• Proceedings of the KSEEG Conference
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• 2002.04a
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• pp.469-471
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• 2002

• The Journal of the Petrological Society of Korea
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• v.12 no.1
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• pp.32-52
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• 2003

The Mt. Baegyang in Busan, composed of sedimentary basement rocks (Icheonri Formation), andesite (lava), andesitic pyroclastic rocks, fallout tuff and tuffaceous sedimentary rocks, rhyolitic pyroclastic rocks, intrusive rocks (granite-porphyry, felsite, and biotite-granite) of Cretaceous age in ascending order. The volcanic rocks show a section of composite volcano which comprised alternation of andesitic lava and pyroclasitc rocks, rhyolitic pyrocalstic rocks (tuff breccia, lapilli tuff, fine tuff) from the lower to the upper strata. From the major element chemical analysis, the volcanic and intrusive rocks belong to calc-alkaline rock series. The trace element composition and REE patterns of volcanic and plutonic rocks, which are characterized by a high LILE/HFSE ratio and enrichments in LREE, suggest that they are typical of continental margin arc calc-alkaline rocks produced in the subduction environment. Primary basaltic magma might have been derived from partial melting of mantle wedge in the upper mantle under destructive plate margin. Crystallization differentiation of the basaltic magma would have produced the calc-alkaline andesitic magma. And the felsic rhyolitic magma seems to have been evolved from andesitic magma with crystallization differentiation of plagioclase, pyroxene, and hornblende.

• Economic and Environmental Geology
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• v.50 no.5
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• pp.375-387
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• 2017

Amphibolite-hosted Fe-Ti mineralization at the Soyeonpyeong Island, located in central western part of the Korean Peninsula is a typical orthomagmatic Fe-Ti oxide deposit in South Korea. The amphibolite intruded into NW-SE trending Precambrian metasedimentary rocks. Lower amphibolite is characterized by igneous layering, consisting of feldspar-dominant and amphibole-Fe-Ti oxide-dominant layers. The igneous layering shows complicated and/or sharp contact. In contrast, upper amphibolite has a more complicated lithofacies (garnet-bearing, coarser, and schistose), and massive Fe-Ti oxide ore alternates with schistose amphibolite. NS- and EW-trending fault systems lead to redistribute upper amphibolite-hosted Fe-Ti orebody and igneous layering of lower amphibolite, respectively. The whole-rock compositions of amphibolite and Fe-Ti oxide ore reflect their constituent minerals. Amphibolite shows significantly positive Eu anomalies whereas Fe-Ti oxide ore has weak negative Eu anomalies. Plagioclase (Andesine to oligoclase) and Fe-Ti oxide minerals have constant composition regardless of their distribution. Amphibole has a compositionally variable but it doesn't reflect the chemical evolution. Mineral compositions within individual layers and successive layers are relatively constant not showing any stratigraphic evolution. This suggests that there are no successive injections of Fe-rich magma or assimilation with Fe-rich country rocks. Contrasting Eu anomalies between amphibolite and Fe-Ti oxide ore also suggest that extensive plagioclase fractionation during early crystallization stage cause increase in $Fe_2O_3/FeO$ ratio and overall Fe contents in the residual magma. Thus, Fe-rich residual liquids may migrate at the upper amphibolite by filter pressing mechanism and then produce sheeted massive Fe-Ti mineralization during late fractional crystallization.

• The Journal of the Petrological Society of Korea
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• v.12 no.1
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• pp.16-31
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• 2003

The granites in the southern Gimcheon area can be divided into two parts, marginal hornblende biotite granodiorite (Mgd) and central biotite granodiorite to granite (Cgd). Mgd and Cgd are gray in color and display gradational contact relations and are mainly composed of coarse-grained and medium-grained rocks, respectively. Mgd has more frequent and larger mafic enclaves than Cgd, and the two granites partly show parallel foliation at thire contact with gneisses. From representative samples of the granites, K-Ar biotite ages of 197∼207 Ma were obtained. Considering the blocking temperature of biotite, it is suggested that the emplacement age of the granitic magma was probably late Triassic. The anorthite contents of plagioclases in Mgd display less variation than those of Cgd, indicating that Mgd crystallized within a narrow range of temperatures. In the Al$\_$total/-Mg diagram, the biotites from the granites plot within the subalkaline field, and the smooth slope indicates differentiation from a single magma. All amphiboles from the granites belong to magnesio-hornblende. The linear trends of major oxides, AFM and Ba-Sr-Rb indicate that Mgd and Cgd were fractionally differentiated from a single granitic magma body crystallizing from the margin inwards. The relations of modal (Qz+Af) vs. Op, K$_2$O vs. Na$_2$O, Fe$_2$ $O_3$ vs. FeO, Fe$\^$+3/(Fe$\^$+3/+Fe$\^$+2/) and K/Rb vs. Rb/Sr show that they belong to I-type and magnetite-series granitic rocks developed by the progressive melting products of fixed sources. REE data, normalized to chondrite value, have trends of enriched LREE and depleted HREE together with weakly negative Eu anomalies.

• The Journal of the Petrological Society of Korea
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• v.12 no.4
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• pp.155-169
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• 2003

In the northwest Okcheon metamorphic belt, the metaigneous rocks in the Gyemyeongsan Formation have wider chemical ranges for major, trace and REE elements compared with metaigneous rocks in the Munjuri Formation and do not represent bimodal igneous activity which is characteristic for a continental rifting. The metaigneous rocks in the Munjuri Formation are regarded as products of single magmatic evolution, whereas those in the Gyemyeongsan Formation may be formed through multiple magmatic episodes. The felsic metavolcanic rocks in the Gyemyeongsan Formation show weaker Eu negative anomalies compared with those in the Munjuri Formation but those in both formations show similar degrees of enrichment from LREE to HREE. The metabasites in the Munjuri Formation do not show Eu anomalies but those in the Gyemyeongsan Formation show both positive and negative Eu anomalies(0.59

• Journal of the Mineralogical Society of Korea
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• v.21 no.3
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• pp.239-246
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• 2008

Yeongweol sericite deposit of Gangwon Province is regarded as one of the sericite deposits derived from granitic rocks due to post-magmatic alkali metasomatism, and the other sericite deposit of the same origin is the Daehyun mine of Gyungbug Province. Sericite ores were originated from leucocratic granitic stocks of Cambrian-Triassic age which intruded the pegmatitic migmatite of the unknown age and granite of the Pre-cambrian age, respectivcly. Jangsan quartzite of the lowermost formations of the Paleozoic era, which played as the capping rock protected from the leakage of the hydrothermal solution. It is well known that those sericite deposits arc formed during formation of the geosyncline, and they are also situated in the margins of the Hambaeg Syncline. Leucocratic granites commonly contain pegmatites with tourmaline crystals, and are rich in potassium feldspars, and sodium plagioclase as well. Sericitized ores are mainly found as we go up to the higher elevations or to the margins of the stocks. And some of the Highest grade sericite ores show the monominerallic character composed of nearly pure sericite probably doc to the ultra greisenization. Chemical analysis shows higher $Na_{2}O$ and $K_{2}O$ contents $(2.00\sim7.03wt%)$ as the sericitizations arc preceded and they represent obvious greisenization. But low CaO contents $(0.05\sim4.51wt%)$ indicate that albitizations are so weak. Pyrophyllite of the Youngweol area is often accompanied by the sericite, indicating rather stronger thermal effect than the Daehyun mine. It is known that there are several Sn deposits originated from greisenization in the Taebaegsan region. And greisens are inclined to contain W, Mo and several REE's such as Be, Nb and Li, and so Taebaegsan region interbedded with lots of carbonate formations are still worthwhile to survey for those metallic deposits.

• Economic and Environmental Geology
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• v.28 no.6
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• pp.587-597
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• 1995

Two distinct precious-metal mineralizations actively occur at central and southeastern Korea which display consistent relationships among geologic, geochemical and genetic environments. A large number of preciousmetal vein deposits in the central Korea occur in or near Mesozoic granite batholiths elongated in a NE-SW direction. Whereas, gold and/or silver deposits in the southeastern Korea occur within Cretaceous volcanic and sedimentary rocks. However, most of the precious-metal deposits in the southeastern Korea show characteristics of the silver-rich deposits than the gold-rich deposits in the central Korea. Two epochs of main igneous activities are recognized: a) Jurassic Daebo igneous activity between 121 and 183 Ma, and b) Cretaceous Bulgugsa igneous activity between 60 and 110 Ma. Precious-metal mineralization took place between 158 and 71 Ma, coinciding with portions of the two magmatic activities. Contrasts in the style of mineralization, together with radiometric age data and differences in geologic settings reflect the genetically variable natures of hydrothermal activities from middle Jurassic to late Cretaceous time. The compilation and re-evaluation of these data suggest that the genetic types of hydrothermal precious-metal vein deposits in the central and southeastern Korea varied with time. The Jurassic and early Cretaceous mineralizations are characterized by the Au-dominant type, but tend to change to the Au-Ag and/or Ag-dominant types at late Cretaceous. The Jurassic Au-dominant deposits commonly show several characteristics; prominent associations with pegmatites, simple massive vein morphologies, high fmeness values in ore-concentrating parts, and a distinctively simple ore mineralogy such as Fe-rich sphalerite, galena, chalcopyrite, Au-rich electrum, pyrrhotite and/or pyrite. The Cretaceous precious-metal deposits are generally characterized by some- features such as complex vein morphologies, low to medium fmeness values in the ore concentrates, and abundance of ore minerals including Ag sulfosalts, Ag sulfides, Ag tellurides and native silver. Mineralogical and fluid inclusion studies indicate that the Jurassic Au-dominant deposits in the central area were formed at the high temperature (about $300^{\circ}$ to $500^{\circ}C$) and pressure (about 4 to 5 kbars), whereas mineralizations of the Cretaceous Au-Ag and Ag-dominant deposits were occurred at the low temperature (about $200^{\circ}$ to $350^{\circ}C$) and pressure (<0.5 kbars) from the ore fluids containing more amounts of less-evolved meteoric waters.

• Economic and Environmental Geology
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• v.34 no.1
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• pp.25-38
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• 2001

Contrasts in the style of the gold-silver mineralization in geologic and tectonic settings in Korea, together with radiometric age data, reflect the genetically different nature of hydrothermal activities, coinciding with the emplacement age and depth of Mesozoic magmatic activities. It represents a clear distinction between the plutonic settings of the Jurassic Daebo orogeny and the subvolcanic environments of the Cretaceous Bulgugsa igneous activities. During the Daebo igneous activities (about 200-130 Ma) coincident with orogenic time, gold mineralization took place between 197 and 127 Ma. The Jurassic deposits commonly show several characteristics: prominent association with pegmatites, low Ag/Au ratios in the ore-concentrating parts, massive vein morphology and a distinctively simple mineralogy including Fe-rich sphalerite, galena, chalcopyrite, Au-rich eIectrum. pyrrhotite and/or pyrite. During the Bulgugsa igneous activities (120-60 Ma), the precious-metal deposits are generally characterized by such features as complex vein morphology, medium to high AgiAu ratios in the ore concentrates, and abundance of ore minerals including base-metal sulfides, Ag sulfides, native silver, Ag sulfosalts and Ag tellurides. Vein morphology, mineralogical, fluid inclusion and stable isotope results indicate the diverse genetic natures of hydrothermal systems. The Jurassic Au-dominant deposits were formed at the relatively high temperature (about 300 to 450$^{\circ}$C) and deep-crustal level (>3.0 kb) from the hydrothermal fluids containing more amounts of magmatic waters (3180; 5-10 %0). It can be explained by the dominant ore-depositing mechanisms as CO2 boiling and sulfidation, suggestive of hypo/mesothermal environments. In contrast, mineralization of the Cretaceous Au-Ag type (108-71 Ma) and Agdominant type (98-71 Ma) occurred at relatively low temperature (about 200 to 350$^{\circ}$C) and shallow-crustal level «1.0 kb) from the ore-fonning fluids containing more amounts of less-evolved meteoric waters (15180; -10-5%0). These characteristics of the Cretaceous precious-metal deposits can be attributed to the complexities in the ore-precipitating mechanisms (mixing, boiling, cooling), suggestive of epilmesothermal environments. Therefore, the differences of the emplacement depth between the Daebo and the Bulgugsa igneous activities directly influence the unique temporal and spatial association of the deposit type.