Two‐Period Magmatism and Mineralisation in the Galinge Skarn Fe‐Co Deposit, East Kunlun, Qinghai: Constraints From Geochronology and Geochemistry

ABSTRACT The Galinge Fe‐Co deposit in the East Kunlun orogenic belt is a large skarn iron deposit associated with critical metal cobalt. This study elucidates its two‐period magmatism and mineralisation and their genetic links on the basis of petrography, geochronology and geochemistry. The early granodiorite (236.1 ± 1.4 Ma) is associated with the early magnetite‐sulphide period (major metallogenic event), whereas later intermediate–mafic dikes (227.1 ± 1.7 Ma) correspond to the late veined magnetite period. Petro‐geochemical results show that both intrusions are metaluminous I‐type granites with similar geochemical signatures (parallel REE patterns, high Mg#, LILE enrichment, HFSE depletion), suggesting derivation from partial melting of the lower crust with mantle and a postcollisional setting. H‐O‐S isotopes show that ore‐forming fluid and ore materials during the major metallogenic period were predominantly from a deep magmatic source. EPMA and LA‐ICP‐MS analyses classify two‐period magnetite as skarn‐type magnetite. Early magnetite formed at higher temperatures with Co incorporated via isomorphism, while late magnetite crystallised under more reduced conditions with Co mainly in sulphide inclusions. Co/Ni ratios for magnetite (< 1) indicate deep magmatic origins. Collectively, temporal–spatial correlations, shared deep magmatic provenance and geochemical coherence demonstrate that both magnetite formations are related to two periods of magmatic intrusion activity.