This paper deals with some characteristics of oxygen isotope of Cenozoic basalts and inclusions. All these samples were collected from North China, such as Datong alkaline basalts (Quarternary) and tholeiites(Quarternary), Wuan alkaline basalts(Neogene), Xiyang alkaline basalts (Neogene), Zhangbei alkaline basalts and tholeiites (Neogene), Fanshi alkaline basalts and tholeiites (Paleogene), Beijing alkaline basalts and tholeiites(Paleogene). The oxygen isotope characteristics of these Cenozoic basalts and inclusions of this area are as follows:(1)The range of δ~(18)O values of basalts is from 5‰ to 7.58‰, which means the origin of basalts is upper mantle; (2) The mean δ~(18)O values of alkaline basalts(δ~(18)O) are slightly higher than those of tholeiites (δ~(18)0), despite the different period, e.g. the values of (?)_Al ~(18)O and (?)_Th ~(18)O in Quarternary basalts are 5.63‰ and 5.56‰, respectively; the values of (?)_Al ~(18)O and (?)_Th ~(18)O in Neogene basalts are 6.90‰ and 6.13‰; the values of (?)_Al ~(18)O and (?)_Th ~(18)O in Paleogene basalts are 5.80‰ and 5.62‰. However, even at the same area, the values of (?)_Al ~(18)O are also slightly higher than (?)_Th ~(18)O values; (3)From the δ~(18)O values of olivine and clinopyroxene in isotope equilibrium system, the equilibrium temperature (1049～1167℃) can be calculated, which is very similar to the temperature(950～1160℃) calculated from chemical composition of minerals.
Acta Petrologica Sinica