Geochemical characteristics and prospecting significance of Early Cretaceous rhyolite porphyry in the Yangjiayingzi area, northern Hebei

• First determination of the epithermal-porphyry type Mo-polymetallic deposit. • Identification of rhyolite porphyry with A-type granite affinity. • Petrogenesis of rhyolite porphyry and Mo-polymetallic metallogenic. The Yangjiyingzi area in northern Hebei is situated on the important Mo-polymetallic metallogenic belt along the northern margin of the North China Craton (NCC). Based on a systematic analysis of regional geology, ore deposit geology, mineralization characteristics, and country rock alteration, combined with litho-geochemical research, this study defines the genetic type of the molybdenum deposit in this area. Research indicates that the ore bodies primarily occur within rhyolitic volcaniclastic rocks of the third member of the Zhangjiakou Formation in the Early Cretaceous; the ore-bearing country rock is the Early Cretaceous rhyolite porphyry, controlled by the regional F 45 fault and its secondary structures, presenting as stratiform-like and fine-vein disseminated occurrences. Country rock alteration is characterized by silicification, potassic alteration, fluoritization, and pyritization, with the development of colloidal sulfur molybdenum mineralization. Litho-geochemical characteristics show that the ore-hosting rhyolite porphyry is high in silica (SiO 2 = 64.90%-67.01%) and potassium (K 2 O = 4.57%-6.24%), and peraluminous (A/CNK = 1.10-1.22). The rare earth elements (REEs) distribution pattern is right-inclined, with a moderate negative Eu anomaly (δEu = 0.49-0.81). The rocks are enriched in Rb, Th, K, Zr, and Hf, and depleted in Ba, Sr, P, and Ti. Integrating its geological and geochemical characteristics, the Yangjiayingzi deposit is interpreted as a typical porphyry-type molybdenum deposit. Its formation is closely related to strongly acidic, volatile-rich magmatic-hydrothermal activity against the backdrop of lithospheric thinning and extension of the NCC during the Yanshanian period. The determination of this genetic type holds significant guiding importance for deepening the understanding of regional metallogeny and directing further prospecting and exploration