• 자원환경지질
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• 제21권3호
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• pp.209-221
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• 1988

The ore deposit of the Ohtani mine is one of repesentatives of plutonic tungsten-tin veins related genetically to acidic magmatism of Late Cretaceous in the Inner zone of Southwest Japan. Based on macrostructures of vein filling on the order of ore body, three major mineralization stages, called stage I, stage II, and stage ill from earliest to latest, are distinguished by major tectonic breaks. The alteration zories are characterized by specific mineral associations in pseudomorphs after biotite. The alteration zones can be divided into two parts, i. e. a chlorite zone and a muscovite zone, each repesenting mineralogical and chemical changes produced by the hydrothermal alteration. The chloritic alteration took place at the beginning of mineralization, and muscovite alteration in additions to chloritic alteration took place at stage II and ill. The alteration zones are considered to be formed by either of two alteration mechanism. 1) The zones are formed by reaction of the rock with successive flows of solution of different composition and different stage. 2) The zones are formed contemporaneously as the solution move outward. Reaction between the solution and the wall-rock results in a continuous change in solution chemistry. The migration of the successive replacement of the fresh zone$\rightarrow$the chlorite zone$\rightarrow$the muscovite zone may have transgressed slowly veinward, leaving metasomatic borders between the different zones.

• 자원환경지질
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• 제24권4호
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• pp.363-378
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• 1991

Field and microscopic evidence, XRD,EPMA and chemical data suggest that parent rock of talc ore deposits of Yesan district was originated from ultramafic igneous rock. Parent rock can be divided into serpentinized dunite, serpentinized peridotite, metagabbro, amphibolite and hornblende schist. The ore deposits are highly sheared, and show many evidences of hydrothermal alteration and metamorphism at the greenschist and albite-epidote amphibolite facies. The process of steatitization is variable depending upon the composition, and the degree of alteration and metamorphism of the parent rocks. Steatitization can be divided into two processes with or without serpentinization. The parent rocks with serpentinization are serpentinized dunite, serpentinized peridotite and metagabbro, showing the following alteration process; olivine ${\rightarrow}$ serpentine${\rightarrow}$ talc. The rocks without serpentinization are amphibolite and hornblende schist showing the following sequence; hornblende${\rightarrow}$ chlorite${\rightarrow}$ talc. Formation of talc deposits is summarized as following six stages; I) Intrusion of ultramafic rocks, 2) autometamorphism, 3) metamorphism at greenschist and albite-epidote-amphibolite facies, 4) brittle deformation, 5) hydrothermal alteration, 6) purification of low-grade talc by late dyke intrusion.

• 터널과지하공간
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• 제30권4호
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• pp.417-431
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• 2020

이 연구에서는 라이다(LiDAR) 반사강도를 이용하여 암반 풍화도 및 변질도를 산정하는 작업의 기초연구를 진행하였다. 실내 시험을 통하여 라이다 반사강도에 직접적으로 영향을 미치는 인자와 그 영향 정도를 정량적으로 고찰하고자 하였다. 영향 인자로는 주사거리, 입사각, 표면거칠기, 표면색상, 암석물성, 광물조성, 포화도를 선정하였다. 실험에서는 FARO 라이다 장비와 12가지 종류의 시험편을 사용하였다. 실험 결과 반사강도는 표면색상, 입사각, 주사거리, 암석물성, 포화도 혹은 표면습윤상태, 표면거칠기 순으로 영향을 크게 미치는 것으로 나타났다.

• 자원환경지질
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• 제25권3호
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• pp.225-232
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• 1992

The hydrothermal alteration is evaluated using multicomponent equilibrium calculations with the program CHILLER for the reactions between hydrothermal water and rhyolite at the temperature of $300^{\circ}C$ and pressure of 500 bars. The chemical-reaction model on the depositional processes of the sericitite confirms that the hydrothermal water-rock interaction(hydrothermal alteration) is the main mechanism of the sericitite formation. The principal change in the aqueous phase during the reaction is the pH increase. Overall trends for the major species are the increase in total molalities of K, Ca, $SiO_2$, Al, Mg, Fe, Na, and sulfide in solid phase with hydrothermal water-rhyolite reaction and the decrease of them in aqeous solution by precipitation of hydrothermal products. Quartz and sericite are the first minerals to form. The sequence of minerals to precipitate following them is chlorite, epidote, pyrite and microcline as water/rock ratio decreases. Although calculated results cannot duplicate the complexities of natural hydrothermal alteration, the calculation provides thermodynamic constraints on the natural process. The calculation results resemble those of experimental studies. Sericitite forms where pH decreases and water/rock ratio increases.

• 자원환경지질
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• 제1권1호
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• pp.83-97
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• 1968

• 자원환경지질
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• 제26권1호
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• pp.1-10
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• 1993

The Andong serpentinite body is distributed along the Andong fault, and shows an elliptical shape. The serpentinite is composed of serpentine minerals and other various minerals such as forsterite, pyroxene, talc, tremolite, chlorite, prehnite, calcite and dolomite. The serpentine minerals consist primarily of lizardite with minor chrysotile. Antigorite rarely occurs in some veins. The serpentinite is largely divided into two alteration zones by the occurrence and mineral assemblages. One of the alteration zones is composed of a large amount of serpentine minerals. The other is characterized by tremolite and chlorite. The alteration zone composed of tremolite and chlorite seems to have been formed by hydrothermal alteration after the formation of serpentinite. It is considered that the serpentinite have been formed by alteration of the ultramafic rock such as peridotite.

• 자원환경지질
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• 제26권3호
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• pp.289-309
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• 1993

Milyang pyrophyllite deposit which was formed by hydrothermal alteration occurs in Late Cretaceous andesitic tuff in the Milyang area, Gyeongsangnamdo. The wall rock alteration and genesis of the Milyang pyrophyllite deposit were studied. The ore minerals are composed dominantly of pyrophyllite accompanied by small amounts of quartz, kaolinite, pyrite, dumortierite and diaspore. The alteration halo of this deposit can be divided into three zones on the basis of mineral assemblage; pyrophyllite, sericite and chlorite zone. The common mineral assemblages of each alteration zone are as follows: (1) pyrophyllite zone; pyrophyllite-quartz-kaolinite-pyrite-dumortierite-diaspore, (2) sericite zone; sericite-quartz-pyrite-kaolinite, and (3) chlorite zone; chlorite-plagioclase-quartz. Major element chemistry shows that characteristic depletion in MgO, CaO, and $Na_2O$ and relative increase in FeO from less altered chlorite zone to extensively altered pyrophyllite zone corresponding to variation in mineral assemblages. The paragenesis of ore minerals, oxygen isotope data, chlorite and illite geothermometry suggest that ore deposit was formed at about $250{\sim}330^{\circ}C$. Both hydrogen and silica activities are high in pyrophyllite zone. Potassium activity increases in sericite zone while hydrogen activity becomes low in chlorite zone. The pyrophyllite zone was formed relatively higher temperature than those of sericite and chlorite zones. The ore fluid was considered to be magmatic water in origin derived from the residual granitic magma which interacted with meteoric water.

• Geosciences Journal
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• 제22권6호
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• pp.1001-1013
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• 2018

A new type of uranium occurrence in Korea was identified in pegmatitic and hydrothermally altered granite in the Daejeon area. The U-bearing parts typically include muscovite, pink-feldspar and sericite as alteration minerals. In this study, the geochemical characteristics and alteration age of the granitic rocks were examined to provide evidence for hydrothermally-enriched uranium. The K-Ar ages of muscovite coexisting with U-bearing minerals were determined as 123 and 128 Ma. The U-bearing rocks have relatively low ($CaO+Na_2O$), high $K_2O$ contents, and high alteration index values by major element geochemistry. The trace element geochemistry shows that the uraniferous rocks have significantly low Th/U ratios and strongly differentiated features. The rare earth element patterns indicate that the uraniferous rocks have a low total REE and LREE contents with depletion of Eu. Considering the geochemical variation of the granitic rock major, trace and rare earth elements, it can be concluded that uranium enrichment in pegmatites and altered granite should be genetically related to post-magmatic hydrothermal alteration of K-metasomatism after emplacement of the two-mica granite. This is the first report for geochemical characteristics of Mesozoic granite-related U-occurrences in South Korea. This study will help further research for uranium deposits with similarities in geological setting, mineralogy and age data between South China and Korea, and can also be expected to help solve the source problems related to high uranium concentrations in some groundwater occurring in the granitic terrane.

• 자원환경지질
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• 제28권1호
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• pp.1-8
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• 1995

The smectite-rich clays were found locally in Paleozoic calcareous sedimentary rocks in the Samcheok area. Their occurrences were investigated in detail, and the physico-chemical properties of the clays were also determined by X-ray diffraction, chemical analysis, thermal analysis and cation exchanging experiment. The smectite clays occur as the fissure filling dyke developed in calcareous sedimentary rock and as alteration products of intrusive rhyolite. Most of clays occur at the contact between the sedimentary rock and the rhyolite, and the alteration zone was observed only in rhyolite body close to the contact. Judging from their occurrences, it is believed that the smectite-rich clays in this area were formed by the hydrothemal alteration. The smectite clays from the area are mainly composed of Ca-montmorillonite, and associated with small quantities of quartz, opal-CT and feldspar. The montmorillonites from this area are lower in Fe content, and higher in exchangeable Ca ion, compared to those of bentonite from the Yangnam-Yeongil area.

• 한국지형학회지
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• 제18권1호
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• pp.57-71
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• 2011

남해안의 고성에 위치하는 월치고개 단면은 10m 두께의 화강암 풍화층으로써, 10YR 4/4에 가까운 적색을 띠고 있어서 고온다습했던 고기후의 산물로 판단되기 쉬운 단면이다. 그러나 단면관찰과 박편분석, XRD 동정과 지화학적 분석을 통해 살펴본 결과, 열수변성의 대표광물인 할로이사이트가 단면 전체에서 보편적으로 나타나고 있으며, 한반도의 일반적 화강암 풍화층의 화학적 풍화율인 60~70%보다 훨씬 높은 97%에 달하였다. 이는 기후지형학적 풍화에 의해 형성된 적색풍화층이 아니라, 지열수에 의한 열수변성 가능성이 매우 높게 단면으로 판단된다.