The　Tianshan　orogenic　belt　hosts　several　world-class　gold　deposits　and　is　one　of　the　largest　gold　provinces　on　Earth.　The　Katbasu　Au-Cu　deposit　in　the　Chinese　Western　Tianshan　is　hosted　in　a　granite　intrusion.　Previous　researchers　have　shown　that　the　main　gold　ores　formed　much　later　than　the　ore-hosting　granite.　However,　the　formation　age　of　Cu　mineralization　and　its　possible　link　to　Au　mineralization　remain　poorly　understood.　This　paper　reports　detailed　mineralogical　studies,　combined　with　zircon　U-Pb,　in　situ　hydrothermal　monazite　as　well　as　rutile　U-Pb　ages　to　constrain　the　timing　of　Cu　mineralization　and　its　possible　link　to　Au　mineralization.　The　two　main　ore　types　in　the　Katbasu　deposit　include　Cu-Au　ores　with　pyrite-chalcopyrite　veins　that　crosscut　the　granite　and　Au　ores　with　massive　pyrite　and　quartz　as　the　main　minerals.　The　Cu-Au　ores　are　spatially　associated　with　diorite　that　intruded　the　granite,　and　they　are　overprinted　by　massive　gold　ores.　Detailed　mineralogical　studies　show　that　chalcopyrite　is　the　main　Cu-bearing　mineral　in　the　Cu-Au　ores,　and　it　is　closely　associated　with　some　native　gold,　monazite,　and　rutile.　Secondary　ion　mass　spectrometer　(SIMS)　U-Pb　dating　of　zircon　grains　from　the　ore-hosting　granite　and　mafic　enclave　yielded　concordant　ages　of　354.1　+/-　1.6　and　355.8　+/-　1.7　Ma,　respectively.　The　diorite　that　intruded　the　granite　has　a　zircon　U-Pb　age　of　352.0　+/-　3.2　Ma.　The　trace　element　compositions　of　the　monazite　suggest　they　were　formed　by　hydrothermal　fluids　rather　than　inherited　from　the　ore-hosting　granite.　Hydrothermal　monazite　coexisting　with　chalcopyrite　and　native　gold　yielded　a　concordant　age　of　348.7　+/-　2.3　Ma,　and　the　W-rich　hydrothermal　rutile　grains　associated　with　the　chalcopyrite　yielded　a　U-Pb　age　of　345　+/-　27　Ma,　indicating　an　early　Cu-Au　mineralization　event　prior　to　the　major　Au　mineralization　(ca.　323-311　Ma).　The　formation　time　of　early　Cu-Au　mineralization　is　consistent　with　the　emplacement　age　of　the　diorite　and　may　be　of　magmatic-hydrothermal　origin,　whereas　the　main　Au　has　no　genetic　associations　with　magmatic　rocks　in　the　ore　district　and　may　belong　to　the　orogenic　type.　Monazite　geochronology　provided　a　more　reliable　age　constraint　than　rutile　in　the　Katbasu　Au-Cu　deposit,　and　we　suggest　hydrothermal　monazite　has　advantages　over　rutile　in　dating　the　complex　mineralization　ages　of　gold　deposits.