1998/06/30 by K.-H. Park, C.-S. Cheong
Computer Science · Earth and Planetary Sciences · Engineering · #Geochemistry and Elemental Analysis #Internet of Things and Social Network Interactions #Marine and Coastal Research
paper · doi:10.14770/jgsk.1998.34.2.81
openalex publication_date 1998/06/30 · openalex created_date 2026/01/23 · openalex updated_date 2026/07/25
The ⁸⁷Sr/⁸⁶Sr ratios analyzed from the Ogcheon metasedimentary rocks (0.708278 ~ 0.829766) are considerably higher than those of the basic metavolcnic rocks of the Ogcheon Belt. It appears that the Rb-Sr isotopic system provides an adequate measure for the age determiation of the fine-grained metasedimentary rocks of the Ogcheon Belt, e.g. slates of Changri Formation from southern part of Taejeon. However, it is observed that the enhanced mobility of Rb and/or Sr during the overprinted contact metamorphism may hinder the successful age determination. Carbonate rocks from three formations of Ogcheon Belt, i.e. Hyangsanri, Hwajeonri, and Changri Formations, reveal heterogeneous ⁸⁷Sr/⁸⁶Sr ratios reflecting the various extent of crustal strontium involvement. The lowest ⁸⁷Sr/⁸⁶Sr ratio of the Hyansanri Formation (0.708278) should be the closest ⁸⁷Sr/⁸⁶Sr ratio to the seawater value at the time of formation among currently available data, because crustal contamination could increase the ⁸⁷Sr/⁸⁶Sr ratios. We suggest as the maximum formation age of 442±63(2σ) Ma for the Changri Formation based on the Rb-Sr isotope data and 430-470 Ma or 530-590 Ma for the Hyansanri Formation based on comparison with the seawater ⁸⁷Sr/⁸⁶Sr evolution curve.