• The Journal of the Petrological Society of Korea
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• v.16 no.4
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• pp.196-207
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• 2007

Miocene basalt plugs in Goseong contain a large variety of crustal and mantle xenoliths and xenocrysts. One of basalt plugs, Unbongsan, are derived from 160 km depth. Whole-rock geochemistry and pressure and temperature conditions of mineral phases indicate that Unbongsan volcanic rocks are alkali basalts and the source magma of the alkali basalts was generated from about $0.2{\sim}2%$ partial melting of depleted garnet peridotite. Crystallization pressures and temperatures of mineral phases within ascending magma of Unbongsan alkali basalt indicate that olivines, clinopyroxenes, and plagioclases were crystallized at $75{\sim}110km,\;40{\sim}52km,\;37{\sim}54km$ depth, respectively. The ascending magma of Unbongsan alkali basalts enclosed mantle xenoliths at about $57{\sim}67km$ depth.

• Journal of the Korean Magnetics Society
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• v.25 no.5
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• pp.169-173
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• 2015

Fe compounds of volcanic basalt samples distributed at the Hantan riverside in Cheorwon were investigated by means of X-ray diffractometry (XRD), X-ray fluorescence spectroscopy (XRF) and $M{\ddot{o}}ssbauer$ spectroscopy. We found that samples were typical basic rock which consisted of augite, anorthite, albite and sanidine etc. They had the total amount of iron compounds including hematite (${\alpha}-Fe_2O_3$) varies from 6.20 w% to 12.8 w% depending on the different regions by XRF. The $M{\ddot{o}}ssbauer$ spectra of the samples were consisted of three doublets. The balance state of Fe ions of all samples were chiefly $Fe^{2+}$, and $Fe^{2+}/Fe^{3+}$ ratios were 2.27~3.42.

• Economic and Environmental Geology
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• v.11 no.2
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• pp.47-57
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• 1978

The study focused on the petrology and petrochemistry of the so called "Ganghwa syenitic rocks" which intruded into metasediment of basement in southeastern part of Ganghwa Island. The geologic sequence of the mapped area was shown in table 1, 10 model analyses and 7 chemical analyses on the rock samples taken from the Ganghwa syenitic rocks and Manisan granite have been used to discuss the nomenclature of the rocks and petrological relationship between rock types. The petrograpical and petrochemical features based on, the analyses are as follows: 1) Ganghwa syenitic rocks consist of Ganghwa alkali syenite and Ganghwa diorite porphyry which based on the classification of the subcommision on systematics of igneous of IGUS. Ganghwa diorite porphyry which occured as dike forms are intruded into Ganghwa alkali syenite. The rock forming minerals of Ganghwa alkali syenite are composed of perthite, plagioclase, quartz, hornblend and chlorite in major, and zircon, apatite, sericite and magnetite in minor. Ganghwa diorite porphyries consist of plagioclase, biotite, hornblend, orthoclase and chlorite, with, porphyritic texture. 2) In silica-oxides variation (Fig. 2) and AMF diagram (Fig_ 3), the Ganghwa alkali syenite is similar to the trend of Daly's average basalt-andesite-dacite-rhyolite than Skaergaard which shows the trend of the fractional crystallization of magma, and equivalent to the alkali rock series by Peacock. 3) The general trend of data points shift to plagioclase, and are superimposed on the alkali rich terminal part of the granodiorite province of SW Finland in normative Q-Kf-Pl(Fig. 4) and Or-Ab-An diagram respectively. The above-mentioned evidences suggested that the Ganghwa syenitic rocks are the differential products resulted by assimilation of intermediated magma and metasedment rock under relatively rapid cooling condition.

• Tunnel and Underground Space
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• v.25 no.2
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• pp.144-154
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• 2015

Mechanical energy is accumulated in the object when stress is exerted on rock specimens, and the failure is occurred when the stress is larger than critical stress. The accumulated energy is emitted as various forms including physical deformation, light, heat and sound. Uniaxial compression strength test and point load strength test were carried out in low temperature environment, and thermal variation of rock specimens were observed and analyzed quantitatively using thermal infrared camera images. Temperature of failure plane was increased just before the failure because of concentration of stress, and was rapidly increased at the moment of the failure because of the emission of thermal energy. The variations of temperature were larger in diorite and basalt specimens which were strong and fresh than in tuff specimens which were weak and weathered. This study can be applied to prevent disasters in rock slope, tunnel and mine in cold regions and to analyze satellite image for predicting earthquake in cold regions.

• Economic and Environmental Geology
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• v.16 no.1
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• pp.19-36
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• 1983

The study revealed that the sequence of volcanism in Ulrung island can be classified into 5 stages, and the volcanic history is summerized as follow: 1st stage: Eruption of basaltic agglomerates, tuffs and lavas, 2nd stage: Eruption of trachytic and trachyandesitic agglomerates and tuffs, 3rd stage: Eruption of trachyte lavas and their lapilli tuffs, 4th stage: Eruption of trachyte lavas and nepheline phonolites, 5th stage: Eruption of pumice, trachytic ash and lapilli, and plutonic ejecta (fragments of alkali gabbro, monzonite and alkali feldspar syenite) and a subsequent caldera formation. Finally, a small scale eruption of leucite bearing trachyandesite lava in the caldera. Several evidences show that there have been long erosional intervals between the 1st and 2nd stages and between the 4th and 5th stages. A K-Ar age for trachybasalt lava of the 1st stage was determined to be 1.8 Ma, and a $C^{14}$ age, 9300Y. (Machida, 1981) is available for these volcanic events. Therefore, it is considered that volcanic activity of the island above sea level began at least in early Pleistocene, and continued to until 9300 years ago exploding large amount of pumice, prior to pouring out of leucite bearing trachyandesite from the inner caldera. Using solidification index (SI) of Kuno, microscopic texture and mineral composition as criteria of the classification, the volcanic rocks are classified into alkali basalt, trachybasalt, trachyandesite, trachyte and phonolite. These are mostly prophyritic in texture. Main constituent minerals of alkali basalt and trachybasalt are plagioclase, olivine, Ti-augite and magnetite. Principal minerals of trachyandesite are plagioclase, anorthoclase, clinopyroxenes, kaersutite, biotite and magnetite. Trachyte and phonolite consist mainly of anorthoclase, clinopyroxene and magnetite, showing typical trachytic texture in groundmass. In solidification index, alkali basalt ranges from 39 to 27, trachybasalt 17 to 14, trachyandesite 12 to 9 and trachyte 8.15 to 0.72. A trend of compositional variation showing a typical alkali volcanic rock series is revealed on $SiO_2$-oxides and SI-oxides diagrams. In $SiO_2$-total alkali diagram, alkali lime index and An-Ab'-Or diagram, the samples fall into the fields of potassic series of the alkali volcanic rock series, whereas in A-F-M diagram show a trend toward the alkali enrichment with a curve approaching toward the iron apex. In particular, trachybasalt lavas in this island have higher total iron contents which is comparable to alkali rocks in other areas, e. g. as Gough and Tristan volcanic islands located near the Mid-Oceanic ridge in South Atlantic Ocean.

• Economic and Environmental Geology
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• v.7 no.3
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• pp.123-152
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• 1974

The study focused to the so called "Yangpyeong Igneous Complex" which intruded into the Gyeong Gi gneiss complex of Pre-cambrian basement of Yangpyeong area. The geologic sequence of the mapped area was shown in table 1. In laboratory work, 31 modal analyses and 7 chemical analyses on the rock samples taken from the igneous complex have been made to discuss the nomenclature of the rocks and the petrological relationship between rock types. The petrographical and petrochemical features based on the analyses are as follow; 1) The classification of this rocks based on the systematics of igneous rocks of IUGS showed that Yangpyeong Igneous complex consist of hornblende gabbro, diorite and porphyritic monzonite. The major rock forming minerals in hornblende gabbro are hornblende and plagiodase ($An_{46{\sim}55}$), in diorite, hornblende, biotite and plagioclase ($An_{23{\sim}33}$) and in porphyritic monzonite, K-feldspar, plagioclase ($An_{21{\sim}35}$), hornblende and biotite. Hornblende gabbro and diorite show coarse to medium grained hypidiomorphic granular texture and porphyritic monzonite was named by the characteristically porphyritic texture of K-feldspar phenocrysts. 2) Silica-oxides variation diagram (Fig.4) illustrate that the igneous complex is similar ttl that of Daly's average basalt-andesite-dacite-rhyolite and equivalent to the calc-alkalic rock series of Peacock's rock series. In AMF diagram (Fig. 5), the trend of the igneous complex is nearly pararell to that of the Skaergaard intrusion which shows the trend of the fractional crystalization of magma. 3) In normative Or-Ab-An diagram (Fig. 6) the general trend of the data points from gabbro to porphyritic monzonite of the igneous complex directs to a point of Or/Ab=1:1 on the side of Or-Ab. The field and laboratory evidences suggested that the Yangpyeong igneous complex was thought to be a series of comagmatic differential products.

• Journal of the Korean Geosynthetics Society
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• v.9 no.3
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• pp.19-27
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• 2010

In this study, a series of triaxial tests to Jeju basalt were carried out and then shear strength parameters of rock were estimated by the Lade's three-dimensional failure criterion. Also, the characteristics of shear strength parameters and failure plane which were estimated by the three-dimensional failure criterion were analyzed and this failure criterion was compared with the Mohr-Coulomb failure criterion. The variables of ${\eta}_1$ and m are derived from the relationship between ($I_1^3/I_3-27$) and ($P_a/I_1$) during the failure period using the Lade's three-dimensional failure criterion. The failure plane size of Tracy-basalt has the largest plane and that of Scoria has the smallest plane among other octahedral planes which is the three-dimensional failure plane. Also, the failure plane of Tracy-basalt is formed as a triangle and that of Scoria is formed as a circle among other octahedral planes. As the result of comparison with the triaxial test results and the Lade's failure envelope and the Mohr-Coulomb failure envelope, the Lade's failure envelope matched up under higher stress, while the Mohr-Coulomb failure envelope matched up under lower stress. Also, the Lade's three-dimensional failure plane is larger than the Mohr-Coulomb three-dimensional failure plane. It means that the shear strength parameters estimated by the Lade's failure criterion is larger than that of the Mohr-Coulomb failure criterion.

• The Journal of the Petrological Society of Korea
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• v.9 no.1
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• pp.1-12
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• 2000

The Cretaceous basaltic rocks in Gyeongsang Basin are temporally and spatially dispersed widely in thick sedimentary piles: Chilgog basaltic rock (CGB) and Cheongyongsa basaltic rock (CSB) in the Shindong Group, and Hakbong basaltic rocks (HBB), Osibbong basalt (OSB), Secheondong basaltic rocks (SCB), Haman basaltic rocks (HAB), Hama basaltic rocks (HMB), and Chaeyaksan basaltic rocks (CYB) in the Hayang Group, upwardly in their stratigraphy. Chilgog basaltic rock is merely identified as pebbles in the Shilla Conglomerate and its provenance has not been found, and it is characteristics that the volcanics except Osibbong basalt and Chaeyaksan basaltic rocks are very small in both of their thickness and extension. Petrochemical diversity of the basaltic rocks are revealed; OSB and SCB distributed in the Yeongyang Minor Basin preserve the calc-alkaline natures in major and immobile minor element geochemistry, but CGB, HBB, HAB, and CYB reflect that they might be originated from calc-alkaline basaltic magma of volcanic arc in continental margin area by trace elements and altered to alkaline suites in the viewpoint of their major element geochemistry. Major and trace element geochemistry of CSB and HMB suggests that they may be derived from within -plate alkaline magma contaminated by the upper continental crust, especially in the case of the former.

• Tunnel and Underground Space
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• v.27 no.2
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• pp.77-88
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• 2017

The geology of the study area is composed mainly of conglomerate, sandstone, and shale and basalt. It is a rock that has been observed to move relatively recently through various brittle deformation and various stress fields during the recent period. To form a gentle terrain with severe crushing. The slope is located at the intersection of the Taegok Fault in the north-northeast direction and the Bukok Fault in the western north-west direction, and many faults, fault zones and fracture zones of various sizes are developed in the rock bed. In this study, the geological characteristics of the slope are investigated and the countermeasure method is suggested. It is suggested that periodical measurement and analysis should be performed by installing a measuring instrument according to each structure for safety management of the surrounding roads and grounds during construction or reinforcement by the countermeasure method for the slope of the study area.

• Journal of the Korean association of regional geographers
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• v.18 no.2
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• pp.129-140
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• 2012

In order to examine geomorphic characteristics such as form and retreat process of waterfalls in Jeju Island, 26 waterfalls were classified based upon materials forming a fall face. The waterfalls could be categorized into three types such as single unit, multiple units and basal soft-rock based upon the number and type of a lava flow. A block fall, composed of a pile of large blocks, could be added to the typology of waterfalls in Jeju Island. While the single unit fall is distributed in a region of trachyte or trachyandecite, the multiple units fall and basal soft-rock fall are largely developed in a region of basalt or trachybasalt. A retreat process of the single unit fall is an inclination or a replacement, but the basal soft-rock fall shows a parallel retreat. The multiple units fall exhibits three types of a retreat process according to the physical properties of a lava flow. The fall face is generally vertical due to well-developed vertical joints of a lava flow.