The Yangyang iron-oxide-apatite deposit in South Korea has undergone multiple episodes of igneous activity, deformation, hydrothermal alteration, and iron-oxide-apatite (IOA) mineralization. The iron orebodies occur as concordant- to discordant-layered lenticular or massive magnetite and/or magnetite-pyrite ores. The iron mineralization occurs along a N-S-trending shear zone within the Yangyang syenite, which experienced both early ductile and later brittle deformations. Alteration was caused mainly by the injection of hydrothermal fluid through the shear zone, leading to Fe-P mineralization. We recognize multiple stages of alteration in the Yangyang deposit, based on a paragenesis that is defined by distinct mineral assemblages including Na-Ca-K alteration phases (e.g., albite, diopside, actinolite, and biotite) and accessory minerals containing high field strength elements (e.g., apatite, sphene, allanite, and monazite). The alteration around the magnetite ore body shows an evolutionary trend from Ca (-Na) alteration, through K to phyllic alterations. The Fe-P mineralization is associated with the Ca-K and K alteration products. The iron orebodies are hosted by deformed and altered syenite, which intruded the Paleoproterozoic gneiss complexes at 233. ±. 1. Ma (SHRIMP U-Pb zircon age) in a post-collisional tectonic setting. LA-ICP-MS U-Pb dating of REE-rich sphene and apatite from the iron ores and alteration products yields Fe mineralization ages of 216. ±. 3. Ma (sphene) and 212. ±. 13. Ma (apatite). This is the first time, which IOA-type mineralization in the Korean Peninsula was dated as Triassic age related to post-collisional magmatism within the Gyeonggi Massif, South Korea. The U-Pb system was subsequently reset (208. ±. 3. Ma-sphene and 151. ±. 13. Ma-apatite) by Jurassic and Cretaceous magmatism. This unique geological evolution was responsible for Mesozoic metal enrichment and remobilization into suitable structural traps in the Yangyang district.
Bibliographical noteFunding Information:
This research was supported by a grant from the Korea Institute of Energy Technology Evaluation and Planning (KETEP; 2012T100201564 ). And this research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning ( 20122010300050 , 20100027347 ). We thank Prof. Whattam for comments on the manuscript and the Korea Basic Science Institute for performing the SHRIMP analyses.
© 2015 Published by Elsevier B.V.
- IOA deposit
- LA-ICP-MS U-Pb apatite and sphene dating
- SHRIMP U-Pb zircon dating
ASJC Scopus subject areas
- Geochemistry and Petrology
- Economic Geology