The Kekebieketi mining area is located on the southern margin of the Altai Mountains in Northern Xinjiang and is at the junction of the Siberia and Kazakhstan-Junggar plates. Faults and magmatic rocks are well developed, and the main stratum is the Middle Devonian Kaxiweng Formation. The Kekebieketi-Kalatongke-Xibodu basic to ultrabasic mixed rock strip is an appropriate area for mineral resources and a good target to study the crustal and mantle evolution. This study explored the tectonic age and setting of basic rocks in the Kekebieketi mining area and provides a basis for the study of basic rocks and discrimination of the wider formation. The basic rocks were mainly gabbro, pyroxenolite, basic subvolcano rock, and diabase. They have all been altered to different degrees through amphibolization, sub-amphibolization, actinolitization, chloritization, epidotization, zoisitization, uralitization, and serpentinization. Similar rare earth element compositions of the different rock types suggest that they are homologous. Enrichment of large ion lithophile elements (Cs, Rb, Sr, and U) and depletion of high field strength elements (Nb, Ta, Zr, and Hf) showed that the basic rocks have the characteristics of island arc magmatic rocks. A single zircon U–Pb age of 321 ± 2.5 Ma was obtained from a hornblende gabbro. Based on the petrological and geochemical features, we concluded that the basic rocks in the study area were formed during the post-collision period in East Junggar. The parental magma is mainly composed of metasomatic mantle wedge material and upwelling asthenosphere, which is why it showed geochemical characteristics of subduction.