17:15 〜 19:15
[SCG53-P02] Orogenic-Type Chungju Fe-REE-Nb-Zr Deposit in South Korea
キーワード：Chungju, Rare earth elements (REE) deposit, Orogenic deposit, Hydrothermal mineralization
The Fe-REE-Nb-Zr mineralization in Chungju, South Korea, represents one of the country's largest zirconium, niobium, and heavy rare earth element (HREE) resources. The deposit is hosted within the 890-860 Ma Gyemyeongsan Formation of the Ogcheon Metamorphic Belt (OMB), composed mainly of felsic meta-trachyte with minor mafic metabasite. Mineralization occurs in NW-dipping sub-tabular layers, which are structurally controlled by a shear zone, concordant with the foliation of the formation. Fe is primarily hosted by magnetite, LREE by allanite-(Ce), Nb by fergusonite-(Y), Zr by zircon, and HREE by fergusonite-(Y) and britholite-(Y).
The deposit is classified as orogenic-type due to its close association with regional metamorphism, deformation, and hydrothermal alteration related to orogenic processes. The Gyemyeongsan Formation, part of the OMB, was subjected to compressional tectonics, which led to the formation of shear zones that served as conduits for hydrothermal fluids, enhancing REE-Nb-Zr mineralization. The peralkaline nature of the host rocks, combined with a supercritical mixed-volatile fluid (H2O-CO2-CH4-F-Cl), contributed to the enrichment of high field strength elements (HFSE), especially HREE (HREO/TREO = 30%). Subsequent hydrothermal activity, driven by metamorphism and Jurassic granite intrusion, further concentrated REE and HFSE through F- or Cl-complexation, enhancing metal mobility. The orogenic setting facilitated fluid-rock interaction and mineral replacement, resulting in the sequential formation of HFSE minerals and extensive Fe mineralization. Magnetite, forming in the final stage, replaced earlier minerals and created lens-shaped orebodies between granite and the Gyemyeongsan Formation. The inferred fluorine-enriched magmatic-hydrothermal fluid led to the development of magnetite, zircon, ferro-allanite-(Ce), britholite-(Y), fergusonite-(Y), K-feldspar, albite, quartz, biotite, fluorite, and hematite.
The deposit is classified as orogenic-type due to its close association with regional metamorphism, deformation, and hydrothermal alteration related to orogenic processes. The Gyemyeongsan Formation, part of the OMB, was subjected to compressional tectonics, which led to the formation of shear zones that served as conduits for hydrothermal fluids, enhancing REE-Nb-Zr mineralization. The peralkaline nature of the host rocks, combined with a supercritical mixed-volatile fluid (H2O-CO2-CH4-F-Cl), contributed to the enrichment of high field strength elements (HFSE), especially HREE (HREO/TREO = 30%). Subsequent hydrothermal activity, driven by metamorphism and Jurassic granite intrusion, further concentrated REE and HFSE through F- or Cl-complexation, enhancing metal mobility. The orogenic setting facilitated fluid-rock interaction and mineral replacement, resulting in the sequential formation of HFSE minerals and extensive Fe mineralization. Magnetite, forming in the final stage, replaced earlier minerals and created lens-shaped orebodies between granite and the Gyemyeongsan Formation. The inferred fluorine-enriched magmatic-hydrothermal fluid led to the development of magnetite, zircon, ferro-allanite-(Ce), britholite-(Y), fergusonite-(Y), K-feldspar, albite, quartz, biotite, fluorite, and hematite.