Mangbang　area　is　located　in　the　east　of　Tengchong　with　widely　distribution　of　the　Late　Cenozoic　volcanoes.　40Ar/39Ar　analysis　on　matrix　separate　from　two　trachyandesite　samples　collected　from　the　Mangbang　area　yielded　a　high-precise　plateau　age　of　2.1　±0.1Ma　and　2.0　±　0.1Ma,　indicating　the　effusive　age　as　Early　Pleistocene.　Analyzed　samples　appear　as　high-potassium　calc-alkaline　features,　and　are　enriched　in　large　ion　lithophile　elements　(LILE),　but　depleted　in　high　field　strength　elements　(HFSE),　which　show　the　arc　volcanic　and　intraplate　volcanic　transition　characteristic,　speculating　that　they　may　form　in　post-orogenic　environment.　The　generation　of　Pleistocene　volcanic　rocks　in　the　Tengchong　Block　is　related　to　extension　collapse　after　the　India-Asia　collision　result　in　partial　melting　of　an　enriched　mantle　source.　The　Indosinian　Block　escape　to　the　southeast　and　rejuvenation　of　Tengchong　arcuate　strike-slip　fault　zone　(e.　g.,　Longchuanjiang　fault　belt　and　Dayingjiang　fault　belt)　induced　the　volcanic　eruption　and　emplacement.　©　2017　Science　Press.　All　rights　reserved.