• Tunnel and Underground Space
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• v.19 no.6
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• pp.473-478
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• 2009

The accuracy of point load apparatus is depend on point to point coaxial fitting. Also, the estimation of applied point load using the pressure gauge frequently lead to erroneous results. An improved point load apparatus has been developed in this study by mounting linear bearing on polished support rod, and eccentric error of point to point axis has been sustained less than 0.1 mm even under series of extreme work load conditions. Two digital displacement gauges are attached to measure the distance from point to point with sample specimen. A load cell mounted at the end of upper conical platen measure the applied net load on sample instead of preassure gauge. Total of 107 point load tests has been achieved to assure the quality and performance of developed apparatus. This exercise turned out to be successful.

• Economic and Environmental Geology
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• v.9 no.2
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• pp.85-106
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• 1976

The Bulgugsa acidic igneous rocks of the late Cretaceous age are largely distributed in Busan area, which is located in the southeastern corner of the Korean Peninsula. These igneous rocks comprise in ascending order, felsite, dacitic-rhyolitic welded tuffs, granite porphyry and granitic rocks. The former three members represent the early phase of volcanic activities, so that they are named as Jangsan volcanic rocks. The granitic rocks consist of granodiorite, hornblende biotite granite, Kumjongsan granite, fine grained granite, and Daebyen granite, represent the late phase of igneous activities. The Kumjongsan grainte, the largest pluton of the granitic mass, emplaced between two great vertical faults trending NNE. New chemical analyses of 33 rock samples of these acidic rocks are given. Their chemical compositions are generally similar to those of the late Mesozoic acidic igneous rocks of the northern Ashio mountains, and C-Zone granite group of the Ogcheon geosyncline, with their characteristic variation trends of several oxides. Their chemical compositions also show that $Al_2O_3$ is high value, and differentiation index is high, too. Systematically developing joints in Kumjungsan granite are divisible into two types at least. One is the NS-N $20^{\circ}E$ trendirig, $85^{\circ}{\sim}90^{\circ}$ dipping type of joint system which coincides with the trends of distribution of the granite mass and the dikes intruding this granite. Joints of this type may be cooling joints generated as tension cracks. The other is the $N60^{\circ}{\sim}70^{\circ}W$ or $N40^{\circ}{\sim}60^{\circ}E$ trending type of joint systems. It is considered that. joints belonging to this type may be shear joint occurring under the state of south-north tectonic couple acting at the east and west side of the granite mass. Igneous activities of the the Bulgugsa acidic igneous rocks in Busan area was taken place as. follows, formation of the magma reservoir, eruption and intrusion of felsite, consolidation of vents. and increasing vapor pressure in magma reservoir, eruption of pyroclastic flows, caldera collapse, intrusion of granite porphyry, and intrusion of granitic rocks at the latest stage.

• Economic and Environmental Geology
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• v.14 no.4
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• pp.167-182
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• 1981

Skarn silicates from the Shinyemi lead-zinc ore deposits can be distinguished as following three mineral assemblages: 1) garnet-pyroxene-phlogopite-wollastonite assemblages, 2) garnet-pyroxene assemblages, 3) garnet-epidote assemblages The assemblages are considered to be related with occurrences and kindes of ore minerals, and stage of mineralization in the deposits. Microprobe analyses of some garnets from the deposits show strong chemical zoning which is due to the changing equilibrium condition during growth of garnet crystal. Depositional condition of ore deposits and place of the ore-related igneous rock are discussed in the light of chemical composition of garnet and occurence of skarns in the Shinyemi.

• Economic and Environmental Geology
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• v.14 no.4
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• pp.183-191
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• 1981

Major and trace elements analyses are presented for 13 amphibolites by wet chemical and emission spectroscopic methods. These chemical data were compared with limestone and quartzite closely associated with the amphibolites. The chemical similarity of the amphibolites studied to the basic igneous rock and low oxidation ratios (<30) are indicative of the igneous intrusive, especially middle stage differentiates. Petrographic and stratigraphic study of the rocks suggest the more igneous features rather than those of sedimentary progenitors.

• The Journal of Engineering Geology
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• v.16 no.1 s.47
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• pp.23-30
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• 2006

This study was carried out to understand the relationship between orientation of tecto-lineaments obtained from aero-photograph and orientation of discontinuities measured at field for the rock types of igneous, sedimentary and metamorphic rocks in Andong area. Total 847 tecto-lineaments were extracted from the aero-photographs and total 1,940 discontinuities including joints, foliations and faults were measured during geologic survey. By using the software DIPS, preferred trends of tecto-lineaments were deduced as N30E-N40E for igneous rocks and N50E-N60E for both sedimentary and metamorphic rocks, while the trends of discontinuities were found as N40E-N50E for igneous rocks, N50E-N80E for sedimentary rocks and N50E-N60E for meta morphic rocks. Even though both orientations for a given rock type showed relatively good agreement in its trend, some discrepancy is also appeared. Since construction safety of geo-structures such as tunnel and slope, etc., is significantly affected by the orientation of discontinuities in rock masses, it is highly recommended to perform a detailed geologic survey as well as an aero-photograph interpretation at a design stage.

• The Journal of Engineering Geology
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• v.2 no.2
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• pp.113-130
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• 1992

Groundwater in crystalline basement is controlled primarily by tectonic fractures. It is evident that the delineation of the heavily faulted area and/or fractures deeply developped should be considerable value in deep-seated low enthalphy geothermal water. Electrical and electromagnetic methods have effectively been employed to map hydraulic faults and shear zones for groundwater exploration. In this study VLi; dipoledipole resistivity, controlled source audio~frequency magneto-telluric(CSAMT) and magnetic methods were applied in the Bomun resort area, adjacent to Kyongju city, southeastern part of Korea. The integrated geophysical tools employed in this experiment can be manifested themselves as: 1. Magnetic high for granite intrusions which is more favorable for geothermal gradient increase in depth. 2. VLF cross-over trends for mapping linear shallow conductive fractures and shear zones. 3. Dipole-dipole resistivity distributions for the deep-seated(less than 500m in depth) fractures and shear zones. The dipole-dipole resistivity field data were inverted to the true resistivity distribution with two-dimensional automatic inversion program based on the finite-difference method. 4. CSAMT provides an efficient way of delineating fractures and fault zones if the depth is greater than about 500m.

• Economic and Environmental Geology
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• v.31 no.6
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• pp.473-483
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• 1998

The igneous rocks in the Goseong area are composed of the volcanic rocks (andesitic lapilli tuff and rhyodacite), Bulgugsa granites (Hornblende-biotite granite and two pyroxene granite) and intrusive andesites. In the variation diagrams of the trace and rare earth element contents and elemental ratios as well as the REE patterns, the three igneous rock types show different variational trends and patterns. The geochemical features represent that the igneous rocks in the area were formed from three different magmatic pulses. Two independently carried out Rb-Sr isotope experiments for the Goseong granites show that the whole rock ages and Sr initial ratios of the granites are $66.4{\pm}6.2Ma$, $0.70517{\pm}22(2{\sigma})$ and $71.3{\pm}6.8Ma$, $0.70506{\pm}18(2{\sigma})$, respectively. These results suggest that the granites magma originated from the lower crustal materials of igneous origin intruded into the area during the late Cretaceous period. Masan hornblende-biotite granite emplaced at the vicinity of the Goseong area is very similar to the Goseong granite in its mineral compositions, major, trace and rare earth element contents and patterns. The intruding age (100 Ma) of the Masan granite is order than that of the Geseong granite, however. The similarity of the geochemical natures but the contrast of the intruding ages between the Masan and Goseong granites possibly indicate that the magma generation from the same source materials occurred at a temporal interval of ca. 30 Ma.

• Journal of the Korean earth science society
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• v.34 no.4
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• pp.329-335
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• 2013

Based on mineral assemblages, field occurrences, the volcanic rocks distributed in the Geumdang Island area are divided into three types: rhyolite, porphyritic rhyolite and intermediated dyke rock. In a diagram of [TAS (total alkali-silica)], rhyolites and porphyritic rhyolites belong to the rhyolite-dacite field and rhyolite field, respectively. As to the times when the rhyolite and porphyritic rhyolite rocks were formed a whole rock K-Ar age was obtained. These absolute age determinations have revealed that the former (rhyolite) has an age of 76-78 Ma and belongs to the Late Cretaceous (Campanian) and the latter (porphyritic rhyolite) is 71-72 Ma in age and thus belongs to the boundary between the Campanian and Maastrichtian. These geological ages are associated with the igneous activity of the Yuchon Group which occurred vigorously in the southern part of the Korean peninsula during the Late Cretaceous. The various geological ages of volcanic rocks distributed in the southwestern part of the peninsula and of igneous rocks found in the Cretaceous formation which contain a wide variety of minerals indicate that in this area, volcanic activities continued vigorously as a result of the collision of the Eurasian and Pacific Plates between 108-71 Ma.

• Economic and Environmental Geology
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• v.45 no.6
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• pp.709-719
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• 2012

Prospection was performed on the tin mineralized belt in Mwanza and Kongolo areas of Katanga, DR Congo. Most of deposits in Katanga areas are related to the granites which are located in Kibaran belt in NE and SW trends of mid Proterozoic. Metasedimentary rocks in the Kibaran belt are intruded by granites, and tin, niobium and tantalum deposits are especially developed along with tin-granite. Cassiterite, coltan and gold are developed in the pegmatite, quartz vein and greisen in related to the tin-granite in Mwanza and Katanga areas, and they are exploited by artisan in the smale scale. And we conducted the works with the alluviums and stream sediments in the case of no outcrops. With the results of analysis of samples, we will choose a few potential mineralized zones and con-tinue to prosepect precisely.

• The Journal of the Petrological Society of Korea
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• v.21 no.2
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• pp.113-128
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• 2012

The chemical composition of the continental crust play an important role in understanding of crustal formation and evolution and quantifying other processes taking place within continental crust. We summarized geochemical data reported in the previous literature for the crustal rocks in the Korean Peninsula and divided their chemical composition into geologic time scale. In the variation diagram normalized by average composition of the upper crustal rocks, the geochemical characteristics of the upper crust during Triassic period is different from those of the upper crustal rocks after Jurassic period or before Precambrian. However, the geochemical characteristics of the Jurassic and Precambrian period are similar each other. Our summarized data indicate that the source material of Triassic upper crust may be different from that of Jurassic or Precambrian upper crust.