19 ± 0.67 Ma, and 137.65 ± 0.84 Ma, respectively. Molybdenite Re-Os dating indicates a mean age of 134.94 ± 0.76 Ma and an isochron age of 134.7 ± 1.5 Ma, linking the Mo-polymetallic mineralization closely to the Early Cretaceous porphyry. The Houyu Cretaceous porphyry exhibits enrichment in light rare earth elements (LREEs), depletion in heavy rare earth elements (HREEs), and distinct positive Eu anomalies. Additionally, they are enriched in fluid-mobile large-ion-lithophile elements (LILEs) and significantly depleted in high-field-strength elements (HFSEs). These geochemical attributes suggest that the Cretaceous porphyry belongs to I-type adakitic granites. All samples exhibit consistently negative εNd(t) values ranging from −15.76 to −14.87 and εHf(t) values between −20.69 and −14.78, along with restricted 206Pb/204Pb (16.557–16.663), 207Pb/204Pb (15.262–15.300), and 208Pb/204Pb (36.601–36.747) ratios, indicating that they were derived from an ancient thickened lower continental crust (LCC). The Cretaceous magmatism and mineralization of the Houyu Mo-polymetallic deposit could be closely linked to the lithospheric thinning and destruction of the NCC triggered by the Paleo-Pacific or Izanagi Plate.