• Economic and Environmental Geology
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• v.22 no.4
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• pp.355-370
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• 1989

Igneous rocks of study area consist of Pre-Cambrian orthogneiss, Devonian granite, Triassic foliated granites and Jurassic granites distributed along the southeast margin of Ogcheon Geosynclinal belt(SE-zone), and irregular shaped granitic stocks in the central part of the belt(C-zone). Anorthosite and gaabbro are also present in southern part of the SE-zone in the belt and intruded into gneiss complex of Ryongnam massif. Distribuition of foliated granites shows three linear arrangements which are composed of hornblende-biotite foliated granodiorite, porphyritic foliated granodiorite, biotite foliated granodiorite, leuco foliated granite and two mica foliated granite. Foliated granites generated by dextral strike slip movement at deep level. Jurassic granites composed of several rock facies are considered to be formed by differentiation of magma during Daebo Orogeny. A general trend of the chemical composition of these igneous rocks in study area suggests that most of them corresponding to calc-alkaline rock series was affected under orogeny and I-type granite except for two mica foliated granite. In chondrite normalised REE pattern of these igneous rocks, LREE shows more variable range and strong (-)Eu anomaly than HREE. Geochronological episodes of igneous activity from early Proterozoic to Cretaceous in SE-zone of Ogcheon Geosynclinal belt are two more Pre-Cambrian Orogeny, Devonian Orogeny(Variscan), Songrim Disturbance, Daebo Orogeny and Bulkuksa Disturbance.

• Journal of the Korean earth science society
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• v.31 no.3
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• pp.205-213
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• 2010

A hydrochemical comparative study of groundwater in uraniferous sedimentary rock of the Ogcheon belt was carried out to investigate the genetic relationship between uraniferous groundwater of Daejeon area and uraniferous sedimentary rocks of the Ogcheon zone. The groundwater shows weak alkaline pH values rangingfrom 6.4 to 8.1 and low Eh values ranging from -50 to 225 mV. The groundwaters to Ca-$HCO_3$ type that shows high concentration of $Ca^{2+}$ and $HCO_3^_$ due to the dissolution of carbonate mineral in limestone. The concentration of uranium in the groundwater was measured very low below $3.2{\mu}g/L$, while it was detected as much as $1165{\mu}g/L$ in the mine waste water. The low Eh value of groundwater is one of the main causes of low uranium concentration of groundwater in uraniferous sedimentary rocks in the Ogcheon belt. It is suggested that the uranium of groundwater in granitic region of Daejeon area was not mainly provided from uraniferous sedimentary rocks in the Ogcheon belt.

• The Journal of the Petrological Society of Korea
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• v.23 no.4
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• pp.325-336
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• 2014

Even though Mesozoic Mudeungsan tuff, located within Neungju Basin, has been named several rock names, it should be named as Mudeungsan tuff due to several evidences, such as fiamme, welded texture and rock fragments in the Mudeungsan tuff. Volcanic eruption boundary between the Cheonwangbong and Anyangsan areas is not clear, but petrochemical and mineral chemical evidences with different ages indicate clear petrological boundary between Cheonwangbong and Anyangsan. The Mudeungsan tuffs from Cheonwangbong and Anyangsan is welded crystal tuff with dacitic composition and were generated from cogenetic calc-alkaline magma in the volcanic arc environment. Geochemical events indicate that magma beneath Cheonwangbong was seems to have been evolved from the magma beneath Anyangsan due to fractional crystallization dominated by plagioclase.

• Journal of Soil and Groundwater Environment
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• v.29 no.3
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• pp.1-13
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• 2024

This study investigated the hydrogeochemical and microbiological characteristics of freshwater on Ulleung Island, a volcanic island in the Ulleung Basin on the East Coast of Korea. The shallow groundwater (CSW, NRGW) and the surface water (SISW) samples are classified as Na-HCO₃ type, reflecting an alkaline rock type and an oxidizing environment due to the influence of a highly permeable pyroclastic rock layer. In contrast, the deep groundwater sample (DMW) is classified as Ca-HCO₃ type, suggesting the influence of deep-sourced carbon dioxide and reducing conditions. Microbial communities in the water samples are generally dominated by Proteobacteria, with the relative abundance of major genera varying depending on water quality and environmental conditions. Network analysis reveals the ecological characteristics of microbial communities adapted to specific environments. The presence of pathogenic genera in the shallow groundwater suggests potential groundwater contamination, necessitating appropriate management to ensure its use as drinking water or domestic water. The findings of this study provide valuable insights into the ecological characteristics of Ulleung Island's groundwater resources and can inform future groundwater management strategies.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.205-217
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• 2024

This study evaluated the physical characteristics and quality of volcanic rocks distributed in the Jeju Island-Ulleung Island area as aggregate resources. The main rocks in the Jeju Island area include conglomerate, volcanic rock, and volcanic rock. Conglomerate is composed of yellow-red or gray heterogeneous sedimentary rock, conglomerate, and encapsulated conglomerate in a state between lavas. Volcanic rocks are classified according to their chemical composition into basalt, trachybasalt, basaltic trachytic andesite, trachytic andesite, and trachyte. By stratigraphy, from bottom to top, Seogwipo Formation, trachyte andesite, trachybasalt (I), basalt (I), trachybasalt (II), basalt (II), trachybasalt (III, IV), trachyte, trachybasalt (V, VI), basalt (III), and trachybasalt (VII, VIII). The bedrock of the Ulleung Island is composed of basalt, trachyte, trachytic basalt, and trachytic andesite, and some phonolite and tuffaceous clastic volcanic sedimentary rock. Aggregate quality evaluation factors of these rocks included soundness, resistance to abrasion, absorption rate, absolute dry density and alkali aggregate reactivity. Most volcanic rock quality results in the study area were found to satisfy aggregate quality standards, and differences in physical properties and quality were observed depending on the area. Resistance to abrasion and absolute dry density have similar distribution ranges, but Ulleung Island showed better soundness and Jeju Island showed better absorption rate. Overall, Jeju Island showed better quality as aggregate. In addition, the alkaline aggregate reactivity test results showed that harmless aggregates existed in both area, but Ulleungdo volcanic rock was found to be more advantageous than Jeju Island volcanic rock. Aggregate quality testing is typically performed simply for each gravel, but even similar rocks can vary depending on their geological origin and mineral composition. Therefore, when evaluating and analyzing aggregate resources, it will be possible to use them more efficiently if the petrological-mineralological research is performed together.

• Journal of Environmental Science International
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• v.25 no.11
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• pp.1541-1554
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• 2016

To understand the characteristics of vanadium leaching from soils formed by the weathering of basalts, paleo soil at Gosan, Jeju Island, Korea, and several present-day soils from neighboring areas were collected. Leaching experiments were carried out by two approaches: 1) batch experiments under various geochemical conditions (redox potential (Eh) and pH) and 2) continuous leaching experiments under conditions similar to those of natural environments. From the batch experiments, leached vanadium concentrations were highest under alkaline (NaOH) conditions, with a maximum value of $2,870{\mu}g/L$, and were meaningful (maximum value, $114{\mu}g/L$) under oxidizing ($H_2O_2$) conditions, whereas concentrations under other conditions (acidic-HCl, $neutral-NaHCO_3$, and $reducing-Na_2S_2O_3$) were negligible. This indicated that the geochemical conditions, in which soil-water reactions occurred to form groundwater with high vanadium concentrations, were under alkaline-oxidizing conditions. From the continuous leaching experiments, the pH and leached vanadium concentrations of the solution were in the ranges of 5.45~5.58 and $6{\sim}9{\mu}g/L$, respectively, under $CO_2$ supersaturation conditions for the first 15 days, whereas values under $O_2$ aeration conditions after the next 15 days increased to 8.48~8.62 and $9.7{\sim}12.2{\mu}g/L$, respectively. Vanadium concentrations from the latter continuous leaching experiments were similar to the average concentration of groundwater in Jeju Island ($11.2{\mu}g/L$). Furthermore leached vanadium concentrations in continuous leaching experiments were highly correlated with pH and Al, Cr, Fe, Mn and Zn concentrations. The results of this study showed that 1) alkaline-oxidizing conditions of water-rock (soil) interactions were essential to form vanadium-rich groundwater and 2) volcanic soils can be a potential source of vanadium in Jeju Island groundwater.

• Journal of the Korean earth science society
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• v.30 no.3
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• pp.267-281
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• 2009

Cretaceous intrusive and extrusive rocks are widely distributed in the southern part of the Korean peninsula, possibly the result of intensive magmatism which occurred in response to subduction of the Pacific plate beneath the northeastern part of the Eurasian plate. Geochemical and petrological study on the Cretaceous granitic rocks of the Yeosu area were carried out in order to constrain the petrogenesis of the granitic rocks and to establish the paleotectonic environment of the southwestern part of the Korean peninsula. Igneous rocks of the Yeosu area consist of diorite, hornblende biotite pite and micrographic granite. Chondrite normalized REE patterns show generally enriched in LREE ($(La/Lu)^{cN}$=4.2-13.3). Diorites show flat to slight negative Eu anomalies while micrographic granites have strong negative Eu anomalies. The ${\Sigma}REE$ of the granites are 76.2-235 ppm, which corresponds to the range of the continental margin granite. Whole rock chemical data of the granitic rocks from the Yeosu area indicate that the rocks have characteristics of calc-alkaline series in the subalkaline field. On the A/NK vs. A/CNK and tectonic discrimination diagrams, parental magma type of the granites corresponds to I-type and volcanic arc granite (VAG). Interpretations of the chemical characteristics of the granitic rocks favor their emplacement in a compressional tectonic regime at continental margin during the subduction of Pacific plate.

• The Journal of the Petrological Society of Korea
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• v.12 no.1
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• pp.32-52
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• 2003

The Mt. Baegyang in Busan, composed of sedimentary basement rocks (Icheonri Formation), andesite (lava), andesitic pyroclastic rocks, fallout tuff and tuffaceous sedimentary rocks, rhyolitic pyroclastic rocks, intrusive rocks (granite-porphyry, felsite, and biotite-granite) of Cretaceous age in ascending order. The volcanic rocks show a section of composite volcano which comprised alternation of andesitic lava and pyroclasitc rocks, rhyolitic pyrocalstic rocks (tuff breccia, lapilli tuff, fine tuff) from the lower to the upper strata. From the major element chemical analysis, the volcanic and intrusive rocks belong to calc-alkaline rock series. The trace element composition and REE patterns of volcanic and plutonic rocks, which are characterized by a high LILE/HFSE ratio and enrichments in LREE, suggest that they are typical of continental margin arc calc-alkaline rocks produced in the subduction environment. Primary basaltic magma might have been derived from partial melting of mantle wedge in the upper mantle under destructive plate margin. Crystallization differentiation of the basaltic magma would have produced the calc-alkaline andesitic magma. And the felsic rhyolitic magma seems to have been evolved from andesitic magma with crystallization differentiation of plagioclase, pyroxene, and hornblende.

• Journal of the Korean earth science society
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• v.38 no.1
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• pp.49-63
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• 2017

The geochemical results of the Chunyang granites located in the northeastern part of the Yeongnam Massif, indicate that these rocks have characteristics of calc-alkaline series in the sub-alkaline field, I-type and peraluminous. Most of the geochemical features in major and trace elements show systematic trends, which are similar to differentiation trends of the general Jurassic granitoids in South Korea. The Chunyang granite is largely enriched in mobile LILE (Sr, K, Rb and Ba) relatively immobile HFSE. They show LREE enriched patterns [$(La/Lu)_{CN}=41.8-73.2$] with a slightly negative Eu anomaly [$(Eu/Eu^*)_{CN}=0.89-1.10$]. There are no meaningful correlations in major and trace elements between the Chunyang granites and the Buseok plutonic rock which is the main unit of the Yeongju batholith. This result may suggest that these two plutonic rocks be not derived from the same parent magma. Tectonic discrimination diagrams indicate that the Chunyang granite was formed in volcanic arc environments. These geochemical characteristics results suggest that the Chunyang granite must have been generated at the active continental margin during the subduction of the Jurassic proto-Pacific plate.

• The Journal of the Petrological Society of Korea
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• v.16 no.3
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• pp.116-128
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• 2007

Detailed geological mapping, petrographic study, analyses of geochemistry and magnetic susceptibility, and K-Ar dating were carried out in order to determine the origin, age, and stratigraphic implications of granitic rock fragments in the pyroclastic rocks, SE Jinhae city, southern part of the Gyeongsang Basin. As a result, it was found that the area is composed of volcanics and tuffaceous sediments of the Yucheon Group, Bulguksa granites, pyroclastics bearing granitic rock fragments, $basalt{\sim}basaltic$ andesite, and rhyolite in ascending stratigraphic order. The granitic rock fragments in the pyroclastic rocks are divided into granodiorite and biotite granite, which have approximately the same characteristics as the granodiorite and the biotite granite of the Bulguksa granites, respectively, in and around the study area including color, grain size, mineral composition, texture (perthitic and micrographic textures), intensity of magnetic susceptibility (magnetite series), and geochemical features (calc-alkaline series and REE pattern). This leads to the conclusion that the rock fragments originated from the late Cretaceous Bulguksa granites abundantly distributed in and around the study area, but not from the basement rocks of the Yeongnam massif or the Jurassic granites. Based on relative and absolute ages of various rocks in the study area, the pyroclastics bearing granitic rock fragments are interpreted to have erupted between 52 and 16 Ma, i.e. during the Eocene and early Miocene. These results indicate that the various volcanisms, acidic to basic in composition, occurred after the intrusion of the Bulguksa granites, contrary to the general stratigraphy of the Gyeongsang Basin. Very detailed and cautious mapping together with relative and absolute age determinations are, thus, necessary in order to establish reliable stratigraphy of the Yucheon Group in other areas of the Gyeongsang Basin.