• The Journal of the Petrological Society of Korea
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• v.19 no.1
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• pp.67-87
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• 2010

This article deal with petrotectonic setting and petrogenesis from petrography and chemical analyses of the Cretaceous volcanic and intrusive rocks in the Cheolwon basin. The volcanic rocks are composed of basalts in Gungpyeong Formation, Geumhaksan Andesite, and rhyolitic rocks (Dongmakgol Tuff, Rhyolite and Jijangbong Tuff), and intrusive rocks, Bojangsan Andesite, granite porphyry and dikes. According to petrochemistry, these rocks represent medium-K to high-K basalt, andesite and rhyolite series that belong to calc-alkaline series, and generally show linear compositional variations of major and trace elements with increase in $SiO_2$ contents, on many Harker diagrams. The incompatible and rare earth elements are characterized by high enrichments than MORB, and gradually high LREE/HREE fractionation and sharp Eu negative anomaly with late strata, on spider diagram and REE pattern. Some trace elements exhibit a continental arc of various volcanic arcs or orogenic suites among destructive plate margins on tectonic discriminant diagrams. These petrochemical data suggest that the basalts may have originated from basaltic calc-alkaline magma of continental arc that produced from a partial melt of upper mantle by supplying some aqueous fluids from a oceanic crust slab under the subduction environment. The andesites and rhyolites may have been evolved from the basaltic magma with fractional crystallization with contamination of some crustal materials. Each volcanic rock may have been respectively erupted from the chamber that differentiated magmas rose sequentially into shallower levels equivalenced at their densities.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.583-586
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• 2003

부산 동래지역 지열수에 대한 지화학적 진화과정을 밝히기 위하여 지열수, 지하수 및 해수에 대한 수리화학 특성과 이들의 연관성을 고찰하였다. 또한 심부환경에서의 지화학 특성을 규명하기 위하여 각종 이온지질온도계와 다성분 지질온도계를 적용하였으며, 동위원소특성과 함께 지화학 모델링을 통하여 심부환경에서의 온천수의 지화학특성을 밝히고자 하였다. 동래 지열수의 수리화학적 특성은 해수의 영향을 받아 높은 이온함량을 보이며 Na-Cl형을 보여준다. 지열수는 주변 지하수와의 크게 혼합된 양상을 나타낸다. 지화학 모델링에 따르면 지열수는 심부에서 약 5% 영향을 받은 것으로 추정된다. 즉, 심부로 순환하는 지열수가 해수와 혼합되며, 이들이 지열에 의해 가열되면서 광물의 용해 및 침전, 이온 교환반응 등 물-암석 반응을 거치면서 심부지열수를 형성하였으며, 지열수가 천부환경으로 상승하는 과정에서 동래지역 주변 천부지하수와 다양하게 혼합되면서 현재 동래온천수의 화학조성을 갖는 온천수를 형성하는 것으로 지열수의 진화 과정을 설명할 수 있다.

• Economic and Environmental Geology
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• v.41 no.1
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• pp.93-113
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• 2008

This study presents petrochemistry and $^{40}Ar/^{39}Ar$ absolute ages of subsurface volcanic rock cores from twenty(20) boreholes in the eastern lowland (altitude loom below) of Jeju Island, Handeong-Jongdal-Udo-Susan-Samdal-Hacheon areas, and discusses topography and volcanism in the area. The subsurface volcanic rock cores are mainly basalts in composition with minor tholeiitic andesites and basaltic trachyandesites. Sequences of intercalated tholeiitic, transitional and alkalic lavas suggest that tholeiitic and transitional to alkalic lavas must have erupted contemporaneously. Especially, occurrences of trachybasalts and basaltic trachyandesites at the bases in the area imply that the volcanism in the area was initiated with slightly differentiated alkaline magma activity. The $^{40}Ar/^{39}Ar$ absolute ages of the subsurface volcanic rock cores range from $526{\pm}23ka\;to\;38{\pm}4Ka$. The lava-forming Hawaiian volcanic activities of the eastern lowland can be divided into five sequences on the basis of sediment distribution, whole rock geochemistry and $^{40}Ar/^{39}Ar$ absolute ages of the subsurface volcanic rock cores; stage I-U$(550{\sim}400Ka)$, stage II$(400{\sim}300Ka)$ and stage III$(300{\sim}200Ka)$ during syn-depositional stage of Seoguipo Formation, and stage IV$(200{\sim}100Ka)$ and stage V(younger than 100Ka) during post-depositional stage. In the eastern lowland of Jeju Island, compositional variations and local occurrences of the subsurface volcanic rocks as well as existences of various intercalated sediment layers (including hydrovolcanogenic clasts) suggest that the volcanism must have continued for long time intermittently and that the land has been progressively glowed from inland to coast by volcanic activities and sedimentation. It reveals that the subsurface volcanic rocks in the eastern lowland of Jeju Island must have erupted during relatively younger than 200Ka of stages IV and V. The results of this study are partly in contrast with those of previous studies. This study stresses the need that previous reported volcanic activities in Jeju Island based on K-Ar ages of volcanic rocks should be carefully reviewed, and that stratigraphic correlation from boreholes should be conducted by quantitative criteria combined with petrography and petrochemstry as well as radiometric studies of volcanic rock cores.

• Journal of the Korean Geotechnical Society
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• v.28 no.5
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• pp.41-54
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• 2012

The weathering process of rocks leads to the reduction of geotechnical bearing capacity. The weathering of granite is frequently used to refer to the degradation of geotechnical property in the design and construction of infra-structure. In this study, the range of values of CIA (chemical index of alteration) and the change of mineral compositions by weathering have been analysed with igneous rock, which covers 45.5% in South Korean territory. Several weathering indices were studied for various rocks found in Korea and significant relationships between different indices were delineated via statistical analysis. The applicability of CIA was found to be the most significant among all weathering indicies. The composition of illite, the secondary weathering residual, generally increases for the felsic rock, and swelling clay material is not included. The weathering of felsic rock will follow a sequential process, starting from bed rock, illite, and chlorite to kaoline. The mafic rock will show weathering process, from bed rock, smectite, and chlorite to kaoline. The intermediate rocks such as andesite and tuff will show similar weathering procedure and the composition of kaoline, chlorite, and smectite tends to increase more than that of illite when the mafic rock is dominated. This means the increase of rock material which has high CEC (cation exchange capacity) during secondary weathering process. However, the characteristics of a specific rock cannot be completely analyzed using merely CIA, since it is exclusively based on chemical composition and corresponding alteration. The CIA can be used to quantify the weathering process in a limited range, and further considerations such as rock composition, strength characteristics will be required to configure the comprehensive weathering impact on any specific region.

• The Journal of the Petrological Society of Korea
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• v.17 no.3
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• pp.154-165
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• 2008

Rock bowls and pots used in restaurants are one of the popular usages of natural rocks in Korea. Most rock bowls and pots are made of Mg- and Ca-rich amphibolite composed of hornblende, actinolite, tremolite, diopside, plagioclase. Hornblende occurs as prismatic crystal habit, and belongs to Mg-hornblende to tschermakite. Actinolite and tremolite occur as acicular form (aspect ratio $0.10{\sim}0.13$), and ranges 0.65 to 0.90 in Mg/(Mg+Fe) ratio. These acicular actinolite and tremolite are non-asbestos minerals. However to use of rocks containing these minerals as tableware it is needed to regulatory guidelines for stability and utility based on petrological and mineralogical characteristics. Discrepancy of rock occurrence and mineral chemistry between commercial rock bowls and original rocks indicate that most rock bowls are made of uncertain amphibolite in original location. Consequently, there is a potential risk to use inappropriate amphibolites as tableware. Therefore, it is needed to systematically research on geology and biology, and manage commercial rock bowls and pots used in Korean restaurants.

• The Journal of the Petrological Society of Korea
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• v.15 no.3 s.45
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• pp.128-138
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• 2006

The west stone pagoda of Gameunssji temple site (National Treasure No. 112) has been damaged mainly by fracture, exfoliation and granular disintegration. In this study, the source area of the rocks using the west stone pagoda was examined in terms of petrological feature, magnetic susceptibility, and ${\gamma}-ray$ spectrometer. The stones include abundant crystal fragments of biotite, quartz and feldspars in the fine-grained matrix; they are petrographically discriminated to vitric-crystal tuff or crystal tuff. Measured magnetic susceptibility values are of from 10 to 20 $({\times}10^{-3}\;SI\;unit)$. From the ${\gamma}-ray$ spectrometer measurement K, eU, and eTh contents of the stones are about 3%, 0 to 8ppm, and 9 to 18 ppm, respectively. These features are used as indicators to presume the source area of the stones. Comparing the petrographical and chemical characteristics between the stones of the west stone pagoda and the country rocks near the Gameunsaji temple site, it is suggested that the most similar country rock to the stones could be dacitic volcanic rocks of the Beomgokri group in the Waeup basin. The Beomgokri group is lithostratigraphically divided into Waeupri tuff, Yongdongri tuff and Beomgokri volcanic rocks. Among the three rocks, the crystal tuff of the Beomgokri volcanic rocks seems likely to have been the source rock of the stones of the west stone pagoda.

• Economic and Environmental Geology
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• v.34 no.3
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• pp.255-269
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• 2001

The geochemical studies on groundwater in the borehole, which is straddled by multi-packer (MP) system, were carried out from a volcanic terrain in the Yeosu area. The pH of groundwater collected from selected sections in the MP-installed borehole is much higher (up to 9.6) than that of the borehole groundwater (7.0-7.9) collected using conventional pumping technique. Hydrochemistry shows that the groundwater has a typical chemical change with increasing sampling depth, suggesting that the groundwater is evolved through water-rock interaction along the fracture-controlled flow paths. The groundwater from the deeper part (138-175 m below the surface) in borehole KI is characterized by the Ca-C11 type with high Ca (up to 160 mg/L) and Cl (up to 293 mg/L) contents, probably reflecting seawater intrusion. The groundwater also has high sodium and sulfate contents compared to the waters from other boreholes. These observed groundwater chemistry is explained by the cation exchange, sulfide oxidation, and mixing process with seawater along the flow path.

• Journal of the Korean Society of Groundwater Environment
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• v.6 no.4
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• pp.159-170
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• 1999

The hydrogeochemical study on the $CO_2$-rich water in the Chojeong area was carried out. The $CO_2$-rich water of Ca-$HCO_3$type is characterized by low pH (5.0~5.8). high $CO_2$concentration ($Pco_2$＜$10^{0.31}$atm) and high TDS. The water chemistry indicates that the $CO_2$-rich water was probably evolved by the local suppy of deep seated $CO_2$gas resulting in the enhanced water/rock (granite) interaction under low pH conditions. High $NO_3$concentration indicates that the $CO_2$water was mixed and diluted with low $CO_2$groundwater in the vicinity of the area, in which the extensive groundwater abstraction occurred during the past years. The evoiution of the $CO_2$-rich water in the Chojeong area for the process of $CO_2$injection water/rock interaction and mixing processes was thermodynamically simulated by PHREEQC. Although the simulation was limited to water/plagioclase interaction, the results show the feasible explanation about the observed trend of pH and Ca and Na concentrations of the $CO_2$-rich water.

• Proceedings of the KSEEG Conference
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• 2003.04a
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• pp.89-92
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• 2003

폐금은광산 지역은 토양, 작물 및 수계와 같은 지구화학적 환경에서의 비소의 부화가 환경오염의 특성으로 나타난다. 오염지역에 대한 시료채취 지점 상부에 존재하는 암석과 토양의 풍화산물인 하상퇴적물을 대상으로 하는 연구는 이들의 해당 집수지역에 존재하는 원소들의 평균 함량을 반영하므로 환경오염평가 및 광역지구화학도의 작성에 적절한 대상 시료로 사용되어 왔다. (중략)

• Journal of the Korean earth science society
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• v.36 no.6
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• pp.543-552
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• 2015

This study examines the processes of rock weathering and tafoni formation targeting tafoni at Mt. Cheonsaeng, Gumi-si, Gyeongsangbuk-do. In the study area, a frequency of tafoni is high in conglomerate and conglomeratic sandstone among regional sedimentary rocks, which means that an initial stage of the formation begins a breakaway of gravel from bedrock and also exfoliation from rock surface. Geomorphologically tafoni have intensively been developed at the southfacing slope with exposed rocks, which means that its formation was favorably controlled by environmental conditions including strong influences of mechanical weathering in winter and chemical weathering in summer times. The results of measuring water content at a tafoni-bearing rock surface using GIS interpolation analysis indicate that moisture rate in/around tafoni is higher than the periphery. Thus, it is considered that moisture distribution at a rock surface plays a role in its formation. Analysis of percipitation and secondary minerals induced by chemical weathering is in progress.