• Economic and Environmental Geology
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• v.51 no.4
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• pp.309-322
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• 2018

Naturally occurring asbestos (NOA) occurs in rocks and soils as a result of natural weathering and human activities. It is proved that inhalation of asbestos fibers can lead to increase risk of developing several diseases such as lung cancer and malignant mesothelioma. The parent rocks of asbestos have been mainly associated with (ultra)mafic and carbonate rock. The previous studies on NOA were mainly limited to (ultra)mafic rock-hosted asbestos, but studies on carbonate rock-hosted asbestos are relatively rare in S. Korea. Therefore, this study was aimed to examine mineralogical characteristics of carbonate rock-hosted NOA at three sites including Muju and Jangsu, Jeonbuk province and Asan, Chungnam province. Types of rocks at the three sites mainly consisted of Precambrian metasedimentary rocks, carbonate rock, and Cretaceous and Jurassic granites. Asbestos-containing carbonate rock samples were obtained for mineralogical characterization. XRD, PLM, EPMA, SEM and EDS analyses were used to characterize mineralogical characteristics of the carbonate rock-hosted NOA. From the carbonate rock, fibrous minerals were occurred acicular and columnar forms in the three sites. Fibrous minerals were composed of mainly tremolite and associated minerals included possibly asbestos containing materials (ACM) such as talc, vermiculite, and sepiolite. The length and aspect ratios of tremolite were similar to the standard asbestiform (length >$5{\mu}m$, length:width = 3:1). These results indicate that both non-asbestiform and asbestiform tremolite with acicular forms occurred in carbonate rocks at three sites. Geological and geochemical characteristics and mineral assemblages indicate tremolite and associated minerals might be formed by hydrothermal alternation and/or hydrothermal veins of carbonate rocks due to intrusion of acidic igneous rocks.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.402-404
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• 2005

2004년 7월부터 2005년 2월까지 8개월 동안 강원도 정선지역 탄산염지대 지하수 및 하천수의 ${\delta}^{13}C$의 조사 결과, 탄산염 지대 지하수의 13C는 $-12.07{\sim}-8.63$ (평균 -10.34 ), 탄사염지대 하천수의 ${\delta}^{13}C$는 $-10.32{\sim}-6.80$ (평균 -7.944 ) 이었다. 하천수와 지하수 ${\delta}^{13}C$는 수온(T)과 음의 상관관계를 보이고 물의 전기전도도(EC)와 양의 상관관계를 보이며, 여름보다 겨울에 높은 값을 보이는 반면 산화환원 전위(Eh), 용존산소(DO), pH와는 상관관계가 미약함을 보이고 있다. 탄산염지대 지하수 및 하천수의 ${\delta}^{13}C$는 연구지역의 지하수와 하천수가 탄산염암의 용해, 대기 $CO_2$와 용존 $CO_2$의 교환, 유입된 대기 $CO_2$가 물 분자와 반응하여 ${HCO_3}^-$ 이온으로 전환될 때 있는 분별작용의 효과에 의해 주로 영향을 받았으며 수중생물의 신진대사에 의한 변화는 미미한 것으로 나타났다.

• 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.

• Economic and Environmental Geology
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• v.49 no.5
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• pp.335-347
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• 2016

The mineralogical and geochemical characteristics of diverse carbonate rocks can be investigated by using VNIRSWIR(visible near infrared-short wavelength infrared) spectroscopic analysis as a rapid, nondestructive, and inexpensive tool. Comparing whole rock analysis to VNIR-SWIR spectroscopic analysis, the analytical method was investigated to estimate CaO contents, mud impurity, and whiteness of carbonate rocks involved in high-grade limestones in the field. We classify typical carbonate rocks in the upper Pungchon Formation in high-grade limestone mine area such as the Gangweon, Chungmu and Baegun mine in the Jeongseon area. The results show that powdered specimen has much higher reflectance than cutted specimen between the same sample. Whiteness is highly correlated with reflectance(0.99) for powdered specimen. The absorption of mineral mixtures shifts in position as a result of the mass ratio of calcite and dolomite in the Chungmu mine by changing to 75:25, 50:50, and 25:75. The absorption peak position in carbonate mixtures is highly correlated with CaO contents(0.98~0.99). Based on color system, the carbonate rocks are grouped into (milky) white, light grey, light brown, grey, and dark grey. The absorption peak position shifts from 2340 nm to 2320 nm as CaO contents decrease from 55.86 wt.% to 29.71 wt.%. We confirmed that absorption peak position shifts depending on the amount of Ca, which is bonded to $CO{_3}^{-2}$, Mg, and Fe contents replacing Ca. This result suggests that CaO contents in carbonate rocks can be considered to quantitative analysis in the field by spectroscopic analysis.

• Economic and Environmental Geology
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• v.47 no.5
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• pp.467-477
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• 2014

Naturally occurring asbestos (NOA) occurs in rocks and soils as a result of natural weathering and human activities. The asbestos have been associated with ultramafic and mafic rocks, and carbonate rock. The previous studies on NOA were mainly limited to ultramafic and mafic rock-hosted asbestos in Korea. But, studies on carbonatehosted asbestos are relatively rare. Therefore, the purposes of this study were to investigate mineralogical characteristics of carbonate-hosted and metapelite-hosted NOA and to examine genesis of NOA occurred in the both rocks. The study area was Daerori, Seosan, Chungnam Province, Korea. The major rock formation consisted of limestone and schist which have been known to contain asbestos. Sampling was performed at outcrop which contained carbonate rock showing acicular asbestos crystals as well as pegmatitic intrusion that contacted with carbonate rock. PLM, XRD, EPMA, and EDS analyses were used to characterize mineral assemblages, mineralogical characteristics, and crystal habits of amphiboles and other minerals. BSEM images were also used to examine the genesis of asbestos minerals. The amphibole group was observed in all of the carbonate rocks, and actinolite and tremolite were identified in all rocks. These mineral habits were mainly micro-acicular crystals or secondary asbestiform minerals on the surface of non-asbestiform minerals appearing split end of columnar crystals produced by weathering. BSEM images showed residual textures of samples. The residual textures of carbonate rocks showed dolomite-tremolite-diopside mineral assemblages that formed during prograde metasomatism stage. Some carbonate rock also showed diopside-tremolite-talc mineral assemblages which were formed during retrograde metasomatism stage, as the residual textures. In result the presence of asbestos actinolite-tremolite in the carbonate rocks were confirmed in the areas where actinolite-tremolite asbestos was influenced by low temperature hydrothermal solution during metasomatism stage. These asbestos minerals showed the acicular asbestiform minerals, but even non-asbestiform minerals, a bundle or columnar shape, could transform to asbestiform minerals as potential NOA by weathering because the end of columnar shape of non-asbestiform minerals appeared as multiple acicular shaped fibers.

• The Journal of the Petrological Society of Korea
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• v.12 no.3
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• pp.135-153
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• 2003

In order to understand its origin and petrogenesis, petrochemical studies of major, trace elements, REE, and stable isotopes of oxygen and carbon from the Hongcheon Fe-REE deposits have been investigated. The Hongcheon Fe-REE deposit intruding into Precambrian metasedimentary rocks consists of magnetite, various carbonates such as ankerite, siderite, magnesite and strontianite, monazite, aegirine-augite, Na-amphibole, and sulfides. Compared with major elements abundances of typical ferro-carbonatites, the Hongcheon Fe-REE deposit is enriched in FeO and depleted in CaO with increasing of $SiO_2$, where $TiO_2$and $A1_2O_3$increased and CaO, FeO, MgO and $P_2O_5$ are slightly decreased, but those are rather scattered and their trends are somewhat ambiguous. V Ni, U and Rb slightly increasing with of $SiO_2$increase and scattering or no trends of other detected elements. Nb, Zr and Zn are depleted then the abundances of typical ferro-carbonatites (Woolley and Kempe, 1989). In rare earth elements a large enrichment of total REE (maximum 14.8 wt%) and LREE relative to chondrites and HREE depleted more then the values of ferro-carbontites therefore La/Lu ratios shows large abundances (max. 16,197). The results of stable isotopes of O and C from minerals of ankerite and strontianite and whole rocks represent studied rocks are from igneous carbonatitic melts. Although petrochemical characteristics of the Hongcheon Fe-REE deposits are somewhat different from normal ferro-carbonatites from the world, this discrepancy suggests another conclusion that petrochemical characteristic of the studied Fe-REE mineralized rocks are similar to those of phoscorites from Kovdor, Russia and Sokli, Finland showing the same petrochemical compositions described above.

• Economic and Environmental Geology
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• v.43 no.2
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• pp.85-100
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• 2010

Devonian Cairn Formation is one of the important hydrocarbon reservoirs in Alberta, Canada. However, the Cairn Formation, outcropped in the study area, is not prospective reservoir with poor porosity and permeability by some late diagenetic processes. In this study, geochemical characteristics of the Cairn Formation were studied to use these preliminary results for advanced geological and geophysical petroleum explorations in the near future. Rock-Eval pyrolysis showed that total organic carbon content is less than 0.3 wt.%, indicating a minor amount of bitumen and/or other hydrocarbons. The carbonates in the Cairn Formation are mainly composed of subhedral and anhedral dolomites. Pore sizes in the carbonate are various, ranging from nanometer to micrometer. Clastic sediments increase in the upper and lower parts of the Cairn Formation, probably due to changing its depositional conditions. The Cairn Formation can also be divided into several intervals based on Ca/Mg ratio in dolomite and degree of amount of calcite. These could be formed by different sedimentary environment, degree of cementation and recrystallization, different saline/fresh water, etc.

• The Journal of Engineering Geology
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• v.21 no.1
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• pp.79-85
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• 2011

We investigated the flow properties of groundwater in areas of carbonate rocks at Yeongwol and Jeongseon, Gangwon Province, based on measurements of hydraulic conductivity. Existing hydraulic conductivity data were compiled from 46 wells in the study area. These wells were sunk close to Golji stream and the Joyang and Dong rivers, which flow through the study area. The hydraulic conductivities range from 0.004 to 1.1 m/day, and show a gradually decreasing trend with decreasing well depth (y=-0.003x - 0.927, $r^2$=0.129). The study area was classified into zone A (< 0.1 m/day), zone B (0.1-1.0 m/day), and zone C (> 1 m/day) according to hydraulic conductivity. Zones A, B, and C make up 87% (n = 40), 11 % (n = 5), and 2% (n = 2) of the surface of the study area, respectively. Among the three zones, zone A contains few fractures whereas zone C contains many fractures. These results indicate that groundwater flow in carbonate regions is strongly influenced by the fracture network.

• Economic and Environmental Geology
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• v.47 no.4
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• pp.381-393
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• 2014

Seismic reflection data are integrated with fieldwork data in order to understand startigraphy, structural geology and hydrocarbon potentials of Cretaceous strata in the Mesopotamian basin, Northeastern Iraq. Cretaceous strata in the basin divided into the Qamchuqa, Kometan, Bekhme and Shiranish formations, which are composed of carbonates deposited in shallow marine environment. The geological structures in these formations are mainly recognized as thrusts, detachment folds, fault propagation folds and fault bend folds. As well, NW-SE trending fractures are regularly developed, and are horizontal or perpendicular to the structures. The distribution and frequency of fractures are related to the development of the thrusts. In terms of hydrocarbon potentials, Cretaceous strata in the basin have limited capacities for source rocks and seal rocks due to the lack of organic carbon content and the well-developed fractures, respectively. Although these carbonates have limited primary porosity, however, development of the secondary porosity derived from the fractures contributes to enhance the reservoir quality. Most important factor for the reservoir quality of Cretaceous strata seems to be the frequency and connectivity of fractures relative to locations of folds and faults. The results delineated in this study will use as reference for recognizing stratigraphy and structures of Cretaceous strata and will provide useful information on hydrocarbon potentials of Cretaceous strata in the Mesopotamian basin, NE Iraq.

• Economic and Environmental Geology
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• v.52 no.1
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• pp.107-118
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• 2019

Two assertions about the process the formation of the high-purity limestone in the Taebaeksan Basin, categorized into syngenetic and epigenetic origin, are verified on the basis of its oxygen-carbon stable isotopic characteristics. The carbonate rocks sampled from the selective six high-purity limestone mines and several outcrops in the Daegi formation are featured by various colors such as the gray, light gray and dark gray. They show a wide range of oxygen stable isotope ratios (4.5 ~ 21.6 ‰), but a narrow range of carbon stable isotope ratios (-1.1 ~ 0.8 ‰, except for vein calcite), which means that they had not experienced strong hydrothermal alteration. In addition, there is no difference in the range of the oxygen stable isotope ratios by mine and color, and it is similar to the range from surrounding outcrop samples. These results indicate that the effect of the hydrothermal alteration were negligible in the generation of high-purity limestone in deposit scale. Whereas, the carbonate rocks can be divided texturally into two groups on the basis of an oxygen isotope ratio; the massive-textured or well-layered samples (>15 ‰), and the layer-disturbed (or layer-destructed) and showing over two colors in one sample (<15 ‰). In the multi-colored samples, the bright parts are characterized by the very low oxygen stable isotope ratios, compared to the dark parts, implying the increase in brightness of the carbonate rocks could be induced by the interaction between hydrothermal fluid and rock. However, these can be applied in a small scale such as one sample and are not suitable for interpretation of the generation of high-purity limestone as a deposit scale. In particular, the high oxygen isotope ratios from the recrystallized white limestone suggest that hydrothermal fluids are also rarely involved during recrystallization process. In addition, the occurrences of the high-purity limestone orebody strongly support the high-purity limestone in the area are syngenetic rather than epigenetic; the high-purity limestone layers in the area show continuous and almost horizontal shapes, and is intercalated between dolomite layers. Consequently, the overall reinterpretation based on the sequential stratigraphy over the Taebaeksan basin would play an important role to find additional reserves of the high-purity limestone.