• Journal of the Korean association of regional geographers
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• v.17 no.3
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• pp.348-356
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• 2011

Someday Mt. Baekdu could erupt by records of orogeny activity until today. This study is to predict influence area of lava flow and volcanic ash by simulation of volcanic eruption in the Mt. Baekdu. Simulation for eruption applied to supposing 7 grade of volcanic explosivity index, season from fall to spring. As a simulation results, lava flewed down into slope of China and volcanic ash diffused over the North Korea. Volcanic ash spreads to Ulneung area after nine hours. It was predicted that 61 cities and villages out of 27 administrative districts of Si-Gun were affected by volcanic ash in North Korea and an immense volume of volcanic ash was blown into farm lands, city areas and forests. This results expected to utilize information for disaster preparation of North Korea and joint research with South-North Korea and China.

• Economic and Environmental Geology
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• v.18 no.4
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• pp.381-397
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• 1985

A petrological study has been done in the pyeongchang-Jaecheon area which is a northwestern part of the basement of Ogcheon zone for the purpose of comparison of the area to the Nogjeon-Yeongchun area which is the antipodal basement of the zone in the petrological and geotectonical view points. The major units of the area are Precambrian granitic gneissic complex, banded gneiss, linea ted leucocratic gneiss and pegmatitic leucogranitic gneiss in the west, elongated exposure of quartz schist (or partly quartzite) and phyllite, named as Jungdaegal-bong Group correlated to the lower sequence of Joseon Group, in the middle, and limestone and calcic dolomite, Iptanri Formation, correlated to the middle of Joseon Group in the east. Igneous plutons are distributed in the areas of gneissic complex and limestone formation as well as in the Eosangcheon and Daedaeri areas in the southeastern out of the area. Present study reveals that the gneissic complex are the products of granitization to metamorphism of amphibolite facies in the order of above mentioned from the metasediments of schists and calcareous rocks. A notable characteristics of the phyllite of Jungdaegal-bong Group is the presence of syntectonically segregated quartz rods in the forms of lens, swirl or boudinage in evenly distributed in the phyllitic to chloritic matrix. Igneous rocks range in composition from gabbro through diorite, granodiorite, to schistosed and porphyritic granites in stock and dike. The orogenic movement of the Ogcheon zone initiated in the middle Proterozoic time, pre-sedimentation of Ogcheon Group and superposed the granitization in Permian, Jurassic Daebo orogeny with granitic batholiths and stocks, and Cretaceous plutonic intrusion.

• Economic and Environmental Geology
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• v.18 no.1
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• pp.23-39
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• 1985

The northeastern part of Ogcheon zone which consisted mainly of Cambro-Ordovician arenaceous, argillaceous and calcareous formations and Carboni-Triassic arenaceous and argillaceous formations is delineated as the eastern mass of a thrust fault along Choongju-Moongyong-Cheongsan in the middle of the zone. The present study proposes a geotectonic line, Imgye-Samchog fault(see, figure 1) which divides the northeastern part into two blocks, Hambacksan block in the west and East coast block in the east. The igneous rocks in the Hambacksan block ranging from granite to gabbro are distributed in a symmetrical zones parallel to general direction of Ogcheon zone as follows (Fig. 2 and Table 2). Southeast igneous rock zone: it aligns Jurassic granites in its south and Precambrian leucocratic granites in its north. Central igneous rock zone: it aligns Cretaceous granites in its south and Jurassic granites, and some of diorite and gabbro in its north. Northwest igneous rock zone: aligns Jurassic granites in its south and huge batholithic granodiorite in its north. The distribution of the igneous rocks in the East coast block shows an entirely different features from those of Hanbacksan block. In the southern part of the block they assemble in a narrow area ranging in age from Early Proterozoic, through Middle to Late Proterozoic, Devonian, Jurassic, Cretaceous to Tertiary, whereas, the igneous rocks in the northern part of the block gathered to a restricted area, in ages of Middle Proterozoic and Cretaceous. The assemblage of the igneous rocks in the studied area shows a compositionally restricted, mixed S-type and I-type granites, $^{87}Sr/^{86}Sr$ > 0.706, rare volcanics and shortening with upright folding. These lithologic and structural features suggest that the igneous activity in this part related intimately to Hercynotype Orogeny of Pitcher(1979). Chronological episodes of igneous activity from Early Proterozoic to Early Tertiary in the northeastern part are figured.

• Economic and Environmental Geology
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• v.23 no.4
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• pp.453-463
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• 1990

The Yechon shear zone developed by strike-slip movement was formed in a relatively high temperature condition just after the Jurassic syntectonic granites had been emplaced during Daebo Orogeny. Post-emplacement formation of the shear zone is favored by continuity of foliations and lineations within and without the granites, development of mylonitic structures in the wallrocks, deformation of pegmatite and felsite dikes, and pretectonic growth of porphyroblasts in the wallrocks. A variety of shear sense indicators in the shear zone are predominantly observed in the intensely to extremely deformed rocks. They show that bulk non-coaxial detormation has occurred, and that the sense of shear is consistently dextral with S-C fabrics, grain shape fabrics, asymmetric porphyroclast systems, mica fish, asymmetric extension structures and quartz C-axis fabrics.

• Economic and Environmental Geology
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• v.53 no.3
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• pp.259-269
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• 2020

The use of the geophysical method in mining prospecting has been studied in the Asdaf region (South-East of Morocco). The objective of the study is to examine the aptitude of the electrical technique, in this case induced polarization (IP) and electric tomography, combined with the electromagnetic method (VLF), in the exploration of barite . The result obtained by the pseudo-sections of electrical tomography and that of KH filtration highlighted anomalies of resistant contact (greater than 400Ω.m) and of high charge chargeability (5mV / V). These contacts are hosted in less resistant Devonian age shale and sandstone. The resistivity response obtained at their level is characteristic of the venous structures associated with barite mineralization. The direction of the mineralized veins is parallel to the direction of the fractured zones (NE-SW), which indicates that the mineralization in place is due to the tectonic movements of the Hercynian orogeny (from Devonian to Permian). These veins are aligned with the locations of abandoned mine shafts and with surface mining areas. Geophysical technique therefore seems to play a key role in barite mining exploration.

• Journal of the Korean earth science society
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• v.21 no.4
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• pp.488-501
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• 2000

'The Voyage of the Beagle' , one of the best record of scientific travels ever made, written by Charles Darwin (1809-82), the greatest naturalist ever born, is reviewed in the viewpoint of the Earth Sciences. Various observations and interpretations on the Earth Sciences are told in the Voyage. First of all, Darwin understood the geological time much more longer than accepted then as well as the geological phenomena and processes such as orogeny, uplifting, subsidence, erosion, and deposition. And he also provided a perfect interpretation on the formation of coral reefs and a good theory on the evolution of organisms. Reasonable paleoenvironmental reconstructions and interpretations based on the fossils were given in the Voyage. His observations on meteorological phenomena were from the dust composed of organisms collected on the 'Beagle' in the Atlantic Ocean, to the movement of air and extreme clear dry condition experienced on the crest of the Andes, and etc. He made several observations on the general oceanography such as the discoloration of the sea, the lights on the sea surface, conchoidal provinces noted on the Galapagos Archipelago, the trees and plants found in the remotely separated islands, and etc. However relatively scarce observation was carried out on astronomy probably due to his relatively much land travelling. Most of his interpretations and suggestions are accepted in this time.

• Economic and Environmental Geology
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• v.24 no.3
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• pp.261-276
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• 1991

The main aspect of this study are to clarify igneous activity of igneous rocks, which is a member of various intrusives and volcanics exposed in Naju-Namchang area of southern central zone of Ogcheon Geosynclinal Belt, southern part of Youngdong-Kwangju depression zone of tectonic provinces in Korea. Naju-Namchang area are subdivided into three rock belts based on occuring of Cretaceous granites. Three rock belts consist of foliated granites, Jurassic granites and Cretaceous granites in central granitic rock belt (C-C), and acidic tuff and lavas in northwest volcanic rock belt(C-NW) and southeast volcanic rock belt(C-SE). Chemical composition of these igneous rocks show mostly similar trend to the Daly's values on Harker diagram and correspond to VAG + Syn-COLG region on Pearce's discrimination diagram. These igneous rocks vary wide range in total REE amount(37.4-221.3ppm) characterized by enriched LREE content and steep negative slope in Eu(-) anomaly. It is concluded each synchronous granites which composed of serveral rock facies is considered to formed by differentiation of co-magma at continental margin, and igneous activity of study area are two more Pre-Cambrian Orogenies, Songrim Disturbance, Daebo Orogeny and Bulkuksa Disturbance.

• Economic and Environmental Geology
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• v.52 no.5
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• pp.357-366
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• 2019

Deposition of the Daedong Supergroup has been considered to be related with the Triassic Songrim and Jurassic Daebo orogenies. The Chungnam Basin fills is an important sedimentary succession to understand the geological evolution of the Early to Middle Mesozoic Korean Peninsula. Previous paleontological and paleomagnetic studies have suggested the Late Triassic to Early Jurassic sedimentation of the Chungnam Basin fills. However, the orogenic model of the basin development has remained controversial because recently reported zircon U-Pb isotopic ages are not harmonious with the previous studies. This paper aims to review the stratigraphy, depositional age, and composition of the Chungnam Basin fills, together with test of the basin development models.

• The Journal of the Petrological Society of Korea
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• v.1 no.1
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• pp.34-41
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• 1992

The Precambrian granitic gneisses are widely distributed in the Danyang-Yecheon area, eastern part of Korea, where the Ryeongnam massif borders the Ogcheon fold belt. They are composed of migmatitic, biotite granitic, garnet-bearing and granoblastic granitic gneisses. The common joint sets of the granitic gneiss are NE and NS directions, which are probably related to the effects of Daebo orogeny and Bulgugsa disturbance, respectively. Mineral assemblages of the banded gneiss xenolith in the garnet-bearing granitic gneiss are quartz-plagioc1ase-biotite-mus-covite-orthoclase and quartz-plagioc1ase-biotite-garnet, belonging to the amphibolite facies. The granoblastic granitic gneiss is felsic, metaluminous, and granitic, and shows subalkaline trend. The garnet-biotite geothermometry of garnet-bearing granitic gneiss yields 640$^{\circ}$-708$^{\circ}C$ at pressure of 4 kb.

• The Journal of the Petrological Society of Korea
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• v.28 no.3
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• pp.217-225
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• 2019

This study describes a large recumbent fold, which occurs at the north entrance slope of the Batjae tunnel, Pyeongchang-gun, Gangwon-do, and interprets its formation mechanism. The several-hundred-meter scale fold, developed in the Jeongseon Limestone of the Paleozoic Joseon Supergroup, has a nearly horizontal axial plane and its head is facing north. Stretching lineations ($L_1$) observed on the composite foliations of bedding and axial plane cleavage plunge southward at about $10^{\circ}$. Small A-type or eye-shaped sheath folds together with S-shaped asymmetrical folds are often observed in the fold limbs and their axes are nearly parallel to the lineations ($L_1$) within center and rear parts of the fold. It is thus interpreted that the recumbent fold is a large sheath fold produced by the top-to-the-north ductile shearing due to the Songrim orogeny during the late Paleozoic to Triassic.