• The Journal of the Petrological Society of Korea
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• v.5 no.1
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• pp.108-120
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• 1996

This study reports petrography and geochemical characteristics of the Cretaceous volcanic rocks that are distributed in the vicinity of the Cheonsungsan area, Yangsan-Gun, Gyeongsangnam-Do. The Cretaceous volcanic rocks composed of andesitic rocks, Wonhyosan tuff, Cheonsungsan tuff in ascending order. Sedimentary rock is the basement in the study area cofered with volcanic rocks. These volcanic rocks are Wonhyosan tuff and Cheonsungsan tuff that represented the early phase of the Bulgugsa igneous activity. Wonhyosan tuff are classified into dacite tuff and dacite welded tuff based on the rock texture and their mineral composition. They are covered with Cheonsungsan tuff. Dacite tuff composed of lithic lapilli ash-flow tuff and vitric ash-flow tuff. Most dacite welded tuff are lapilli ash-flow tuff. Cheonsungsan tuff overlying the Wonhyosan tuff consists of rhyolite tuff and rhyolite welded tuff. Rhyolite tuff are lithic crystal ash-flow tuff and crystal vitric ash-flow tuff with somewhat accidental fragments of andesitic and sedimentary rocks. Rhyolite welded tuff is distinguishe from rhyolite tuff by is typical eelded fabrics and its rock color. According to petrochemical data, the volcanic rocks in study area belong to high-K orogenic suties. On the discriminant diagrams such as La/Yb versus Th/Yb, these rocks falls into the discriminant fields for the normal continental margin arc.

• The Journal of the Petrological Society of Korea
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• v.28 no.2
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• pp.71-83
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• 2019

The volcanic rocks in Saryangdo area are composed of Witseom Andesite, Punghwari Tuff, Araetseom Andesite, Obido Formation, Namsan Rhyolite and Saryangdo Tuff in ascending order. The volcanic rocks has a range of andesite-rhyodacite-rhyolite, which indicates calc-alkaline series and volcanic arc of orogenic belt. In Harker diagrams for trace element and REE pattern, these are also distinguished into so three groups(Witseom Andesite, Araetseom Andesite and Saryangdo Tuff) that each unit is interpreted to have originated in different magma chamber. The Saryangdo Tuff exhibits systematically(chemical zonations that gradually change) from lower dacite to upper rhyolite in section. The systematic sequence of compositional variations suggests that the tuffs were formed by successive eruptions of upper to lower part of a zoned magma chamber in which relatively dacitic magma is surrounded around rhyolitic magma of the central part. The zoned magma chamber was formed from marginal accretion and crystal settling that resulted form magmatic differentiations by fractional crystallization.

• Journal of the Korean earth science society
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• v.39 no.3
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• pp.250-259
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• 2018

We investigated the petrological features of the stone materials used in the Jeolla Usuyeong rampart and estimated their provenance through the geological survey. The Jeolla Usuyeong was designated as a historic site (No. 535) on 2016. Since the remaining rampart is less than 15%, it is necessary to make conservation on it. In this study, we discriminated the stone materials used for the rampart according to their petrographic characteristics and estimated the volume proportion of each stone by the rock type. Also, we measured the whole-rock magnetic susceptibility. The petrographic features of the stones in the rampart were compared with those in the vicinity by their mineral composition and texture. The stone materials of the rampart mainly consist of the tuff, lapilli tuff, and lapilli stone. Among these three kinds of rocks, lapilli tuff is quantitatively the most abundant (60.3%), the next is tuff (34.7%), and lapilli stone (2.5%) shows the least amount. The whole-rock magnetic susceptibility of the tuffaceous rocks can be divided by the value of $1.0{\times}10^{-3}$ SI unit. Also, the compressive strength of tuff exhibits about 156 MPa, which is adequate to reuse for the repairing work. Petrological comparisons between stone materials and outcrop rocks distributed around the Hwawon peninsula leads to a conclusion that the stone materials of the rampart are likely to have been delivered from the Dongoeri and Sindeok-ri. Judging from the results of the comparison on the frequency of use and physical properties among the tuffaceous rocks, tuff is considered to suitable for restoring the rampart.

• Economic and Environmental Geology
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• v.29 no.3
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• pp.381-393
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• 1996

Cretaceous volcanics and volcaniclastic sediments are abundantly distributed in the Haenam area located at the tip of the southwestern part of the Yongdong-Kwangju depression zone. The Cretaceous strata correlated with the Yuchon Group of the Kyongsang Supergroup are divided into three formations: Hwawon Formation, Uhangri Formation and Haenam Formation in ascending order. The stratovolcanic Hwawon Formation is mainly composed of andesite and andesitic pyroclastics. The Uhangri Formation is the lacustrine sedimentary deposit. The Haenam Formation is composed of Hwangsan tuff, Haenam tuff, Yongdang tuff, Seoho tuff, and also Acidic lava, both being formed by a cogenetic acidic volcanism. The topographic circular structure of the Cretaceous strata was controlled by the doming of Jurassic Sani granite. Cretaceous volcanism in the study area is characterized by the two stages of intermediate volcanic activity in Cenomanian to Albian, and acidic volcanic activity in Campanian to Coniacian.

• The Journal of the Petrological Society of Korea
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• v.18 no.2
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• pp.115-135
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• 2009

We have studied general orientational characteristics of microcracks distributed in Tertiary crystalline tuff from the northeastern part of the Gyeongsang Basin. 108 sets of microcracks on horizontal surfaces of 6 rock samples from Heunghae-eup and Cheongha-myeon, Pohang-si areas were distinguished by image processing. Those microcrack sets show a distinct linear array in 38 images. Whole domain of the directional angle(${\theta}$)-frequency(N) chart for crystalline tuff can be divided into 20 domains in terms of the phases of the distribution of microcracks. From the related chart, microcrack sets show preferred orientation which are coincident with the direction of vertical common joints. Consequently, the potential for macroscopic vertical joints in a rock body can be inferred from the directional angle showing high frequency in each domain of the related chart. This joint pattern is nearly the same in Mesozoic granites from Seokmo-do, Gwanghwa-gun. From the rose diagram for orientations of microcrack in crystalline tuff, orientations of dominant sets of microcracks in terms of frequency orders reflect representative orientations of maximum principal stress acted on crystalline tuff. Meanwhile, orientations of microcracks in crystalline tuff were compared with those of open microcracks in Bulgugsa granites from the southwestern part of the Gyeongsang Basin, and vertical rift/grain planes from Mesozoic granite quarries in Korea. In regional distribution chart, the agreement of distribution pattern between above two types of microcrack sets and vertical planes suggests that microcrack systems developed in crystalline tuff probably occur regionally in Mesozoic granites in Korea.

• Korean Journal of Heritage: History & Science
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• v.37
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• pp.285-307
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• 2004

Synthesize and examine petrological characteristic and geochemical characteristic by weathering formation of rock and progress of weathering laying stress on stone cultural properties of Unjusa temple of Chonnam Hwasun county site in this research. Examine closely weathering element that influence mechanical, chemical, mineralogical and physical weathering of rocks that accomplish stone cultural properties and these do quantification, wish to utilize by a basic knowledge for conservation scientific research of stone cultural properties by these result. Enforced component analysis of rock and mineralogical survey about 18 samples (pyroclastic tuff; 7, ash tuff; 4, granite ; 4, granitic gneiss; 3) all to search petrological characteristic and geochemical characteristic by weathering of Unjusa temple precinct stone cultural properties and recorded deterioration degree about each stone cultural properties observing naked eye. Major rock that constitution Unjusa temple one great geological features has strike of N30-40W and dip of 10-20NE being pyroclastic tuff. This pyroclastic tuff is ranging very extensively laying center on Unjusa temple and stone cultural properties of precinct is modeled by this pyroclastic tuff. Stone cultural propertieses of present Unjusa temple precinct are accomplishing structural imbalance with serious crack, and because weathering of rock with serious biological pollution is gone fairly, rubble break away and weathering and deterioration phenomenon such as fall off of a particle of mineral are appearing extremely. Also, a piece of iron and cement mortar of stone cultural properties everywhere are forming precipitate of reddish brown and light gray being oxidized. About these stone cultural properties, most stone cultural propertieses show SD(severe damage) to MD(moderate damage) as result that record Deterioration degree. X-ray diffraction analysis result samples of each rock are consisted of mineral of quartz, orthoclase,plagioclase, calcite, magnetite etc. Quartz and feldspar alterated extremely in a microscopic analysis, and biotite that show crystalline form of anhedral shows state that become chloritization that is secondary weathering mineral being weathered. Also, see that show iron precipitate of reddish brown to crack zone of tuff everywhere preview rock that weathering is gone deep. Tuffs that accomplish stone cultural properties of study area is illustrated to field of Subalkaline and Peraluminous, $SiO_2$(wt.%) extent of samples pyroclastic tuff 70.08-73.69, ash tuff extent of 70.26-78.42 show. In calculate Chemical Index of Alteration(CIA) and Weathering Potential Index(WPI) about major elements extent of CIA pyroclastic tuff 55.05-60.75, ash tuff 52.10-58.70, granite 49.49-51.06 granitic gneiss shows value of 53.25-67.14 and these have high value gneiss and tuffs. WPI previews that is see as thing which is illustrated being approximated in 0 lines and 0 lines low samples of tuffs and gneiss is receiving esaily weathering process as appear in CIA. As clay mineral of smectite, zeolite that is secondary weathering produce of rock as result that pick powdering of rock and clothing material of stone cultural properties observed by scanning electron micrographs (SEM). And roots of lichen and spore of hyphae that is weathering element are observed together. This rock deep organism being coating to add mechanical weathering process of stone cultural properties do, and is assumed that change the clay mineral is gone fairly in stone cultural properties with these. As the weathering of rocks is under a serious condition, the damage by the natural environment such as rain, wind, trees and the ground is accelerated. As a counter-measure, the first necessary thing is to build the ground environment about protecting water invasion by making the drainage and checking the surrounding environment. The second thing are building hardening and extirpation process that strengthens the rock, dealing biologically by reducing lichens, and sticking crevice part restoration using synthetic resin. Moreover, it is assumed to be desirable to build the protection facility that can block wind, sunlight, and rain which are the cause of the weathering, and that goes well with the surrounding environment.

• The Journal of the Petrological Society of Korea
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• v.15 no.3 s.45
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• pp.128-138
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• 2006

The west stone pagoda of Gameunssji temple site (National Treasure No. 112) has been damaged mainly by fracture, exfoliation and granular disintegration. In this study, the source area of the rocks using the west stone pagoda was examined in terms of petrological feature, magnetic susceptibility, and ${\gamma}-ray$ spectrometer. The stones include abundant crystal fragments of biotite, quartz and feldspars in the fine-grained matrix; they are petrographically discriminated to vitric-crystal tuff or crystal tuff. Measured magnetic susceptibility values are of from 10 to 20 $({\times}10^{-3}\;SI\;unit)$. From the ${\gamma}-ray$ spectrometer measurement K, eU, and eTh contents of the stones are about 3%, 0 to 8ppm, and 9 to 18 ppm, respectively. These features are used as indicators to presume the source area of the stones. Comparing the petrographical and chemical characteristics between the stones of the west stone pagoda and the country rocks near the Gameunsaji temple site, it is suggested that the most similar country rock to the stones could be dacitic volcanic rocks of the Beomgokri group in the Waeup basin. The Beomgokri group is lithostratigraphically divided into Waeupri tuff, Yongdongri tuff and Beomgokri volcanic rocks. Among the three rocks, the crystal tuff of the Beomgokri volcanic rocks seems likely to have been the source rock of the stones of the west stone pagoda.

• Economic and Environmental Geology
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• v.40 no.3 s.184
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• pp.319-330
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• 2007

The Muposan Tuff is a stratigraphic unit which is distinguished as a cooling unit in the volcanic rocks of the northeastern Kyeongsang Basin. The Muposan Tuff commonly belongs to tuff field according to the granulometric classification and to vitric tuffs according to the constituent classification. The tuffs are mostly densely to partially welded to include very flattened and sometimes stretched pumices and shards, and involve several flow indicator and lateral gradings in maximum diameter and content of their constituents. Movement pattern from flow lineation, lithic and pumice imbrications, asymmetric flow folds, and lateral gradings in maximum diameter and content of their constituents indicate that the Muposan Tuff had a source from the southeastern part.

• Journal of the Mineralogical Society of Korea
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• v.24 no.4
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• pp.265-278
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• 2011

Clayey ores of the Jeonnam province mainly consist of pyrophyllite (monoclinic), kaolinite (1T), and minor amounts of quartz, muscovite, and feldspars. Mineralogical studies revealed that two kinds of clay minerals were mainly produced from the volcanic sediments with similar ages and compositions. Kaolinite deposits sometimes contain neither diaspore nor corundum, but alunites are often found in the upper portions of the kaolin ore bodies. On the other hand, corundum and diaspore are commoner in the pyrophyllite deposits than the kaolin deposits. As ages of rock formations are becoming younger, amounts of pyrophyllite and kaolinite are rather radically decreased, and finally disappeared. But muscovite, quartz, and plagioclase feldspars are inclined to be preserved because of weak alteration. Most of clay ore bodies contain purple tuff beds on the uppermost portion, and silicified beds, tuff, and lapillistone are found in an ascending order in the most of clay quarries. Chemical analyses show that higher contents of $Al_2O_3$ might not necessarily be due to the argillization, since some tuffs contain higher $Al_2O_3$ contents originated from feldspars. $SiO_2$ contents are fairly higher in the silicified beds than in those of adjacent formations, which might have been introduced from the ore bodies. And $K_2O$ contents are obviously lower than those of $Na_2O$ and CaO in the ores and their vicinities. Ignition losses of some of clays represent much higher contents than those of the ordinary ones because of the sporadic presence of alunite, diaspore and corundum which are accompanied with lots of $SO_4$ and $Al_2O_3$ contents. REE (rare earth element) abundances of most of volcanics and clay ores show rather higher LREE (light rare earth elements) contents, and represent small to moderately negative Eu anomalies. Though most of ores ususally show milky white color, fine-grained and well bedded formations which could be easily discernible in the most of outcrop. But more distinct characteristics are desirable where rather massive ore bodies exist. Purple tuffs and silicified beds above the ore bodies would be useful as marker horizons/key beds since they have rather obvious lithology, extension and mineralogy than those of other adjacent formations.

• The Journal of the Petrological Society of Korea
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• v.6 no.1
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• pp.1-18
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• 1997

Andesitic pyroclastics and lava flows are deposited as a part of composite volcanoes by Cretaceous volcanic activity in Geojae Island, off the coast of Korea. The andesitic pyroclastics are composed of tuff breccia and lapilli tuff minor intercalated tuff. Lava flows are divided into dense and porphyritic andesite containing phenocrysts of plagioclase, pyroxene, and/or hornblende. The andesitic rocks represent charactersitcs of carc-alkaline BAR association with basalt, basaltic andesite, andesite, and dacite to rhyolite. Major element variations of the volcanic rocks show that $Al_2O_3$, total FeO, CaO, MgO and $TiO_2$ decrease with increasing $SiO_2$ but $K_2O$ and total alkalis increase, and represent differntiation trend of calc-alkaline rock series. In spider diagram, contents of Sr, K, Rb, Ba, and Th are relatively high, but contents of Nb, P, Ti and Cr are low. These petrochemcial characteristics are similar to those of rocks from island arc or continental margein related to plate subduction. Chondrite-normalized REE patterns of volcanic rocks are paralle to subparallel, with LREE enriched than HREE, and show gradual increase of negative Eu anomaly from basalt to dacite and rhyolite, suggesting comagmatic fractional crystallization with minor effects of assimilation and magma mixing. Andesitic rocks are assumed medium-K orogenic andesites that formed in the tectomagmatic environment of subduction zone under normal continental margin arc.