• Economic and Environmental Geology
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• v.22 no.2
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• pp.117-127
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• 1989

Devonian Geochang foliated granite and Jurassic plutonic rocks intrude Precambrian metamorphic Complex at Geochang area, southern part of the Korean Peninsular. Among them hornblendes from four Jurassic plutonic bodies which have had no trace of metamorphism or deformation since their intrusion were dated by K-Ar method. Hornblende gabbro dike which intruded Anorthosite of unknown age revealed $204{\pm}10Ma$, and hornblende granite and hornblende-biotite granodiorite were $178{\pm}9Ma$ and $181{\pm}9Ma$, repectively. Also, hornblende diorite which partly showing primary foliations were $178{\pm}9Ma$, so igneous activity of Geochang area, northern part of Jirisan, were active about 180 Ma before. Microprobe data of dated hornblends and other major constituent minerals such as plagioclases and biotites were also reported, and their chemical composition showed systematic changes in terms of lithologic types.

• Economic and Environmental Geology
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• v.9 no.1
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• pp.13-26
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• 1976

The basic rocks distributed in the Okchon paleogeosynclinal zone have been previously considered as intrusive in majority, but as sedimentary parensis in few variety. The present study is to find out some clues to conclude otherwise, if any, by clarifying 1) the nature and characteristics of the rocks, 2) type of the associated sedimentary rocks if any, and 3) their occurrence in related to regional geologic structure. The finding are as follows: 1) The basic rocks are identified and classified to hornblende gabbro, amphibolite, basalt and andesite (in part metamorphosed to meta-volcanics), green schist and peridotite(which appears in separate locality from the others). 2) Associated sedimentary rocks which appear to overlie the basic rocks are known as Kunjasan and Baekwhasan formations. The two formations are probably same, but been used differently by different authers at different localities. The rocks is exclusively consisted of cherty looking siliceous quartzite and some localitis it shows very calcarious nature. The formation seems to indicate a sort of pelagic siliceous sediments although it contain some pebbles. 3) The basic rock suites are always underlain by the same continuous, great thrust, which separates the Okchon paleogeosyncline zone from the neogeosynclinal zone in the area studied. The comparison of Okchon basic rocks suite to the ophiolite suites in other parts of the world indicates some similarity with which the writers suggested the probalility of Okchon basic rocks being ophiolites that occur along ancient geosuture line now represented by the great thrust.

• Tunnel and Underground Space
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• v.5 no.3
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• pp.251-265
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• 1995

One of the most important matters in stress measurement by hydraulic fracturing technique is the determination of the breakdown pressure, reopening pressure, and shut-in pressure, since these values are the basic input data for the calculation of the in-situ stress. The control of the fracture propagation is also important when the hydraulic fracturing technique is applied to the development of groundwater system, geothermal energy, oil, and natural gas. In this study, a laboratory scale hydraulic fracturing device was built and a series of model tests were conducted with cube blocks of Machon gabbro. A new method called 'flatjack method' was adopted to determine shut-in pressure. The initial stress calculated from the shut-in pressure measured by flatjack method showed much higher accuracy than the stress determined by the conventional method. The dependency of the direction of fracture propagation on the state of the initial stresses was measured by introducin g artificial slots in the borehole made by water jet system. Numerical modeling by BEM was also performed to simulate the fracture propagation process. Both results form numerical and laboratory tests showed good agreement. From this study which provides the extensive results on the determination of shut-in pressure and the control of fracture propagation which are the critical issue in the recent hydraulic fracturing, it is conclued that in-situ stress measurement and the control of fracture propagation could be achived more accurately.

• Economic and Environmental Geology
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• v.27 no.2
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• pp.117-130
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• 1994

Titanomagnetite ore bodies in the Yonchon iron mine are closely associated with alkali gabbroic rocks of middle Proterozoic age which intruded Precambrian metasedimentary rocks. The orebodies can be divided into massive ores in gabbroic rock, skarn ores in calcareous xenoliths and banded ores in gneissic gabbro. Gabbroic rocks from the Yonchon iron mine have unusually high content of $TiO_2$ with an average values of 3.46 wt%. Iron ores are ilmenite (42.25~51.56 wt% in $TiO_2$) and titanomagnetite (1.29~6.57 wt% in $TiO_2$) and the former is dominant Small amount of magnetite, hematite, sphene and sulfide minerals are included in the ores. Grandite garnet, titanoaugite and tschermakite are in iron skarn ores. Hornblendes from ores and gabbroic rocks have a relatively homogeneous isotopic composition with ${\delta}D$ between -110.0 and -133.9‰, and ${\delta}^{18}O$ of +4.5 to +6.5‰, and calculated to have formed in fluids with ${\delta}O_{H_2O}$ of + 6.7 to +8.7‰. and ${\delta}_{H_2O}$ of -87.9 to -111.8‰, which has a similar isotopic value of primary magmatic water. Based on intrusive age, occurrence, mineral chemistry and isotopic compositions of magnetite ores and gabroic rocks, it will be concluded that the gabbroic rocks are responsible for the titanomagnetite mineralization. The titaniferous magnetite melt was immiscibly separated from the high titaniferous gabbroic melts of Proterozoic age.

• The Journal of the Petrological Society of Korea
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• v.15 no.1 s.43
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• pp.1-9
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• 2006

Sr isotopic compositions are determined from the syenite of Sancheong area, yielding age of $211{\pm}23(2\sigma)$ Ma and $^{87}Sr/^{86}Sr$ initial ratio of $0.70598{\pm}0.00060$. Such result confirms that Sancheong syenite was emplaced during the Mesozoic around the Triassic-Jurassic boundary. Rather low initial $^{87}Sr/^{86}Sr$ ratio suggests insignificant influence of old crustal materials. There are strong contrast in rock types of plutonic associations between Sancheong-Macheon area and adjacent Hamyang-Geochang area to the north, i.e. syenite-diorite-gabbro and granite-granodiorite respectively. $^{87}Sr/^{86}Sr$ initial ratios also show distinction between these areas. Such differences suggest regional contrast in tectonic environments between them.

• The Journal of Engineering Geology
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• v.24 no.4
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• pp.473-486
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• 2014

The objective of this study is to produce the rock slope hazard map on the Mt. Hwangryeong located at center of Busan Metropolitan City for evaluating the rock slope hazard susceptibility. The Mt. Hwangryoeng is located between Dongrae and Ilkwang faults and consists of various rocks such as sedimentary rock, andesitic volcanic rock, andesite, gabbro and granitic rocks. Thematic maps were carried out using ArcGIS for Database including the orientations and density of joints, strength of rock constructed through the field survey and results from previous studies. Also, rock slope hazard susceptibility for the Mt. Hwangryoeng area was studied using empirical method through checklists proposed by NDMI (National Disaster Management Institute). Results from using the empirical method indicated that rock slopes are evaluated from very stable to stable, but moderate stability has been partially presented along the edge of the mountain area.

• Journal of Conservation Science
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• v.25 no.3
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• pp.233-244
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• 2009

This study was focused on the transducer and suitable contact material for stone cultural heritage, and the correlation of direct-indirect method in rock types for scientific development and quantitative evaluation technique of the ultrasonic measurements. As a result, it was identified the transducer (UTREXTX(RX)54kHz) and contact material (rubber clay) of the type 3 were appropriate for the ultrasonic measurements of stone cultural heritage. The direct-indirect correction factors of type 3 were calculated 1.50 for granite, 1.38 for gabbro, 1.58 for quartz diorite, respectively. This result is the first study for improvement in reliability for the ultrasonic measurements, and it will contribute to establishment of the ultrasonic survey method for stone cultural heritage. Also, complementary studies considering the surface irregularity of rocks and various contact materials will carry out, and the database about correlation of direct-indirect in rock types will establish.

• Economic and Environmental Geology
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• v.18 no.4
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• pp.381-397
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• 1985

A petrological study has been done in the pyeongchang-Jaecheon area which is a northwestern part of the basement of Ogcheon zone for the purpose of comparison of the area to the Nogjeon-Yeongchun area which is the antipodal basement of the zone in the petrological and geotectonical view points. The major units of the area are Precambrian granitic gneissic complex, banded gneiss, linea ted leucocratic gneiss and pegmatitic leucogranitic gneiss in the west, elongated exposure of quartz schist (or partly quartzite) and phyllite, named as Jungdaegal-bong Group correlated to the lower sequence of Joseon Group, in the middle, and limestone and calcic dolomite, Iptanri Formation, correlated to the middle of Joseon Group in the east. Igneous plutons are distributed in the areas of gneissic complex and limestone formation as well as in the Eosangcheon and Daedaeri areas in the southeastern out of the area. Present study reveals that the gneissic complex are the products of granitization to metamorphism of amphibolite facies in the order of above mentioned from the metasediments of schists and calcareous rocks. A notable characteristics of the phyllite of Jungdaegal-bong Group is the presence of syntectonically segregated quartz rods in the forms of lens, swirl or boudinage in evenly distributed in the phyllitic to chloritic matrix. Igneous rocks range in composition from gabbro through diorite, granodiorite, to schistosed and porphyritic granites in stock and dike. The orogenic movement of the Ogcheon zone initiated in the middle Proterozoic time, pre-sedimentation of Ogcheon Group and superposed the granitization in Permian, Jurassic Daebo orogeny with granitic batholiths and stocks, and Cretaceous plutonic intrusion.

• 보존과학연구
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• s.32
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• pp.99-112
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• 2011

The three-storied stone pagoda located in Seungansaji temple site consists mainly of medium to fine-grained biotite granite and granitic gneiss, and partly macrocrystalline gneiss, muscovite gneiss and gabbro. The surface of the stone pagoda is extensively colonized by lichen and moss due to surrounding trees and lawns, and severly deteriorated. Therefore, a comprehensive deterioration diagnosis has been carried out and conservation treatment was conducted in this study. For the conservation treatment, dry cleaning is performed throughout all the surface of the pagoda for naturally grown lichen and biological contaminants using a soft brush and wooden knife. Crustose lichen strongly adhere to the surface was removed by wet cleaning using distilled water. Also, protective railings were reinstalled to an appropriate height with taking the distance from the stone pagoda into account. Finally, the ground around the stone pagoda was repaired with clay sand, and dike was installed with a natural gradient to facilitate water drainage.

• Proceedings of the Zoological Society Korea Conference
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• 1999.10b
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• pp.150.2-150
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• 1999

To investigate the weathering soil buffering capacities of the artificial acidic precipitation, the weathering soils and their leachate solutions were sampled from the host rocks(granite;GR, rhyolite;RH, gabbro;GA, basalt;BA, two serpentinite;SE1, SE2 and limestone;LI) and analyzed for pH and chemical properties. 1n the soil pH of the GR and RH ,the acidic rocks, were 5.02 and 5.95, respectively. And the GA and BA, basic rocks, were 6.52 and 7.57. The SE1 and SE2 were 8.90 and 8.89. While the LI was 7.84. These results means the typical soil pH properties by host rocks. After the artificial acidic precipitation input 5OOml, the average changes of soil leachate solutions treated by pH levels(pH 5.0, 4.0 and 3.0), were pH 5.73, 5.00 and 4.40. in GR soil, and pH 6.19, 5.99 and 5.57 in RH. GA were pH 6.31, 6.04 and 5.86, BA were pH 7.05, 6.85 and 6.56 and SE1 were pH 8.31, 8.26 and 7.71. SE2 were pH 8.29, 8.24 and 7.96. LI were pH 7.55, 7.46 and 6.79. The soil leachate pHs from volcanic rocks were higher than those from the plutonic rocks and GR soils showed greater response than other soils. With increasing 100ml input-solution, the soil leachate pHs were mainly decreased. Cation concentrations, CEC, EC and total nitrogen concentrations of RH and BA soils, the volcanic rocks, were higher than those of GR and GA soil, the plutonic rocks. On the contrary, Al concentrations of the GR and GA soils were higher than those of RH and BA soils, partly because of high quartz content in GR and Al content in the biotite and plagioclase in GA.