Geochemistry of peridotite xenoliths in alkali basalts from Jeju Island, Korea |
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| Authors: | SEONG HEE CHOI JONG IK LEE CHUNG-HWA PARK and JACQUES MOUTTE |
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| Institution: | Department of Earth Science Education, Seoul National University, Seoul 151-748, Korea (email:;), Polar Sciences Laboratory, Korea Ocean Research and Development Institute, Ansan PO Box 29, Seoul 425-600, Korea,;Department of Geosystem Engineering, College of Engineering, University of Taejeon, Taejeon 300-716, Korea,;
Spin-Geochimie, Ecole des Mines, 158 Cours Fauriel, 42023 Saint Etienne, France |
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| Abstract: | Abstract Ultramafic xenoliths in alkali basalts from Jeju Island, Korea, are mostly spinel lherzolites with subordinate amounts of spinel harzburgites and pyroxenites. The compositions of major oxides and compatible to moderately incompatible elements of the Jeju peridotite xenoliths suggest that they are residues after various extents of melting. The estimated degrees of partial melting from compositionally homogeneous and unfractionated mantle to form the residual xenoliths reach 30%. However, their complex patterns of chondrite-normalized rare earth element, from light rare earth element (LREE)-depleted through spoon-shaped to LREE-enriched, reflect an additional process. Metasomatism by a small amount of melt/fluid enriched in LREE followed the former melt removal, which resulted in the enrichment of the incompatible trace elements. Sr and Nd isotopic ratios of the Jeju xenoliths display a wide scatter from depleted mid-oceanic ridge basalt (MORB)-like to near bulk-earth estimates along the MORB–oceanic island basalt (OIB) mantle array. The varieties in modal proportions of minerals, (La/Yb)N ratio and Sr-Nd isotopes for the xenoliths demonstrate that the lithospheric mantle beneath Jeju Island is heterogeneous. The heterogeneity is a probable result of its long-term growth and enrichment history. |
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| Keywords: | Jeju Island mantle xenolith metasomatism residue |
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