Indium,　as　a　critical　metal,　exhibits　geochemical　behaviors　similar　to　those　of　Sn　during　ore-forming　processes.　Sn-polymetallic　deposits　formed　in　the　magmatic-hydrothermal　system　are　the　most　important　sources　for　indium　resources　worldwide.　Recently,　Sn-poor　magmatic-hydrothermal　deposits　with　conspicuous　indium　enrichments　have　been　found　in　China,　indicating　the　great　potential　of　indium　resources.　Previous　studies　have　suggested　that　granitic　magma　is　the　source　of　indium,　regardless　whether　the　deposits　are　Sn-poor　or　Sn-rich.　However,　the　indium　enrichment　mechanism　during　magma　processes　is　poorly　understood.　The　Chitudian　Pb-Zn-Ag　deposit,　located　in　the　Luanchuan　ore　district,　is　a　typical　example　that　is　Sn-poor　deposit　with　high　indium　content.　The　mineralization　of　this　deposit　is　considered　to　be　associated　with　a　Yanshanian　intrusion　named　Yuku-Shibaogou　granite　(YSG).　Biotite　is　an　important　carrier　of　indium　and　tin,　and　its　chemical　composition　can　be　used　to　characterize　the　physicochemical　conditions　of　magmatic　and　hydrothermal　systems.　In　this　study,　Electron　Probe　Microanalysis　(EPMA)　and　Laser　Ablation-Inductively　Coupled　Plasma-　Mass　Spectrometry　(LA-ICP-MS)　were　used　to　investigate　the　mineralogy　and　geochemistry　of　biotite　from　YSG,　and　the　results　were　compared　with　those　of　Sn-In　mineralized　granites　(SIG)　in　south　China,　aiming　to　identify　factors　controlling　indium　enrichment　during　magma　processes.　The　results　show　that　the　biotites　from　YSG　are　Fe-biotite,　whereas　those　from　SIG　are　Mg-biotite　or　siderophllite.　The　indium　and　tin　contents　of　the　former　are　higher　than　those　of　the　latter,　suggesting　that　SIG　is　significantly　rich　in　indium　and　tin　relative　to　YSG.　Moreover,　the　biotite　geochemistry　indicates　that　SIG,　derived　from　the　partial　melting　of　metasedimentary　rock,　is　characterized　by　higher　temperature,　higher　volatile　contents,　and　lower　oxygen　fugacity　than　YSG.　Such　favorable　conditions　may　play　an　important　role　in　Sn-In　mineralization　in　South　China.　However,　the　physicochemical　conditions　of　YSG　are　quite　different　from　those　of　SIG.　The　indium　enrichment　observed　in　the　Chitudian　deposit　may　result　from　the　remobilization　and　re-enrichment　of　indium,　which　is　induced　by　tectonic　deformation　and　fluid　overprinting.　Therefore,　the　presence　of　indium　enrichment　in　Sn-poor　deposits　doesnot　mean　that　the　ore-related　magma　was　In-enriched　but　rather　Sn-poor.　©　2024　Science　Press.　All　rights　reserved.