• Title/Summary/Keyword: 화강암질암

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Geochemical Characteristics of Groundwater in Korea with Different Aquifer Geology and Temperature -Comparative Study with Granitic Groundwater (대수층 지질 및 온도에 따른 국내 지하수의 지구화학적 특징 -화강암질암내 지하수와의 비교연구)

  • 이종운;전효택;전용원
    • Journal of the Korean Society of Groundwater Environment
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    • v.4 no.4
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    • pp.212-222
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    • 1997

  • Geochemistry of metasedimentary groundwaters and spar waters has been studied in comparison with that of granitic groundwaters in Korea. Metasedimentary groundwaters show $Ca^{2+]$-${HCO_3}^-$ type at depth and low sodium concentrations compared with granitic groundwaters, which is due to the lack of plagioclase in their aquifer mineralogy and, therefore, the predominant reaction of calcite dissolution. According to factor analysis, metasedimentary groundwaters at 100~300 m depth are represented by 1) the dissolution of calcite and Mg-carbonates, 2) transformation of kaolinite to illite, and 3) the presence of sodium as not the product of plagioclase dissolution but a artificial pollutant. Discriminant function between the granitic and metasedimentary groundwaters shows a good discriminating ability with 81.8%, and groundwaters of volcanic aquifer, which has abundant plagioclase, are included in the granitic group by this function. Spa water samples show the result of active water-rock interaction due to high temperature.

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Anisotropy of Magnetic Susceptibility (AMS) of Granitic Rocks in the Eastern Region of the Yangsan Fault (양산단층 동편 화강암질암의 대자율 이방성(AMS))

  • Cho, Hyeong-Seong;Son, Moon;Kim, In-Soo
    • Economic and Environmental Geology
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    • v.40 no.2 s.183
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    • pp.171-189
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    • 2007

  • A study of anisotropy of magnetic susceptibility (AMS) was undertaken on Cretaceous granitic, volcanic and sedimentary rocks in the eastern region of the Yangsan fault, southeast Korea. A total of 542 independently oriented core samples collected form 77 sites were studied. The main magnetic mineral in granitic rocks is magnetite according to the magnitude of bulk susceptibility, high-temperature susceptibility variation and isothermal remanent magnetization. Both of magnetic lineation and foliation with NE-SW trends are revealed in the granitic rocks, while volcanic rocks show scattered directions and sedimentary rocks show only load foliation parallel to the bedding planes. The following evidences read to the conclusion that both magnetic fabrics in the granitic rocks have been obtained by a tectonic stress before full solidification of the magma: (i) A fully hardened granitic rocks would get hardly any fabric, (ii) Difference of the magnetic fabric trends with those of the geological structures in the granitic rocks themselves formed by brittle deformation after solidification (e.g. patterns of small-faults and joints), (iii) Kinking of biotite and undulose extinction in quartz observed under the polarizing microscope, (iv) Discordance of magnetic fabrics in the granitic rocks with those in the surrounding rocks. The NE-SW trend of the magnetic foliations suggests a NW-SE compressive stress of nearly contemporaneous with the emplacement of the granitic rocks. The compression should have caused a sinistral strike-slip movement of the Yangsan Fault considering the trend of the latter. As the age of the granitic rocks in the study area is reported to be around $60\sim70$ Ma, it is concluded that the Yangsan fault did the sinistral strike-slip movement during this time (L. Cretaceous Maastrichtian - Cenozoic Paleocene).

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Effects of Rock Weathering on the Degradation of Engineering Properties (암반풍화도에 따른 지질공학적 특성 저감효과)

  • Lee Chang-Sup;Cho Taechin
    • Tunnel and Underground Space
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    • v.15 no.6 s.59
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    • pp.411-424
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    • 2005

  • Weathering is defined as a process by which surface rock, once formed in the deep ground, is broken down and altered to keep the equilibrium with the ambient environment. In this study granitic rock samples of different weathering grades were collected in the field and the microscopic observation, X-ray diffraction analysis, electron microscopic observation, chemical analysis, and rock property tests were carried out. Formation of secondary minerals, especially clay minerals, by weathering was identified and the mechanism for the change of engineering properties such as rock strength degradation was analyzed. Tunnel model test, Failure behaviour, Shallow tunnel, Unsupproted tunnel length.

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