• Economic and Environmental Geology
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• v.7 no.3
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• pp.101-122
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• 1974

The study area is located in between Susanri and Hwanggangri where the formations of Okcheon group and Chosun group supposedly come in contact so that the area is structurally very import. Present study reveals that the meta-volcanic rocks distribute from south to north along contact zone of Okcheon and Chosun groups in the center of the area. Meta-volcanic rocks seem to be originated from the andesite or andesitic basalt rocks which was known to be Surchangri formation consist of phyllite and black slate by previous workers. The meta-volcanic rocks intruded along the fault zone one existed between Okcheon and Chosun groups but obliterated at present by the intrusion of volcanic rocks. The fault seems to be overthrust, and one of the positive evidences of thrust fault is the Yamisan nappe structure in Yamisan near Susanri. This interpretation coincides with O.J. Kim's work which states that the Precambrian Okcheon group is largely overturned and thrusted over the Chosun group. The relation between the Surchangri and the Majeonri formation marks facies change. This fact together with northpluging anticlinal structure made it possible that both formation came into contact along direction without fault. Yongam formation is not overlain unconformably used to be believed by previous workers, but interbed in the Great Limestone series of Chosun goup. It is also clarified that the rock formerly designated as limesilicate rock was meta-liparite. The origin of amphibole pebbles in the Kunjasan formation is of primary and secondary ones; the secondary pebbles were formed by metamorphism of the fragments of limestone or dolomite.

• Economic and Environmental Geology
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• v.31 no.5
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• pp.399-413
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• 1998

Daegang granite is located around the Namwon-gun, Cheolabuk-do, and is an elongate stock $(80 km^{2})$ in the NNE-SSW direction. Daegang granite has the very same mineralogical and geochemical characteristics as those of the typical A-type granites; (1) it is a one feldspar hypersolvus granite, and is classified as an alkali feldspar granite in the lUGS scheme, (2) has small amounts of Fe-rich biotite (annite) and alkali amphibole (ribeckite) that are late in the crystallization sequence of the granitic magma, (3) always contains opaque oxides, fluorite and zircon, (4) shows high and quite homogeneous $SiO_2$, content (mostly 72~77 wt.%) and $(Na_{2}O+K_{2}O)/Al_{2}O_{3}$ ratio (0.90~0.98), (5) contains high Ga, lOOOO*Ga/Ai, $K_{2}O+Na_{2}O$, $(K_{2}O+Na_{2}O)/CaO$, $K_{2}O/MgO$, FeO/MgO, agpaitic index, Zr, Nb, Ce, Y, Zn value or ratio that resemble to those of the Australian A-type granites (Whalen et al., 1987), and (6) has enriched LREE and HREE that show flat variation pattern with slightly depleted in HREE and profound Eu anomalies (Eu/Eu*=0.04~0.l4). In the tectonic discrimination diagrams of Pearce et al. (1984) and Eby (1992), Daegang granite is classified as a within plate granite and $A_{2}-type$.

• Economic and Environmental Geology
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• v.37 no.3
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• pp.347-354
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• 2004

We report the petrographic and petrochemical results on the rocks which have been classified as hornfelsic sandstones or mudstones of the Gyeongsang Group in Wolseong Area, part of Choyang Geologic Sheet (Tateiwa, 1924) and discuss its origin. The rocks consist of alternating layers with dark. fine-grained and bright, coarse-grained but don't have any clues of thermal alteration such as hornfels. The rocks are composed of quartz, feldspar and rock fragments of volcanic origin. The overall geochemical characteristics of the rocks indicate that the rocks have mainly rhyolitic composition with 64.5-72 wt% SiO$_2$ and are similar to the trend of Cretaceous and Tertiary volcanic rocks around this area. On the contrary, the geochemical characteristics of rocks are distinguished from those of Lower Cretaceous Sindong and Mayans mudrocks in the Gyeongsang Basin. We re-name the rocks as rhyolitic tuffite.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.2
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• pp.129-141
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• 2020

The Mogok metamorphic belt is a highland area mainly consisting of Archean crystalline rocks, where many ruby mines were distributed in the past, and jewelry has been identified in its alluvium as placer deposit. Minerals that are usually identified with ruby include spinel, garnet, and rubellite. The conglomerates that form the alluvium in which jewelry is found mainly consist of gneiss and clastic pegmatites. In Singu, Mogok, and Momeik areas, a number of pegmatites containing jewelry are distributed in the intrusions of Mogok metamorphic rocks, diorites, and granites. In Singu pegmatites, rubellite, goshenite, and blue and violet apatite occur as gems. In Momeik pegmatites, mushroom-type rubellite, petalite, hambergite, pollucite, and aquamarine can be found. In Mogok pegmatites, topaz, aquamarine, goshenite, and herderite occur are present.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.4
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• pp.377-389
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• 2020

In this study, pollution characteristics were investigated for the Andong Dam sediments in the Nakdong River. Sediment samples were collected from the middle, left, and right points of the lake up to 40km upstream of the Andong Dam at intervals of about 5km by stratification and turnover period. In the case of nutrients and total organics such as loss of ignition, total nitrogen, and phosphorus, the degree of contamination is low, but heavy metals of arsenic and cadmium is very high. The contamination level of sediments in the dam area is higher than that of the branch of river and the control group, and concentration of chromium, copper, and lead are higher in the stratification period, and that of zinc is higher in turnover period. Arsenic, cadmium, manganese, and zinc showed contamination variation between upstream and downstream but chromium, copper, mercury, iron and lead didn't show the variation.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.4
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• pp.451-462
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• 2020

There are 82 volcanoes active during the 48 weeks of 2019 (January 30 to December 31, 2019; USGS data) Approximately 80~90 volcanoes are active on the Earth for a year. More than 91% of these volcanoes are took place in the circum-Pacific volcanic belt, which is commonly called 'Ring of Fire'. This status coincides with the distribution maps of active volcanoes on the earth: about 80 percent on subduction zone of the convergent plate boundaries; 15 percent on divergent plate boundaries; 5 percent on intra-plate zone. Typically five volcanoes are most active during the survey period (48 weeks); Dukono (Halmahera, Indonesia) 48 times, Aira (Kyushu, Japan) 47 times, Ebeko (Paramushir Island, Russsia) 46 times, Merapi (Central Java, Indonesia) 37 times, Krakatau (Indonesia) 33 times. The comparison of volcanic activity between 2018 and 2019 showed no significant difference. It is assumed that volcanic activity remains stable.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.1
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• pp.83-93
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• 2021

NASA has a plan for the Artemis manned lunar mission in 2020. In 2030s, not only America but also other countries are considering to prepare for human to stay on the Moon at least for a month and necessary technology is currently being developed. With this plan, the mostly considered thing is lunar in-situ resource utilization. The most essential resources could be water and oxygen for sustain human life on the Moon. These resources are not supposed to be brought from the Earth, and it is economically sensible if they are obtained from the lunar surface. Because oxygen can be used as both oxidizer and propellent when a rocket departs from a lunar base directly to Mars, technology for extraction method of oxygen resource and its utilization has been being developed worldwide. This paper introduces oxygen distribution on the Moon and major oxygen extraction methods.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.4
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• pp.255-264
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• 2021

Asian dust (Hwangsa) deposited on the surface of the Korean Peninsula is difficult to recognize their existence in mountainous terrain undergoing active erosion and weathering. This study examined Asian dust sediments mixed in soils by analysing clay mineralogy, mineral composition, and microtextures of fine silt (< 20 ㎛) in the alkali feldspar granite area of Seoraksan. The fine silt was composed of detrital particles derived from bedrocks, Asian dust sediments, and their weathering products. Clay minerals of 2:1 structural type, chlorite, amphibole, epidote, and Ca-bearing plagioclase were identified as eolian mineral particles. During the weathering of the bedrock composed of quartz and alkali feldspars, albite was partially weathered to produce small amounts of gibbsite and kaolin minerals. Hydroxy-Al interlayered clay minerals were formed by the exchange and fixation of polynuclear Al cationic species into the interlayers of expandable 2:1 clay minerals dominated by illite-smectite series clay minerals. Contribution of Asian dust to the fine silt of soils was estimated around 70% on the basis of total contents of 2:1 phyllosilicates.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.4
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• pp.397-407
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• 2022

Mineralogical analysis of the bedrock of the Gobi Desert in southern Mongolia, the source of Asian dust, was conducted to trace the geological origin of the constituent minerals of Asian dust. The bedrock of the source of Asian dust consists of Paleozoic volcanics and volcaniclastic sedimentary rocks, Paleozoic granitic rocks, and Mesozoic sedimentary rocks. Paleozoic volcanics and volcaniclastic sediments lithified compactly, underwent greenschist metamorphism, and deformed to form mountain ranges. Mesozoic sedimentary rocks fill the basin between the mountain ranges of Paleozoic strata. In comparison to Paleozoic volcanic and sedimentary rocks, Mesozoic sedimentary rocks have lower contents of chlorite and plagioclase, but high contents of clay minerals including interstratified illite-smectite, smectite, and kaolinite. Paleozoic granites characteristically contain amphibole and biotite. Compared with the mineral composition of bedrock in source, Asian dust is a mixture of detrital particles originating from Paleozoic and Mesozoic bedrocks. However, the mineral composition of Mesozoic sedimentary rocks is closer to that of Asian dust. Less lithified Mesozoic sedimentary rocks easily disintegrated to form silty soils which are deflated to form Asian dust.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.3
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• pp.299-311
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• 2022

Rocks exposed to the surface are subject to long-term weathering, and such effects weaken their engineering stability. Especially as weathering progresses, the surface of rocks will be changed by weathering, and such surface changes will affect the engineering safety of the rock mass. In addition, the chemical species produced in the weathered rock have a direct effect on the surrounding environment or on the structure. In areas where rocks are exposed, such as mining areas, chemical species produced by weathering can have a serious impact on the surrounding natural environment. In this study, accelerated weathering experiments using freeze/thaw system were conducted on rocks that had already been weathered and fresh rocks, and surface changes of each rock were observed with confocal laser scanning microscope (CLSM), and chemical species were analyzed using IC/ICP-MS. As the weathering progressed, the surface roughness decreased, and the amount of chemical species produced increased. The results of this study can be used as basic data for evaluating engineering/environmental safety in areas where rocks are exposed.