Late Paleozoic detrital zircon ages from metasedimentary rocks of the Wonnam Formation in northeastern Yeongnam Massif

초록

The Precambrian age of the Wonnam Formation in the northeastern Yeongnam Massif has been re-examined through detrital zircon U-Pb age analysis. LA-ICP-MS analysis was performed on mica schist and quartz-muscovite schist samples collected from the Wonnam Formation in the Jaesan-myeon, Bonghwa-gun, which had been previously classified as Precambrian strata. The mica schist revealed Paleoproterozoic age peaks at 1901, 1864 Ma along with a Paleozoic peak at 332 Ma (Carboniferous), while the quartz-muscovite schist exhibited Paleoproterozoic peaks at 2336 and 1866 Ma as well as Phanerozoic peaks at 530 and 498 Ma (Cambrian), 401 and 375 Ma (Devonian), 331 and 309 Ma (Carboniferous), and 275 Ma (Permian). These results indicate that at least some of the metasedimentary rocks previously classified as the Precambrian Wonnam Formation were deposited during the Late Paleozoic or later. Furthermore, this suggests that Paleozoic metasedimentary rocks in the Yeongnam Massif may be distributed more extensively than previously known, and implies that reconsideration of the stratigraphic framework and geological history of the Yeongnam Massif is necessary.

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