• Geosciences Journal
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• 제22권6호
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• pp.881-889
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• 2018

The Geodo skarn deposit is located in the Taebaeksan Basin, central eastern Korean Peninsula. The geology of the deposit consists of Cambrian to Ordovician calcareous sedimentary rocks and the Cretaceous Eopyeong granitoids. The skarns at Geodo occur around the Eopyeong granitoids, which consist, from early to late, of magnetite-bearing equigranular quartz monzodiorite, granodiorite, and dykes. These dykes emanated randomly from equigranular granodiorite and some of dykes spatially accompany skarns. Skarn Fe mineralization, referred as Prospect I and II in this study, is newly discovered beyond previously known skarns adjacent to the quartz monzodiorite. These discoveries show a vertical and lateral variation of skarn facies, grading from massive reddish-brown garnet-quartz in a lower and proximal zone to banded in an upper and distal zone, reflecting changes in lithofacies of the host rocks. Skarn veins in distal locations are parallel to sedimentary laminae, suggesting that lithologic control is important although proximal skarn has totally obliterated primary structures, due to intense retrograde alteration. Skarns at Geodo are systematically zoned relative to the causative dykes. Skarn zonation comprises proximal garnet, distal pyroxene, and vesuvianite (only in Prospect I) at the contact between skarn and marble. Retrograde alteration is intensely developed adjacent to the contact with dykes and occurs as modification of the pre-existing assemblages and progressive destruction such as brecciation of the prograde assemblages. The retrograde alteration assemblages consist predominantly of epidote, K-feldspar, amphibole, chlorite, and calcite. Most of the magnetite (the main ore mineral), replaces calc-silicate minerals such as garnet in the lower proximal exoskarn, whereas it occurs massive in distal pyroxene and amphibole in the upper and distal exoskarn. The emanation of dykes from the equigranular granodiorite has provided channelways for ascent of skarn-forming fluids from a deep source, whereas the style and nature of skarns suggest that originally structurally-controlled skarn-forming fluids may migrate long distances laterally to produce skarn in calcareous sedimentary rocks.

• 자원환경지질
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• 제19권spc호
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• pp.3-17
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• 1986

Hundred mineral deposits including W-Mo, Pb-Zn-Cu, fluorite and talc occur in the Cambre-Ordovician limestone contacting with the Cretaceous Muamsa and Wolak granitoids in the Susanri-Hwanggangri mineralized zone. In most mineral deposits characterized by metasomatic replacement, skarn and hydrothermal vein types, two distinct tendencies were found as W-Mo mineralization in or/and near granitoid batholith and ($Pb-Zn-Cu(CaF_2)$) mineralization which is gradually increased toward the batholith. W-Mo veins of extensive vein system occupy northly striking fractures whilst $Pb-Zn-Cu-CaF_2$ veins strike northeast or northwest. In this work, three representative lead-zinc-copper deposits choosing the Dangdu, Useog and Eoksu mines were dealt with in detail. Skarn ore bodies in the Dangdu mine were grouped into early diopside rich clinopyoxene-garnet, barren skarn and ore bearing late hedenbergite rich clinopyroxene-garnet skarn. Temperature and $X_{CO_2}$, obtained from hedenbergite-andradite-calcite-quartz mineral equilibria in the Dangdu ore deposits were $580{\sim}650^{\circ}C$ and 0.15~0.3, respectively. Fluid inclusien evidence in the Useog mine indicates that main stage mineralization temperature ranges from 224 to $389^{\circ}C$ with a salinity of 2~17 equivalent wt. percent NaCl. Sphalerites from the Dangdu and Useog mines have 16~17.7 mole percent in FeS which is relatively consistent to those of some other lend-zinc ore deposits in South Korea. Filling tcmjCerature of fluid inclusion frem the Eoksu mine shows deposition of ore within the temperature ranges from 237 to $347^{\circ}C$ and within the salinity ranges from 2.6 to 10.77 equivalent wt. percent NaCl.

• 자원환경지질
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• 제47권4호
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• pp.317-333
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• 2014

선캄브리아기 경기육괴의 북서부에 위치한 포천 철(-동)광상은 다양한 이론이 제시되어 논쟁 대상이 되었으며, 성인적 측면에서 변성(-배기형) 퇴적 광상이 주된 생성이론으로 인지되었다. 본 논문에서는 포천 스카른화작용/철광화작용의 핵심 증거를 통하여 공간적으로 인접한 명성산 화강암이 관계화성암의 가능성을 제시하였다. 포천 스카른은 석회암과 백운암의 다양한 탄산염암을 모암으로 하여 Ca계열, Mg계열 및 Na-Ca계열 스카른이 형성되었다. 철광화작용은 주로 Na-Ca계열 스카른대를 따라 배태되고 있으며, 후퇴 스카른 단계에 국부적으로 동 광화작용이 중첩된다. 포천 후퇴 스카른 단계에 정출된 금운모의 Ar-Ar과 K-Ar연대측정 결과는 $110.3{\pm}1.0{\sim}108.3{\pm}2.8Ma$이며, 스카른 철(-동) 광화작용은 천부 관입암체인 명성산 화강암의 관입시기(112 Ma)와 일치하여 관계화성암으로 추정된다. 주변 탄산염암, 스카른 및 맥상의 탄산염광물간 산소-탄소 동위원소 빈화된 경향성은 개방계 조건($XCO_2=0.1$)에서 열수의 탈탄산염화 작용과 침투작용에서 유도되었다. 한편 황화광물(황동석-황철석 혼합물)과 경석고에서 매우 높은 황 동위원소 값은 황근원물질이 주변 탄산염암에 함유되어 있던 황산염광물로부터 공급되었을 가능성을 지시한다. 포천 광상 주변의 전단대에서는 파쇄대가 중첩되어 발달하여 있으며, 백악기 화강암으로부터 공급된 고온성 광화유체가 이러한 약선대를 따라 유입되어 약 $500^{\circ}{\sim}400^{\circ}C$의 온도범위에서 강력한 근지성 스카른화작용과 함께 광화작용이 유도되었다.

• 한국광물학회지
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• 제31권2호
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• pp.87-101
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• 2018

만장광상은 옥천변성대 화전리층 내에 발달되었으며 열극충전형 동광체인 중앙 및 본광체와 철 스카른형 서부광체로 대분된다. 본 연구에서는 중앙 및 본광체에 대한 광상학적 연구를 수행하여 기존 서부광체 광화작용 특성과 비교하고자 한다. 중앙광체는 맥상조직이 두드러지며 자류철석과 황동석이 주를 이루는 반면, 본광체는 맥상, 괴상, 각력상 조직과 더불어 황철석, 유비철석, 황동석이 주로 산출된다. 이 밖에 섬아연석, 방연석, 자철석, 티탄철석, 금홍석, 석석, 철망간중석, 황석석 등이 수반된다. 스카른이 부분적으로 발달하며 석류석은 그로슐라 계열, 휘석은 헤덴버자이트 계열이 우세한 것으로 보아 대체로 환원환경에서 정출된 것으로 보인다. 중앙광체의 섬아연석-황석석과 본광체의 황철석-유비철석 광물공생군을 이용한 생성온도는 각각 $204-263^{\circ}C$, $383-415^{\circ}C$로서 중앙광체가 상대적으로 낮고, 황분압도 본광체에서 $10^{-6}-10^{-7}atm$로서 비교적 높고 중앙광체로 가면서 점차 감소한 것으로 보인다. 황화광물의 황동위원소조성은 중앙광체 4.6-7.9‰, 본광체 4.3-7.0‰로 상호 유사하며 주로 화성기원이지만 모암의 영향으로 약간 높게 나타난다. 광석광물의 종류와 조직 그리고 광화작용의 물리화학적 조건을 고려할 때 동광화작용이 발달한 본광체와 중앙광체는 잠두화성암에 대하여 각각 근지성과 원지성 광화작용의 특성을 나타낸 것으로 보이며, 스카른 철광상이 발달한 서부광체와는 서로 다른 열수계의 영향을 받아 생성된 것으로 여겨진다.

• 자원환경지질
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• 제21권1호
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• pp.45-56
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• 1988

Many hydrothermal skarn-type iron ore deposits inchiding Mulgeum, Yangseong, Maeri and Kimhae mines are distributed in the south-eastern Gyeongnam Province, Korea. The deposits are magnetite veins which occurred in propylitized andesitic rock near the contact with late Cretaceous Masanite. Symmetrical zoned skarns are commonly developed around the magnetite veins. The order of the skarn zones from the vein is garnet-quartz skarn, epidote skarn, and epidote-orthoclase skarn. The garnets include isotropic or anisotropic andradite($Ad_{100{\sim}70}$), and the epidotes are composed of pistacite($Ps_{21-31}$). Fe contents of the epidotes generally increase toward the magnetite veins. Epidotes and garnets often show compositional variations from grain to grain, that is, their Fe and Al contents vary inversely. This suggests that the variations depend mainly upon $fo_2$ during the skarnization. Oxygen and carbon isotope analyses of minerals from andesitic rock, micrographic granite, major skarn zones and post-mineralization zones were conducted to provide the information on the formation temperature, the origin and the evolution of the hydrothermal solution forming the iron ore deposits. Becoming more distant from the ore vein, temperatures of skarn zones represent the decreasing tendency, but most ${\delta}O^{18}$ and ${\delta}O^{18}_{H_2O}$ values of skarn minerals represent no variation trend, and also the values are relatively low. Judging from all the isotopic data from the ore deposits, the major source of hydrothemal solution altering the skarn zones and precipitating the ore bodies was magmatic water derived from the more deeply seated micrographic granite. This high temperature hydrothermal solution rising through the fissures of propylitized andesitic rock was mixed with some meteoric water, and the extensive isotopic exchange occurred with the propylitized andesitic rock. During this process, the temperature and ${\delta}O^{18}_{H_2O}$ value of hydrothermal solution were lowered gradually. At the stage of iron ore precipitation, because after all the alteration was already finished, the oxygen isotopic exchange with the wall rock was nearly not taken. The relatively high ${\delta}O^{18}$ and ${\delta}O^{18}_{H_2O}$, and relatively low ${\delta}C^{13}$ values of calcites of post mineralization stage, are the results of leaching of the high ${\delta}O^{18}$ chert xenolith in the andesitic rock and low ${\delta}C^{13}$ andesitic rock.

• 자원환경지질
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• 제28권3호
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• pp.185-197
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• 1995

충주 광산 지역은 계명산층과 이를 관입한 중생대 화강암질 암석으로 구성되며, 이들 화강암질 암석중 백악기초(134 Ma) 흑운모 화강암과 계명산층을 구성하는 석영-운모 편암의 접촉부에서 회중석을 수반하는 스카른 광상이 산출된다. 스카른은 구성광물의 공생 특성과 주 구성광물의 양적인 비에 의해 석류석 스카른대, 규회석 스카른대, 녹염석 스카른대 및 녹니삭 스카른대로 분류된다. 석류석의 화학조성은 초기 순수한 안드라다이트 (>Ad96)에서 후기 알루미늄 함량비가 증가하는 안드라다이트-그라슈라(Ad~50)로 점이적인 변화를 나타내며, 녹염석은 $Fe^{3+}$ 의 함량비가 높은 고용체 상(Ps=35)에서 암루미늄 함량비가 높은 고용체 상(Ps=25)으로 변화하는 양상을 띤다. 광물 공생 및 화학 조성상의 특징으로 볼 때 스카른화 작용은 Ca와 Fe의 활동도가 흑운모 화강암의 접촉부에서 높고 Al, Mg, K 및 Si 활동도는 석영-운모 편암내에 발달되는 스카른에서 증가하는 경향을 나타낸다. 녹염석 스카른대에서 산출되는 회중석의 유체포유물 균질화 온도는 $300{\sim}380^{\circ}C$ 이며 NaCl 상당 염농도는 3-8wt. %로, 석영 및 녹염석 유세포유물 균질화 온도는 $300{\sim}400^{\circ}C$이다. 후기 녹니석 스카른대내에서 수반되는 황화광물의 황 동위원소비는(${\delta}^{34}S$) 황철석 $9.13{\sim}9.51%_{\circ}$, 방연석 $5.85{\sim}5.96%_{\circ}$이며, 공존하는 황철석-방연석 광물쌍에 의한 동위 원소 지질온도는 $283{\pm}20^{\circ}C$이다. 이산화탄소 몰분율($X_{CO_2}$)은 $L-CO_2$가 관찰되지 않으며 $H_2O$ 풍부한 유체포유물로 구성되고 있는점과, 안드라다이트 및 규회석의 광물공생 특성과 대비하여 볼때 약 0.01로 추정된다. 광물공생 및 화학조성, 상 안정 관계, 유체포유물 연구, 동위원소 지질온도계등의 연구 결과에 의해 충주광산 지역 스카른화 작용은 $400{\sim}260^{\circ}C$ 온도 조건과 산소분압이 감소($fo_2=10^{-30}{\sim}10^{-25}$)하는 환경에서 진행되었으며, 텅스텐 광화작용은 이러한 스카른 형성 과정 중 온도의 감소($350^{\circ}C$)와 산소분압이 감소($fo_2=10^{-27}$) 하는 조건에서 수반되었다.

• 자원환경지질
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• 제29권4호
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• pp.411-419
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• 1996

The Janggun magnetite deposits occur as the lens-shaped magnesian skarn, magnetite and base-metal sulfide orebodies developed in the Cambrian Janggun Limestone Formation. The K-Ar age of alteration sericite indicates that the mineralization took place during late Cretaceous age (107 to 70 Ma). The ore deposition is divided into two stages as a early skarn and late hydrothermal stage. Mineralogy of skara stage (107 Ma) consists of iron oxide, base-metal sulfides, Mg-Fe carbonates and some Mg- and Ca-skarn minerals, and those of the hydrothermal stage (70 Ma) is deposited base-metal sulfides, some Sb- and Sn-sulfosalts, and native bismuth. Based on mineral assemblages, chemical compositions and thermodynamic considerations, the formation temperature, $-logfs_2$, $-logfo_2$ and pH of ore fluids progressively decreased and/or increased with time from skarn stage (433 to $345^{\circ}C$, 8.8 to 9.9 atm, 29.4 to 31.6 atm, and 6.1 to 7.2) to hydrothermal stage (245 to $315^{\circ}C$, 11.2 to 12.3 atm, 33.6 to 35.4 atm, and 7.3 to 7.8). The ${\delta}^{34}S$ values of sulfides have a wide range between 3.2 to 11.6‰. The calculated ${\delta}^{34}S_{H_2S}$ values of ore fluids are relatively homo-geneous as 2.9 to 5.4‰ (skam stage) and 8.7 to 13.5‰ (hydrothermal stage), which are a deep-seated igneous source of sulfur indicates progressive increasing due to the mixing of oxidized sedimentary sulfur with increasing paragenetic time. The ${\delta}^{13}C$ values of carbonates in ores range from -4.6 to -2.5‰. Oxygen and hydrogen isotope data revealed that the ${\delta}^{38}O_{H_2O}$ and ${\delta}D$ values of ore fluids decreased gradually with time from 14.7 to 1.8‰ and -85 to -73‰ (skarn stage), and from 11.1 to -0.2‰ and -87 to -80‰ (hydrothermal stage), respectively. This indicates that magmatic water was dominant during the early skarn mineralization but was progressively replaced by meteoric water during the later hydrothermal replacement.

• 자원환경지질
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• 제25권1호
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• pp.1-16
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• 1992

The Wondong Fe-Pb-Zn deposit is located in endo and exoskarns formed along the contact between the Makkol limestone interbedding pelitic limestone of Ordovician age and quartz porphyry of Cretaceous age. At the Wondong mine, the endoskarn shows a discontinuous zonal arrangement from quartz porphyry to pelitic limestone as follows: unaltered quartz porphyry, weakly altered quartz porphyry zone, intensively altered pinkish quartz porphyry zone, garnet zone, and greyish white and fine-grained clinopyroxene zone developed at pelitic limestone side. In terms of chemical mass balance, intensively altered pinkish quartz porphyry relative to unaltered quartz porphyry shows substantial enrichments in $K_2O$, $Na_2O$, and HREE and depletions in MgO, CaO, total $Fe_2O_3$, and LREE. On the other hand, garnet zone of endoskarn is enriched in CaO, MnO, total $Fe_2O_3$, MgO and depleted in $K_2O$, $Na_2O$. $Al_2O_3$ seems to be determining inert component. Thus the behavior of elements indicates that the mobility of elements depends on the equilibration of hydrothermal fluid and minerals and affects on enrichments by fractionation from and depletions by partition to hydrothermal fluid, respectively. Traversing toward pelitic limestone from a central zone of exoskarn, the exoskarn also shows a zonal arrangement as follows: garnet zone, clinopyroxene zone, and decolored pelitic limestone. The arrangement of mineral assemblages in skarns of the Wondong mine is the result of an increase in CaO and $K_2O$ toward the pelitic limestone. Skarn and ore minerals were formed in the following sequence: early skarn, late skarn and magnetite, pyrite, sphalerite, galena, and molybdenite. On the basis of stabilities of mineral assemblages, physicochemical conditions of the late skarn and magnetite mineralization are estimated to be $350^{\circ}C{\leq}T{\leq}400^{\circ}C$ at 1 Kb, $-23{\leq}log\;fO_2{\leq}-18$, and $0.005{\leq}XCO_2{\leq}0.01$, while those of the early skarn to be $420^{\circ}C{\leq}T{\leq}550^{\circ}C$ at 1 Kb.

• 자원환경지질
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• 제23권2호
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• pp.127-133
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• 1990

Relation between fluid inclusions and mineralization has been studied for 30 granitoid specimens from 19 localities in South Korea. Polyphase inclusions are found in granitoid specimens of 9 localities. In the vicinities of 6 localities among them occurs any of W, Cu or Fe deposits of the vein-, stockwork-, skarn-or pegmatite-type. On the contrary, no ore deposit is reported near the granitoids characterized by no polyphase inclusion except only one locality. This fact implies that the occurrence of polyphase inclusions is a good indicator for such kinds of mineralization. Ores and country rocks of some of the deposits contain polyphase inclusions in their quartz crystals. The fact that many polyphase inclusions occur in granitoids and ore constituents suggests that highly saline hydrothermal solution played an important role for the formation of such kinds of deposits. On the contrary, the granite and the ore of the Mugug gold deposit have many fluid inclusions, but are free from the polyphase type.

• 자원환경지질
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• 제15권4호
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• pp.189-204
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• 1982

The Geodo mine is located in the southern limb of the Hambaeg syncline. Geology of the area consists of Paleozoic-Mesozoic sedimentary Rocks and Cretaceous igneous rocks. The important igneous rocks presumably related to skarnization and ore mineralization in the area, are the early granodiorite and the late porphyritic granodiorite. Two mineralogical types of ore deposits are recognized in the area. They are the Fe-Cu deposits in the Myobong formation and the Au-Bi-Cu deposits in the Hwajeol formation. Contact metamorphism due to granodiorite intrusion includes hornfelsization, exoskarnization and endoskarnization. Wall-rock alterations related to the Fe mineralization are grouped into the hydrothermal replacement skarnization and the hydrothermal filling skarnization. Another hydrothermal alteration is associated with the Cu mineralization. Various mineralogical analyses have been applied for the identification of minerals. They include optical microscopy, chemical analysis, etching test, X-ray diffraction, and infrared absorption spectroscopic analyses. The ore minerals in these ore deposits are classified into two groups;hypogene and supergene minerals. Hypogene minerals consist of magnetite, pyrite, chalcopyrite, and chalcocite. Supergene minerals consist of chalcocite, bornite, and geothite. Ore minerals show various kinds of ore texture: open-space filling, exsolution, replacement, and cementation texture. The gangue minerals consist of quartz, diopside, epidote, garnet and plagioclase in the hornfelsic zone, garnet, diopside, scapolite, actinolite, sericite, chlorite, quartz, and calcite in the skarn zone, and, epidote, chlorite, sericite, quartz, and calcite in the late hydrothermal alteration zone. This study shows that the Fe-Cu deposits are of metasomatic pipe type with the later hydrothermal fillings, and the Au-Bi-Cu deposits are of hydrothermal fissure-filling type. The mineralization is probably related to the intrusion of porphyritic granite.