Re-Os dating of magnetite from the Shaquanzi Fe-Cu deposit, eastern Tianshan, NW China

Magnetite separates from the Shaquanzi Fe-Cu deposit in the eastern Tianshan are used for Re-Os geochronological study. Re-Os data show that magnetite separates contain ca. 0.7 to 50.9 ppb Re and ca. 16 to 63 ppt Os. Eight samples yield a model 3 isochron age of (303 ± 12) Ma (2 σ), which is within uncertainty consistent with of the Re-Os date (295±7 Ma) of associated pyrite. Tectonic evolution shows that the Late Carboniferous Aqishan-Yamansu belt was a back-arc rift. Therefore, the Re-Os age of ca. 300 Ma indicates that the Shaquanzi Fe-Cu deposit may have formed in a back-arc extensional environment and was closely related to mantle-derived magmatism. The successful application of Re-Os magnetite geochronology in the Shaquanzi Fe-Cu deposit suggests that the purity of magnetite, relatively high Re and Os contents, and the closure of Re-Os systematic are base factors for a successful Re-Os geochronology. There would be a good prospect for Re-Os geochronology for magnetite.