• Journal of the Mineralogical Society of Korea
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• v.18 no.1
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• pp.61-72
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• 2005

Modal and chemical compositions of clinopyroxnes in spinel peridotites from the Baegryeong Island and the Boeun, enclosed in Miocene alkali basalt, are important for understanding the pre-eruptive temperature condition and chemical processes such as mantle depletion and enrichment. All spinel peridotites show transitional texture between protogranular and porphyroclastic textures. Temperature ranges of spinel peridotites from the Baegryeong Island and the Boeun at 15 kb are 773∼1188℃ and 705∼1106℃, respectively. The spinel peridotites from the Baegryeong Island and the Boeun have undergone the 1∼10% and 1∼4% fractional melting, which were determined by using primitive mantle-normalized Y and Yb of clinopyroxenes. LREE enrichment patterns of clinopyroxene indicate that these rocks from both areas have undergone cryptic mantle metasomatism without new minerals.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.4
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• pp.365-376
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• 2023

Songaksan, formed about 3800 year ago, is one of the tuff rings in the Jeju Island. Mantle xenoliths, spinel peridotites, are enclosed in the Songaksan Trachybasalt. The spinel peridotites are less than 2 cm in size and are composed of olivine, orthopyroxene, clinopyroxene, and spinel. The uniform compositions of the minerals from core to rim indicate that equilibrium was reached in the spinel peridotites before these were enclosed in the host magma. The spinel peridotites originated at depths between 55 and 60 km with equilibrium temperatures ranging from 915 to 968℃. The spinel peridotites from Songaksan reveal porphyroclastic texture with a lot of neoblast minerals. Olivines display strong kink banding, indicating that the upper mantle of Songaksan has been deformed. The spinel peridotites from Songaksan have undergone about 5~7% fractional melting, and cryptic metasomatism by an silicate melt. The period of entrainment and transport of the spinel peridotites in the host magma is about 15 days.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.3
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• pp.173-182
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• 2022

Dongsuak crater, located in the mid-mountainous region of Jeju Island, is located at an altitude of about 700 m, and the newly discovered Dongsuak spinel peridotites was enclosed in Dongsuak alkaline basalt. The Dongsuak spinel peridotites are composed of olivine, orthopyroxene, clinopyroxene, and spinel with porphyroclastic texture under the an equilibrium state. The variations of mineral major and trace compositions indicates that the Dongsuak spinel peridotites originate at depth from 66 to 88 km under an equilibrium temperature of about 960℃~1068℃. The Dongsuak spinel peridotites have been undergone about 1~3% fractional melting. The LREE-enriched characteristics indicate that the Dongsuak spinel peridotites have been undergone cryptic metasomatism by silicate melt without new minerals.