Abstract:Alkalirich intrusions have been concerns of many scholars due to their geological significance and relation to mineralization. Late Carboniferous calcalkaline magmatic rocks were widely developed in the northern part of Hebei province, but alkalic rocks are rare in this area and no related mineralization has been found. This study, however, for the first time recognized a bunch of the middlelate Late Paleozoic alkaliarich intrusive rocks related to Au (CuPbZnAg) polymetallic mineralization in the Xiayingfang area, eastern Hebei province. LAICPMS zircon UPb dating yielded three emplacement ages of 300.0±1.5 Ma, 299.3±2.1 Ma and 300.0±2.0 Ma respectively for three alkalirich intrusions distributed in the Xiayingfang area and the results show that these magmas were the results of the late Carboniferous and early Permian. Petrological and geochemical data reflect that the rocks contain abundant alkaline minerals, such as nepheline, orthoclase, microcline, and so on, and are characterized by high Al2O3(16.21%~18.66%), alkaline ((K2O+Na2O)>8%), ΣREE (222.47×10-6~333.16×10-6) contents, indicating they belongs to alkalirich intrusions. They exhibit highly fractionated rare earth element (REE) patterns, with no obvious Eu anomalies. Besides, they show characteristics of high Sr and Ba contents, high La/Y and La/Sm (>5) ratios, low Y contents, enrichment in LILE and LREE and depletion of HFSE (e.g., Nb, Ta), P and Ti elements. These characters show that these alkalirich intrusions were probably related to partial melting of the enriched lithosphere mantle, and might be affected by the fluids (melts) derived from the dehydration of subducted slab and contaminated by crustal material during magma emplacement process. Petrogenic age, combined with the evolution of regional geology, suggests that the alkalirich intrusions in this area may have had genetic links with the southward subduction of the PaleoAsian Ocean beneath the northern margin of the North China Craton, and formed in an extension setting due to slab rollback in late Carboniferous.