Re-Os Isotopic Dating of Pyrite from the Neoproterozoic Datangpo Formation#br# in Tongren, Guizhou and Its Geological Significance

Eight pyrites  from the manganese-bearing rock series of the First Member of Neoproterozoic Datangpo Formation are used for Re-Os isotopic dating at Xixibao orefield in Tongren area, Guizhou province. The analyses yield an isochronic age 459±16 Ma, significantly later than the interglacial depositional age of Datangpo Formation (670~635 Ma), which suggest that the Datangpo Formation was probably affected by the tectonic 〖JP〗thermal activity of Late Caledonian. The pyrites also show high  Re, low Os abundance, high Re/Os and 187Os/188Os  ratio. The initial 187Os/188Os value is 1.02±0.41, significantly higher than the eigenvalue of mantle magma, which indicate the ore-forming materials are mainly derived from the crustal source.