Geochemistry and Geochronology of Granites in South‐Eastern Kalba (Eastern Kazakhstan): Implications for Sn‐W Exploration

This study presents new geochemical and geochronological data on granites from the south-eastern part of the Kalba-Narym batholith, Eastern Kazakhstan, which hosts several rare-metal (Sn-W) deposits. The granites are assigned to the first and second intrusive phases of the Kalba Complex. U-Pb dating of magmatic zircon indicates crystallisation ages of 297-290 Ma for the first-phase granites and 292-289 Ma for the second-phase granites. The geochronological and geochemical data suggest that the granitoids of both intrusive phases are genetically related and most likely evolved through differentiation of a common parental magma. The transition from the first-phase to the second-phase granites is characterised by increasing SiO2 and Na2O contents and enrichment in volatile components, accompanied by decreasing concentrations of TiO2, Fe2O3, MgO, CaO, Al2O3, Ba, Th, Nb, Sr, Zr, Eu and Y. The geological characteristics and inferred timing of formation of the rare-metal deposits in the study area are also discussed. The results suggest that the Palatsy, Leninskoye and Cherdoyak deposits formed through differentiation of granitic magmas in magma chambers, followed by the partitioning of rare metals into an exsolved fluid phase and the development of Sn-W-enriched greisen stockworks. Based on these findings, the south-eastern part of the Kalba-Narym batholith is considered prospective for additional tin-tungsten mineralisation, particularly within the exocontact zones and apical parts of large granite massifs of the Kalba Complex.