The　Katbasu　Au-Cu　deposit　in　the　Chinese　western　Tianshan　is　hosted　in　the　ca.　355　Ma　granite　intrusion.　This　paper　reports　whole-rock　geochemical　and　zircon　Hf-O　isotopic　data　for　the　granites　and　the　mafic　enclaves　as　well　as　in　situ　S　isotopic　data　for　the　sulfides　from　the　Katbasu　Au-Cu　deposit.　Our　results　provide　constraints　on　the　petrogenesis　and　ore　genesis　of　the　Katbasu　Au-Cu　deposit.　Geochemical　characteristics　suggest　that　the　Katbasu　granites　are　metaluminous　rocks,　exhibiting　mineral　assemblages　and　geochemical　characteristics　of　I-type　granites.　The　granites　have　positive　zircon　ΕHf(t)　values　of　7.1–10.2　and　zircon　δ18O　values　of　6.2–7.2‰,　suggesting　a　juvenile　crustal　origin.　Mixing　processes　between　felsic　and　mafic　magmas　were　involved　in　their　generation.　The　mafic　enclaves　are　enriched　in　LILEs　and　depleted　in　HFSEs,　and　have　zircon　ΕHf(t)　values　of　7.5–15.8　and　zircon　δ18O　values　of　5.4–6.9‰,　suggesting　that　they　were　derived　from　a　subduction-modified　mantle　and　underwent　subsequent　crustal　contamination　and/or　magma　mixing　processes.　In　situ　S　isotopic　analyses　show　that　pyrite　grains　from　the　pre-ore　stage　and　post-ore　stage　have　positive　δ34S　values　of　7.0–8.5‰　and　8.2–9.0‰,　respectively.　Pyrite　and　chalcopyrite　grains　from　an　early　magmatic-hydrothermal　Cu-Au　mineralization　stage　show　δ34S　values　of　8.8–11.1‰,　and　pyrite　grains　from　the　main　orogenic　Au　mineralization　stage　have　positive　δ34S　values　of　5.9–8.4‰.　The　heavy　S　isotope　characteristics　of　magmatic-hydrothermal　Cu-Au　mineralization　indicate　that　the　magma　source　might　be　metasomatized　by　subduction　materials,　whereas　the　heavy　S　isotope　characteristics　of　the　late　orogenic　Au　mineralization　suggest　that　the　ore-forming　materials　mainly　originated　from　the　metamorphic　devolatilization　of　the　source　rocks.　The　ca.352–349　Ma　early　magmatic-hydrothermal　Cu-Au　mineralization　in　the　Katbasu　deposit　formed　in　a　subduction　tectonic　setting,　whereas　the　ca.　323–311　Ma　late　orogenic　Au　mineralization　formed　in　an　orogenic　environment　during　the　final　stage　of　subduction.　©　2023　The　Author(s)