Abstract: Zircon U-Pb dating， major and trace elements of whole-rocks，oxygen isotope compositions of mineral separates，and carbon concentrations and isotope compositions of apatite and whole-rocks were determined for Mesozoic mafic-ultramafic intrusions at Shacun and Jiaoziyan in the Dabie Mountains．The results show that these mafic-ultramafic rocks are characterized by strong LI E enrichment，negative HFSE anomalies(Nb，Zr and Ti)，and positive anomalies of Pb and Ba．Zircon U-Pb dating yields the Early Cretaceous(122 to 128Ma)magma crystallization ages and also the younger post-magmatic hydrothertmal overgrowth ages (105 to 116 Ma)．There is a large variation in oxygen isotope ratios of minerals and their host rocks(whole rock：1．1‰ ～6．6 ‰ ，clinopyroxenite：3．85 ‰ ～ 5．7 ‰ ，plagioc lase ：2．8 ‰ ～ 7．3 ‰ ，zircon：3．85 ‰ ～6．04 ‰ ． Most zircons have O values different from normal mantle zircon． Equilibrium fractionations of oxygen isotopes among minerals have been preserved for some samples ，but for the others obvious disequilibriaum of oxygen isotope s is detected ，indicating alteration by postmagmatic subsolidus water-rock interactions．Carbon concentrations and isotope compositions vary widely from 0．03 ％ to 0．18 ％ and from -27．0 ‰ to -5．8 ‰ ．respectively．Comparison of element and isotope data for Mesozoic mafic-ultramafic rocks with eclogites from the Dabie Mountains shows that they share many common geochemical features ，and thus there should be genetic links between them ． Protholiths of these ecologites are considered mafic rocks，corresponding to rift magmatism in the northern margin of the Yangtze plate related to Neoproterozoic rifting tectonics．Partial melting of old lithosphere mantle and overlying crust is considered to produce these early Cretaceous mafic-ultramafic rocks．