The Tuomoerte medium type iron deposit can be found in the metavolcanic-sedimentary sequence of the upper Kangbutiebao Formation from the Upper Silurian to Lower Devonian. The source of ore materials, mineralogenetic epoch and metallogenesis were studied by S stable isotope and geochronology and are reported in this paper. Three periods of mineralization can be distinguished on the basis of field evidence and petrographic analyses: volcano-sedimentation, magmatic-hydrothermal, and regional metamorphism. The zircon U-Pb ages indicate that the Fe-Mn mineralization period during the volcano-sedimentation and magmatic-hydrothermal periods coincides with early Devonian timing (401~407 Ma). The Fe-Mn and Fe-Cu mineralization were found to be related to volcanic eruption deposition and magma intrusion activities, respectively.