The Central Hebei Basin（CHB） is one of the largest sedimentary basins in the North China Craton,extending in a northeast-southwest direction with an area of >350 km2.We carried out SHRIMP zircon dating,Hf-in-zircon isotopic analysis and a whole-rock geochemical study on igneous and metasedimentary rocks recovered from drill holes that penetrated into the basement of the CHB.Two samples of gneissic granodiorite（XG1-1） and gneissic quartz diorite（J48-1） have magmatic ages of 2500 and2496 Ma.respectively.Their zircons also record metamorphic ages of 2.41-2.51 and 2.5 Ga,respectively.Compared with the gneissic granodiorite,the gneissic quartz diorite has higher ∑REE contents and lower Eu/Eu* and（La/Yb）n values.Two metasedimentary samples（MG1,H5） mainly contain 2.5 Ga detrital zircons as well as late Paleoproterozoic metamorphic grains.The zircons of different origins haveεHf（2.5 Ga） values and Hf crustal model ages ranging from 0 to 5 and 2.7 to 2.9 Ga.respectively.Therefore,2.5 Ga magmatic and Paleoproterozoic metasedimentary rocks and late Neoarchean to early Paleoproterozoic and late Paleoproterozoic tectono-thermal events have been identified in the basement beneath the CHB.Based on regional comparisons,we conclude that the early Precambrian basement beneath the CHB is part of the North China Craton.
