The　basalt　and　trachydacite　with　about　10　m　in　thickness　are　found　overlying　on　the　Late　Triassic　granite　at　Qitaidaban,　about　10km　east　to　the　Xinjiang-Tibet　Highway　and　5600m　above　sea　level.　Geochemical　data　showed　that　the　high-alkaline　volcanic　rocks　are　enriched　in　LILE　and　LPvEE,　loss　of　HPvEE,　middle　negative　Eu　anomaly　and　high　Sr,　low　Nd.　They　belong　to　shoshonitic　series　and　may　arise　from　a　crust-mantle　mixed　layer.　Determination　of　whole-rock　40Ar-39Ar　plateau　age　is　8.27　Ma±0.32　Ma　(900~1400°C,　39Ar　cumulant　66%).　The　apatite　fission　track　age　of　the　granite　after　baking　by　the　volcanic　rocks　is　7.9　Ma±1.0　Ma.　The　similar　ages　of　volcanic　rocks　and　the　apatite　track　of　granites　indicate　that　the　eruption　of　volcanic　rocks　occurred　at　about　8　Ma　in　the　Late　Miocene.　In　addition,　they　have　similar　age　to　Dahongliutan　volcanic　rocks　(7.97　Ma±0.14　Ma).　The　discovery　of　Qitaidaban　volcanic　rocks　make　the　data　relating　to　Late　Cenozoic　magmatic　activity　in　the　northwestern　margin　of　the　Qinghai-Tibet　Plateau　more　plentiful　and　the　results　showing　that　the　volcanic　acitivity　is　frequent　along　Kangxiwa-Quanshuigou　during　Late　Miocene-Pliocene,　and　indicate　that　volcanic　activity　and　the　movement　of　large-scale　fault　zone　have　very　close　relationship.