Geology, Geochronology, Geochemistry, fluid inclusions and H-O isotopic compositions of the newly discovered Tesiketu fluorite deposit, North Qaidam, Qinghai Province, NW China

Fluorite (CaF 2 ) is a strategic non-metallic mineral resource. The newly discovered Tesiketu fluorite deposit in the North Qaidam (NQ) region, Qinghai Province, NW China, provides an excellent opportunity to understand fluorite mineralization in this area. This study, for the first time, comprehensively employs petrography, Sm-Nd geochronology, fluid inclusion microthermometry, H-O isotopes, and trace element geochemistry to conduct multi-dimensional genesis analysis of this deposit. The ore bodies occur as fault-controlled fluorite-quartz veins hosted in granite and silty slate. Mineralization is divided into early and late stage. Sm-Nd dating of fluorite yielded an unreliable isochron age of 119 ± 35 Ma due to open-system behavior. Instead, cross-cutting relationships and regional tectonic evolution constrain the mineralization to the Late Silurian–Early Devonian (∼425–380 Ma), contemporaneous with post-collisional extension. Fluid inclusion data show that the ore-forming fluids belong to a low-temperature, low-salinity NaCl-H 2 O system. H-O isotopes indicate that early stage fluids were dominated by meteoric water with a minor hydrothermal component, while late stage fluids were predominantly meteoric. Trace elements (Y/Ho, Eu/Eu* and Ce/Ce*) in fluorite suggest a consistent hydrothermal source linked to felsic magmatism and indicate increasing oxygen fugacity from early to late stage. Fluorite precipitation was triggered by fluid mixing and water–rock reaction in the early stage and by cooling in the late stage. The Tesiketu deposit is a typical fault-controlled, low-temperature hydrothermal vein-type deposit, probably formed in a post-collisional extensional setting. This study enhances the understanding of fluorite mineralization in the NQ region and provides guidelines for future exploration.