• Journal of the Mineralogical Society of Korea
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• v.19 no.4 s.50
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• pp.311-324
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• 2006

In the Pohang-Gampo area, several diatomite beds occurred in mostly thinner than 1 m are embedded in the Pohang Formation of marine environment and the pyroclastic Eoil Formation. The diatomite from the Eoil Formation is constituting the high-grade ore altered slightly by diagenesis. In contrast, the diatomite intercalated within the upper horizon of the Yeonil Group is comparatively low-grade and highly altered in places. During diagenesis, an increasing of crystallinity of opal, i.e., the original mineral component of diatom, results in ultimately the mineral transition to quartz with accompanying a drastic change in morphology and texture of the altered diatomite. The diagenetic alteration appears to have undergone by way of the chemical diagenesis, which is largely controlled by degree of fluid contact, rather than burial diagenesis. For the diatomite from the Pohang-Gampo area, careful SEM observations, XRD, chemical analyses, and determination of specific surface area were done to identify the fossil species, mineral and chemical composition, and other physical properties in the view of assesment of grade and quality. The domestic diatomite ores are evaluated to be not good in grade and quality, compared to those of famous foreign localities. However, some diatomite deposits of marin,: origin from the Pohang Formation is constituting a peculiar clay-rich type, i.e., moler applicable to the special usage such as a manufacturing of lightweight brick. Because such a diatomite is frequently intercalated relatively as a thicker bed in the upper part of the Yeonil Group, a systematic and careful investigation should be done for the exploitation and development of an economic diatomite deposit of the moler type.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.4
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• pp.214-227
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• 1998

This study was carried out to investigate the composition and diagenesis of the carbonate rocks from the seamounts in the Federated States of Micronesia, Central Pacific. Most of the samples were dredged from the water depth of about 1000-3000 m mainly in Chuuk Island, Hunter Bank, Caroline Ridge and Yap Trench. The carbonate rocks are either pelagic sediment mainly of planktonic foraminifera or shallow-marine sediment of corals, calcareous algae, mollusks and echinoderms. The rocks are altered texturally and chemically, except for those from the Hunter Bank and Yap A. The presence of shallow-marine cements suggests that the carbonate sediment has been subsided or reworked to the present water depth after deposition in shallow-marine environments. The texture of the carbonate sediment is reminiscent of meteoric diagenesis; however, the stable carbon isotopic composition of the altered rock samples shows affinity with that of sea water and the oxygen isotopic values are slightly enriched or same as compared to those of unaltered samples. These stable isotopic data suggest that the carbonate sediment of the study area has been diagenetically altered in the present deep-marine environment.

• 한국해양학회지
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• v.30 no.3
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• pp.216-226
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• 1995

Stable isotopic and elemental compositions were analyzed for well- preserved calcareous skeletons (gastropods, pectenids, brachiopods, a scaphopod, and other bivalves) of the Pleistocene Seoguipo Formation from Cheju Island, Korea. Mineralogically and texturally, aragonitic and calcitic fossils still retain their original mineralogy and microstructure. High $\delta$$\^$18/O and $\delta$$\^$13/C contents indicate that the shells have not been altered by the post-burial diagenesis. Also, this is supported by high Na and Sr contents as well as low Mn and Fe compositions of the shells. Oxygen isotopic compositions of the well preserved fossils show that the organisms had lived under the lower paleotemperature or within the isotopically enriched paleo-seawater during the deposition of the Seoguipo Formation. This result strongly implies that the Seoguipo Formation was deposited during a glacial period. The paleotemperature variation throughout the sequence during the deposition of the Sewguipo Formation was negligible.

• Journal of the Mineralogical Society of Korea
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• v.5 no.2
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• pp.61-71
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• 1992

Through the low-temperature(60-150${\circ}C$) hydrothermal treatment of perlite with the alkaline solution at various NaOH concentrations, the mode of volcanic glass alteration and resultant zeolite formation were investigated in a closed system. At a temperature of 80${\circ}C$ and alkalinities of pH range 8 to 12, corresponding to the natural environments of diagenetic zeolite formation, only weak dissolution of perlitic glass occurs without zeolite formation despite the residence time of 100 days. Activities of Si and Al increase progressively, as a consequence of increasing pH, whereas activity ratios of Si/Al decrease. Zeolites were synthesized from perlite in the alkaline solution at above 0.1M NaOH concentrations. Below the temperature of 100${\circ}C$ Na-P was mainly formed, whereas analcime was the dominant zeolite at the temperature range of 100-150${\circ}C$. During Na-P synthesis chabazite and Na-X were also formed as by-products in case of lower proportion of solution/sample(<10ml/g) and higher NaOH concentraion (>3M), respectively. The alteration modes of perlite in the zeolite synthesis reflect that the formation of synthetic zeolites occurs as an incongruent dissolution likely with the diagenetic formation of natural zeolites from volcanic glass. Considering much difference in reaction kinetics between natural and synthetic systems, however, the evaluated synthetic conditions in these experiments were not directly applicable to the natural diagenetic system.

• The Korean Journal of Petroleum Geology
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• v.3 no.1 s.4
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• pp.16-27
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• 1995

The Early Miocene Temblor Formation forms an important sandstone reservoir at Kettleman North Dome oil field, California. Sandstones are mostly arkosic in composition except deepest sandstones containing much volcanic rock fragments. Arranged in paragenetic sequence prior to feldspar alteration, the Temblor sandstones contain cements of early calcite, dolomite, quartz, albite, mixed-layer ohloriteismectite (C/S) and smectite, and anhydrite. Diagenetic changes associated with feldspar are albitization of plagioclase, late calcite and laumontite cementation and grain replacement, plagioclase dissolution, and kaolinite cementation. Plagioclase albitization and late calcite and laumontite cementation in Temblor sandstones occurred at the time of maximum burial with temperatures up to $130^{\circ}C$. Volcanic plagioclases were selectively albitized. Most diagenetic changes are interpreted to have occurred before the maior uplift which occurred within the last one million years ago. Since then to the time of hydrocarbon emplacement plagioclase dissolution and kaolinite cementation occurred. This reaction occurred in relatively closed system due to the occurrence of kaolinite next to the site of plagioclase dissolution. Unaltered part of volcanic plagioclase and plutonic plagioclase which escaped albitization during maximum burial were preferentially dissolved to make plagioclase porosity. Secondary porosity resulting from dissolution of plagioclase and carbonate and anhydrite cements was mainly produced by formation waters containing organic acids released during atagenesis of organic matter.

• Journal of the Mineralogical Society of Korea
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• v.23 no.4
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• pp.377-393
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• 2010

Pumiceous tuffs occurring in the Beomgockri Group are examined applied-mineralogical characteristics and their controling factors to evaluate their potentials as the adsorption-functional mineral resources. The pumiceous tuffs are diagenetically altered to low-grade zeolitcs and bentonites in the Janggi area. Compositional specialty due to the presence of pumice fragments induces the altered tuffs to exhibit the characteristic adsorption property combined with cation exchange capacity, specific surface area, and acidic pH. Unusual lower pH in the adsorption-functional mineral substances is turned out to be originated from the presence of H-smectite having $H^+$ in the interlayer site of the sheet structure. On account of disordered crystallinity resulting from the exchanged $H^+$ in the interlayer site, the smectite commonly forms crenulated edges in the planar crystal form and exhibits characteristic X-ray diffraction patterns showing comparatively lower intensities of basal spacings including (001) peak than conventional Ca-smectite. Based on the interpretation of paragenetic relations and precursor of the H-smectite, a genetic model of the peculiar clay mineral was proposed. The smectite formation may be facilitated resulting from the precipitation of opal-CT at decreasing pH condition caused by the release of H+ during diagenetic alteration of pumice fragments. Because of the acidic smectite, the low-grade mineral resources from the Beomgockri Group may be applicable to the adsorption industry as the raw materials of acid clays and bed-soil.

• Annual Conference of KIPS
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• 2000.10a
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• pp.129-132
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• 2000

버퍼넘침(buffer overflow)은 특정 프로그램 언어에서 발생하는 배열의 경계파괴 현상을 말한다. 그 대표적인 언어로서 C/C++을 들 수 있는데. 이들 언어는 기본적으로 스트링(문자열)을 정의함에 있어서 크기속성을 배제하고 끝을 의미하는 종료문자(delimiter character. NULL)를 사용함으로써 배열(버퍼)의 경계침범 가능성을 허용하고 있다. 이 때 스택영역에 할당된 버퍼가 넘친다면, 주변에 위치한 지역변수, 레지스터 보관, 복귀주소 둥의 값이 변질되어 원래의 의도된 제어흐름을 보장할 수 없게 된다. 특히 복귀주소 부분을 의도적으로 침범하여 특정 값을 덮어쓸 수 있다면 해당 프로그램의 동작을 인위적으로, 그리고 자유롭게 변경할 수 있게 된다. 본 논문에서는 이와 같은 스택영역에서의 버퍼넘침을 사용한 제어흐름 변경 해킹기법의 과정을 현존하는 UNIX 시스템 및 C/C++ 언어를 이용하여 살펴보고 대응방향을 모색한다.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10a
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• pp.653-655
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• 2000

버퍼넘침(buffer overflow)은 특정 프로그램 언어에서 발생하는 배열의 경계파괴 현상을 말한다. 그 대표적인 언어로서 C/C++을 들 수 있는데, 이들 언어는 기본적으로 스트링(문자열)을 정의함에 있어서 크기속성을 배제하고 끝을 의미하는 종료문자(delimiter character, NULL)을 사용함으로써 배열(버퍼)의 경계침범 가능성을 허용하고 있다. 이때 스택영역에 할당된 버퍼가 넘침다면, 주변에 위치한 지역변수, 레지스터 보관, 복귀주소 등의 값이 변질되어 원래의 의도된 제어흐름을 보장할 수 없게 된다. 특히 복귀주소 부분을 의도적으로 침범하여 특정 값을 덮어쓸 수 있다면 해당 프로그램의 동작을 인위적으로, 그리고 자유롭게 변경할 수 있게 된다. 본 논문에서는 이와 같은 스택영역에서의 버퍼넘침을 사용한 제어흐름 변경 해킹기법의 과정을 현존하는 UNIX 시스템 및 C/C++ 언어를 이용하여 살펴보고 대응방향을 모색한다.

• Journal of the Mineralogical Society of Korea
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• v.26 no.2
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• pp.111-118
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• 2013

Diagenetic black chert nodules occur in the Paleozoic dolostone in Susan, Jecheon, Korea. They reacted with dolomite to form alteration rim around the nodules during the contact metamorphism probably related to the intrusion of biotite granite. In the earlier stage of alteration, talc and calcite replaced both the chert and dolomite, which were subsequently replaced by tremolite. Significant mass of tremolite occurs along the horizon enriched with chert nodules. Scanning electron microscopy and optical microscopy of the tremolite specimens revealed the elongated morphology of diverse aspect ratios coexisting in several mm scale. Non-asbestiform tremolite columns were also common as well as asbestiform fibrous bundles. Quantitative estimation of asbestos should be more cautious for naturally occurring materials because all the tremolite particles in the outcrop are not asbestiform. The occurrence of asbestiform tremolite in the Susan area indicates that a combination of chert-bearing dolostone, heat source, and aqueous fluids is one of the geological environments for the formation of asbestiform tremolite.

• Journal of the Mineralogical Society of Korea
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• v.17 no.3
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• pp.245-265
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• 2004

This study was to compare the geological occurrences and geneses of the Myogi, Tsukinuno, Dobuyama and Kawasaki bentonite deposits distributed in the Tertiary sedimentary basins of NE Japan, and to compare the mineralogical and physicochemical properties of their bentonites. The Japanese bentonite deposits are mainly distributed in the Green-tuff region which was formed in Neogene. The shape of ore body of the Myogi, Tsukinuno and Kawasaki deposits formed by the diagenesis are layered and stratiform. In contrast to this, the Dobuyama deposit formed by hydrothermal alteration shows the cone shape. The mineralization age of four deposits are 1.8 ～ 21 Ha from Early Miocene to Pliocene. The Dobuyama bentonite with the highest montmorillonite content shows the highest surface area, CEC, MB adsorption, and strengths. The Tsukinuno bentonite with a little high montmorillonite content is characterized by strong alkalinity, high viscosity and swelling. The Kawasaki bentonite, the Na-Ca mixed type, shows higher viscosity and swelling than the Ca-type Dobuyama bentonite. The Myogi bentonite with the lowest montmorillonite content shows the properties of low viscosity, In adsorption, strengths and a little high CEC and surface area. The high CEC and surface area of this deposit is due to the sufficient occurrence of zeolite. A strong dispersion in the Na-type bentonite and a strong flocculation in the Ca-type bentonite took place, and both the types show a slow flocculation with time. The physicochemical properties of the bentonite are mainly controlled by the montmorillonite content, interlayer cations, and impurity minerals such as zeolite. But bentonites inconsistent to this factors are sometimes occurred. This is maybe due to the crystal chemistry such as layer charge of montmorillonite and crystal morphology of montmorillonite such as aspect ratio.