한국광물학회:학술대회논문집 (Proceedings of the Mineralogical Society of Korea Conference)
- 한국광물학회.한국암석학회 2001년도 공동학술발표회 논문집
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- Pages.75-75
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- 2001
Sr, Nd and Pb isotopic investigations of ultramafic xenoliths and their host basalts from Jeju Island, Baekryeong Island, Boeun and Ganseong, Korea: Implications for a large-scale difference in the source mantle beneath East Asia
- Park, Seong-Hee (Department of Earth System Sciences, Yonsei University) ;
- Kwon, Sung-Tack (Department of Earth System Sciences, Yonsei University) ;
- Hee Sagong (Department of Earth System Sciences, Yonsei University) ;
- Cheong, Chang-Sik (Korea Basic Science Institute)
- 발행 : 2001.06.01
초록
We report Sr, Nd and Pb isotope data of clinopyroxene separates from ultramafic xenoliths and their host basaltic rocks in Jeju Island, Baekryeong Island, Boeun and Ganseong, Korea. The isotopic data of the xenoliths and host basalts are distinctly different from those of Korean basement rocks. Except for two xenoliths from Ganseong, all samples in this study have isotopic ratios within the combined range of MORB-OIB data. All basaltic rocks have Nd-Sr-Pb isotope compositions different from those of xenoliths, indicating that the host basaltic magma did not derive from the lithospheric mantle where the xenoliths originated. The range of isotopic composition of xenoliths is much greater than that observed in host basalts, which reflects small-scale heterogeneity of the lithospheric mantle. The greater isotopic heterogeneity of the lithospheric mantle probably reflects its long-term stability. The spinel peridotite xenolith data of Jeju Island, Baekryeong Island and Boeun display mixing hyperbolas between DMM and EM II end members. Since Jeju basalts have EM II-like isotopic signature, the mixing relationship shown by the isotopic data of the Jeju xenoliths can be interpreted as the result of infiltration of metasomatic fluid or melt derived from basaltic magma into DMM-like lithospheric mantle. In contrast to other xenolith sites, the Ganseong xenoliths are dominantly clinopyroxene megacryst and pyroxenite. Clinopyroxene megacrysts have different isotopic ratios from their host basalt, reflecting its exotic origin. Two Ganseong xenoliths (wherlite and clinopyroxenite) have much enriched Sr and Nd isotopic ratios and Nd model ages of 2.5-2.9 Ga, and plot in an array away from the MORB-OIB field. The mantle xenoliths from Korean Peninsula have similar
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