• Journal of the Mineralogical Society of Korea
• /
• v.26 no.4
• /
• pp.219-228
• /
• 2013

To understand characteristics of biogeochemical corrosion for the metal canisters that usually contain the radioactive wastes for a long-term period below the ground, some metal materials consisting of cast iron and copper were reacted for 3 months with D. desulfuricans, a sulfate-reducing bacterium, under a reducing condition. During the experiment, concentrations of dissolved metal ions were periodically measured, and then metal specimen and surface secondary products were examined using the electron microscopy to know the chemical and mineralogical changes of the original metal samples. The metal corrosion was not noticeable at the absence of D. desulfuricans, but it was relatively greater at the presence of the bacterium. In our experiment, darkish metal sulfides such as mackinawite and copper sulfide were the final products of biogeochemical metal corrosion, and they were easily scaled off the original specimen and suspended as colloids. For the copper specimen, in particular, there appeared an accelerated corrosion of copper in the presence of dissolved iron and bacteria in solution, probably due to a weakening of copper-copper binding caused by a growth of other phase, iron sulfide, on the copper surface.

• Economic and Environmental Geology
• /
• v.43 no.5
• /
• pp.455-466
• /
• 2010

Seabed mineral resources explored by Korea are categorized into major three types of deposit; manganese nodule, manganese crust and polymetallic sulfides. Pt displays high enrichment factors (400, ore/crust ratios) in manganese nodule. Rare earth oxide content in manganese nodule ranges from 0.037 to 0.302 REO % with mean value of 0.12 REO %. Both of Te and Pt are enriched elements in manganese crust, displaying enrichment factors of 10800 and 150, respectively. Rare earth oxide's contents of manganese crust are slightly higher than manganese nodule's (0.013~0.387 REO %, average = 0.18 REO %). Se and In are outstanding rare metals from seabed polymetallic sulfides, showing enrichment factors of 1300 and 110, respectively. Au (0.8~26.3 g/t) and Ag (0.9~348.0 g/t) are another enriched elements in polymetallic sulfides. The main concern at exploiting seabed mineral resource will be a securing rare metals for high-technology industries and rare metals from subsea mineral deposits will add economic values to commodity candidates such like Co, Ni and Cu.

• Journal of the Speleological Society of Korea
• /
• no.92
• /
• pp.9-18
• /
• 2009

A number of closed metal mines act as point sources of contamination on nearby streams, soils and plants in our country. The contamination of twelve decomposed samples had earned from nine closed metal mines had been evaluated by TEA-3000. The contents of heavy metal with ion fraction exchange and carbonate fraction forms had been showed that the speciation of heavy metals represented with easy solubility, mobility and bioavailable of plants, and in case of sulfide compounds and organic residuals forms are related with the speciation of metals which may be stable forms because of strong bindable capacity. Also heavy metals elements in mosts of mines got with relative stable within crystal lattice, but results of trace element analyser showed that, in the most of tailings from mine areas, large portions of concentration of heavy metals were explained as stable from, sulfides/ organics and residual. In tailing from Imchun mines, the concentrations extracted by water were relatively high as compared with other mine areas whose total concentrations were very high because of large quantities of exchangeable ions and carbonates and low soil pH. Danger Index (D.I.) suggested in this study was based on the cumulative concentrations of step 1 and 2 from the result of trace element analyser. When the soil pH was considered, this index became better indicator to determine the priority for the remediation of mine area.

• Proceedings of the Mineralogical Society of Korea Conference
• /
• 2002.10a
• /
• pp.119-136
• /
• 2002

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 (c.a. 200-150 (?) Ma) coincident with orogenic time, gold mineralization took place between c.a. 195 and 135 (127 ?) Ma. The Jurassic Au deposits commonly show several characteristics; prominent association with pegmatites, low Ag/hu ratios in the ore-concentrating parts, massive vein morphology and a distinctively simple mineralogy including Fe-rich sphalerite, galena, chalcopyrite, arsenopyrite, Au-rich electrum, pyrrhotite and/or pyrite. During the Bulgugsa igneous activities $(110\~50Ma)$, the precious-metal deposits are generally characterized by such features as complex vein morphology, medium to high AE/AU ratios in the ore concentrates, and diversity of ore minerals including base-metal sulfides, pyrite, arsenopyrite, Ag-rich electrum and native silver nth Ag sulfides, Ag-Sb-As sulfosalts and Ag tellurides. Vein morphology, mineralogical, fluid inclusion and stable isotope results indicate the diverse genetic natures of hydrothermal systems in Korea. The Jurassic Au-dominant deposits (orogenic type) were formed at the relatively high temperature $(about\;300^{\circ}\;to\;450^{\circ}C)$ and deep-crustal level $(4.0{\pm}1.5\;kb)$ from the hydrothermal fluids containing more amounts of magmatic waters $(\delta\;^{18}O_{H2O}\;5\~10\%_{\circ})$. It can. It can be explained by the dominant ore-depositing mechanisms as $CO_2$ boiling and sulfidation, suggestive of hypo- to mesothermal environments. In contrast, the Cretaceous Au-dominant $(l13\~68\;Ma),\;Au-Ag \;(108\~47\;Ma)$ and Ag-dominant $(103\~45\;Ma)$ deposits, which correspond to volcanic-plutonic-related type, occurred at relatively low temperature $(about\;200^{\circ}\;to\;350^{\circ}C)$ and shallow-crustal level $(1.0\{pm}0.5\;kb)$ from the ore-forming fluids containing more amounts of less-evolved meteoric waters$(\delta\;^{18}O_{H2O}\;-10\~5\%_{\circ})$. These characteristics of the Cretaceous precious-metal deposits can be attributed to the complexities in the ore-precipitating mechanisms (mixing, boiling, cooling), suggestive of epi- to mesothermal 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 styles.

• Proceedings of the KSEEG Conference
• /
• 2002.10a
• /
• pp.119-136
• /
• 2002

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. Dunng the Daebo igneous activities (c.a. 200～150 (\ulcorner) Ma) coincident with orogenic time, gold mineralization took place between c.a. 195 and 135 (127 \ulcorner) Ma. The Jurassic Au 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, arsenopyrite, Au-rich electrum, pyrrhotite and/or pyrite. During the Bulgugsa igneous activities (110～50 Ma), the precious-metal deposits are generally characterized by such features as complex vein morphology, medium to high Ag/Au ratios in the ore concentrates, and diversity of ore minerals including base-metal sulfides, pyrite, arsenopyrite, Ag-rich eletrum and native silver with Ag sulfides, Ag-Sb-As sulfosalts and he tellurides. Vein morphology, mineralogical, fluid inclusion and stable isotope results indicate the diverse genetic natures of hydrothermal systems in Korea. The Jurassic Au-dominant deposits (orogenic type) were formed at the relatively high temperature (about 300$^{\circ}$ to 45$0^{\circ}C$) and deep-crustal level (4.0$\pm$1.5 kb) from the hydrothermal fluids containing more amounts of magmatic waters ($\delta$$^{18}$ $O_{H2O}$; 5～10$\textperthousand$). It can be explained by the dominant ore-depositing mechanisms as $CO_2$ boiling and sulfidation, suggestive of hypo- to mesothermal environments. In contrast, the Cretaceous Au-dominant (l13～68 Ma), Au-Ag (108～47 Ma) and AE-dominant (103～45 Ma) deposits, which correspond to volcanic-plutonic-related type, occurred at relatively low temperature (about 200$^{\circ}$ to 35$0^{\circ}C$) and shallow-crustal level (1.0$\pm$0.5 kb) from the ore-forming fluids containing more amounts of less-evolved meteonc waters ($\delta$$^{18}$ $O_{H2O}$;-10～5$\textperthousand$). These characteristics of the Cretaceous precious-metal deposits can be attributed to the complekities in the ore-precipitating mechanisms (mixing, boiling, cooling), suggestive of epi- to mesothermal 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 styles.les.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.11 no.2
• /
• pp.95-102
• /
• 2013

There was a study for biological characteristics, except for physico-chemical and mineralogical properties, on the natural bentonite that is considered as a buffer material for the high-level radioactive waste disposal site. A bentonite slurry that was prepared from a local 'Gyeongju bentonite' in Korea was incubated in a serum bottle with nutrient media over 1 week and its stepwise change was observed with time. From the activated bentonite in the nutrient media, we can find a certain change of both solid and liquid phases. Some dark and fine sulfides began to be generated from dissolved sulfate solution, and 4 species of sulfate-reducing bacteria (SRB) were identified as living cells in samples that were periodically taken and incubated. These results show that sulfate-reducing (or metal-reducing) bacteria are adhering and existing in the powder of bentonite, suggesting that there may be a potential occurrence of longterm biogeochemical effects in and around the bentonite buffer in underground anoxic environmental conditions.

• Economic and Environmental Geology
• /
• v.29 no.2
• /
• pp.105-117
• /
• 1996

The Baegjeon Au-Ag and Sb deposits, small of disseminated-type gold deposits are formed as a result of epithermal processes associated a shallow-seated Cretaceous Yeogdun granitoids intrusion. The orebodies are formed by the replacement of carbonate minerals in thin-bedded oolitic limestone beds favorable for mineralization within the upper-most Cambrian Pungchon Limestone Formation. The mineralization can be recognized one stage, ore minerals composed of base metal sulfides, electrum, AgSb-S, Ag-Cu-S, and Sb-S minerals. Gold-bearing minerals consist of electrum and submicroscopic invisible gold in pyrite and arsenopyrite. The composition of electrums ranges from 33.58 to 63.48 atomic % Ag. Fluid inclusion studies reveal that ore fluids were low saline $NaCl-CO_2-H_2O$ system. Temporary fluid mixing and boiling occured in later stage. Fluid inclusion data indicates the homogenization temperatures and salinities of NaCl eqivalent wt% were 176 to $246^{\circ}C$ and from 0.0 to 4.8 wt%, respectively. And $-logfs_2$, of mineralization obtained by thermodynamic considerations as 12.4 to 13.8 atm. The ${\delta}^{34}S_{H_2S}$, values of hydrothermal sulfides were calculated to be 6.8 to 10.2‰ which was of sedimentary origin. The ${\delta}^{18}O_{H_2O}$ and ${\delta}^{13}C_{CO_2}$, range from -3.9 to 9.6‰, from -1.1 to -2.2‰, and ${\delta}D$ range from -89 to -118‰, respectively. The Au deposition during mineralization seems to have occurred as a result of decrease of temperature, $fs_2$, $fo_2$, and pH probably due to oxidation by meteoric water mixing, which destabilized original $Au(HS)^-{_2}$. The mineralization of the Baegjeon deposits is similar to the Carlin-type deposits characterized by sediments-hosted epithermal bedding replacement disseminated gold deposits.

• Economic and Environmental Geology
• /
• v.18 no.4
• /
• pp.331-342
• /
• 1985

The Dongbo tungsten-molybdenum deposits are fissure-filling veins emplaced in granites of late Cretaceous age. Integrated field, mineralogic and fluid inclusion studies were undertaken to illuminate the characters and origin of the ore deposits. Mineral paragenesis is complicated by repeated fracturing, but four distinct depositional stages can be recognized; (I) tungsten-molybdenum minerals-quartz-chlorite stage, (II) iron-oxide and sulfides-quartz stage, (III) iron -oxide-base metal sulfides-sulfosalts-quartz-carbonates stage, (IV) barren rhodochrosite-zeolite stage. Fluid inclusion studies were carried out for stage I quartz and stage III quartz, sphalerite and calcite. Fluid inclusion studies reveals highly systematic trends of homogenization temperature and salinity throughout the mineralization. Ore fluids during stage I were complex, NaCl rich brine and salinity reached values as high as 34.4 weight percent equivalent NaCl, but the later ore fluids were more dilute and reached to 9.7 weight percent equivalent NaCl during stage III. Intermittent boiling of ore fluid during stage I is indicated by the fluid inclusions in stage I quartz. Depositional temperatures and pressures during stage I range from $520^{\circ}C$ to $265^{\circ}C$and from 600 to 400 bars. Homogenization temperatures of the stage III quartz, sphalerite and calcite range from $305^{\circ}C$ to $190^{\circ}C$. Fluid inclusion data from the Dongbo mine are nearly similar to those from other hydrothermal tungsten deposits in the Kyeongsang basin. Depositional temperature and salinity of ore fluids during precipitation of tungsten-molybdenum minerals in Dongbo mine were much higher, but $CO_2$ contents were much lower than those from hydrothermal tungsten-molybdenum deposits of late Cretaceous plutonic association in central parts of Korean peninsula.

• Transactions of Materials Processing
• /
• v.8 no.3
• /
• pp.301-301
• /
• 1999

Austenitic stainless steels such as AISI 316L have been used in equipment in which fluid flows at high speeds which can induce cavitation erosion on metallic surfaces due to the collapse of cavities, where the collapse is caused by the sudden change of local pressure within the liquid. Usually AISI 316L is susceptible to cavitation erosion. This research focuses on developing a better material to replace the AISI 316L used in equipment with high speed fluid flow, such as impellers. The effects of Rare Earth Metal (REM) additions on the cavitation erosion-corrosion resistance of duplex stainless steels were studied using metallographic examination, the potentiodynamic anodic polarization test, the tensile test, the X-ray diffraction test and the ultrasonic cavitation erosion test. The experimental alloys were found to have superior mechanical properties due to interstitial solid solution strengthening, by adding high nitrogen (0,4%), as well as by the refinement of phases and grains induced by fine REM oxides and oxy-sulfides. Corrosion resistance decreases in a gentle gradient as the REM content increases. However, REM containing alloys show superior corrosion resistance compared with that of other commercial alloys (SAF 2507, AISI 316L). Owing to their excellent mechanical properties and corrosion resistance, the alloys containing REM have high cavitation erosion-corrosion resistance.

• Journal of Powder Materials
• /
• v.29 no.3
• /
• pp.252-261
• /
• 2022

Cobalt is a vital metal in the modern society because of its applications in lithium-ion batteries, super alloys, hard metals, and catalysts. Further, cobalt is a representative rare metal and is the 30th most abundant element in the Earth's crust. This study reviews the current status of cobalt extraction and recycling processes, along with the trends in its production amount and use. Although cobalt occurs in a wide range of minerals, such as oxides and sulfides of copper and nickel ores, the amounts of cobalt in the minerals are too low to be extracted economically. The Democratic Republic of Congo (DRC) leads cobalt mining, and accounts for 68.9 % of the global cobalt reserves (142,000 tons in 2020). Cobalt is mainly extracted from copper-cobalt and nickel-cobalt concentrates and is occasionally extracted directly from the ore itself by hydro-, pyro-, and electro-metallurgical processes. These smelting methods are essential for developing new recycling processes to extract cobalt from secondary resources. Cobalt is mainly recycled from lithium-ion batteries, spent catalysts, and cobalt alloys. The recycling methods for cobalt also depend on the type of secondary cobalt resource. Major recycling methods from secondary resources are applied in pyro- and hydrometallurgical processes.