• Title/Summary/Keyword: Au/Ag

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Element Dispersion and Wall-rock Alteration from Daebong Gold-silver Deposit, Republic of Korea (대봉 금-은광상의 모암변질과 원소분산 특성 연구)

  • Yoo, Bong-Chul;Chi, Se-Jung;Lee, Gil-Jae;Lee, Jong-Kil;Lee, Hyun-Koo
    • Economic and Environmental Geology
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    • v.40 no.6
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    • pp.713-726
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    • 2007
  • The Daebong deposit consists of gold-silver-bearing mesothermal massive quartz veins which fill fractures along fault zones($N10{\sim}20^{\circ}W,\;40{\sim}60^{\circ}SW$) within banded gneiss or granitic gneiss of Precambrian Gyeonggi massif. Ore mineralization of the deposit is composed of massive white quartz vein(stage I) which was formed in the same stage by multiple episodes of fracturing and healing and transparent quartz vein(stage II) which is separated by a major faulting event. The hydrothermal alteration of stage I is sericitization, chloritization, carbonitization, pyritization, silicification and argillization. Sericitic zone occurs near and at quartz vein and includes mainly sericite, quartz, and minor illite, carbonates and epidote. Chloritic zone occurs far from quartz vein and is composed of mainly chlorite, quartz and minor sericite, carbonates and epidote. Fe/(Fe+Mg) ratios of sericite and chlorite range 0.36 to 0.59($0.51{\pm}0.10$) and 0.66 to 0.73($0.70{\pm}0.02$), and belong to muscovite-petzite series and brunsvigite, respectively. Calculated $Al_{IV}-Fe/(Fe+Mg)$ diagrams of sericite and chlorite suggest that this can be a reliable indicator of alteration temperature in Au-Ag deposits. Calculated activities of chlorite end member are $a3(Fe_5Al_2Si_3O_{10}(OH){_6}=0.00964{\sim}0.0291,\;a2(Mg_5Al_2Si_3O_{10}(OH){_6}= 9.99E-07{\sim}1.87E-05,\;a1(Mg_6Si_4O_{10}(OH){_6}=5.61E-07{\sim}1.79E-05$. It suggest that chlorite from the Daebong deposit is iron-rich chlorite formed due to decreasing temperature from $T>450^{\circ}C$. Calculated $log\;{\alpha}K^+/{\alpha}H^+,\;log\;{\alpha}Na^+/{\alpha}H^+,\;log\;{\alpha}Ca^{2+}/{\alpha}^2H^+$ and pH values during wall-rock alteration are $4.6(400^{\circ}C),\;4.1(350^{\circ}C),\;4.0(400^{\circ}C),\;4.2(350^{\circ}C),\;1.8(400^{\circ}C),\;4.5(350^{\circ}C),\;5.4{\sim}6.5(400^{\circ}C)\;and\;5.1{\sim}5.5(350^{\circ}C)$, respectively. Gain elements (enrichment elements) during wallrock alteration are $K_2O,\;P_2O_5,\;Na2O$, Ba, Sr, Cr, Sc, V, Pb, Zn, Be, Ag, As, Ta and Sb. Elements(Sr, V, Pb, Zn, As, Sb) represent a potentially tools for exploration in mesothermal and epithermal gold-silver deposits.

Metallogeny on Gold-Silver in South Korea (남한(南韓)의 금(金)·은광화작용(銀鑛化作用)에 대(對)한 고찰(考察))

  • Kim, Won Jo
    • Economic and Environmental Geology
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    • v.19 no.4
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    • pp.243-264
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    • 1986
  • This work is a metallogeny on gold-silver deposits in South Korea based on the close examination of the author's own data and a broad review of existing literature available. The metallogenic epochs in Korea are temporarily connected with the history of tectonism and igneous activities, and are identified as the Precambrian, Paleozoic, Jurassic to early Cretaceous, late Cretaceous to early Tertiary, and Quaternary epochs, whereas the metallogenic provinces are spatially associated with some of the felsic to intermediate igneous rocks, lacking mineralization related to basic and ultrabasic rocks. The metallogeny on the gold-silver deposits is mostly related to the granitic rocks intrusives. Epigenetic gold-silver mineralization in South Korea ranges in metallogenic epochs from Precambrian through Triassic, Jurassic and Cretaceous to Eocene (?), in genetic types from hypothermal through mesothermal and epithermal quartz-sulfide veins to volcanogenic stockworks, with some disseminated types. Reporting on metallic association from gold without silver, gold-silver, silver-gold, silver without gold, and gold or silver as a by-product from other metallic ores. The most representative genetic types and metal associations of gold-silver deposits are hydrothermal quartz veins associated with the Daebo and Bulgugsa granitic magmatism. The most closely associated paragenetic metallic minerals in gold-silver hydrothermal quartz-sulfide vein type deposits are: copper, lead, zinc, pyrite and arsenopyrite. More than 560 gold-silver mines are plotted in the distribution map grouped within the 10 different metallogenic provinces of South Korea. Specific mineralizations with related mineral association in both sulfides and gangues observed selected from 18 Korean and 8 Japanese Au-Ag deposits. The 7 selected individual gold-silver mines representing specific mineralization types are described in this report.

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Iron, Manganese and Cadmium Contents of Sphalerites and their Genetical Implications to Hydrothermal Metallic Ore Deposits in Korea (국내산(國內産) 섬아연석(閃亞鉛石)의 Fe, Mn, Cd함량변화(含量變化)와 열수금속광상(熱水金屬鑛床) 성인(成因)과의 관련성(關聯性))

  • Chon, Hyo Taek;Shimazaki, Hidehiko
    • Economic and Environmental Geology
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    • v.19 no.spc
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    • pp.139-149
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    • 1986
  • Compositional variation of sphalerites from various hydrothermal metallic ore deposits in Korea were investigated in mine and local, and regional scale. The sphalerites were partially analyzed for iron, manganese, and cadmium by using an electron probe microanalyzer(EPMA). The contents of iron and cadmium in sphalerites collected from the Weolam deposit of the No.1 Yeonhwa mine are not variable with increase of depth, but manganese content is highly variable. Sphalerites from lead-zinc deposits which are geologically associated with hypabyssal and effusive activity are characterized by high manganese (more than 1.0 MnS mole %) and low cadmium contents (less than 0.5 CdS mole %). Relatively manganese rich sphalerites are found in the deposits where sphalerites are enriched in iron content. Variation of cadmium content is very limited compared with that of manganese content. Sphalerites from most tungsten and some gold-silver deposits are remarkably high in cadmium content, but most of base metal and iron deposits are low in cadmium content. Cadmium content in sphalerites which occur in the metallic ore deposits genetically associated with plutonic activity shows a tendency to high variation. Available amounts of cadmium in sphalerites could be originated from the initial enrichment during the magmatic and postmagmatic processes.

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Genetic Model of Mineral Exploration for the Korean Au-Ag Deposits; Mugeug Mineralized Area (한국 금-은 광상의 효율적 탐사를 위한 성인모델;무극 광화대를 중심으로)

  • 최선규;이동은;박상준;최상훈;강흥석
    • Economic and Environmental Geology
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    • v.34 no.5
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    • pp.423-435
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    • 2001
  • The gold-silver vein deposits in the Mugeug mineralized area are emplaced in late Cretaceous biotite granite associated with the pull-apart type Cretaceous Eumseong basin. Mugeug mine in northern part is composed of multiple veins showing relatively high gold fineness and is characterized by sericitization, chloritization and epidotization. The ore-forming fluids were evolved by dilution and cooling mechanisms at relatively high temperature and salinity (=30$0^{\circ}C$,1~9 equiv. wt. % NaCl) and highly-evolved meteoric water ($\delta$$^{18}$ O;-1.2~3.7$\textperthousand$) and gold mineralization associated with sulfides tormed at temperatures between 260 and 22$0^{\circ}C$ and within sulfur fugacity range of 10$^{-11.5}$ ~ 10$^{-13.5}$ atm. In contrast, Geumwang, Geumbong and Taegueg mines show the low fineness values, in southern part are characterized by increasing tendency of simple and/or stockwork veins and by kaolinitization, silicificatitan, carbonatization and smectitization. These droposits formed at relatively low temperature and salinity (<23$0^{\circ}C$, <3 equiv. wt. % NaCl) from ore-forming fluids containing greater amounts of less-evolved meteoric waters ($\delta$$^{18}$ O;-5.5~4.0$\textperthousand$), and silver mineralization representing various gold-and/or silver-bearing minerals formed at temperatures between 200 and 15$0^{\circ}C$ and from sulfur fugacity range of 10$^{-15}$ ~10$^{-18}$ atm These results imply that mineralization in the Mugueg area formed at shallow-crustal level and categorize these deposits as low-sulfidation epithermal type. The genetic differences between the northern and southern parts reflect the evolution of the hydrothermal system due to a different physicochemical environment from heat source area (Mugeug mine) to marginal area (Taegeum mine) in a geothermal field.

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Risk Assessment of Arsenic by Human Exposure of Contaminated Soil, Groundwater and Rice Grain (오염된 토양, 지하수 및 쌀의 인체노출에 따른 비소의 위해성 평가)

  • Lee Jin-Soo;Chon Hyo-Taek
    • Economic and Environmental Geology
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    • v.38 no.5 s.174
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    • pp.535-545
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    • 2005
  • Environmental survey from some abandoned metal mine areas was undertaken on to assess the risk of adverse health effects on human exposure to arsenic influenced by past Au-Ag mining activities. Elevated levels of As were found in tailings from the studied mine areas. This high concentration may have a impact on soils and waters around the tailing piles. In order to perform the human risk assessment, chemical analysis data of soils, rice grains and waters fur As have been used. The HQ values fer As via the rice grain and groundwater consumption were significantly higher compared with other exposure pathways in all metal mine areas. However, there were minimal soil and water dermal contact risks. The resulting Hl values of As from the Dongil, Okdong and Hwacheon mine areas were higher than 5.0, and their toxic risk due to drinking water and rice grain was strong in these mine areas. The cancer risk of being exposed to As by the rice grain route from the Dongil, Okdong and Hwacheon mine areas was $5.2\times10^{-4},\;6.0\times10^{-4}\;and\;8.1\times10^{-4}$, respectively. The As cancer risk via the exposure pathway of drinking water from these mine areas exceeded the acceptable risk of 1 in 10,000 fer regulatory purposes. Thus, the daily intakes of groundwater and rice grain by the local residents from the Dongil, Okdong and Hwacheon mine areas can pose a potential health threat if exposed by long-term arsenic exposure.

The Transition of Production, Consumption and Price of Non-ferrous Metals (비철금속(非鐵金屬)의 생산(生産), 소비(消費), 시세(時勢)의 추이(推移))

  • Moon, W.J.
    • Economic and Environmental Geology
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    • v.2 no.3
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    • pp.1-25
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    • 1969
  • In considering the mining industry, it is necessary to study the production, consumption and price of ore and metals in every country of the world in order to determine the trend of the industry in the present and for the future. This study is necessary especially for exporting domestically produced are which is in excess of domestic consumption and for importing are, or metal where local production does not meet domestic demand. It will be treated of Au, Ag, Cu, Pb, Zn, W, Mo, which are the most important non-ferrous metals, and which greatly affect the mining industry of Korea. The presentation will concern itself only with the free world. About 1, 200 ton of gold are produced annually with little fluctiation in recent years. Most of the gold produced is consumed by advanced countries for industrial uses as well as for producing precious objects. The U.S.A. expends yearly about four times its domestic production and Japan about three times its domestic production for industry and arts. Because of the instability of the currency of the U.S.A., England and France, recently, the price of gold has been $ 41-42 per ounce, whereas the official price is $35.00 per ounce. It will be expected that the official price will be raised in the near future. As for silver, about 6,500 tons are produced annually with no special fluctuation change in recent years. However, the annual consumption is about 14,000 ton, so the supply and demand is extremely unbalanced. The shortage is made up by the sale of the U.S. treasury's reserve stock and the reclaiminig of silver from coins and other scrap. As the Treasury'S reserves will be exhausted in a year or two, the price of silver which is $1. 64 per ounce, will go up drastically in about a year. As for copper, 5,257,000 ton's were mined in 1966. It's production is being increased about 5% annually. However, consumption exceeds production by about 100,000 ton a year. The recent Foreign refinery copper price in the U.S.A is $ 60 per pound. The supply of copper being insufficient to meet international demands, the price will go up and with no prospect of being lowered in the near future even with the slight annual increase in production. About 2,100,000 to 2,200,000 tons of lead are produced annually. Consumption exceeds production by about 50,000-60,000 tons annually. The current price of lead in New York is $ 155 per pound. As the supply of lead is internationally stable, It will be believed that there will be no significant change in its price in the near future. In 1967, 3,926,000 tons of Zinc were produced. There is annual increase of 4-7% in production. The annual consumption exceeds production by 100,000 to 200,000 tons. The current zinc price in the St. Louis market inthe U.S.A. is $ 145 per pound. Even though its supply is stable and sufficient world wide, the consumption rate will increase at a faster pace than before; hence, the price will slowly go up. Tungsten mines yield about 11,000 tons a year. Its production has been relatively constant in the past few years. The amount of its consumption increases slowly world wide, but in the free world· there has been a slight annual decrease. However, since Red China has not been exporting their tungsten to other countries for several months, the price on the London market of S.T.U. of $Wo_3$ has increased to $ 44~46. Should Red China begin to export actively again the price will drop to $ 40~42. In 1967, 56,000 tons of Molybdenum were produced. Production exceeds consumption by 200,000 -30,000 tons annually. The current price in the U.S.A. is $ 1.72 per Mo pound. Since the rate of production in the U.S.A. is on the increase with large amounts of ore reserve, the price of molubdenum should not go up.

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Characterization of Arsenic Immobilization in the Myungbong Mine Tailing (명봉광산의 광미 내 비소의 고정화 특성 연구)

  • Lee, Woo-Chun;Jeong, Jong-Ok;Kim, Ju-Yong;Kim, Soon-Oh
    • Economic and Environmental Geology
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    • v.43 no.2
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    • pp.137-148
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    • 2010
  • The Myoungbong mine located in Boseong-gun, Jellanamdo consists of Au-Ag bearing quartz veins which filled the fissures of Bulguksa granitic rocks of Cretaceous. The tailings obtained from the Myungbong mine were used to investigate the effects of various processes, such as oxidation of primary sulfides and formation(alteration) of secondary and/or tertiary minerals, on arsenic immobilization in tailings. This study was conducted via both mineralogical and chemical methods. Mineralogical methods used included gravity and magnetic separation, ultrasonic cleaning, and instrumental analyses(X-ray diffractometry, energy-dispersive spectroscopy, and electron probe microanalyzer) and aqua regia extraction technique for soils was applied to determine the elemental concentrations in the tailings. Iron (oxy)hydroxides formed as a result of oxidation of tailings were identified as three specific forms. The first form filled in rims and fissures of primary pyrites. The second one precipitated and coated the surfaces of gangue minerals and the final form was altered into yukonites. Initially, large amounts of acid-generating minerals, such as pyrite and arsenopyrite, might make the rapid progress of oxidation reactions, and lots of secondary minerals including iron (oxy)hydroxides and scorodite were formed. The rate of pH decrease in tailings diminished, in addition, as the exposure time of tailings to oxidation environments was prolonged and the acid-generating minerals were depleted. Rather, it is speculated that the pH of tailings increased, as the contribution of pH neutralization reactions by calcite contained in surrounding parental rocks became larger. The stability of secondary minerals, such as scorodite, were deteriorated due to the increase in pH, and finally arsenic might be leached out. Subsequently, calcimn and arsenic ions dissociated from calcites and scorodites were locally concentrated, and yukonite could be grown tertiarily. It is confirmed that this tertiary yukonite which is one of arsenate minerals and contains arsenic in high level plays a crucial role in immobilizing arsenic in tailings. In addition to immobilization of arsenic in yukonites, the results indicate that a huge amount of iron (oxy)hydroxides formed by weathering of pyrite which is one of typical primary minerals in tailings can strongly control arsenic behavior as well. Consequently, this study elucidates that through a sequence of various processes, arsenic which was leached out as a result of weathering of primary minerals, such as arsenopyrite, and/or redissolved from secondary minerals, such as scorodite, might be immobilized by various sorption reactions including adsorption, coprecipiation, and absorption.

Environmental effects from Natural Waters Contaminated with Acid Mine Drainage in the Abandoned Backun Mine Area (백운 폐광산의 방치된 폐석으로 인한 주변 수계의 환경적 영향)

  • 전서령;정재일;김대현
    • Economic and Environmental Geology
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    • v.35 no.4
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    • pp.325-337
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    • 2002
  • We examined the contamination of stream water and stream sediments by heavy metal elements with respect to distance from the abandoned Backun Au-Ag-Cu mine. High contents of heavy metals (Pb, Zn, Cu, Cd, Mn, and Fe) and aluminum in the waters connected with mining and associated deposits (dumps, tailings) reduce water quality. In the mining area, Ca and SO$_4$ are predominant cation and anion. The mining water is Ca-SO$_4$ type and is enriched in heavy metals resulted from the weathering of sulfide minerals. This mine drainage water is weakly acid or neutral (pH; 6.5-7.1) because of neutralizing effect by other alkali and alkaline earth elements. The effluent from the mine adit is also weakly acid or neutral, and contains elevated concentrations of most elements due to reactions with ore and gangue minerals in the deposit. The concentration of ions in the Backun mining water is high in the mine adit drainage water and steeply decreased award to down stream. Buffering process can be reasonably considered as a partial natural control of pollution, since the ion concentration becomes lower and the pH value becomes neutralized. In order to evaluate mobility and bioavailability of metals, sequential extraction was used for stream sediments into five operationally defined groups: exchangeable, bound to carbonates, bound to FeMn oxide, bound to organic matter, and residual. The residual fraction was the most abundant pool for Cu(2l-92%), Zn(28-89%) and Pb(23-94%). Almost sediments are low concentrated with Cd(2.7-52.8 mg/kg) than any other elements. But Cd dominate with non stable fraction (68-97%). Upper stream sediments are contaminated with Pb, and down area sediments are enriched with Zn. It is indicate high mobility of Zn and Cd.

Mineralogy and Genetic Environments of the Seongdo Pb-Zn deposit, Goesan (괴산 성도 연-아연 광상의 산출광물과 생성환경)

  • Ahn, Seongyeol;Shin, Dongbok
    • Economic and Environmental Geology
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    • v.50 no.5
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    • pp.325-340
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    • 2017
  • The Seongdo Pb-Zn deposit, located in the northwestern part of the Ogcheon Metamorphic Belt, consists of skarn ore replacing limestone within the Hwajeonri Formation of Ogcheon Group and hydrothermal vein ore filling the fracture of host rock. Skarn minerals comprise mostly hedenbergitic pyroxene, garnet displaying oscillatory zonal texture composed of grossular and andradite, and a small amount of wollastonite, tremolite, and epidote, indicating reducing condition of formation. Ore minerals of skarn ore include sphalerite and galena with a small amount of pyrite, pyrrhotite, and chalcopyrite. In hydrothermal vein ore, arsenopyrite, sphalerite, chalcopyrite, and pyrite occur with a small amount of galena, native Bi, and stannite. Chemical compositions of sphalerite vary from 17.4 mole% FeS in average for dark grey sphalerite, 3.6 mole% for reddish brown sphalerite in skarn ore, and to 10.3 mole% FeS in hydrothermal vein ore. In comparison with representative metallic deposits in South Korea on the FeS-MnS-CdS diagram, skarn and hydrothermal vein ore plot close to the field of Pb-Zn deposits and Au-Ag deposits, respectively. Arsenic contents of arsenopyrite in hydrothermal vein ore decrease from 31.93~33.00 at.% in early stage to 29.58~30.21 at.% in middle stage, and their corresponding mineralizing temperature and sulfur fugacity are $441{\sim}490^{\circ}C$, $10^{-6}{\sim}10^{-4.5}atm$. and $330{\sim}364^{\circ}C$, <$10^{-8}atm$. respectively. Phase equilibrium temperatures calculated from Fe and Zn contents for coexisting sphalerite and stannite in hydrothermal vein are $236{\sim}254^{\circ}C$. Sulfur isotope compositions are 5.4~7.2‰ for skarn ore and 5.4~8.4‰ for hydrothermal vein ore, being similar or slightly higher to magmatic sulfur, suggesting that ore sulfur was mostly of magmatic origin with partial derivation from host rocks. However, much higher sulfur isotope equilibrium temperatures of $549^{\circ}C$$487^{\circ}C$, respectively for skarn ore and hydrothermal ore, than those estimated from phase equilibria imply that isotopic equilibrium has not been fully established.

Characterization on the Behavior of Heavy Metals and Arsenic in the Weathered Tailings of Songcheon Mine (송천광산의 풍화광미 내 중금속 및 비소 거동 특성)

  • Lee, Woo-Chun;Kim, Young-Ho;Cho, Hyen-Goo;Kim, Soon-Oh
    • Journal of the Mineralogical Society of Korea
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    • v.23 no.2
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    • pp.125-139
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    • 2010
  • Behavior of heavy metals and arsenic in the tailings of Songcheon Au-Ag mine was characterized via both mineralogical and geochemical methods. Mineral composition of the tailings was investigated by X-ray diffractometry, energy-dispersive spectroscopy, and electron probe micro-analyzer (EPMA) and total concentrations of heavy metals and arsenic and their chemical forms were analyzed by total digestion of aqua regia and sequential extraction method, respectively. The results of mineralogical study indicate that the tailings included mineral particles of resinous shape mainly consisting of galena, sphalerite, pyrite, quartz, and scorodite, and specifically socordite was identified in the form of matrix. EPMA quantitative analyses were performed to evaluate the weatherability of each mineral, and the results suggest that it decreased in the sequence of arsenopyrite > galena > sphalerite > pyrite. The weathering pattern of galena was observed to show distinctive zonal structure consisting of secondary minerals such as anglesite and beudantite. In addition, almost all of arsenopyrite has been altered to scorodite existing asmatrix and galena, sphalerite, and pyrite which have lower weatherability than arsenopyrite were identified within the matrix of scorodite. During the process of alteration of arsenopyrite into scorodite, it is likely that a portion of arsenic was lixiviated and caused a great deal of detrimental effects to surrounding environment. The results of EPMA quantitative analyses verify that the stability of scorodite was relatively high and this stable scorodite has restrained the weathering of other primary minerals within tailings as a result of its coating of mineral surfaces. For this reason, Songcheon tailings show the characteristics of the first weathering stage, although they have been exposed to the surface environment for a long time. Based on the overall results of mineralogical and geochemical studies undertaken in this research, if the tailings are kept to be exposed to the surface environment and the weathering process is continuous, not only hazardous heavy metals, such as lead and arsenic seem to be significantly leached out because their larger portions are being partitioned in weakly-bound (highly-mobile) fractions, but the potential of arsenic leaching is likely to be high as the stability of scorodite is gradually decreased. Consequently, it is speculated that the environmental hazard of Songcheon mine is significantly high.