• Economic and Environmental Geology
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• v.38 no.2 s.171
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• pp.113-127
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• 2005

Cretaceous intrusive and extrusive rocks are widely distributed in the southwestern part of the Korean peninsula, possibly the result of intensive magmatism which occurred in response to subduction of the western proto-Pacific plate beneath the north-eastern part of the Eurasian plate. Geochemical and petrological study on the Cretaceous granitic rocks were carried out in order to constrain the petrogenesis of the granitic magma and to establish the paleotectonic environment of the area. Whole rock chemical data of the granitic rocks from the study area indicate that the all the rocks have characteristics of calc-alkaline series in the subalkaline field. The overall geochemical features show systematic variations in each granitic body, but the source materials of each granitic body are thought to have been different in their chemical composition. Higher values of $Fe_2O_3/FeO$ of the granitic rocks in the western area suggest that the granitoids had been solidified under highly oxidizing environment. The granitic bodies in the eastern area also show higher contents of Li, Ni, Co, Sr, Cr, Sc and lower Rb and Nb compared to the those of the western area. Chondrite normalized REE patterns show generally enriched LREE and strong negative Eu anomalies in the western wet while slight to flat Eu anomalies in the east-ern area. The REE and $(La/Lu)_{CN}$ of the granites are $60{\~}499ppm$ and $8.9{\~}66$ correspond to the range of the continental margin granite. On the ANK vs. ACNK and tectonic discrimination diagrams, parental magma type of the granites corresponds to I-type, VAG and syn-collision granite. Interpretations of the chemical characteristics of the granitic rocks favor their emplacement in a compressional tectonic regime at continental margin during the subduction of proto-Pacific plate.

• Journal of the Korean earth science society
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• v.30 no.4
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• pp.427-443
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• 2009

Cretaceous intrusive and extrusive rocks in the southwestern part of the Yeongnam Massif are possibly the result of intensive magmatism which occurred in response to subduction of the Pacific plate beneath the northeast portion of the Eurasian plate. Geochemical and petrological study on the granitic rocks were carried out in order to constrain the petrogenesis of the granitic magma and to establish the paleotectonic environment of the area. Whole rock chemical data of the granitic rocks from the study area indicate that all the rocks have characteristics of calc-alkaline series in the subalkaline field. The overall geochemical features show systematic variations in each granitic body, but the source materials of each granitic body are thought to have been different in their chemical composition. The granodiorites distributed around Donggyori in the Bognae area (DGd) are different from other granitic rocks within the study area in the contents and differentiation trends of $Al_2O_3$ and MgO as well as in the contents of the trace elements such as Ba, Sr, Pb, Ni, Cr and Y DGd have geochemical features similar to slab-derived adakites such as high $Al_2O_3$, Sr contents and high Sr/Y, La/Yb ratios, but low Y and Yb contents. The major and trace element contents of the DGd fall well within the adakitic field, whereas other Cretaceous granites in the study area are plotted in the island arc ADR area in Sr/Y vs. Y diagram. On the ANK vs. A/CNK and tectonic discrimination diagrams, parental magma type of the granites corresponds to I-type and volcanic arc granite (VAG). Interpretations of the chemical characteristics of the granitic rocks favor their emplacement in a compressional tectonic regime at continental margin during the subduction of Pacific plate. The geochemical and tectonic features reveal that adakite-like signatures of the DGd were generated by the interaction of mantle peridotite and subducted slab-derived adakitic melts (caused by the thermal effect of ridge subduction), and which slightly modified by crustal contamination during emplacement.

• Journal of The Geomorphological Association of Korea
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• v.20 no.4
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• pp.15-28
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• 2013

This paper was made on the basis of geotourism to explain morphological characteristics of Patagonia and Atacama region in the Andes through 10-day fieldwork. The Patagonian landscape was focused on the Torres del Paine National Park, Chile and the Los Glacier National Park, Argentina; on the other hand, the Atacama morphological landscape was investigated around the San Pedro de Atacama. Many geomorphological features such as uplift, semiarid and glacier landscapes can be found in Patagonia, so it is strongly recommended to have an opportunity to enjoy these landforms by geotourism. Massive intrusive rock bodies of granite can be shown in those two National Parks declared a Biosphere Reserve by UNESCO. And, the Atacama Desert located on the forearc depression in the Andes, Chile has also many geomorphological destinations of arid and volcanic landforms; badland, pediplain, pediment, salt lake and geyser. Especially, huge pediplain is one of the greatest view points in the Atacama Desert. Patagonia and Atacama are the best geographical tourism sites to know diverse tectonic landforms made by the conflict between South American and Pacific plates.

• The Journal of the Petrological Society of Korea
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• v.23 no.3
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• pp.167-185
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• 2014

SHRIMP zircon U-Pb ages and major element and Sr-Nd isotopic compositions were determined for drill cores (374-3390 m in depth) recovered from three boreholes in the Pohonag basin, southeastern Korea. Shallow-seated volcanic rocks and underlain plutonic rocks were geochemically classified as rhyolite and gabbro-granite, respectively. They showed high-K calc-alkaline trends on the $K_2O-SiO_2$ and AFM diagrams. Zircons from volcanic rocks of borehole PB-1 yielded concordia ages of $66.84{\pm}0.66Ma$ (n=12, MSWD=0.02) and $66.52{\pm}0.55Ma$ (n=12, MSWD=0.46). Zircons from volcanic rocks of borehole PB-2 gave a concordia age of $71.34{\pm}0.85Ma$ (n=11, MSWD=0.79) and a weighted mean $^{206}Pb/^{238}U$ ages of $49.40{\pm}0.37Ma$ (n=11, MSWD=1.9). On the other hand, zircons from plutonic rocks of borehole PB-3 yielded weighted mean $^{206}Pb/^{238}U$ ages of $262.4{\pm}3.6Ma$ (n=21, MSWD=4.5), $252.4{\pm}3.6Ma$ (n=8, MSWD=1.9) and $261.8{\pm}1.5Ma$ (n=31, MSWD=1.3). Detrital zircons from the sedimentary strata overlain the volcanic rocks showed a wide age span from Neoproterozoic to Cenozoic, with the youngest population corresponding to $21.89{\pm}1.1Ma$ (n=15, MSWD=0.04) and $21.68{\pm}1.2Ma$ (n=10, MSWD=19). These dating results indicate that the basement of the Pohang basin is composed of Late Permian plutonic rocks and overlain Late Cretaceous to Eocene volcanic sequences. Miocene sediments were deposited in the uppermost part of the basin, possibly associated with the opening of the East Sea. The Sr-Nd isotopic compositions of the Permian plutonic rocks were comparable with those reported from Permian-Triassic granitoids in the Yeongdeok area, northern Gyeongsang basin. They may have been recycled into parts of the Cretaceous-Paleogene magmatic rocks within the Gyeongsang basin.

• The Journal of the Petrological Society of Korea
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• v.26 no.3
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• pp.235-254
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• 2017

We investigate the geological history that formed geology and landscapes of the Juwangsan National Park and its surrounding areas. The Juwangsan area is composed of Precambrian gneisses, Paleozoic metasedimentary rocks, Permian to Triassic plutonic rocks, Early Mesozoic sedimentary rocks, Late Mesozoic plutonic and volcanic rocks, Cenozoic Tertiary rhyolites and Quaternary taluses. The Precambrian gneisses and Paleozoic metasedimentary rocks of the Ryeongnam massif occurs as xenolithes and roof-pendents in the Permian to Triassic Yeongdeok and Cheongsong plutonic rocks, which were formed as the Songrim orogeny by magmatic intrusions occurring in a subduction environment under the northeastern and western parts of the area before a continental collision between Sino-Korean and South China lands. The Cheongsong plutonic rocks were intruded by the Late Triassic granodiorite, which include to be metamorphosed as an orthogneiss. The granodiorite includes geosites of orbicular structure and mineral spring. During the Cretaceous, the Gyeongsang Basin and Gyeongsang arc were formed by a subduction of the Izanagi plate below East Asia continent in the southeastern Korean Peninsula. The Gyeongsang Basin was developed to separate into Yeongyang and Cheongsong subbasins, in which deposited Dongwach/Hupyeongdong Formation, Gasongdong/Jeomgok Formation, and Dogyedong/Sagok Formation in turn. There was intercalated by the Daejeonsa Basalt in the upper part of Dogyedong Formation in Juwangsan entrance. During the Late Cretaceous 75~77 Ma, the Bunam granitoid stock, which consists of various lithofacies in southwestern part, was made by a plutonism that was mixing to have an injection of mafic magma into felsic magma. During the latest Cretaceous, the volcanic rocks were made by several volcanisms from ubiquitous andesitic and rhyolitic magmas, and stratigraphically consist of Ipbong Andesite derived from Dalsan, Jipum Volcanics from Jipum, Naeyeonsan Tuff from Cheongha, Juwangsan Tuff from Dalsan, Neogudong Formation and Muposan Tuff. Especially the Juwangsan Tuff includes many beautiful cliffs, cayon, caves and falls because of vertical columnar joints by cooling in the dense welding zone. During the Cenozoic Tertiary, rhyolite intrusions formed lacolith, stocks and dykes in many sites. Especially many rhyolite dykes make a radial Cheongsong dyke swarm, of which spherulitic rhyolite dykes have various floral patterns. During the Quaternary, some taluses have been developed down the cliffs of Jungtaesan lacolith and Muposan Tuff.

• Journal of Conservation Science
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• v.24
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• pp.23-36
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• 2008

The stone Buddhas and Shrine of Unjusa temple (Korea Treasure No. 797) in Hwasun formed in Koryo Dynasty are unique style which the Buddha faces each other the back parts of south and north within the stone Shrine. The stone Buddhas and Shrine are highly evaluated in historical, artistic and academic respects. But, the stone properties have been exposed in the open system various aspects of degradations weathered for a long time without specific protective facilities. The rock materials of the stone Buddhas and Shrine are about 47 blocks, and total press load is about 56.6 metric ton. The host rocks composed mainly of white grey hyaline lithic tuff and rhyolitic tuff breccia. In addition, biotite granite used as part during the restoration works. The chemical index of alteration for host tuffaceous rocks and the replacement granites range from 52.1 to 59.4 and 50.0 to 51.0, respectively. Weathering types for the stone Buddhas and Shrine were largely divided with physical, chemical and biological weathering to make a synthetic deterioration map according to aspects of damage, and estimate share as compared with surface area. Whole deterioration degrees are represented that physical weathering appeared exfoliation. Chemical weathering is black coloration and biological weathering of grey lichen, which show each lighly deterioration degrees. According to deterioration degree by direction of stone Buddhas and Shrine, physical weathering mostly appeared by 39.1% on the sorthern part, and chemical weathering is 61.2% high share on the western part. Biological weathering showed 38.3% the largest distribution on the southern part. Therefore, it is necessary to try hardening for the parts with serious cracks or exfoliations, remove secondary contaminants and organisms through regular cleaning. Also necessary to make a plan to remove moisture of the ground which causes weathering, and estimate that need established and scientific processing through clinical demonstration of conservation plan that chooses suitable treatment.