期刊
MINERALOGY AND PETROLOGY
卷 106, 期 1-2, 页码 107-130出版社
SPRINGER WIEN
DOI: 10.1007/s00710-012-0222-x
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资金
- National Research Foundation of Korea (NRF)
- Ministry of Education, Science and Technology [2011-0024709]
- [20244085]
- Grants-in-Aid for Scientific Research [21244083] Funding Source: KAKEN
- National Research Foundation of Korea [2011-0024709] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
Group II xenoliths, corresponding to the lithology of dunite, wehrlite to olivine clinopyroxenite and olivine websterite to websterite, occur in Pleisto-Holocene alkali basalts from Jeju Island, South Korea. The large grain size (up to 5 mm), moderate mg# [=100 x Mg/(Mg + Fe-total) atomic ratio] of olivine (79-82) and pyroxenes (77-83), and absence of metamorphic textural features indicate that they are cumulates of igneous origin. Based on textural features, mineral equilibria and major and trace element variations, it can be inferred that the studied xenoliths were crystallized from basaltic melts enriched in incompatible trace elements and belong to the Jeju Pleisto-Holocene magma system. They appear to have been emplaced near the present Moho, an estimated 5-8 kbars beneath Jeju Island. Consolidation of cumulates was followed by infiltration of silica-enriched metasomatic melt, producing secondary orthopyroxenes at the expense of olivine. The metasomatic agent appears to have been a silica-enriched residual melt evolved from an initially slightly silica-undersaturated alkali basalt to silica-saturated compositions by fractional crystallization under relatively high pressure conditions. The result of this study indicates that relatively young olivine-bearing cumulates could have been metasomatized by a silica-enriched melt within underplates, suggesting that silica enrichment can occur in intraplate Moho-related rocks as well as in the upper mantle of the subarc area.
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