• 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.

• Economic and Environmental Geology
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• v.32 no.1
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• pp.33-41
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• 1999

A new sedimentary basin is reported from the marine multi-channel seismic data which were acquired for the hydrocarbon exploration on the southwestern Korean continental shelf in 1970. Along the southeastern part of Line 1192, the about 60-km-long basin with the thickness of 0.55~1.1 s is observed on the near-trace gather. However, both new and previous 24-fold stack sections fail to show the basin image probably due to its rugged top beneath the shallow water. The boundary contact between the basement with the velocity of about 5200m/s and the basin filling with the velocities of 4300~4700 m/s is unclear. These velocites are calculated from the corresponding shot gathers. Compared with the Haenam Basin, a neighbouring onshore Cretaceous sedimentary basin, we interpret that the new basin includes the volcanics and volcaniclastic sequences deposited in the lacustrine environment. This nonmarine basin was possibly formed as the result of the tectonic movement during the Cretaceous, implying the wide occurrence of the Cretaceous basins over the southern Korean Peninsula as well as its southwestern continental shelf.

• Economic and Environmental Geology
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• v.33 no.3
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• pp.217-228
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• 2000

We use spectral correlation method to analyze gravity and magnetic anomalies of Euiseong Sub-basin for distribution of rock facies and gelogic structures. The analysis reveals distinct polarity between gravity and magnetic anomaly correlation ; intermediate to mafic intrusives, extrusives, and the Tertiary basin shows positive gravity (+G) and positive magnetic (+M) correlation. Granitic gneiss and felsic volcanics negative gravity 9-G) and negative magnetic (-M) correlation. The Palgongsan granite, felsic to mafic extrusives and Mesozoic granites are characterized by -G and + M correlation. +G and -M correlations in the sedimentary formations are interpreted by uplift of pre-Cretaceous basement rocks . The + G and + M correlation characteristics in northeastern part of Euiseong Sub-basin including the Tertiary sedimentary basin result from the uplift of crustal materials. Major axes of spectrally correlated amomalies have mostly NW-SE or NE-SW directions. The former is due to the intrusives along strike-slip faults, and the latter which is observed in sedimentary formations is related to geological structures of basement associated new insight into the boundary between Euiseong and Milyang Sub-basin.

• Economic and Environmental Geology
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• v.21 no.2
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• pp.139-148
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• 1988

The altered volcanic rocks, ranging from tuffaceous to andesitic rocks are widely distributed around the "caldera" area in the southeastern part of Kyeongsang province. The volcanic activity and tectonic movement are assumed to be followed by the hydrothermal activities in the area. From the mineral assemblage the type of alteration can be divided into two types; propylitic and argillic. The average concentration of gold in hydrothermally altered rocks is somewhat lower (about 20 ppb) than that of fresh rocks (45-25 ppb), but for Ag, vice versa. During the hydrothermal process, the concentration of the trace elements Ag, Hg, Co, As, Hf, Sc, Si, Al increased, and that of Na, Rb, K, Au, Mg, Ca etc. decreased. The high anomalous contents of silver for altered rocks range from 4-7 ppm and 1-3 ppm for relatively fresh rocks.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.254-256
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• 2003

A total of one hundred and twenty three goldbearing mineral deposits in the Charters Towers area west of Townswille, Queensland, Australia were initially classified into four named and unnamed separate vein styles, with different trends and alteration patterns, a breccia-style deposit and placer gold deposits. The area has vein deposits in Ordovician and Silurian granitoids and breccia-style in the Carboniferous volcanics. In this paper a modeling of these deposits is described using geological mapping, landscape analysis and digital imagery (Landsat TM and geophysics) to improve the classification and identification of possible new target for exploration.

• Geophysics and Geophysical Exploration
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• v.1 no.2
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• pp.101-109
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• 1998

Using airborne magnetic data, magnetic characteristics were studied at the Samryangjin caldera area developed in the volcanics of the Yuchon sub-basin, the south eastern part of the Gyeongsang basin. Residual magnetics, reduction to the pole, horizontal derivative, and vertical derivative maps are prepared. Using these maps, the magnetic lithofaces are zoned and the geological structures such as caldera and faults were qualitatively interpreted. In addition, the two quantitative interpretations were performed. Firstly, the forward modelling were done to the 14.5 line km crossing the caldera area to the northeast-southwest direction. Applying the 3-D Euler deconvolution method to the whole study area, the depth extent and the characteristics of the magnetic anomalous bodies were studied. According to the results, the magnetic lithofaces of the area are zoned by 4 units. In general, these are well matched with the geological distributions. But the biotite granites intruded in the northern boundary of the Samryangjin caldera show the high magnetic intensity, while the biotite granites of the other areas show the low magnetic intensity and the different magnetic lithofaces. Thus, we interpreted that the biotite granites are closely related with the volcanic activity of the Samryngjin caldera, and are intruded in the fracture zones developed along the caldera rim. The Samryangjin caldera and fault structures of the area can be easily recognized by the distinct magnetic structures from the various magnetic anomaly maps. Also the topographic characteristics well reflect these structures. The results of the forward modelling show that the magnetic basement depth of the Gyeongsang sedimentary basin is on the average about 6 km and in maximum 10 km. And the depth becomes shallower toward the caldera boundary due to the shallow intrusion of the volcanics. The results of the 3-D Euler method also show the caldera and fault structures. And the relatively shallow magnetic anomalous bodies which are related with the volcanics are generally developed to the east-west and northeast directions, while the deep magnetic anomalous bodies to the northwest direction.

• Journal of the Mineralogical Society of Korea
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• v.27 no.2
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• pp.63-72
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• 2014

This study is conducted to investigate mineralogical characteristics and estimate firing temperature and condition of earthenwares in the 5-6th Century which are found at ancient tombs in Gyo-dong, Gyo-ri, Changnyeong-eup, Changnyeong-gun, Gyeongsangnam-do, TKorea by applying petrological methods. For this study, mineralogical analysis, microtexture observation and chemical analysis were conducted. According to observations using a polarization microscope, the potshreds are mainly composed of quartz and feldspar and consist of some felsic volcanics, tempers, opaques and mullite, hematite and spinel were found under XRD and FTIR analysis. The flow pastes are observed in many potshreds, and it indicate that this textures made by the mixing process or the pottery made from the mixture of 2 sorts of clays at least. They dose not show the features of the potshreds firing under temperature of $1,200-1,300^{\circ}C$ rather than the earthenware firing under relatively low temperature of $1,000^{\circ}C$ approximately because of the existence of a number of pores and the crystals of the specific minerals. The growths mostly of mullite on the surface and into the cracks of the potshreds indicate that the firing condition was not uniform to make even temperature and oxidation. Most of the pottery shreds have felsic volcanic fragments and some of them have cristobalite which is formed at the temperature of more than 1,470^{\circ}C$. But considering the estimated firing temperature, these are not formed during firing but included in the original clay.

• Economic and Environmental Geology
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• v.30 no.6
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• pp.603-612
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• 1997

Cretaceous sedimentary-volcanoclastic formations of the Kyeongsang Supergroup were intruded by granitic rocks in the late Cretaceous and early Tertiary. In the Euiseong and Shinryeong area, these intrusives have various compositions including gabbro, diorite，biotite granite and feldspar porphyry. Associated volcanic rocks consist of two chemically distinct types: the bimodal suite of basalt and rhyolite in the Keumseongsan caldera, and the felsic suite of andesite and rhyolite in the Sunamsan-Hwasan calderas. Most rocks are subalkaline, and follow a typical differentiation path of the calc-alkaline magma. The granitic rocks can be distinguished chemically from the volcanics by high Zr/Y ratios. Differences in Zr/Y and K/Y ratios between the two volcanic suites can be accounted for by mantle source and fractionation. Chondrite-normalized trace element abundances of granitic rocks are depleted in Th and K, whereas those of the Keumseongsan rhyolites are depleted in Sr and Ti. Rb, La and Ce is enriched in rhyolites of the Sunamsan-Hwasan calderas. $Rb-SiO_2$ and Rb-Y+Nb discrimination diagrams suggest that the intrusives and volcanics have a volcanic arc setting. K-Ar ages indicate four plutonic episodes : diorite (89 Ma), granite (66~62 Ma), granite and porphyry (55~52 Ma) and gabbro (52~45 Ma), and two volcanisms : bimodal basaltic and rhyolitic volcanism (71~66 Ma) in the Keumseongsan caldera, and felsic andesitic and rhyolitic volcanism (61~54 Ma) in the Sunamsan-Hwasan calderas. Geochemical and age data thus suggest that the igneous rocks are related to several geologic episodes during the late Cretaceous to early Tertiary.

• Economic and Environmental Geology
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• v.46 no.5
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• pp.411-424
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• 2013

Assessment and damage reduction strategy of acidic rock drainage were conducted in a section of ${\bigcirc}{\bigcirc}$ highway construction site. The geology of the studied section consists of Icheonri sandstone and intermediate to acidic volcanic rocks. Sulfides occur as a disseminated type in sandstone and volcanics which were altered by the hydrothermal solution of granite intrusion. Volcanics and sandstone with a high content of sulfide were classified as a potentially acid rock drainage(ARD) forming rock. The drainage originated from those rocks may acidify and contaminate the surrounding area during the highway construction. Therefore, the drainage should be treated before it is discharged. A slope landslide hazard due to the ARD was also expected and the coating technology was recommended for the reduction of ARD generation as a preemptive measure before reinforcement work for enhancing slope stability such as shotcrete and anchor. According to the ARD risk analysis, those rocks should not be used as cement aggregate, but only to be used as a bank fill material of a filling-up system that allows minimal contact with rainfall and groundwater.

• The Journal of the Petrological Society of Korea
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• v.18 no.2
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• pp.137-151
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• 2009

Synthetic analyses of field data, including rock facies, contact relationships, petrography, structural elements, and etc., and previous geochemical and absolute age data of the Tertiary Churyeong Breccia and its surrounding volcanics in the Gyeongju city, Korea, have led to the following results. (1) The Tertiary rocks are divided into the dacitic tuffs, Churyeong Breccia, and andesitic rocks in ascending order. The dacitic tuffs are unconformably overlain by the Churyeong Breccia which is intruded by or conformably overlain by the andesitic rocks. (2) The dacitic tuffs are correlated with the Paleocene${\sim}$Eocene Wangsan dacitic volcanics, while the Churyeong Breccia and andesitic rocks are correlated with the early Early Miocene Andongri Formation and Yongdongri Tuffs in the Waeup Basin, respectively. (3) The Churyeong Breccia accumulated rapidly in the NE-trending graben about 1.5 km in width during the crustal extension in the NW-SE direction due to the East Sea opening. (4) Dacitic${\sim}$andesitic volcanism and crustal extension were active during the early Early Miocene times in SE Korean peninsula. During the deposition the Churyeong Breccia, especially, the volcanism ceased for some time, but the active normal faulting led to the formation of grabens in places.