• Economic and Environmental Geology
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• v.16 no.1
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• pp.1-10
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• 1983

The Yeonhwa (I, II) and Keodo mines, neighboring in the middle part of the Taebaegsan mineral belt, contain three distinct classes of skarn deposits: the zinc-lead skarn at Yeonhwa (I, II), the iron skarn at Keodo south (Jangsan orebodies), and the copper skarn at Keodo north (78 orebodies). The present study characterizes the three classes of skarn deposits mainly in terms of skarn/ore associations examined from chemical compositional point of view, and applies existing quantitative phase diagrams to some pertinent mineral assemblages in these mines. At Yeonhwa I the Wolam I orebody shows a vertical variation in skarn minerals ranging from clinopyroxene/garnet zone on the lower levels through clinopyroxene (without garnet) zone on the intermediate levels, and finally to rhodochrosite veins on the upper levels and surface. Ore minerals, sphalerite and galena, associate most closely with the intermediate clinopyroxene zone. At Keodo, the Jangsan iron skarn hosted in quartz monzodiolite as a typical endoskarn, shows a skarn zoning, from center of orebody to outer side, magnetite zone, magnetite/garnet zone, garnet clinopyroxene zone, and clinopyroxene/epidote/plagioclase zone. The 78 copper skarn in the Hwajeol limestone indicates a zoning, from quartz porphyry side toward limestone side, orthoclase/epidote zone, epidote/clinopyroxene zone, and clinopyroxene/garnet zone; chalcopyrite and other copper sulfides tend to be in clinopyroxene/garnet zone. Mioroprobe analyses of clinopyroxenes and garnets from the various skarn zones mentioned above revealed that the Yeonhwa zinc/lead skarns are characterized by johansenitic clinopyroxene (Hd 25-78, Jo 15-23) and manganoan andraditic garnet (Ad 13-97, Sp 1-24), whereas the Jangsan iron skarn at Keodo by Mn-poor diopsidic clinopyroxene (Di 78-93, Jo 0.2-1.0) and Mn-poor grossularitic grandite (Gr 65-77, Sp 0.5-1.0). The 78 copper skarn at Keodo is characterized by Mn-poor diopsidic-salite (Di 66-91, Jo 0.2-1.1) and Mn-poor andraditic grandite(Ad 40-74, Sp 0.5-1.1). The compositional charateristics of iron, copper, and zinc-lead skarns in the Yeonhwa-Keodo mines are in good correlations with those of the foreign counterparts. Compiling a $T-XCO_2$ phase diagram for the Jangsan endoskarns, a potential upper limit of temperature of the main stage of skarn formation is estimated to be about $530^{\circ}C$, and a lower limit to be $400^{\circ}C$ or below assuming $XCO_2=0.05$ at P total=1kb. Applying a published log $fS_2$-log $fo_2$ diagram to the Keodo 78 and Yeonhwa exoskarns, it is revealed that copper sulfides and zinc-lead sulfides do not co-exist stably below log $fS_2=-4$ and log $fO_2=-23$ at $T=400^{\circ}C$ and ${\times}CO=1$ atm.

• Economic and Environmental Geology
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• v.16 no.1
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• pp.37-49
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• 1983

The skarn type tungsten deposits are developed in the contact aureole of Jurassic biotite-hornblende granodiorite and limestone beds. The latter can be divided into the Great Limestone Series of Joseon System and Gabsan Formation which is correlative to the Hongjeom Series of Pyeongahn System. The skarns are impregnated in the limestone, sandstone, schist and granodiorite, and showing zonal distribution. The five skarn zones are from fresh limestone inwards to wollastonite-skarn, clinopyroxene-skarn, clinopyroxene-garnet skarn, garnet skarn and vesuvianite skarn zone. The ore mineral, scheelite, disseminates in the clinopyroxene-garnet and vesuvianite skarn zone, and the size of the scheelite crystals in vesuvianite skarn zone is larger than in clinopyroxene- garnet skarn zone. According to the mineral paragenesis and the composition of skarn minerals, oxygen fugacity ($fo_2$) is low. Fluid inclusions in quartz comprise much $LCO_2$ and fluid inclusion studies revealed that the homogenization temperatures range $240-290^{\circ}C$.

• Journal of the Mineralogical Society of Korea
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• v.2 no.1
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• pp.26-36
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• 1989

Clinopyroxene in the Geodo mine belongs to diopside-hedenbergite series. It is widely distributed throughout the mine area together with garnet and is also closely related with Fe-mineralization. Clinopyroxenes in the Geodo mine including two samples from the sangdong and Ulchin Mines are studied using polarized microscope, EPMA, XRD, and IR spectroscopy for occurrence, chemistry, structure, and crystal chemistry. Especially, variations in unit-cell parameters are examined in relation with the substitution scheme between Fe and Mg cations. Clinopyroxenes in the Geodo mine occur in both endoskarn and exoskarn zone. It is mostly anhedral to subhedral with fine- to medium-grained in texture, but some have bigger crystals of short prismatic or columnar habits. Clinopyroxene occurs as monomineralic or is associated with mostly garnet and sometimes with actinolite, magnetite, epidote, and chlorite. Chemical analysis reveals that the Geodo clinopyroxene is diopsidic in composition (Di: 65-96%). This fact is in good contrast with garnet chemistry showing mostly andraditic (An: 41-82%). Especially, clinopyroxene coexisting with magnetite belongs to nearly end member diopside (Di: 97-99%). Thus, diopside-andradite pair indicates that Geodo skarns were formed under the reduced environment. X-ray diffraction analysis shows unit-cell parameters vary with increase of Fe contents: a = 9.765-9.838$\AA$, b = 8.943-9.020$\AA$, c= 5.240-5.253$\AA$.$\beta$ = 105.70-104.83$^{\circ}$, and V =440.64-448.19$\AA$3. It is noted from the least square regression that a, b and V increase linearly with increase of Fe content, while $\beta$ slightly decreases and c remains nearly unchanged as change in Fe content. These trends are to difference between synthetic and natural clinopyroxenes. This fact is also recognized in IR spectra which show a slight shift of several absorption bands toward lower wavenumber region with increasing Fe content.

• Economic and Environmental Geology
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• v.46 no.2
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• pp.123-140
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• 2013

The Dangdu Pb-Zn deposit is located at approximately 10 km south of Jecheon, Korea. Geology of Dangdu deposit area consists of Pre-cambrian metamorphic rocks, Ordovician sedimentary rocks, Jurassic and Cretaceous igneous rocks. The ore deposit is developed along the fracture trending $N20{\sim}40^{\circ}W$ in Ordovician limestone and is considered to be a skarn type ore deposit. The shape of ore bodies developed in the Dangdu ore deposit can be divided into lens-form(two ore bodies of -30 m level adit and one ore body of -63 m level adit) and pocket-form developed in -30 m level adit. Ore minerals observed in the ore deposits are magnetite, pyrrhotite, pyrite, chalcopyrite, sphalerite, galena, cosalite, marcasite, hessite, native Bi and bismuthinite. Chemical composition of sphalerite ranges FeS 14.14~18.08 mole%, CdS 0.44~0.70 mole%, MnS 0.52~1.13, 1.53~2.09 mole%. Galena contains a small amount of silver with an average of 0.54 wt.%. An average composition of cosalite is Ag 2.43 wt.%, Bi 44.36 wt.%, Pb 35.05 wt.% which results the chemical formula of cosalite as $Pb_{1.7}Bi_{2.1}Ag_{0.2}S_5$. Skarn minerals consist of epidote, garnet, pyroxene, tremolite, quartz and calcite. The zoning pattern of the ore deposit can be subdivided into epidote-clinopyroxene zone, epidote-clinopyroxene-chlorite zone and epidote-garnet-clinopyroxene zone from the central part of the ore body towards the wall rocks. The chemical composition of garnet shows an increasing trend of grossular from epidote-clinopyroxene zone to epidote-garnet-clinopyroxene zone. Clinopyroxene occurs as a solid solution of diopside and hedenbergite, and the ratio of johannsenite increases from epidote-clinopyroxene zone to epidote-clinopyroxene-chlorite and epidote-garnet-clinopyroxene zones. The mineralization of the ore deposit is considered to be one stage event which can be separated into early skarn mineralization stage, middle ore mineralization stage and late low temperature mineralization stage. The temperature estimation from the low temperature mineralization range from $125{\sim}300^{\circ}C$ which is considered to be representing the temperature of late mineralization.

• Economic and Environmental Geology
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• v.45 no.1
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• pp.1-8
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• 2012

Copper-zinc-bearing skarns of the Kasihan area developed at limestone layers in the sedimentary facies of the Late Oligocene Arjosari Formation. The skarns consist mainly of fine-grained, massive clinopyroxene-garnet, garnet, garnet-epidote, and epidote skarns. Most copper and zinc(-lead) ore mineralization occur in the clinopyroxene-garnet and garnetepidote skarn, respectively. Clinopyroxene occurs as a continuous solid solution of diopside and hedenbergite (from nearly pure diopside up to ${\approx}34$ mole percent hedenbergite), with a maximum 28.2 mole percent johannsenite component. The early and late pyroxenes of Kasihan skarns are diopsidic and salitic, respectively. They fall in the fields typical Cu- and Zn-dominated skarns, respectively. Garnet displays a relatively wide range of solid solution between grossular and andradite with up to ${\approx}2.0$ weight percent MnO. Garnet in early pyroxene-garnet skarn ranges from 49.1 to 91.5 mole percent grossular (mainly ${\geq}78$ mole % grossular). Garnets in late garnet and garnet-epidote skarns range from 2.8 to 91.4 mole percent grossular (mainly ${\geq}70$ mole % for garnet skarn). Epidote compositions indicate solid solutions of clinozoisite and pistacite varying from 65.8 to 76.2 mole percent clinozoisite. Phase equilibria indicate that skarn evolution was the result of interaction of water-rich fluids ($X_{CO_2}{\leq}0.1$) with original lithologies at ${\approx}0.5$ kb with declining temperature (early clinopyroxene-garnet and garnet skarn, ${\approx}450$ to $370^{\circ}C$; late garnet-epidote and epidote skarn, ${\approx}370$ to $300^{\circ}C$).

• Journal of the Mineralogical Society of Korea
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• v.27 no.3
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• pp.135-147
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• 2014

This study analyzed spectroscopic methods for characterization of skarn minerals and sphalerite occurring in Dangdu ore deposit, and effectiveness of portable spectrometer in skarn mineral resources exploration is discussed. The spectroscopic analyses identified clinopyroxene, garnet, epidote, calcite, chlorite and sphalerite where spectral curves of clinopyroxene, garnet, epidote, and sphalerite show single mineral spectral characteristics and those of chlorite are in a mixed form with calcite and clinopyroxene. The assessment of spectroscopic analyses based on XRD analysis and microscopic observation reveals that clinopyroxene, garnet, epidote correspond well with more than 80% of detection, but sphalerite, chlorite, and calcite showed below 50% of detection rate. It is expected that skarn deposit exploration using a portable spectrometer is more effective in detection of clinopyroxene, garnet, and epidote whereas spectroscopic data of sphalerite, chlorite, and calcite needs to be utilized as a supplementary data. For the effective detection of chlorite and calcite, their content in the samples needs to be sufficient.

• Journal of the Mineralogical Society of Korea
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• v.23 no.4
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• pp.413-428
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• 2010

The Gukjeon Pb-Zn mine was recognized as skarn deposits which replaced the limestone layer of the Jeongkansan Formation by intrusion of biotite granite in late Cretaceous. The Jeongkansan Formation is mainly composed of tuffaceous shale, and interlayers of sandstone, andesitic tuff, limestone, and conglomerate. The limestone layer is located in the lower part of the Jeongkansan Formation with 6~8 m in thickness and about 500 m in length. The Gukjeon deposits are divided into the Jukgang ore bodies once mined underground and the eastern ore bodies. Main ores are sphalerite and galena, in association with small amounts of chalcopyrite, arsenopyrite, pyrite, and pyrrhotite, etc. Skarns mainly consist of clinopyroxenes and Ca-garnets, associated with actinolite, chlorite, axinite, and calcite, etc. The Jukgang ore bodies show symmetrical distribution of zoning outward, representing clinopyroxene (hedenbergite) zone, clinopyroxene-garnet (grossular) zone, garnet (andradite) zone, and alteration zone of hornfels. $Fe^{2+}$ contents in clinopyroxenes increase with decreasing sphalerite grade. Sphalerite ores are found in all zones and $Fe^{2+}$ contents in sphalerite increase in the same way as those in clinopyroxenes, implying that clinopyroxene and sphalerite are closely related each other. It is concluded that the Gukjeon ores occurred in the ore rich zone of high grade sphalerite with less pyrite in assoication with clinopyroxene.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.4
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• pp.277-291
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• 2021

A mineral phase contained in a rock sample can be categorized into several crystal populations with distinct origins and crystal growth histories. A detailed textural and mineralogical investigation on a clinopyroxene megacryst-bearing porphyritic dike with glassy chilled margins (tachylyte) in the southeastern Ulleung Island was conducted to decipher its crystal populations. During this study, we have measured glass and mineral major element compositions using electron microprobe analyzer. Tachylyte has a homogeneous trachyandesitic composition without any significant alteration characteristics, suggesting that its composition may represent the original melt composition of the dike. Clinopyroxene and plagioclase larger than 0.5 mm are antecrysts equilibrated with a more primitive melt composition than trachyandesitic tachylyte. Meanwhile, clinopyroxene and plagioclase microlites (<0.5mm) are regarded as primocrysts crystallized in-situ. According to our results, all clinopyroxenes in the Stage I Dodong Basalt are sectored into basal and prismatic parts, whose compositional ranges systematically vary: [Mg+Si+Fe]_basal ↔ [Al+Ti+Na]_prism. Therefore, we suggest that the effect of the elemental partitioning caused by the clinopyroxene sector zonation in Stage I volcanism should be considered in the future works.

• Journal of the Korean earth science society
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• v.36 no.5
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• pp.447-459
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• 2015

Dok island comprises Pliocene volcanic products such as a series of volcanoclastic rocks and lavas ranging in composition from alkali basalts, and trachyandesites to trachytes. Compositional variation of the basaltic rocks can be attributed to fractional crystallization of olivine, clinopyroxene, plagioclase, and magnetite. Chemical variations among the trachyandesites are caused by fractionation of clinopyroxene, plagioclase, and magnetite with minor amphibole, while trachytes are controlled mainly by feldspar fractionation. Incompatible element abundance ratios and chondrite normalized LREE/HREE ratios (e.g., (La/Yb)c: 24.8 to 32.8 for basalts, 15.6 to 31.2 for trachyandesites) suggest that the origins of the basalts and trachyandesites involve both different degrees of partial melting and subsequent fractional crystallization processes. Trace element ratios of the basalts from Dok island are characterized by high Ba/Nb, La/Nb, Ba/Th and Th/U and isotopic ratios (Tasumoto and Nakamura, 1991) that are similar to the EM 1 type of oceanic island basalts such as Gough and Tristan da Cunha basalts.

• Journal of the Mineralogical Society of Korea
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• v.25 no.4
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• pp.249-261
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• 2012

Phlogopite-bearing orthopyroxenite occurs in Andong ultramafic complex in a planar body of about 1 meter thick, and consists mostly of coarse subhedral to euhedral orthopyroxene crystals. Minor minerals are clinopyroxene, phlogopite, and plagioclase with trace chromian spinel, pentlandite, apatite, and zircon. Clinopyroxene occurs as either exolution lamella or interstitial fillings with phlogopite and plagioclase. Electron microprobe analysis showed that orthopyroxenes are entatite, while clinopyroxenes are diopside with little chemical variation through samples. Hydrous alteration resulted in the formation of talc, amphibole, and serpentine from orthopyroxene, clinopyroxene, and plagioclase, respectively. The orthopyroxenite was probably formed by the fractional crystallization of the ultramafic magma. Radiogenic dating of phlogopite and zircon of the orthopyroxenite would reveal the age of the Andong ultramafic complex.