• The Journal of the Petrological Society of Korea
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• v.23 no.3
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• pp.209-220
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• 2014

SHRIMP zircon U-Pb age dating is carried out for the Yeongju and Andong granite batholiths intruding the Precambrian metamorphic complex and Paleozoic sedimentary formations within the NE Yeongnam Massif, Korea. Dating of zircons from a hornblende-biotite tonalite and an equigranular biotite granodiorite in the Yeongju granite has yielded ages of ca. 187 Ma and ca. 186 Ma, respectively. Also, dating of zircons from a biotite granodiorite and a very coarse-grained biotite granite in the Andong granite has yielded ages of ca. 182Ma and ca. 186Ma, respectively. These data indicate that the main intrusions of the Yeongju and Andong granite batholiths occur almost at the same age. The oldest age of ca. 194 Ma has been determined on zircons from a hornblende gabbro in the Andong granite, and the youngest age of 175 Ma is obtained from the Chunyang granite pluton, mainly consisting of fine-grained two-mica granite, of the Yeongju batholith. These results indicate that Jurassic Daebo magmatism in the Yeongju-Andong area, NE Yeongnam massif, started early at the Early Jurassic with an intrusion of mafic magma, and followed by an emplacement voluminous granite magma during the middle of the Early Jurassic, and was finalized with the emplacement of relatively small amount of much evolved granite magma at the end of Early Jurassic.

• The Journal of the Petrological Society of Korea
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• v.10 no.1
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• pp.36-55
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• 2001

Hornblende geobarometry has been applied to estimate the emplacement depth of the Jurassic Yeongiu, Andong, and Gimcheon granites in the Yeongnam Massif. Geobarometry was determined from the twenty two samples of the Yeongiu granite, ten samples of the Andong granite and twelve samples of the Gimcheon granite, using the composition of hornblende rims coexisting with the mineral assemblage required for pressure determination. Amphibole compositions in the three granites vary from edenite to ferropargasite with the increase of pressure. According to the equation of Schmidt(1992), the pressures of emplacement of the Yeongiu, Andong, and Gimcheon granites are 5.6 to 7.9 kb, 5.5 to 7.5 kb, and 4.1 kb to 5.3 kb, respectively. The emplacement depth in the Yeongiu granites increase systematically from about 6 kb in the northwest to about 7.5 kb in the southeast. Andong granite shows no systematic change of the pressure estimates. The Gimcheon granite shows almost consistent pressure distribution. The pressure difference of about 1.5 kb across the Yeongiu granite may be explained by a model combining late postemplacement upsurge of a deeper part of the pluton in the south with tilting of the batholith by Yecheon shear zone.

• The Journal of Engineering Geology
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• v.24 no.2
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• pp.179-189
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• 2014

We analyzed the three-dimensional distribution of micropores and internal structures in both fresh and weathered granite using micro-focus X-ray computed tomography (micro-CT). Results show that the pore radius in fresh granite is mostly in the range of $17-50{\mu}m$, the throat radius is in the range of $5-25{\mu}m$, and the coordination number (CN) of pores is less than 10. In contrast, the pore radius in weathered granite is mostly in the range of $20-80{\mu}m$, the throat radius is in the range of $8-30{\mu}m$, and the CN is less than 12. In general, a positive linear relationship exists between pore radius and CN. In addition, both the size and the density of pores increase with an increasing degree of rock weathering. The size of the throats that connect the pores also increases with an increasing degree of weathering, which induces fracture propagation in rocks. Micro-CT is a powerful and versatile approach for investigating the three-dimensional distributions of pores and fracture structures in rocks, and for quantitatively assessing the degree of pore connectivity.

• Journal of the Korean Society of Safety
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• v.15 no.2
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• pp.103-110
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• 2000

This paper deal with the stability evaluation and suggestion of progressive failure slope in biotite granite area of Andong. Based on geological site investigation and field test, stability analysis of slope was performed in conjunction with limit equilibrium methods and stereographic projection. Additionally, initial design and construction procedure was critically evaluated. Series of the slope stability analysis reveals the detection of local wedge and plane failure under the current slope condition. It is additionally appeared that a certain synthetic behavior of circle and plane failure exists on the right spot where the overall failure's going in progress. In order to construct more stable slope based on the suitability for the real state of the slope circumstances, this study issues a solution to eliminate the primary factors which cause the instability, by means of the grade of weathering and RMR classification of rock mass.

• The Journal of Engineering Geology
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• v.18 no.1
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• pp.103-115
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• 2008

The purposes of this study are to understand characteristic water-rock interaction mechanisms of groundwater in the granite area of Geochang and Hapcheon areas, Gyeongnam-do and to clarify the origin of fluoride. The possible water-rock interaction process and the source of fluorine were studied using water chemistry, rock chemistry, mineralogy by XRD, and microtexture analysis by backscattered electron image of the electron microprobe. No clear relationships between F and hardness was found. But the fluorine content increases to some extent with pH and well depth. Preferential alteration due to water-rock interaction took place along edges or cleavage, or margins of biotite. Because biotite is highly subject to alteration in granite aquifer, fluorine in groundwater is originated from the leaching of biotite.

• The Journal of the Petrological Society of Korea
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• v.25 no.1
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• pp.89-93
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• 2016

Yeongju and Andong granites, located in the northeastern Yeongnam massif, reveal very similar emplacement ages but distinct initial isotopic compositions of strontium. However, previous studies used different boundaries to distinguish these batholiths. In this study, we determined Sr isotopic compositions of apatite separated from the granites of the area to find out the proper boundary and propose the location of such boundary based upon analysis.

• Journal of the Mineralogical Society of Korea
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• v.19 no.1 s.47
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• pp.39-48
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• 2006

X-ray diffaction and chemical analysis were used for mineralogical characteristics of weathering grade of granite and biotite gneiss. Granite is composed mainly of quartz, albite, and minor K-feldspar and biotite gneiss is biotite, quartz, albite. Illite and kaolinite increased in granite, and vermiculite and halloysite in biotite gneiss as increasing weathering process. The percentages of $Al{2}O_{3}$ increase but that of CaO, $Na_{2}O,\;K_{2}O$ decrease as the weathering process. $Fe_{2}O_{3}$ different from granite and biotite gneiss.

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.299-304
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• 2015

Slope stability analysis of unsaturated soil slopes due to rainfall infiltration is an important issue in evaluating landslide analysis and stability assessment. The purpose of this study is to establish the critical depth considering weathered soil of parent rock and rainfall intensity at main scarp in national landslide. Based on the analytical results, it is found that as rainfall duration and Slope angle increased, the critical depth of gneiss-weathered soil increased from 3.00 m to 3.77 m, the critical depth of granite weathered-soil increased from 1.75 m to 2.40 m, and the critical depth of mudstone-weathered soil increased from 3.00 m to 4.15 m, respectively. The critical depth of granite-weathered soil with low cohesion and high internal friction angle is much lower than those of other soils. It is interestingly shown that a decrease in the safety factor is highly significant, much affected by the slope increase rather than the rainfall intensity.

• The Journal of Engineering Geology
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• v.17 no.1 s.50
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• pp.135-142
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• 2007

Although rock itself has high strength or low permeability, engineering properties of rock masses are significantly influenced by discontinuities such as cracks and joints. Considered with possibility of groundwater flow in massive rock mass of deep subsurface, the connectivity of micro cracks should be analyzed as a conduit of ground-water flow. The objective of this study is to estimate permeability characteristics of granite dependent on damage process with application of joint distribution analysis and modeling of permeability analysis in rock masses. In case of average permeability coefficients, the modeling results based on micro cracks data are well matched with the results from permeability tests. Based on the visualization result of three dimensional model, the average permeability coefficients through the discharge plane have a positive relationship with the number of microcrack induced by rock damage.

• Structural Engineering and Mechanics
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• v.4 no.6
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• pp.631-644
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• 1996

Geomaterials such as soil and rock are composed of discrete elements of microstructures with different grains and microcracks. The studies of these microstructures are of increasing interest in geophysics and geotechnical engineering relating to underground space development We first show experimental results undertaken for direct observation of microcrack initiation and propagation by using a newly developed experimental system, and next a homogenization method for treating a viscoelastic behavior of a polycrystalline rock.