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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 3isochron age of(303±12)Ma(2),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.
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. Light samples yield a model 3 isochron age of (303 ± 12) Ma (2), which is within consistent 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.