• The Journal of the Petrological Society of Korea
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• v.14 no.4 s.42
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• pp.212-225
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• 2005

This study has been designed to elucidate the morphology of Jisagae columnar joints and the petrography and petrochemistry of Daepodong basalt in Jeju Island, distributed along the 3.5 km-long coast from Seongcheonpo to Weolpyeongdong. Colonnade of the Jisagae columnar joint typically occurs within the upper part of a flow and consists of relatively well-formed basalt columns. Most columns are straight with parallel sides and diameters from 100 cm to 205 cm, $130\~139\;cm$ in maximum. Length of the columns extends up to 20 m. Most columns tend to have 6 or 5 sides but sometimes they have as few as $3\~4$ or as many as 7 or 8 sides. The Daepodong basalt consists of plagioclase, olivine, orthopyroxene, clinopyroxene, ilmenite and magnetite. Plagioclase is labradorite, clinopyroxene is augite, orthopyroxene is bronzite and olivine is chrysolite and hyalosiderite. The Daepodong basalt shows porphyritic texture with matrix of mainly intersetal texture. The Daepodong basalt is plotted into alkali rock series on the TAS diagram. The tectonic setting of the Daepodong basalt represents within plate environment.

• Economic and Environmental Geology
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• v.57 no.4
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• pp.449-471
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• 2024

We investigated the radiometric ages and petrological characteristics of basaltic rocks with columnar joints, basalt gorge, pillow lava, and mantle xenolith, from the geoheritages designated as Natural Monuments of Korea in recognition of their historical, academic, and scenic excellence. A total of 7 Natural Monuments were selected. They are 'Basalt gorge along Daegyocheon Stream of Hantangang River', 'Basalt gorge and Bidulginangpokpo Falls of Hantangang River, Pocheon', 'Pillow lava in Auraji, Pocheon' distributed along the Chugaryeong Fault System, 'Peridotite xenolith-bearing basalt in Jinchon-ri Baengnyeongdo Island, Ongjin', 'Columnar joint in Daljeon-ri, Pohang', 'Columnar joint in Yangnam, Gyeongju', and 'Columnar joint along Jungmun and Daepo Coasts, Jeju'. They ranged in age from the Cenozoic Neogene Miocene to the Quarternary Pleistocene. Based on the composition of major elements, Hantangang Basalt corresponded to trachybasalt, Daljeon Basalt to phonotephrite, Eoil Basalt to sub-alkaline basalt, and Daepodong Basalt to alkaline basalt. And in the composition of trace and rare earth elements, only Eoil Basalt showed the characteristics of arc basalt, while the others showed the characteristics of oceanic island basalt.