The　Weilasituo　tin-polymetallic　deposit,　located　in　Hexigten　Banner　of　Inner　Mongolia,　is　a　newly　discovered　large　tin　deposit　associated　with　tungsten,　zinc,　copper,　molybdenum,　rubidium,　niobium　and　tantalum　the　west　slope　of　the　southern　Great　Xing＇an　Range.　Three　types　of　mineralization　developed　in　the　deposit:　the　deep　section　altered　granite-type　orebody　is　dominated　by　Sn　and　associated　with　Zn,　Rb,　Nb;　the　middle　section　cryptoexplosive　breccia-type　orebody　is　mainly　of　Sn　with　Cu　and　Zn;　and　the　shallow　section　comprises　quartz　vein-type　Sn,　W,　Zn,　Cu,　and　Mo　ore　bodies.　The　quartz　vein-type　ore　bodies　are　the　most　economically　valuable　ores,　they　are　hosted　within　the　NNE-trending　shattered　fault　zones　of　the　Paleoproterozoic　Baoyintu　Group　and　Middle　Variscan　quartz　diorite,　whereas　the　altered　granite-　and　cryptoexplosive　breccia-type　ore　bodies　are　usually　low　grade　ores.　A　cassiterite　sample　from　the　quartz　vein-type　Sn　ore　of　the　Weilasituo　deposit　was　selected　for　LA-ICP-MS　dating,　which　yielded　a　206Pb/207Pb-238U/207Pb　isochron　age　of　136.0±6.1　Ma　(MSWD=0.94)　and　a　207Pb/206Pb-238U/206Pb　concordant　age　of　132.3±5.4　Ma　(MSWD=2.8).　The　result　suggested　that　the　Weilasituo　Sn-polymetallic　mineralization　took　place　during　the　Early　Cretaceous.　A　zircon　sample　from　the　Beidashan　granite　was　also　selected　for　LA-ICP-MS　dating,　and　the　result　of　a　weighted　mean　206Pb/238U　age　of　140±2　Ma　(MSWD=0.10)　indicated　the　ore　causative　intrusion　also　formed　during　the　Early　Cretaceous.　The　Weilasituo　tin-polymetallic　deposit　belongs　to　a　granite-related　magmatic-hydrothermal　deposit.　Our　dating　results,　together　with　previous　researchers＇　rock-　and　ore-forming　ages　of　other　Sn-polymetallic　deposits　in　the　southern　Great　Xing＇an　Range,　demonstrated　that　almost　all　Sn-polymetallic　deposits　formed　during　140-135　Ma,　which　suggests　that　the　Early　Cretaceous　is　the　peak　era　for　the　formation　of　the　Sn-polymetallic　deposits　in　the　southern　Great　Xing＇an　Range.　©　2018,　Editorial　Office　of　Earth　Science　Frontiers.　All　right　reserved.