Based on the 1∶50,000 regional geological survey carried out in the Chaokewula area of Inner Mongolia,a basic magmatic activity dominated by gabbro was discovered. The purpose of this study is to explore the formation age,petrogenesis and geological significance of gabbro.Methods:Taking the gabbro as the research object,we carried out the isotopic age determination and rock geochemical testing.Results:Our study demonstrates that the ages of the gabbro zircons U-Pb in the Chaokewula area are 142.62±0.51 Ma and 145.1±2.1 Ma,indicating that the rock is a product of the Late Jurassic to Early Cretaceous.Gabbro is a series of tholeiite rocks, characterized by low silicon,low titanium,lean alkali,high sodium and low potassium.Its differentiation is extremely weak.The Eu anomalies are not obvious,and trace elements Ba,Ta,Sr,and Hf are enriched,and Rb,Th,Nb,and P are deficient.Conclusions:The rock geochemistry shows that the source area of gabbro magma is depleted spinel Lherzolite,which is formed by partial melting of more than 30% of the mantle,and characterized by fluid-influenced geochemistry.There is a certain degree of separation and crystallization of magma during its evolution,and the crustal mixing is very weak.Through analogy with the supporting rock series of ophiolite in Hegen Mountain,and the combination of Paleozoic to Mesozoic tectonic background in the study area and the comprehensive analysis of hegenshan back-arc suture zone crust—mantle electrical structure,we concluded that the island arc imprinting characteristics of Late Jurassic—Early Cretaceous gabbro are the reflection of the ancient island arc environment developed during the Hegenshan Ocean period,and gabbro is only the product of mantle-derived magma upwelling along deep and large faults under extensional background.