• Economic and Environmental Geology
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• v.18 no.2
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• pp.107-124
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• 1985

More than fifty copper veins are emplaced around late Cretaceous granitoid stock in Haman-Gunbuk district, southernmost part of Korea. These veins cut both late Cretaceous granitoids and hornfels of Jindong formation which is intruded by the granitoids. The paragenesis of veins is nearly the same, consisting of (1) an early vein stage in which most iron oxide minerals, tourmaline and other silitcate minerals were deposited, (2) a calcite and quartz with base·metal sulfide stage and (3) late vein lets of barren calcite stage. Fluid inclusion studies reveal highly systematic trends of salinity and temperature during mineralization. Ore fluids of early vein stage were complex NaCl-KCl rich brines. Salinities of polyphase inclusions in quartz and scapolite in thie stage reached up to 72 wt.% and gradually decreased to 10.5wt. % in closing stage. Homogenization temperatures of inclusions in the beginning of this stage were up to $490^{\circ}C$ and then declined steadly to $290^{\circ}C$ in the late stage. Salinities of fluid inclusions in quartz and calcite of base·metal sulfide stage were 37.4~5.7wt. % and homogenization temperatures range from $373^{\circ}C$ to $170^{\circ}C$. Intermittent boiling of early vein fluid is indicated by fluid inclusions in quartz. Potassic alteration of granodiorite adjacent to early vein seems to be related to early saline vein fluid. Fluid inclusion data of base-metal sulfide stage of this area reveal nearly the same range as those of Koseong copper mining district about 30km apart from this area.

• Economic and Environmental Geology
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• v.32 no.6
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• pp.669-688
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• 1999

The Yeongju granitoid batholith is a plutonic complex of huge area (1180km2) intruding the metamorphic rocks of the Yeongnam massif. The batholith, which is divided into fivelithofacies, consists of three separate plutons. The oldest Buseok pluton comprises four lithofacies: hornblende biotite tonalite, porphyrotoc biotite granodiorite, equigranular biotite grandiorite and biotite granite. The middle Chunyang pluton has been called as Chunyang granite that ranges in compostion from granodiorite to granite. The youngest Jangsu pluton is intrusions that has lithofacies of two mica granite. The contact between Buseok pluton and the rest two plutons shows obvious intrusive relations, but relation between the Chunyang and the Jangsu pluton is far away, so gives no indication of relative ages. Changes in nextures and micristructures, as well as in the mineral contents, take place between rock types og the plutons. only the Buseok pluton shows faliations of two type: magmatic foliation and regional mylonal foliation. K-Ar age deteminations fall into 171.7$\pm$3.2~162.3$\pm$3.1 Ma in the Buseok pluton, 153.9$\pm$2.9 Ma in the Chunyang pluton and 145.3$\pm$2.7 Ma in the jangsu Pluton. The batholith presents three separate intrusive phases which range in composition from tonalite to granite to granite. Each intrusive phase apperars to have been intruded in a pulse from an underlying, differentiating magma. The petrochemical data showthat three plutons are within the diagnostic range for continental arc orogenic tectonic setting, whereas Jangsu pluton approaches postorogenic setting. The data suggest that three plutons are calc-aclkalline series, and that temporal compositional variations change progerssively from tonalite through grandiorite to granite between the intrusive phases. so we consider that the magmas for all the phases were probably derived from a differentiation by fractional crystallization of a parental magma. The tonalite magma of the Buseok phase was tapped was tapped from a chamber deep in the crust, and then would have to rise at a rapid rate to its final level of emplacement. The tonalite magma in the chamber was gradually enolved through granodiorite magma into granite magma by fractional crystallization. The magmas of the younger phases were respectively tapped with temporal interval from a evolved magma of the chamber that rose into a shallower lever in the crust, and rose to their present level of emplacement.

• The Journal of the Petrological Society of Korea
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• v.15 no.1 s.43
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• pp.25-38
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• 2006

Metamophic rocks of Samcheog area, northeastern Yeongnam massif, was studied petrochemically. This area includes Precambrian Hosanri Formation (schists and gneisses) and granitoid (Icheon granitic gneiss, leucocratic granite and Hongjesa granite), Cambrian sedimentary rocks, and Cretaceous sedimentary and acidic volcanic rocks. Hosanri formation is composed of quartz+plagioclase+K-feldspar+biotite+muscovite+granet${\pm}$cordierite${\pm}$sillimanite. Mineral assemblage of biotite granitic gneiss, which is massive granodioritic rock with weak foliation, is similar to Hosanri formation. According to mineral assemblages, metamorphic rocks of studied area can be divided into two metamorphic zones (garnet and sillimanite zones). From Icheonri area, major, trace and rare earth element data of biotite granitic gneiss and luecocratic granite suggest that source rock is politic rocks of Hosanri formation and source magma was formed by anatexis and experienced fractionation of plagioclase. Trace element diagram show collisional environment such as syn-collisional, volcanic arc granite. Orientation of faults in study area have three maximum concentrations, $N54^{\circ}\;W/77^{\circ}\;SW,\;N49^{\circ}\;W/81^{\circ}\;NE\;and\;N10^{\circ}\;W/38^{\circ}\;NE$. Structure analysis suggests that faults in study area ware formed by uplift and compression. Faulting age is guessed after Tertiary because some shear joints is developed in dikes to intrusive Cretaceous acidic volcanic rock. Hosanri formation and Icheon granitic gneiss had experienced similar deformation history because they have maximum concentration to foliations, $N89^{\circ}\;E/55^{\circ}\;SE\;and\;N80^{\circ}\;E/45^{\circ}\;SE$, respectively.

• Journal of the Korean earth science society
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• v.22 no.4
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• pp.278-291
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• 2001

Mesothermal gold vein minerals of the Seolhwa mine were deposited in a single stage of massive quartz veins which filled the mainly NE-trending fault shear zones exclusively in the granitoid of the Gyeonggi Massif. The Seolhwa mesothermal gold mineralization is spatially associated with the Jurassic granitoid of 161 Ma. The vein quartz contains three main types of fluid inclusions at 25$^{\circ}$C: 1) low-salinity (< 5 wt.% NaCl), liquid CO$_{2}$-bearing, type IV inclusion; 2) gas-rich (> 70 vol.%), aqueous type II inclusions; 3) aqueous type I inclusions (0${\sim}$15 wt.% NaCl) containing small amounts of CO$_{2}$. The H$_{2}$O-CO$_{2}-CH$_{4}$-N$_{2}$-NaCl inclusions represent immiscible fluids trapped earlier along the solvurs curve at temperatures from 430$^{\circ}$ to 250$^{\circ}$C and pressures of 1 kbars. Detailed fluid inclusion chronologies may suggest a progressive decrease in pressure during the auriferous mineralization. The aqueous inclusion fluids represent either later fluids evelved through extensive fluid unmixing (CO$_{2}-CH$_{4}$ effervescence) from a homogeneous H$_{2}$O-CO$_{2}-CH$_{4}$-N$_{2}$-NaCl fluid due to decreases in temperature and pressure, or the influence of deep circulated meteoric waters possibly related to uplift and unloading of the mineralizing suites. The initial fluids were homogeneous containing H$_{2}$O-CO$_{2}-CH$_{4}$-N$_{2}$-NaCl components and the following properties: the initital temperature of >250$^{\circ}$ to 430$^{\circ}$C, X$_{CO}\;_{2}$ of 0.16 to 0.62, 5 to 14 mole% CH$_{4}$, 0.06 to 0.3 mole% N$_{2}$ and salinities of 0.4 to 4.9 wt.% NaCl. The T-X data for the Seolhwa gold mine may suggest that the Seolhwa auriferous hydrothermal system has been probably originated from adjacent granitic melt which facilitated the CH$_{4}$ formation and resulted in a reduced fluid state evidenced by the predominance of pyrrhotite. The dominance of negative ${\delta}\;^{34}$S values of sulfides (-0.6 to 1.4$%_o$o) are consistent with their deep igneous source.

• Economic and Environmental Geology
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• v.51 no.3
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• pp.213-222
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• 2018

Metasediment-hosted Pb-Zn mineralized zone has been found in Dyusembay of Kazakhstan. Its petrological properties, metal index, alteration index and redox-sensitivity are compared with those of SEDEX type deposit. Mineralization is developed along foliation of host rock (graphitic phyllite) and controlled by folds and faults; major ore minerals including pyrite, pyrrhotite, sphalerite, and galena are disseminated or interlayered with fine-grained quartz. The margin of the mineralized zone is metamorphosed accompanying sericite and chlorite. Hydrothermal brecciation and Pb-Zn mineralization formed in quartz-calcite stockworks are confirmed at the around of Maytyubin granitoid intrusions. The mineralization is classified into three types according to those of occurrence, paragenesis, chemical composition and isotopic characteristics. Type 1 whose fine-grained pyrite, pyrrhotite and sphalerite are formed in parallel yet discontinuous to well-developed foliations of the host rock; its geochemistry is similar to those of the earlier stage in SEDEX-type mineralization. In case of type 2, the ore minerals of which are concentrated being parallel to a foliation by regional metamorphism, and most of them associated with quartz and muscovite (${\pm}$ biotite) paragenetically. Type 3 is formed in the hydrothermal breccia zone whose ore minerals are controlled by foliation and breccia and developed in quartz ${\pm}$ calcite veins having a form such as stratification, stockwork or veinlets. Host rocks in the mineralized zone indicate homogeneous metamorphic grade and there is no specific alteration zonation. Also, all types (type 1, type 2, and type 3) represent similar REEs patterns, it can be interpreted that these are originated from a same source. Sulphides occurred in mineralized zone indicate a limited range of sulphur isotope values (type 2, ${\delta}^{34}S=-13.3{\sim}-11.7$‰; type 3, ${\delta}^{34}S=-13.9{\sim}-8.2$‰), and a result of geothermometry presents different temperature ranges: type 2($251{\pm}38^{\circ}C{\sim}277{\pm}40^{\circ}C$); type 3($360{\pm}2^{\circ}C$ to $537{\pm}29^{\circ}C$). It is estimated to be due to the effect of metamorphism and Maytyubin granitoid intrusions, respectively. In addition, ternary chart of thorium, scandium, and zircon for discrimination of tectonic setting and redox sensitivity using V/Mo values indicate that hydrothermal sediments put on reduction environment after precipitation, before being affected by metamorphism and intrusion activity. Geochemical data are plotted on a distal trend of SEDEX-type with discrimination plot using SEDEX index. As a result, petrological-geochemical properties demonstrate that Dyusembay Pb-Zn mineralized zone is comparable to distal-type of SEDEX deposit.

• Economic and Environmental Geology
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• v.28 no.6
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• pp.613-621
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• 1995

It is understood that many big tungsten deposits such as the Sangdong in Korea, Fugigatami in Japan, Yukon in Canada, Pine Creek in U.S.A and Vostok in Russia were formed at late Cretaceous ages. However, most of tungsten mineralization in China where half the total world tungsten ores is reserved took place in late Jurassic to early Cretaceous ages. While the close association of molybdenum with tungsten mineralization is observed in the deposits related with Cretaceous magma, tungsten deposits in China related with late Jurassic to early Cretaceous show a close association of tin as well as molybdenum mineralization. It is characteristic that tungsten mineralization in China was followed by tin mineralization. The mode of occurrence of tungsten ore deposits in China is various and may represent the origin of tungsten in general, since the larger half of total amount of tungsten ores in the world are reserved in China. In case of Korea, more than 90% of total production of tungsten was occupied by the Sangdong tungsten deposit, which produced molybdenite as a byproduct Even if tin is detected in ppm unit content, no cassiterite is found in the Sangdong tungsten orebody. A similar type of two tungsten deposits is comparatively studied in order to confirm the published data; one is the Moping tungsten deposit in China and the other is the Dehwa tungsten deposit in Korea. Mineral assemblages occurring in quartz veins of both deposits are more or less same except that zinnwaldite and cassiterite occur only in the former deposit Ages of zinnwaldite and muscovite closely with molybdenite in the former deposit are 181.1 Ma and 167.8 Ma respectively, while muscovites associated with molybdenite in the latter deposit show ages of 80.9 Ma and 80.2 Ma. These results may represent deficient supply of tin from the source granitoid from which tungsten was derived in Korean peninsula during Cretaceous period, while tin supplied during tungsten mineralization tended to increase and the active tin mineralization followed the Jurassic tungsten mineralization in China.

• Economic and Environmental Geology
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• v.35 no.6
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• pp.509-521
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• 2002

The purpose of this study is to find out geochemical characteristics of stream sediments which are good indicator of geochemical hazard valuation and water in primary channels of the Jangheung area. We separated three groups which were granitoid area, granite gneiss area and tuffeous area by petrological properties. Physical and chemical characteristics of stream water such as temperature, pH, and EC were measured in the field between 1999 and 2001 and stream sediments samples were collected from April to May in 1999. For the chemical analysis of stream sediments samples, XRF, ICP-AES and NAA were used. The contents of the major elements had a similar contents in three groups and those of rare earth elements in granite gneiss area were lower value than those of other two groups. Zn and Cu were higher value than the other toxic elements. Through the enrichment factor and enrichment index features of the elements, we knew that $Fe_2O_3$, MgO, $TiO_2$, MnO and Eu, Yb of the tuffeous area samples and Co, Cr, Zn were enriched.

• The Journal of the Petrological Society of Korea
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• v.8 no.2
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• pp.71-80
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• 1999

We report zircon morphology of granitoids in the Mt. Keumjeong district, Pusan. There are a series of granitoids in the study area of the late Cretaceous: granodiorite, hornblende granite, adamellite, tonalite, biotite granite, and micrographic granite. Generally, the shapes of zircon crystals are short prismatic to middle prismatic and are dominant in {loo) prism and {101) pyramid in total average morphological data of the granitoids. The crystal forms of zircon in the granitoids can be distinguished by the PPEF diagram and the prism index (PI). The prism index values of zircon crystal forms in granodoirite and hornblende granite are higher than those of tonalite and micrographic granite. The finishing temperature range ($820~800^{\circ}C$) for crystallization of zircon crystals in granodoirite and hornblende granite is higher than the temperature ($790~770^{\circ}C$) at which the zircon crystals are created in tonalite and micrographic granite. The last differentiates (biotite granite and micrographic granite) have mainly intermediate zircon ({110)={100)) crystals, respectively. As differentiation proceeds, the zircons of granitoids become from short prismatic to middle prismatic in the each granitoid types.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.05a
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• pp.57-65
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• 2009

Selection of good mineralized area is a combination of the integration of all the available geo-scientific (i.e., geological, geochemical, and geophysical) information, extrapolation of likely features from known mineralized terrenes and the ability to be predictive. The time-space relationships of the hydrothermal deposits in the East Asia are closely related to the changing plate motions. Also, two distinctive hydrothermal systems during Mesozoic occurred in Korea: the Jurassic/Early Cretaceous deep-level ones during the Daebo orogeny and the Late Cretaceous/Tertiary shallow geothermal ones during the Bulguksa event. Both the Mesozoic geothermal system and the mineralization document a close spatial and temporal relationship with syn- to post-tectonic magmatism. The Jurassic mineral deposits were formed at the relatively high temperature and deep-crustal level from the mineralizing fluids characterized by the relatively homogeneous and similar ranges of ${\delta}^{18}O$ values, suggesting that ore-forming fluids were principally derived from spatially associated Jurassic granitoid and related pegmatite. Most of the Jurassic auriferous deposits (ca. 165-145 Ma) show fluid characteristics typical of an orogenic-type gold deposits, and were probably generated in a compressional to transpressional regime caused by an orthogonal to oblique convergence of the Izanagi Plate into the East Asian continental margin. On the other hand, Late Cretaceous ferroalloy, base-metal and precious-metal deposits in the Taebaeksan, Okcheon and Gyeongsang basins occurred as vein, replacement, breccia-pipe, porphyry-style and skarn deposits. Diverse mineralization styles represent a spatial and temporal distinction between the proximal environment of sub-volcanic activity and the distal to transitional condition derived from volcanic environments. However, Cu (-Au) or Fe-Mo-W deposits are proximal to a magmatic source, whereas polymetallic or precious-metal deposits are more distal to transitional. Strike-slip faults and caldera-related fractures together with sub-volcanic activity are associated with major faults reactivated by a northward (oblique) to northwestward (orthogonal) convergence, and have played an important role in the formation of the Cretaceous Au-Ag lode deposits (ca. 110-45 Ma) under a continental arc setting. The temporal and spatial distinctions between the two typical Mesozoic deposit styles in Korea reflect a different thermal episodes (i.e., late orogenic and post-orogenic) and ore-forming fluids related to different depths of emplacement of magma (i.e., plutonic and sub-volcanic) due to regional changes in tectonic settings.

• Economic and Environmental Geology
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• v.40 no.1 s.182
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• pp.87-101
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• 2007

A variety of informations obtained from satellite image, digital elevation relief map (DEM), borehole logging, televiewer, geophysical prospecting, etc were synthetically analyzed to investigate subsurface geological and structural characteristics and to evaluate geohazard pertinent to fault-damage in the Busan metropolitan city. It is revealed that the geology is composed of the Cretaceous andesitic$\sim$dacitic volcanics, gabbro, and granitoid and that at least three major faults including the Dongrae fault are developed in the study area. Based on characteristics of topography, fault-fractured zone, and isobath maps of the Quaternary sediments and weathered residuals of the basement, the Dongrae fault is decreased in its width and fracturing intensity of damaged zone from south toward north, and the fault is segmented around the area between the Seomyeon and Yangieong junctions. Meanwhile, we drew a geohazard sectional map using the five major parameters that significantly suggest damage intensity of basement by fault, i.e. distance from fault core, TCR, RQD, uniaxial rock strength, and seismic velocity of S wave. The map is evaluated as a suitable method to express the geological and structural characteristics and fault-damaged intensity of basement in the study area. It is, thus, concluded that the proposed method can contribute to complement and amplify the capability of the present evaluation system of rock mass.