Geochemical signatures and melt inclusion evidence in peridotite xenoliths of Sinsanri, South Korea

Jeju Island, located in South Korea, is a Cenozoic intraplate volcanic feature in the East Asian region. The Sinsanri area on Jeju Island is well-known for its rich presence of xenoliths, making it a key site for finding these geological features. Various xenolith types – such as spinel lherzolite, spinel harzburgite, and wehrlite – have been entrapped within Quaternary intraplate alkali basalts in the Sinsanri area of Jeju Island, corresponding to both the early and later stages of Quaternary volcanic events. In this study, we presented primary elemental composition of the xenoliths, complemented by Raman spectroscopy analysis of melt inclusions within olivine. The most notable xenoliths are spinel lherzolites, exhibiting a transition from proto-granular to porphyroclastic textures. Mg# in the xenoliths ranges from 80.3 to 93.8 and CO2-rich melt inclusions found within mantle peridotite xenoliths vary in size from 20 to 40 µm. The CO2 density within the melt inclusions was found to range between 0.303 g cm−3 and 0.977 g cm−3. Fayalite (Fe-containing olivine) with a peak of 817.79–849.88 cm−1 host the CO2 melt inclusion. Many of the melt inclusions within the xenoliths likely developed as they ascended to the surface along with the host basalt after the eruption (post eruption) as an evolved melt.