• Title/Summary/Keyword: Characteristics of rock

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Element Dispersion and Wallrock Alteration Analysis Using Portable XRF and SWIR in the Samgwang Au Deposit (휴대용 XRF와 단파장적외선 분광분석을 이용한 삼광 금광상의 원소분산 및 모암변질 분석)

  • Kim, Junkyum;Shin, Dongbok;Yoo, Bongchul;Im, Heonkyung;Kim, Ilkyu
    • Economic and Environmental Geology
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    • v.52 no.4
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    • pp.259-274
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    • 2019
  • Using portable XRF and SWIR analyzer, the characteristics of element dispersion and wallrock alterations induced by interaction between hydrothermal fluids and host rocks were investigated and ore exploration factors were estimated for the orogenic-type Samgwang Au deposits. On this purpose, in-situ measurements were conducted for 804 spots at regular intervals with a total of 4,824 times for host rocks, consisting of schist and gneiss, and altered wallrocks contacted with quartz veins in the Bonhang adit of the deposit, and the results were compared with quantitative data obtained by XRF and ICP analysis. The regression coefficients are 0.88 for major elements and 0.56 for trace elements, excluding V. For polished rock slabs, better results came out for major elements, 0.97 and for trace elements, 0.65. In altered wallrocks contacted with quartz veins, elements such as Fe, Zn, and Rb exhibit positive correlations with As in concentrations, while V forms a negative trend. Contour maps demonstrate that As, Zn, Rb, Fe, Ti, Cr, and Ni are enriched together near quartz veins, showing similar elemental behaviors. In-situ analysis using portable SWIR analyzer represents that schist and gneiss contain mica, illite, chlorite, sericite, amphibole, and epidote, while illite, sericite, gypsum, and mica are present in the altered rocks contacted with quartz veins. In contour maps, chlorite occurs mostly in host rocks, while sericite is concentrated near quartz veins. These results are similar to those of previous studies for element dispersion and hydrothermal alteration, and support the possibility for application of in-situ analysis on the exploration of orogenic gold deposit.

Studies on the Mineralogical Characteristics of Apple Orchard Soils (사과원토양(園土壤)의 광물학적특성(鑛物學的特性)에 관(關)한 연구(硏究))

  • Lee, Mahn Jung
    • Korean Journal of Soil Science and Fertilizer
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    • v.6 no.3
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    • pp.141-152
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    • 1973
  • The mineralogical studies of the eleven sub-soil samples derived from granite, granodiorite, diorite and arkose sandstone, taken from apple orchards in the province of Kyungsangbukdo, Korea are made to investigate the relationships between the mineral weathering, soil forming processes and mineralogical composition. The fine sand fraction (less than 0.2mm) and the clay fraction (less than 2 micron) are dispersed with the shaker after hydrogen peroxide treatment for the removal of organic matter, and separated from each suspension by gravity sedimentation. The fine sand are observed by mineral microscope and the clay are observed by X-ray diffraction patterns, differential thermal analysis curves and infrared spectrum. The outline of the results are as follows. 1. The primary minerals ; Quartz, changed-feldspar, plagioclase, alkali-feldspar are dominant in almost all samples, and some samples contain an appreciable amount of hornblende, biotite, muscovite and plant opal. There are also those samples which contain very small quantity of pyroxene group, tourmaline, epidote, cyanite, magnetite, volcanic glass and zircon. They are mainly derived from weathering products of granite, granodiorite, diorite, arkose or its mixtures. 2. All samples contain expanding or nonexpanding $14{\AA}$ minerals, illite and kaolin minerals, and some samples contain chlorite, cristobalite, gibbsite, and those primary minerals as quartz and feldspar, but the quantities vary according to the parent matrials. 3. Non-expanding $14{\AA}$ minerals may be dioctahadral vermiculite which sandwiches gibbsite layer or chlorite in between layer lattices. 4. As for clay minerals, montmorillonite was principal component in the samples derived from weathering products of arkose sandstone and tertiary. Minerals which are derived from weathering products of arkose have kaolin minerals and vermiculite as their principal component, and minerals derived from weathering products of acidic rock group are generally classified into two groups, the kaolin mineral group, and the kaolin minerals and vermiculite group.

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Petrography and Geochemistry of the Ultramafic Rocks from the Hongseong and Kwangcheon areas, Chungcheongnam-Do. (충남 홍성 및 광천 지역 초염기성암의 암석 및 지구화학)

  • Song Suckhwan;Choi Seon Gyu;Oh Chang Hwan;Seo Ji Eun;Choi Seongho
    • Economic and Environmental Geology
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    • v.37 no.5
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    • pp.477-497
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    • 2004
  • In the Hongseong and Kwangcheon areas, two ultramafic rocks are exposed as isolated bodies in the Precambrian Kyeonggi gneiss complex. The ultramafic rocks extend for several hundred meters to NNE direction and are contact with adjacent metasediments by steeply dipping faults. The rocks are dunite or harzburgite showing dominantly equigranular-mosaic and protogranular textures with a minor amount of porphyroclastic textures. They contain varying amounts of fosteritic olivine (F$o_{0.91-0.93}$), magnesian pyroxene (E$n_{0.89-0.93}$) and tremolitic to magnesian hornblende with minor amounts of spinel, serpentine, chlorite, magnetite, phlogopite and talc. The rocks are in contrast with adjacent gneiss complex or metabasite (amphibole, biotite, plagioclase, alkali-feldspar and quartz). Geochemically, these ultramafic rocks are characterized by high magnesium number (M$g_#$> 0.88) and transitional element (mainly, Ni>1716 ppm, Cr>1789 ppm), low alkali element (e.g. $K_2$O<0.09 wt.%, Na$_2$O<0.19 wt.%) and depletion of incompatible elements. The calculated correlation coefficients showed good positive correlations among the ferrous (e.g. Sc, V, Zn) elements, incompatible elements (e.g. REE), and among SiO$_2$ or $Al_2$O$_3$ with ferrous elements, whereas negative correlations are appeared between Ni and major elements. These results involve increasing of the ferrous- and $Al_2$O$_3$-bearing minerals(e.g. amphibole and mica) with decreasing of Mg-bearing minerals (e.g. olivine) depending on the degree of alteration. Calculated geothermometries and mineral assemblages suggest that the ultramafic rocks have been metamorphosed through the condition from the greenschist to amphibolite facies. Compared with ultramafic rocks elsewhere, it is thought that those of the Hongseong and Kwangcheon areas are derivatives of the depleted sources since they are depleted in incompatible elements including REE abundances. Moreover overall characteristics of the ultramafic rocks are similar to the those of orogenic related Alpine type ultramafic rocks, especially, shallow mantle slab varieties.

Spatial Composition and Landscape Characteristics of Shimwon-Pavilion Garden in Chilgok - Focusing on 'Shimwon-pavilion Poem of 25 Sceneries' and 「Shimwon-pavilion Soosukgi(心遠亭水石記)」 - (칠곡 심원정원림의 공간구성과 경관특성 - '심원정 25영(心遠亭 二十五詠)'과 「심원정수석기(心遠亭水石記)」를 중심으로 -)

  • Kim, Hwa-Ok;Park, Yool-Jin;Rho, Jae-Hyun;Shin, Sang-Seop;Cho, Ho-Hyeon
    • Journal of the Korean Institute of Traditional Landscape Architecture
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    • v.34 no.2
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    • pp.27-34
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    • 2016
  • The results of investigation on the spatial composition and landscape characteristics of Shimwon-pavilion garden built and enjoyed by Jo Byeong-sun in 1937 during the period of Japanese colonialism based on 'Shimwon-pavilion Soosukgii(水石記)' and 'Shimwon-pavilion Poem of 25 Sceneries(二十五詠)' contained in 'Anthology of Giheon(寄軒)' are as follows. 1. Shimwon-pavilion garden is assumed as Byeol-Seo garden based on the planning background and contents of Gimun and the observations on spot. By its location, it is classified as 'Planted forest' with a pine forest in the north and 'Byeol-Seo of mooring type' with Guyacheon flowing in the garden. It is about 400m away from the main house in the straight-line distance. 2. The meaning and attributes of reclusiveness are well represented in the 'screening structures' all around Shimwon-pavilion garden with Hakrimsan, a Gasan(假山) in the north, vines on Chwibyeong(翠屛) in the east and west, Eunbyeong(隱屛) of stone walls along with Guyacheon in the south, which shows the spirit of Giheon who adored the Taoistic life. 3. Shimwon-pavilion garden, located in the Songrimsa, a temple of thousand years, is a place of consilience where Buddhism was accepted, Taoistic life was pursued with Tao Yuan-ming's philosophy regarding rural areas and romantic sensibilities of Li Po, called poem master(詩仙), the confucian values of Zhu Xi were realized. Giheon intended to build and enjoy this place as a microcosm and shelther where he unfolded his own view of learning and cultivated his mind. 4. 25 sceneries on Shimwon-pavilion consist of 5 sceneries in the space of pavilion(architecture) and 20 sceneries in the outer garden. First, 5 sceneries consist of ancillary rooms for various uses, including Jeongunru, Amsushil, Wiryujae, Iyeoldang, and Jeong-Gak Shimwon-pavilion embracing them, which shows that Shimwon-pavilion is a place to foster younger students. And 20 scenary is divided into 9 sceneries on the natural spaces and 11 artificially created facilities. 9 sceneries are engraved on the rocks as described in 'Seokgyeonggi'. 5. 4 sceneries of the indoor scenery lexemes(亭閣 心遠亭 怡悅堂 停雲樓 闇修室) were intended to be recognized by the framed pictures, 5 places among the scenery lexemes in garden(龜巖 醒石 隱屛 兩忘臺 東槃) by letters carved on the rocks, and 8 places(君子沼 杞泉 天光雲影橋 芳園 槐岡 柳堤 石扉 東翠屛) by sign stones, but signs of 8 sceneries are not currently identified because they have been be swept away and demolished. 6. A variety of plant landscapes with various meanings and water landscape with various types are contained in 25 sceneries - Sophora symbolizing a tree for scholar in Gehgang(槐岡), Willow symbolizing Tao Yuanming and continued vitality in Yooje(柳堤), Boxthorn symbolizing family togetherness in spring(杞泉), vines and herbal plants and waterfalls(隱瀑), shallow pond(君子沼), pond(湯池), water hole(杞泉), water flowing in the middle of rock(盤陀石), water flowing between the rocks(水口巖). 7. While Shimwon-pavilion garden is a garden near the water, the active involvements with 11 sceneries directly built is distinguished. The other pavilion gardens are faithful in engraving the names by setting the scenery lexemes of the nature-oriented Gyeong(景) and Gok(曲) near and far, but Shimwon-pavilion garden is a garden for active learning(修景) with the spaces built to match with the beautiful nature and to show the depths of space off.

Studies on Forest Soils in Korea (I) (한국(韓國)의 삼림토양(森林土壤)에 관(關)한 연구(硏究)(I))

  • Lee, Soo Wook
    • Journal of Korean Society of Forest Science
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    • v.47 no.1
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    • pp.52-61
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    • 1980
  • This study is carried out to learn the properties of forest soils in Korea and propose the reasonable management methods of forest land. Among 178 soil series surveyed until now in Korea forest soils include 64 series broken down according to the weathered products into 5 categories such as residual materials on mountain and hill, residual materials on rolling and hill, colluvial materials on local valley and fans, alluvial materials and volcanic ash soils. What discussed in this paper are classification system, parent rocks, texture class and drainage conditions of Korean forest soils. The characteristics of Korean forest soil properties classified in U.S.D.A. soil classification system are as follows: 1. Residual soils on mountain and hill (29 soil series) are almost Lithosols without any distinct soil profile development. They have loamy skeletal (11 series), coarse loamy (5 series), fine loamy (3 series), and fine clayey soils (3 series). Their drainage conditions are somewhat excessively drained in 16 series and well drained in 7 series. 2. Residual soils on rolling and hill (19 series) are Red-Yellow Podzolic soils with well developed soil profiles. They have coarse and fine loamy texture in 12 series and fine clayey texture in 5 series mostly with well drained condition. 3. Colluvial soils on local valley and fans (13 series) include mostly Regosols and some Red-Yellow Podzolic Soils and Acid Brown Forest Soils. They have loamy skeletal (4 series), coarse loamy (3 series), fine loamy (3 series), and fine clayey soils (2 series) with well drained condition. 4. Soil textures of weathered products of parent rocks are as follows: 1) Parent rocks producing coarse texture soils are rhyolite, granite gneiss, schist, shale, sandstone, siltstone, and conglomerate. 2) Parent rocks producing fine and heavy texture soils are limestone, basalt, gabbro, and andesite porphyry. 3) Granite is a parent rock producing various textured soils.

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Geochemical Characterization of Rock-Water Interaction in Groundwater at the KURT Site (물 암석 반응을 고려한 KURT 지하수의 지구화학적 특성)

  • Ryu, Ji-Hun;Kwon, Jang-Soon;Kim, Geon-Young;Koh, Yong-Kwon
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.10 no.3
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    • pp.189-197
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    • 2012
  • Geochemical composition of fracture filling minerals and groundwater was investigated to characterize geochemical characteristics of groundwater system at the KURT site. Minerals such as calcite, illite, laumontite, chlorite, epidote, montmorillonite, and kaolinite, as well as I/S mixed layer minerals were detected in the minerals extracted from the fracture surfaces of the core samples. The groundwater from the DB-1, YS-1 and YS-4 boreholes showed alkaline conditions with pH of higher than 8. The electrical conductivity (EC) values of the groundwater samples were around $200{\mu}S/cm$, except for the YS-1 borehole. Dissolved oxygen was almost zero in the DB-1 borehole indicating highly reduced conditions. The Cl- concentration was estimated around 5 mg/L and showed homogeneous distribution along depths at the KURT site. It might indicate the mixing between shallow groundwater and deep groundwater. The shallow groundwater from boreholes showed $Ca-HCO_3$ type, whereas deep groundwater below 300 m from the surface indicated $Na-HCO_3$ type. The isotopic values observed in the groundwater ranged from -10.4 to -8.2‰ for ${\delta}^{18}O$ and from -71.3 to -55.0‰for ${\delta}D$. In addition, the isotope-depleted water contained higher fluoride concentration. The oxygen and hydrogen isotopic values of deep groundwater were more depleted compared to the shallow groundwater. The results from age dating analysis using $^{14}C$ indicated relatively younger (2000~6000yr old) groundwater compared to other european granitic groundwaters such as Stripa (Sweden).

Environmental Interpretation on soil mass movement spot and disaster dangerous site for precautionary measures -in Peong Chang Area- (산사태발생지(山沙汰發生地)와 피해위험지(被害危險地)의 환경학적(環境學的) 해석(解析)과 예방대책(豫防對策) -평창지구(平昌地區)를 중심(中心)으로-)

  • Ma, Sang Kyu
    • Journal of Korean Society of Forest Science
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    • v.45 no.1
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    • pp.11-25
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    • 1979
  • There was much mass movement at many different mountain side of Peong Chang area in Kwangwon province by the influence of heavy rainfall through August/4 5, 1979. This study have done with the fact observed through the field survey and the information of the former researchers. The results are as follows; 1. Heavy rainfall area with more than 200mm per day and more than 60mm per hour as maximum rainfall during past 6 years, are distributed in the western side of the connecting line through Hoeng Seong, Weonju, Yeongdong, Muju, Namweon and Suncheon, and of the southern sea side of KeongsangNam-do. The heavy rain fan reason in the above area seems to be influenced by the mouktam range and moving direction of depression. 2. Peak point of heavy rainfall distribution always happen during the night time and seems to cause directly mass movement and serious damage. 3. Soil mass movement in Peongchang break out from the course sandy loam soil of granite group and the clay soil of lime stone and shale. Earth have moved along the surface of both bedrock or also the hardpan in case of the lime stone area. 4. Infiltration seems to be rapid on the both bedrock soil, the former is by the soil texture and the latter is by the crumb structure, high humus content and dense root system in surface soil. 5. Topographic pattern of mass movement spot is mostly the concave slope at the valley head or at the upper part of middle slope which run-off can easily come together from the surrounding slope. Soil profile of mass movement spot has wet soil in the lime stone area and loose or deep soil in the granite area. 6. Dominant slope degree of the soil mass movement site has steep slope, mostly, more than 25 degree and slope position that start mass movement is mostly in the range of the middle slope line to ridge line. 7. Vegetation status of soil mass movement area are mostly fire field agriculture area, it's abandoned grass land, young plantation made on the fire field poor forest of the erosion control site and non forest land composed mainly grass and shrubs. Very rare earth sliding can be found in the big tree stands but mostly from the thin soil site on the un-weatherd bed rock. 8. Dangerous condition of soil mass movement and land sliding seems to be estimated by the several environmental factors, namely, vegetation cover, slope degree, slope shape and position, bed rock and soil profile characteristics etc. 9. House break down are mostly happen on the following site, namely, colluvial cone and fan, talus, foot area of concave slope and small terrace or colluvial soil between valley and at the small river side Dangerous house from mass movement could be interpreted by the aerial photo with reference of the surrounding site condition of house and village in the mountain area 10. As a counter plan for the prevention of mass movement damage the technics of it's risk diagnosis and the field survey should be done, and the mass movement control of prevention should be started with the goverment support as soon as possible. The precautionary measures of house and village protection from mass movement damage should be made and executed and considered the protecting forest making around the house and village. 11. Dangerous or safety of house and village from mass movement and flood damage will be indentified and informed to the village people of mountain area through the forest extension work. 12. Clear cutting activity on the steep granite site, fire field making on the steep slope, house or village construction on the dangerous site and fuel collection in the eroded forest or the steep forest land should be surely prohibited When making the management plan the mass movement, soil erosion and flood problem will be concidered and also included the prevention method of disaster.

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A Study on the Consideration of the Locations of Gyeongju Oksan Gugok and Landscape Interpretation - Focusing on the Arbor of Lee, Jung-Eom's "Oksan Gugok" - (경주 옥산구곡(玉山九曲)의 위치비정과 경관해석 연구 - 이정엄의 「옥산구곡가」를 중심으로 -)

  • Peng, Hong-Xu;Kang, Tai-Ho
    • Journal of the Korean Institute of Traditional Landscape Architecture
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    • v.36 no.3
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    • pp.26-36
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    • 2018
  • This study aims to examine the characteristics of landscape through the analysis of location and the landscape of Gugok while also conducting the empirical study through the literature review, field study, and digital analysis of the Okgung Gugok. Oksan Gugok is a set of songs set in Ogsan Creek(玉山川)or Jagyese Creek(紫溪川, 紫玉山), which flows in front of the Oksan Memorial Hall(李彦迪), which is dedicated to the Lee Eong-jeok (李彦迪). We first ascertained the location and configuration of Oksan Gogok. Second, we confirmed the accurate location of Oksan Gogok by utilizing the digital topographic map of Oksan Gogok which was submitted by Google Earth Pro and Geographic Information Center as well as the length of the longitude of the gravel measured by the Trimble Juno SB GPS. Through the study of the literature and the field investigation, The results of the study are as follows. First, Yi Eonjeok was not a direct composer of Oksan Gugok, nor did he produce "Oksan Gugokha(Music)". Lee Ia-sung(李野淳), the ninth Youngest Son of Tweo-Kye, Hwang Lee, visited the "Oksan Gugokha" in the spring of 1823(Sunjo 23), which was the 270th years after the reign of Yi Eonjeok. At this time, receiving the proposal of Ian Sung, Lee Jung-eom(李鼎儼), Lee Jung-gi(李鼎基), and Lee Jung-byeong(李鼎秉), the descendants of Ian Sung set up a song and created Oksan Gugok Music. And the Essay of Oksan Travel Companions writted by Lee Jung-gi turns out being a crucial data to describe the situation when setting up the Ok-San Gugok. Second, In the majority of cases, Gogok Forest is a forest managed by a Confucian Scholar, not run by ordinary people. The creation of "Oksan Bugok Music" can be regarded as an expression of pride that the descendants of Yi Eonjeok and Lee Hwang, and next generation of several Confucian scholars had inherited traditional Neo-Confucian. Third, Lee Jung-eom's "Oksan Donghaengki" contains a detailed description of the "Oksan Gugokha" process and the process of creating a song. Fourth, We examined the location of one to nine Oksan songs again. In particular, eight songs and nine songs were located at irregular intervals, and eight songs were identified as $36^{\circ}01^{\prime}08.60^{{\prime}{\prime}}N$, $129^{\circ}09^{\prime}31.20^{{\prime}{\prime}}E$. Referring to the ancient kingdom of Taojam, the nine-stringed Sainam was unbiased as a lower rock where the two valleys of the East West congregate. The location was estimated at $36^{\circ}01^{\prime}19.79^{{\prime}{\prime}}N$, $129^{\circ}09^{\prime}30.26^{{\prime}{\prime}}E$. Fifth, The landscape elements and landscapes presented in Lee Jung-eom's "Oksan Gugokha" were divided into form, semantic and climatic elements. As a result, Lee Jung-eom's Cho Young-gwan was able to see the ideal of mountain water and the feeling of being idle in nature as well as the sense of freedom. Sixth, After examining the appearance of the elements and the frequency of the appearance of the landscape, 'water' and 'mountain' were the absolute factors that emphasized the original curved environment at the mouth of Lee Jung-eom. Therefore, there was gugokga can gauge the fresh ideas(神仙思想)and retreat ever(隱居思想). This inherent harmony between the landscape as well as through the mulah any ideas that one with nature and meditation, Confucian tube.

Conservation Status, Construction Type and Stability Considerations for Fortress Wall in Hongjuupseong (Town Wall) of Hongseong, Korea (홍성 홍주읍성 성벽의 보존상태 및 축성유형과 안정성 고찰)

  • Park, Junhyoung;Lee, Chanhee
    • Korean Journal of Heritage: History & Science
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    • v.51 no.3
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    • pp.4-31
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    • 2018
  • It is difficult to ascertain exactly when the Hongjuupseong (Town Wall) was first constructed, due to it had undergone several times of repair and maintenance works since it was piled up newly in 1415, when the first year of the reign of King Munjong (the 5th King of the Joseon Dynasty). Parts of its walls were demolished during the Japanese occupation, leaving the wall as it is today. Hongseong region is also susceptible to historical earthquakes for geological reasons. There have been records of earthquakes, such as the ones in 1978 and 1979 having magnitudes of 5.0 and 4.0, respectively, which left part of the walls collapsed. Again, in 2010, heavy rainfall destroyed another part of the wall. The fortress walls of the Hongjuupseong comprise various rocks, types of facing, building methods, and filling materials, according to sections. Moreover, the remaining wall parts were reused in repair works, and characteristics of each period are reflected vertically in the wall. Therefore, based on the vertical distribution of the walls, the Hongjuupseong was divided into type I, type II, and type III, according to building types. The walls consist mainly of coarse-grained granites, but, clearly different types of rocks were used for varying types of walls. The bottom of the wall shows a mixed variety of rocks and natural and split stones, whereas the center is made up mostly of coarse-grained granites. For repairs, pink feldspar granites was used, but it was different from the rock variety utilized for Suguji and Joyangmun Gate. Deterioration types to the wall can be categorized into bulging, protrusion of stones, missing stones at the basement, separation of framework, fissure and fragmentation, basement instability, and structural deformation. Manually and light-wave measurements were used to check the amount and direction of behavior of the fortress walls. A manual measurement revealed the sections that were undergoing structural deformation. Compared with the result of the light-wave measurement, the two monitoring methods proved correlational. As a result, the two measuring methods can be used complementarily for the long-term conservation and management of the wall. Additionally, the measurement system must be maintained, managed, and improved for the stability of the Hongjuupseong. The measurement of Nammunji indicated continuing changes in behavior due to collapse and rainfall. It can be greatly presumed that accumulated changes over the long period reached the threshold due to concentrated rainfall and subsequent behavioral irregularities, leading to the walls' collapse. Based on the findings, suggestions of the six grades of management from 0 to 5 have been made, to manage the Hongjuupseong more effectively. The applied suggested grade system of 501.9 m (61.10%) was assessed to grade 1, 29.5 m (3.77%) to grade 2, 10.4 m (1.33%) to grade 3, 241.2 m (30.80%) and grade 4. The sections with grade 4 concentrated around the west of Honghwamun Gate and the east of the battlement, which must be monitored regularly in preparation for a potential emergency. The six-staged management grade system is cyclical, where after performing repair and maintenance works through a comprehensive stability review, the section returned to grade 0. It is necessary to monitor thoroughly and evaluate grades on a regular basis.

Characteristics and Distribution Pattern of Carbonate Rock Resources in Kangwon Area: The Gabsan Formation around the Mt. Gachang Area, Chungbuk, Korea (강원 지역에 분포하는 석회석 자원의 특성과 부존환경: 충북 가창산 지역의 갑산층을 중심으로)

  • Park, Soo-In;Lee, Hee-Kwon;Lee, Sang-Hun
    • Journal of the Korean earth science society
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    • v.21 no.4
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    • pp.437-448
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    • 2000
  • The Middle Carboniferous Gabsan Formation is distributed in the Cheongrim area of southern Yeongwol and the Mt. Gachang area of Chungbuk Province. This study was carried out to investigate the lithological characters and geochemical composition of the limestones and to find out controlling structures of the limestones of the formation. The limestones of the Gabsan Formation are characterized by the light gray to light brown in color and fine and dense textures. The limestone grains are composed of crinoid fragments, small foraminfers, fusulinids, gastropods, ostracods, etc. Due to the recrystallization, some limestones consist of fine crystalline calcites. The chemical analysis of limestones of the formation was conducted to find out the contents of CaO, MgO, Al$_2$O$_3$, Fe$_2$O$_3$ and SiO$_2$. The content of CaO ranges from 49.78-60.63% and the content of MgO ranges from 0.74 to 4.63% The contents of Al$_2$O$_3$ and Fe$_2$O$_3$ are 0.02-0.55% and 0.02${\sim}$0.84% , respectively. The content of SiO$_2$ varies from 1.55 to 4.80%, but some samples contain more than 6.0%. The limestones of the formation can be grouped into two according to the CaO content: One is a group of which CaO content ranges from 49.78 to 56.26% and the other is a group of which CaO content varies from 59.36 to 60.38%. In the first group, the contents of Al$_2$O$_3$, Fe$_2$O$_3$ and SiO$_2$ range very irregularly according to the CaO content. In the second group, the values of MgO, Al$_2$O$_3$, Fe$_2$O$_3$ and SiO$_2$ are nearly same. Detailed structural analysis of mesoscopic structures and microstructures indicates the five phase of deformation in the study area. The first phase of deformation(D$_1$) is characterized by regional scale isoclinal folds, and bedding parallel S$_1$ axial plane foliation which is locally developed in the mudstone and sandstone. Based on the observations of microstructures, S$_1$ foliations appear to be developed by grain preferred orientation accompanying pressure-solution. During second phase of deformation, outcrop scale E-W trending folds with associated foliations and lineations are developed. Microstructural observations indicate that crenulation foliations were formed by pressure-solution, grain boundary sliding and grain rotation. NNW and SSE trending outcrop scale folds, axial plane foliations, crenulation foliations, crenulation lineations, intersection lineations are developed during the third phase of deformation. On the microscale F$_3$ fold, axial plane foliations which are formed by pressure solution are well developed. Fourth phase of deformation is characterized by map scale NNW trending folds. The pre-existing planar and linear structures are reoriented by F$_4$ folds. Fifth phase of deformation developed joints and faults. The distribution pattern of the limestones is mostly controlled by F$_1$ and F$_4$ folds.

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