In-situ trace elements and Fe isotope compositions of magnetite in Gwanin Fe-Ti oxide deposit, South Korea

Magnetite samples from Gwanin Fe-Ti oxide deposit in South Korea were collected to identify the deposit origin and to understand the ore-forming processes. Based on the macro- and micro-scale observation, the Fe-Ti oxide ores were divided into olivine-bearing massive ore, biotite-bearing massive ore, banded ore and skarn ore. Trace elements and Fe isotope compositions of each ore type were analyzed by LA-ICP-MS and MC-ICP-MS, respectively. The results indicated that the ore-forming processes in Gwanin Fe-Ti oxide deposit were governed by magmatic processes. The magnetite from biotite-bearing ore showed slightly lower Ti concentration and depleted HFSEs compositions trace elements than the other ore types, corresponding to lower temperature with relatively consistent fO2 condition. Also, they were plotted in higher fluid-rock ratio field in the (Si + Al)/(Mg + Mn) vs. Mg +Mn diagram. This indicated its formation under the fluid-rich environment in later stage of mineralization process. Fe isotope values of magnetite also represented a significant role of magmatic process on origin of iron.