• Journal of the Korean earth science society
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• v.28 no.4
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• pp.462-477
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• 2007

The purpose of this study is to determine the petrology of basalt and the volcanic process in the Seondol cinder cone, Seobjikoji area, eastern Jeju Island. The Seondol cinder cone is mainly composed of spatters in the lower part, pyroclastic deposits including reddish brown blocks, ashes with volcanic bombs in the middle part, and dark black scoria deposits in the upper part. The volcanic sequences suggest volcanic processes that progress through Strombolian eruption and end with Hawaiian lava effusion which breached the cinder cone northwestward and extended over northwestward as lava delta and basalt emplaced as a volcanic neck in the central part of crater in the cinder cone. The age of basalt lava flows is about $95\;{\pm}\;3\;ka$. The basalts belong to transitional basalt and show products of fractional crystallization of clinopyroxene and olivine from a parental basalt magma on the basis of variation diagram of major, trace and rare earth elements. Basalts in the region of this study are plotted at the region of within plate basalt.

• Computers and Concrete
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• v.2 no.3
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• pp.239-248
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• 2005

The article presents the results of examination of the fractal dimension D of concrete specimen fracture surfaces obtained in fracture toughness tests. The concretes were made from three different types of coarse aggregate: gravel, dolomite and basalt aggregate. Ordinary concretes (C40) and high-performance concretes (HPC) were subjected to testing after 7, 14, 28 and 90 days of curing, respectively. In fracture toughness and compressive tests, different behaviours of concretes were found, depending on the type of aggregate and class of concrete (C40, HPC). A significant increase in the strength parameters tested occurred also after a period of 28 days (up to the $90^{th}$ day of curing) and was particularly large for concretes C40. Fractal examinations performed on fracture replicas showed that the fractal dimension D was diverse, depending on the coarse aggregate type and concrete class being, however, statistically constant after 7 and 14 days for respective concretes during curing. The fractal dimension D was the greater, the worse strength properties were possessed by the concrete. A cross-grain crack propagation occurred in that case, due to weak cohesion forces at the coarse aggregate/mortar interface. A similar effect was observed for C40 and HPC made from the same aggregate. A greater dimension D was exhibited by concretes C40, in which case the fracture was easier to form compared with high-performance concretes, where, as a result of high aggregate/mortar cohesion forces, the crack propagation was of inter-granular type, and the resulted fracture was flatter.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.3
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• pp.183-197
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• 2022

Geochemical data, including Sr-Nd-Pb-Mg-Zn isotopes, reported on the late Cenozoic intraplate basaltic rocks in the Korean Peninsula (Mt. Baekdu, Jeongok, Baengnyeong Island, Pyeongtaek, Asan, Ganseong, Ulleung Island, Dok Island, and Jeju Island) are summarized to constrain their mantle source lithologies, and the nature of mantle end-members required. In the Sr-Nd isotope correlation diagram, Jeju basalts plot in the field of EM2-type oceanic island basalts (OIB), while the other basalts fall in the EM1-type OIB field. In Pb-Pb isotope space, Jeju basalts show a mixing array between Indian MORB and EM2 component, whereas the other basalts display an array with EM1 component. The Korean basalts were derived from a hybrid source of garnet lherzolite and recycled stagnant slab materials (eclogite/pyroxenite, pelagic sediments, carbonates) in the mantle transition zone. The EM1 component could be ancient (~2.0 Ga) K-hollandite-bearing pelagic sediments that were isolated for a long period in the mantle transition zone due to their neutral buoyancy. The EM2 component might have been relatively young (probably Pacific slab) and recently recycled clay-rich pelagic sediments. Eclogite and carbonates are unlikely to account for the EM components, but they are common in the mantle source of the Korean basalts.

• The Journal of the Petrological Society of Korea
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• v.7 no.1
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• pp.27-36
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• 1998

The volcanic piles in the northern Yucheon Minor Basin area are the Hagbong basaltic rocks, the Chaeyaksan basaltic rocks, the Jusasan andesitic rocks, the Unmunsa rhyolitic rocks, and the Tertiary voicanics. Stratigraphically, from the lowermost, (1) the Hagbong basaltic rocks are composed mainly of basaltic tuff with two olivine basalt flows intercalated, (2) the Chaeyagsan basaltic rocks are predominantly in tuffs and agglomerate with 3 basaltic flow interlayers, (3) the Jusasan andesitic rocks consist of thick piles of alternated sequences of 4 andesite flows and 5 andesitic tuffs and tuffaceous sediments and (4) the Unmunsa rhyolitic rocks which embed some rhyolite and obsidian are dominant in tuffs such as ash flow and crystal welded tuff. These volcanics reveal distinguishable characteristics in petrochemistry. In discriminating by major elements, the Hagbong and the Chaeyagsan basaltic rocks are alkaline, whereas the latter is also spilitic. In comparison, the volcanic rocks of the Jusasan andesitic rocks and the Tertiary sequences are characteristically calc-alkaline although their distribution is spatially separated. On the other hand, the variations in immobile trace elements indicate that the Hagbong basaltic rocks range from alkaline to calc-alkaline and from WPB/VAB transition to VAB, whereas the Chaeyagsan basaltic rocks are calc-alkaline WPB/VAB transition type and the two others calc-alkaline VAB. In order to show such a variety in their rock series of the volcanic rocks, the environment during their magma generation, magma rising, and post-eruption alteration could be positively considered.

• Economic and Environmental Geology
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• v.54 no.2
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• pp.187-197
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• 2021

The Hyeongjeseom (Islet) is an erosional remnant of volcano which is located about 2 km northeast of sea shore of the Songaksan tuff ring, and is composed of volcaniclastic deposit, agglomerate and scoria deposit, ponded lava, aa lava flows, reworked deposit and beach deposit in ascending order from the base. The volcano is formed by volcaniclastic deposits and lava flows that recorded a transition from initial phreatomagmatic to magmatic explosions followed by lava effusion. It is interpreted that the outcropped volcaniclastic deposit may be a remaining portion of outer ring of a tuff cone. A bomb and a ponded lava yield geochemically basaltic trachyandesite compositions (SiO2 51.3 wt%, Na2O+K2O 6.0 wt%) and belong to olivine basalt with scarce (<5 %) phenocrysts of olivine, petrographically. By incremental heating Ar-Ar dating method, the plateau age of lava flow in the Heongjesom is 9.2±3.6(2σ) ka, implying that the volcanism of Heongjeseom may have occurred earlier than the Songaksan tuff ring which erupted ca. 3.7 ka. It still remains a task to find a volcano which matches with a historical record of volcanic activity that occurred a thousand years ago.