Transport Of Gold Research Articles

The solubility of gold and silver in the system AuAgSO 2H 2O at 25°C and 1 atm.

During supergene alteration of auriferous carbonate ore, the weathering fluids formed are likely to be alkaline and therefore unsuitable as a medium for gold transport as a chloride complex. Secondary gold remobilization in such deposits can often be attributed instead to gold complexing by sulphur-bearing ligands. Gold and silver solubility in the systems AuSO 2H 2O and AgSO 2H 2O respectively, from the thermodynamic data available, is due to complex formation with thiosulphate and bisulphide ligands. The most stable gold complexes, Au(S 2O 3) 2 3− (at φO 2 > 10 −60) and Au(HS) − 2 ( atφO 2 < 10 −60), exist in neutral or alkaline solutions. Like gold, silver forms a stable thiosulphate complex, Ag(S 2O 3) 3− 2 in moderately oxidizing, and bisulphide complexes, AgHS 0 and Ag(HS) − 2 in reducing, alkaline media. Silver solubility in highly oxidized, neutral or acid solutions is increased by formation of AgS 2O 3 −, Ag + and AgSO 4 − complexes. Colloidal, crystalline and alloyed gold and silver reacted with 0.1 M Na 2S 2O 3 do not, however, demonstrate independent solubility. The rate of gold solubility in 0.1 M Na 2S 2O 3, for example, is increased both by the presence of silver-thiosulphate complexes and alloyed silver. It is possible that such behaviour is due to the formation a mixed metal complex of the type (Au, Ag)(S 2O 3) 2 3−. The nature and mineral association of secondary gold in the oxidized zone of carbonate ore at Wau. in Papua New Guinea, is consistent with prior remobilization as a thiosulphate complex. Here the secondary gold is coarsely crystalline, alloyed with 50–75 at% Ag and enriched at the watertable and with manganese dioxide in the oxidized zone.

Transplacental transport of gold in rats exposed to sodium aurothiomalate

The ultrastructural localization of gold in yolk sacs and fetuses from rats exposed to sodium aurothiomalate (Myocrisin, 25 mg/kg intraperitoneally) was examined by a photochemical technique. Gold was found in epithelial cells of the yolk sac and in hepatocytes of the fetuses. Ultrastructurally, gold was located in lysosome-like bodies. Gold was not detected in the kidney or the central nervous system of the fetuses. Maternal liver and kidney were included as controls for efficacy of gold treatment.

Diffusion of Colloids and Other Waste Species in Brine–Saturated Backfill Materials

ABSTRACTThe diffusion of plutonium (IV) and pertechnetate and the migration of colloidal gold in brine-saturated bentonite was measured. High ionic strength brine characterizes potentially intruding groundwater for radioactive waste repositories in salt. Plastic diffusion cells containing cylindrical diffusion columns were used for low density bentonite. Metal diffusion cells constructed entirely from Hastelloy C-276 were used for the diffusion of pertechnetate in highly compacted bentonite. Apparent distribution coefficients calculated from plutonium diffusion in two columns of low density bentonite are 2 m3/kg and 3 m3/kg. These values are in good agreement with the value of 3m3/kg that was calculated from previous batch sorption data. Pertechnetate anions migrated out of a brine-saturated high density bentonite diffusion column at rates that are too large to be rationalized with a simple diffusion theory. Additional measurements that take into account possible channeling of pertechnetate are required. Colloidal gold was excluded from low density brine-saturated bentonite, but colloidal gold may have channeled between the bentonite and the wall of the diffusion cell. These results support the effectiveness of brine-saturated bentonite as an engineered barrier to plutonium. The results also highlight the need for additional measurements of pertechnetate and gold transport in bentonite. Needs for transport measurements that take into account site-specific materials interactions are also described.

Effects of biological systems on metallic gold

Effects of biological systems on metallic gold

Vein geometry and hydrostatics during Yellowknife mineralisation

Three vein systems with distinct geometry and time relations are located within major ductile shear zones at Yellowknife. En échelon arrays of centimetre width quartz veins initiated at ~45° to the shear zone boundaries and normal to the schistosity during initial translation on the structures. These geometrical relations conform to the simple shear model of Ramsay and Graham. Orientation of the maximum principal stress was ~45° to the 70° dipping shear zone boundaries, implying that the horizontal stress in the crust was greater than the vertical stress.Gold-bearing quartz veins of metre dimensions are disposed parallel to the schistosity, cross cutting early veins. This geometry requires the stress regime to switch from the former orientation such that the maximum principal stress is parallel to the schistosity, and the effective stress normal to the schistosity is tensile. The change of stress orientation is attributed to transient high fluid pressure which generated hydraulic fracturing and correspondingly high values of permeability. Under these conditions the shear zones act as conduits for massive fluid discharge; quartz and gold were precipitated from solutions cooling along a temperature–pressure (TP) gradient. Crustal vertical stress was greater than horizontal stress.Late stage lenticular gold-bearing quartz veins of metre dimensions were emplaced as vertical arrays within the shear zones, oriented normal to schistosity. These tension fractures formed when the stress regime reverted to the ambient conditions for stage 1 veining during a second episode of displacement on the shear zones. Consideration of the kinetics of intergranular diffusion, with reference to the required transport distances of gold into a lode deposit, implies that long-range diffusive transport of gold into veins was not significant.

The role of humic acid in the transport of gold

Experimental data are presented to show that humic acid can dissolve, complex and transport Au. As much as 330 ng Au/ml (ppb) were taken into solution from 0.07 to 0.15 mm Au particles by 500 μ/ml (ppm) solutions of humic acid during a 50 day period. Au was mobilised in electrophoresis experiments in the presence of humic acid, whereas Au alone remains immobile. The formation of a complex between Au and humic acid was indicated by the results of polarographic. solvent extraction and X-ray diffraction investigations. It is apparent that the formation of a humic acid complex of Au may be important in the mobilisation of element at the Earth's surface.

Atomic transport of gold and silver in lead in a dc field. (Germany): Ch Herzig and E Stracke, Phys Stat Sol (a), 27 (1), 1975, 75–84

Atomic transport of gold and silver in lead in a dc field. (Germany): Ch Herzig and E Stracke, Phys Stat Sol (a), 27 (1), 1975, 75–84

Atomic transport of gold and silver in lead in a DC field

Using the steady-state method electromigration of Au195 and Ag110m in Pb was investigated at different temperatures. z*Au eff varies linearly with l/ϱ from −1.12 at 298 to −2.05 at 188 °C. z*Ag eff is about +1. For interpreting the results it has been considered that the friction force results from a scattering by electrons and holes. It is suggested that a slight difference in the scattering cross sections of the moving ions might be responsible for the opposite migration direction of Au and Ag. The results of Au in Pb indicate that and electrostatic force is effective in addition to the friction force. Thermomigration of Ag110m in Pb yielded Q*(Ag/Pb) = 4.3 kcal/mol. Der Elektrotransport von Au195 und Ag110m in Blei wurde bei verschiedenen Temperaturen nach der Methode des stationaren Zustands untersucht. z*Au eff andert sich linear mit l/ϱ von −1,12 bei 298 auf −2,05 bei 188 °C. z*Ag eff betragt etwa +1. Bei der Interpretation der Ergebnisse wurde berucksichtigt, das die Mitfuhrkraft von einer Streuung durch Elektronen und Locher abhangt. Es wird diskutiert, das die entgegengesetzten Wanderungsrichtungen von Gold und Silber durch Unterschiede in den Streuquerschnitten der transportierten Ionen bewirkt werden konnen. Die Ergebnisse von Au in Pb deuten an, das auser der Mitfuhrkraft auch eine elektrostatische Feldkraft wirksam ist. Fur den Thermotransport von Ag110m in Pb ergab sich Q*(Ag/Pb) =4,3 kcal/mol.

Thio complexes of gold and the transport of gold in hydrothermal ore solutions

The solubility of gold in aqueous sulphide solutions has been determined from pH 20°C ≈ 4 to pH 20°C ≈ 9.5 in the presence of a pyrite-pyrrhotite redox buffer at temperatures from 160 to 300°C and 1000 bar pressure. Maximum solubilities were obtained in the neutral region of pH as, for example, with m NaHS = 0.15 m, pH 20°C = 5.96, T = 309° C, P = 1000 bar where a gold solubility of 225 mg/kg was obtained. It was concluded that three thio gold complexes contributed to the solubility. The complex Au 2(HS) 2S 2− predominated in alkaline solution, the Au(HS) 2 − complex occurred in the neutral pH region, and in the acid pH region, it was concluded with less certainty that the Au(HS)° complex was present. Formation constants calculated forAu 2(HS) 2S 2− and Au (HS) 2 − emphasize their high stability. In the temperature range from 175 to 250°C, values of pβ for Au 2(HS) 2S 2− vary from −53.0 to 47.9 (±1.6) and from −23.1 to −19.5 ( ± 1.5) for Au(HS) 2 −. Equilibrium constante for the dissolution reactions, Au° + H 2S + HS − ⇋ Au(HS) 2 − + 1 2 H 2 and 2 Au° + H 2 S + 2 H8 − ⇋ Au( HS) 2 − + H 2 vary from pK m = +2.4 to +2.55 (±0.10) for Au 2(HS) 2S 2− and from pK n = + 1.29 to + 1.19 (±0.10) for Au(HS) 2 − over the temperature range 175 to 250°C. Enthalpies of these dissolution reactions were calculated to be ΔH m ° = −5.2 ±2.0 kcal/mol and ΔH n ° = +1.7 ±2.0 kcal/ mol respectively. It was concluded that gold is probably transported in hydrothermal ore solutions as both thio and chloro complexes and may be deposited in response to changes in temperature, pressure, pH, oxidation potential of the system and total sulphur concentration.

Residual enrichment and supergene transport of gold, Calhoun Mine, Lumpkin County, Georgia

Gold is present in weathered wall rock and quartz veins of the opencut of the Calhoun mine, Lumpkin County, Georgia. Eleven samples of mica schist saprolite contain 0.02 to 0.1 parts per million (ppm) gold and three samples of weathered vein quartz, 0.04 to 0.6 ppm (limit of detection is 0.02 ppm). Gold was not found in any of the 18 samples of fresh mica schist and was found in only 3 of 16 samples of fresh vein quartz from underground workings 40-100 feet below the opencut.Whole-rock chemical analyses of the unweathered schist and schist saprolite show large losses of minor elements and addition of water during weathering. The average specific gravity of the unweathered schist is 2.8 and of the schist saprolite, 1.65. The chemical analyses recalculated to weight per volume show a loss during weathering of large amounts of all major constituents including silica, alumina, and total iron. Of the minor elements, gold and arsenic show the most residual enrichment, but boron, beryllium, cobalt, lanthanum, niobium, nickel, lead, zinc, and zirconium show some enrichment in the saprolite as compared with the fresh rock. Most of the other minor elements have been at least partly removed, the greatest loss being shown by calcium, potassium, magnesium, sodium, and strontium. Fresh limonite coating the wall of the adit contains 2.9 ppm gold and appreciable amounts of these elements leached from the schist, particularly barium, calcium, and manganese.Some layers of unweathered schist contain as much as 1 percent gold-bearing pyrite and may have a gold content of 0.01 and 0.02 ppm, or just at or below the limit of detection. Loss of 30 to 45 percent of the rock during weathering increases the gold content above the lower limit of detection. The gold in recently deposited limonite shows that some gold is also being transported with iron during weathering. If a concentration of limonite were found near the water table, it might be expected to show supergene enrichment in gold.

Hydrothermal transport and deposition of gold [discussion

For reference to the article under discussion, see this Bibliography Vol. 33, No. 5, 02 N69-08762

Transport of gold in the body.

Transport of gold in the body.

Hydrothermal transport and deposition of gold

The chloride system assumed by the writers (ibid., v. 63, no. 6, p. 622-635, 1968) is too simple as a model for the many complex natural systems with As, Sb, Te, and S. Great acidity is not necessary if associated Fe is of local derivation, which is consistent with abundance of carbonate in some gold ores. Dilatancy and related pressure effects are probably more important than temperature.

Hydrothermal transport and deposition of gold

Hydrothermal transport and deposition of gold

The Formation of Functional Types of Settlements in the Southern Tayga

AbstractThe original settlement pattern of farming villages in the Angara-Yenisey river district, which dates from the 17th century, has been greatly altered by the introduction of new economic activities, such as gold mining, lumbering, and transport services. A flow of population from agriculture to industry has been evident in the steady decline of population in farming villages, many of which have been amalgamated with adjoining industrial settlements.

Stability of colloidal gold under hydrothermal conditions

Colloidal silica protects colloidal gold both against electrolyte and against spontaneous coagulation by increase of temperature. The stability of unprotected and, in particular, protected sols toward electrolyte increases with increasing temperature. Unprotected sols containing no added electrolyte coagulate spontaneously at 150 degrees to 250 degrees C., but protected sols are stable at 350 degrees C. The stability of protected and unprotected negative gold sols toward electrolyte is increased by the addition of NaOH, within a certain limit, but is decreased by the addition of HCl. The conditions of transportation and deposition of gold in acid and alkaline hydrothermal solutions are discussed.Silica exists as a colloid in water at 25 degrees and 100 degrees , and probably at 350 degrees , in dilutions considerably under the true solubilities reported by Hitchen and by Gruner. Their values may represent a colloidal peptization equilibrium that simulates a solubility curve.

Transportation of gold by organic solutions

Transportation of gold by organic solutions

The transportation of gold by organic underground solutions

The transportation of gold by organic underground solutions

The transportation and deposition of gold in nature

The transportation and deposition of gold in nature

Experiments on the solution, transportation, and deposition of copper, silver, and gold

Experiments on the solution, transportation, and deposition of copper, silver, and gold