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By Dogan Paktunc, Larry J. Hulbert, Robert C. Carne, D. Conrad Grégoire

Abstract -A thin layer of stratiform Ni-Zn-PGE sulfide mineralization of sedimentary-diagenetic origin was deposited during the Middle to Upper Devonian in the euxinic "Nick basin". The mineralized unit (2:3 cm thick), which seems to have been developed over the entire sedimentary basin of >80 km2, consists of pyrite, vaesite (NiSi), and sphalerite. The average grade of the mineralization is about 5.3% Ni, 0.73% Zn, ?770 ppb (PGE+Au), and up to 61 ppm Re. Anomalous Se, As, Mo, P, Ba and U are present. A minimum of 0.90 x 106 tonnes of Ni were deposited in the basin (based on a bed thickness of 3 cm) during the Devonian. The unique metal association, extensive lateral distribution, persistent metal grade, mineralogical makeup, and stratigraphic control demonstrate that this is a new deposit type and a new geological environment for Ni and PGE +Au. The sulfide layer occurs at the base of a Phosphatic Chert Member which is underlain by a distinctive marker unit consisting of concretionary limestone structures. The limestone spheroids may represent a vent-specific carbonate facies developed adjacent to faults that emanated nutrient­ rich hydrothermal discharges just prior to the main mineralizing event. The suite of elements associated with the Nick mineralization suggests that the ore-forming metals were originally bound to organic matter derived from decaying marine organisms. Discharge of hot brines bearing organic­ matter-bound metals took place along numerous conduits within basin faults that are now manifest as bitumen veins. Our syndiagenetic model proposes that these fluids were discharged laterally from the conduits into the unconsolidated bottom sediment (ooze). The introduction of this metalliferous fluid, rich in organic matter, stimulated biological activity and bacterial reduction of its contained S04 to sulfide. Hot, dense, laterally migrating hydrothermal fluid precipitated thin sulfide-rich 1arninae within bottom sediment. Published thermodynamic studies suggest that the diagnostic vaesite­ pyrite assemblage crystallized at approximately 138°C. The ?34:S values range from -14.7 o/oo to-10.0 o/oo and are up to 34 o/00 lighter than locally surrounding sulfides and age-equivalent mineralized strata elsewhere in the Selwyn Basin. The ?13:C values of calcite in the footwall of the mineralized unit ( -12 o/00 to -6 o/00) are isotopically much lighter than regional values. The lighter isotopic character is attributed to the hydrothermal discharge of fluids enriched in organic compounds. Although geochemical profiles of the lower Earn Group sediments that host the Nick mineralization reveal that these black shales are not distinctive, the unusual Ni, Zn, PGE, U, Ba, and P elemental associations and their anomalous concentrations in stream sediments can be used to explore for this deposit type.

Jan 1, 1992

By Qiling Zhang, Zengqian Hou, Xiaoming Qu

Abstract - The Okinawa trough is an active back-arc-spreading center in which submarine hydrothermal exhalation (black chimneys) and sulfide mineralization are forming. Fluid inclusion composition in minerals of the hydrothermal feeder zones in the JADE field shows that the hydrothermal systems are extremely gas-rich. There are two independent and co-existing fluids, CO2-hydrocarbon and saline fluids. Microthermometry and Laser Raman Microprobe (LRM) analyses on individual fluid inclusions of the CO2-hydrocarbon type, dominated by CO2 and containing minor CH4, C2H4, C2H6, N2 and H2S, are almost equivalent to the fluid inclusion composition of a natural gas field. The saline fluid is mainly composed of H2O and contains minor Na+ and K+. It is close to a H2O-NaCl, or H2O-NaCl-KCl system, with salinities from 3.7% to 7.5% NaCl eq. Before venting on the seafloor, the fluids experienced immiscible separation. One of the end-member fluids is downward circulating seawater that interacted with sub-seafloor rocks. The other was gas (volatile)-rich fluid derived from a shallow magma chamber. The immiscibility separation of fluids resulted from the decrease of temperature and pressure of the hydrothermal system and continuous input of magmatic volatiles. The saline fluids in this system are discharging to form sulfide chimneys and black smoke. Meanwhile, CO2-rich fluid discharges as CO2 bubbles through hydrate pipes. A large amount of CO2-CH4-H2S gas or fluid in the upper part of the hydrothermal system, and reaction of this gas or fluid with saline fluids, finally enables the accumulation of metal sulfides.

Jan 1, 1999

Applying DEM to prediction of tumbling mill performance is challenging because several different modes of breakage are active in the process. As our knowledge of breakage and computational capacity improve, it is worth revisiting previous simulation tasks which did not produce a satisfactorily realistic description of a measured process. At SAG 2006, we reported the simulated and measured outcomes of treating a well characterised ore in a 1.2 m diameter mill. This well instrumented, pilot scale mill at the University of KwaZulu-Natal has been combined with some new approaches to ore testing to allow different modes of breakage to be tested. The mill design allows the rate of generation of fine material to be measured in close to real time for autogenous and SAG mill charges. The updated simulation model estimates mass loss with particle evolution and embeds the cumulative damage and breakage. The simulated results are compared with the measured results. Issues such as relating modelling inputs to particle breakage characterisation data and the accuracy of the predictions of the models are discussed.

Jan 1, 2012

By K. Scalise, M. Teixeira, K. C. Kocsis, J. Parrish

"This paper aims to introduce and discuss a newly developed algorithm, which can be uploaded on smart watches and other mobile devices to inform and protect underground personnel working in hot and humid environments. Using this algorithm, the metabolic rate (M) of a worker can be determined in “real-time”. In addition, besides warning signs and alarm signals emitted by the smart watch, the algorithm has the ability to determine work-rest time periods based on the worker’s physiological parameters (e.g. age, height, weight, gender) and the climatic parameters (Td, Tw, flow velocity). This paper also investigates whether a re-designed auxiliary ventilation system can provide appropriate work conditions in the production stopes. INTRODUCTION An underground environment with high temperature and humidity conditions generated from various heat and moisture sources can significantly affect the thermoregulation processes of the human body. This can lead to heat-related illnesses such as heat rash, heat cramps, heat exhaustion, and heat stroke. Heat stroke is a serious illness that carries a high risk of fatality, if the underground workers are not immediately treated and the climatic conditions are not corrected (McPherson, 1993). There are two methods used to control the climatic conditions in underground mines: (1) Using ventilation and cooling systems to reduce the thermal stress on the mine workers, and (2) Reducing the heat transferred to the ventilating air from major sources such as: strata, auto-compression, mining equipment, groundwater, blasting, etc. The heat from strata and auto-compression is transferred to the ventilating air at varying degrees, based on factors such as the virgin rock temperature (VRT), the thermal properties of the surrounding rock formations, and the surface air temperature. However, the use of mining equipment and blasting processes can be managed to reduce their contribution to the mines’ overall heat load. To provide appropriate work conditions, selecting the most suitable cooling method depends on the level of heat to be removed, the location of the problem areas, and economic constraints (Brake & Bates, 2002; McPherson, 1993). Because every mine is unique, it is essential to monitor the climatic conditions to select the most appropriate method of cooling. A majority of the time, simply adjusting or re-designing the auxiliary ventilation system can efficiently remove the heat and dilute the contaminants. This may involve moving the ducting system, changing the size of the duct, changing the size of the auxiliary fan, or switching from forcing to an exhausting fan arrangement. If the required air volumes are higher than the existing primary ventilation system can supply, other measures may need to be taken to increase the airflow delivery. This may include regulating the flow in some areas of the mine to increase airflow to the desired area, adding booster fans, or replacing the primary fans."

Jan 1, 2019

By Robert A. Creaser, Iain Mitchell, Robert L. Linnen

Abstract - The Bermuda Zn-Pb showing is hosted by dolomitized Blue Fiord Formation of Devonian age, located east of the Ensorcellement dome on the Grinnell Peninsula of Devon Island. Fluid inclusions in hydrothermal calcite indicate that the mineralization precipitated from low-temperature, highly saline brines. The ?34S compositions of sphalerite, galena, and marcasite range from 16.1‰ to 35.2‰. Consequently, the Bermuda showing is interpreted to be Mississippi Valley-type (MVT) mineralization. The apparent age of mineralization has been determined by the Rb-Sr method from sphalerite separates, and a Late Devonian age of 357 ± 50 Ma (MSWD=65), with an initial 87Sr/86Sr ratio of 0.7083 ± 0.0020 is indicated. This date, within error, is the same as the Polaris deposit. This suggests that the mineralization formed during the Ellesmerian Orogen, although it is also possible that mineralization is associated with extension, related to the opening of the Sverdrup basin. The strontium and sulfur isotopes and fluid inclusion analyses indicate the involvement of a brine that acquired its salinity from interaction with evaporites, lower in the stratigraphic succession. The Polaris mine is the type deposit in the Cornwallis Zn-Pb district and is hosted by the Thumb Mountain Formation. The results of this study are significant because they demonstrate that regional brine movement is more widespread than previously recognized, and that MVT mineralization in the Cornwallis Zn-Pb district is not restricted to the Thumb Mountain Formation.

Jan 1, 2004

By Ainul Akhtar, Steve Cockcroft, Daan Maijer, Carl Reilly, Lu Yao, Jun Ou

A coupled thermal-fluid flow-multicomponent model has been developed to aid in understanding the melting/dissolution behavior of solid Al-rich Material (TiAl) in a liquid titanium pool produced by an electron beam. The model is capable of accounting for the significant phenomena present affecting heat, mass and momentum transport including thermal and compositional buoyancy and Marangoni forces, Darcy attenuation, evaporation, melting and solidification, and the associated release or absorption of latent heat. The modeling results have indicated the compositional fluid flow driving forces (compositional buoyancy and Marangoni forces) contribute significantly to the melting/dissolution process. The model is waiting for validation against empirical data.

Jan 1, 2014

By M. Pelegrin Rodríguez, J. Castellanos Suarez, R. Causse Miyares, A. Mosqueda Martínez, Rubén Aja

"This paper will describe the methods and the results of studies to integrate polymetallic nodule extractive metallurgy methods into existing and operating technologies or plants with the aim of reducing the capital cost of deep-sea mining challenges and to streamline the supply chain of raw materials where such opportunities exist (Moa Bay and others). It will also assess the possibility to carry out pre-industrial processing operations with productivity corresponding to pilot mining operation in the Clarion Clipperton Fracture Zone (5–10% of assumed annual production) with the use of existing facilities. The present study shows the results of high pressure acid leaching of polymetallic nodules (PN) mixed with laterite non-commercial ore. It also presents PN processing in the presence of ammoniacal tailings obtained from the Caron process. The experiments were carried out according to 24 full factorial design. The regression equations were determined for extractions of Ni, Co, Cu, Zn, Fe and Mn. The obtained results show that increasing temperature, the acid/ mineral ratio and the leaching time have a positive and significant effect on extraction of all the studied metals. However, increasing the tailings addition favors the extraction of the Co, Zn and Mn. The extraction of Fe diminishes, while the extraction of Ni is not affected. In the following conditions; 180 min, 260°C, 0.5 kg acid /kg minerals and 2.5 kg PN/kg tailing; the following extractions were achieved; 96% Ni, 90% Co, 97% Cu, 99.9% Zn, 43% Mn and 26% Fe."

Jan 1, 2017

By J. Severin

Surface mining operations are increasingly involving the design and development of deeper and larger open pits, often with plans to transition into underground mass mining operations. Experiences at the Palabora Mine in South Africa demonstrate the complex interactions between underground workings and the steep slopes above that may lead to slope movements that potentially pose safety and economic concerns. To properly assess the rock mass response to these interactions for planning of future developments, understanding the controlling influence of geological and geomechanical structures is crucial. Preliminary results are presented from a detailed review of historical slope monitoring data from the Palabora Mine, before and after the initiation of block caving 400-m beneath a 800-m deep pit. This paper demonstrates that a detailed analysis of geology and monitoring data can be used to better understand the kinematic controls of complex rock slope displacements and interactions between open pits and underground mines. This investigative treatment of the monitoring data is important in understanding the failure mechanisms prior to undertaking sophisticated 3-D numerical models.

May 1, 2009

"Abstract - An estimation of resources of structurally complex gold lodes and stockworks represents a challenging task for geoscientists due to the complex geometry of the lodes and discontinuous grade. In the present case study, the resource of a gold stockwork has been estimated by uniform conditioning after the lode has been subdivided into geostatistically defined domains using the indicator probability model. The indicator probability model represents a powerful tool for structural interpretation of the mineralization and can be applied when traditional 3D volume constraining methods (wireframing) have failed to produce a unique, non-subjective model. For comparison, the resources of the same zone have been estimated without domaining. Results of the study clearly show that estimates obtained without domaining of the mineralization can yield a substantial error due to excessive smoothing of the grade.Application of uniform conditioning for modelling the grade distribution has a significant advantage over linear methods (e.g., ordinary kriging). Uniform conditioning enables estimation of local recoverable resources at different selective mining unit sizes that can be substantially smaller than the drilling density without creation of biases or over smoothed local values."

Jan 1, 2002

By D. R. Nagaraj, Napoleon Tercero, Raymond Farinato

"Several studies conducted recently have shown that molybdenite flotation from Cu-Mo ores is adversely impacted in sea water at pH >~ 10.0 irrespective of the pH modifier; under the same conditions Cu sulfide flotation is relatively unaffected. This has been attributed to the presence of Mg2+ ions and their hydrolysis products in the sea water which adsorb and precipitate on molybdenite surfaces as Mg(OH)2. However, why and how Mg(OH)2 impacts only molybdenite flotation in the complex flotation pulps containing a multitude of minerals is not understood. The work presented in this paper probes the interface and interphase regions near the edge and basal planes of natural molybdenite (MoS2) in aqueous solutions and flotation pulps, particularly in the presence of copper ore pulp and added Mg2+. Differences in interaction of metal ions and their hydrolysis products (Mg2+, Mg(OH)+) were measured on the two faces of this anisotropic mineral. How those differences relate to molybdenite floatability and the impact of aqueous solution chemistry are discussed.INTRODUCTIONWater resource management is an important sustainability challenge in mineral processing. In view of the shortage of fresh water in many parts of the world, mineral processing plants are evaluating alternative sources. Seawater flotation has received much attention recently and there have been several important studies reported in the literature, particularly for the processing of Cu-Mo ores (S. Castro, 2012; S. Castro, Rioseco & Laskowski, 2012; S. Castro et al., 2012; Laskowski & Castro, 2012; Ramos, Castro & Laskowski, 2013; S. Castro & Laskowski, 2013; Laskowski, Castro & Ramos, 2013; Nagaraj & Farinato, 2014; S. Castro, Uribe, & Laskowski, 2014; Veki, 2013). The main conclusions from these studies on Cu-Mo ores in seawater at elevated pH were: a) flotation recovery of Cu sulfides is either unaffected or only marginally reduced, b) molybdenite recovery is adversely affected in seawater at pH values necessary for rejecting pyrite (i.e. pH > 10 to 10.8 depending upon particular system), and c) the precipitation of Mg2+ in seawater as Mg(OH)2 is responsible for the adverse effect on Mo flotation. In order to further investigate the individual effects of Mg2+ and Ca2+ on molybdenite depression in Cu-Mo ore flotation, Nagaraj & Farinato (2014) conducted flotation tests wherein individual metal ions were spiked into tap water during grinding of Cu-Mo ores. They showed the strong adverse effect of Mg2+ addition on Mo recovery and, to a lesser extent, on Cu recovery when pH > 9.5. Under similar conditions, Ca2+ had virtually no effect on either Cu or Mo sulfide flotation. Figure 1 below shows the previous results for Cu- Mo ores in tap water and the effect of addition of Ca2+ and Mg2+ ions. Note that in seawater the adverse effect of Mg2+ on Cu recovery was much smaller than that in tap water (Nagaraj & Farinato, 2014; Figure 4a and 4b and Table 4 therein)."

Jan 1, 2016

By Roy O. Ifill, W. Charle Cooper, Alan H. Clark

"A detailed study of the compositional relationships of the Uand Th-bearing minerals in Elliot Lake uranium ores has been conducted, particularly with regard to uranothorite, which clearly plays a critical role in hydrometallurgical processing. Application of the rotating disc progressive-leaching technique to individual mineral grains and intergrowths of known compositions has defined for the first time the solubilization behaviour ofthe minerals in question.In descending order of leachability, regardless of leaching conditions, the phases are: uranothorite, uraninite, and monazite. Inclusions of secondary uranothorite enhance the dissolution kinetics of uraninite, which exhibits a complex dissolution mode. U-rich uranothorite dissolves more readily than Th-rich. Monazite is soluble in HJ)04 and HCI solutions only at temperatures exceeding 85°C. Consequently, it is deduced that the 15% to 20% of thorium not leached from the ore is lost both as monazite and as uranothorite inclusions locked in monazite which persists to the tailings. INTRODUCTIONThe importance of precise information on the mineralogy of ore and gangue constituents for the optimization of metal recovery in hydrometa Uurgical processing has been recognized for some years (e.g. Burkin, 1969), and numerous investigations integrating mineralogical studies and experimental leaching have been reported for ores of gold, nickel, copper and uranium (see summary by Henley, 1983). The complex mineralogy of uranium ores hosted by Precambrian pyritiferous, quartz-pebble, conglomerates has prompted particular attention in this regard (e.g. Liebenberg, 1956; Liebenberg and Taverner, 1958; Feather and Snegg, 1978). In the great majority of documented studies, however, petrographic examination has been followed by bulk leaching, an approach which, although providing valuable information, does not permit precise definition of the evolution of mineral dissolution processes. The authors contend that experimentation involving the step-by-step leaching and mineralogical study of ores is more likely to reveal the actual dissolution events which control the release of metals and, hence, may better define the optimal conditions for hydrometallurgical processing. Such studies (e.g. Hausen, 1983; Horlick et al., 1981) in addition lend themselves to the prediction of changes in the leaching behaviour of ores in which one or more mineralogical feature is subject to modification, a common characteristic of mineral deposits."

Jan 1, 1989

By G. Deschênes

"In 2013, as the prices of precious metals dropped, investors moved their positions to equity markets for higher returns. As a result, the price of gold dropped further to below US$1200 per ounce, prompting additional substantial outflows from gold investments. In response to lagging gold prices, major gold producers initiated large asset write-downs and cost-cutting programmes. In 2015, this trend continues and gold mining stocks are close to lows not seen since the global financial crisis (GFC) of 2008. In the current economic climate many projects have marginal economics, and the number of projects that have competitive development and production costs is declining. A competitive edge is particularly important with the decreasing grades of orebodies, increasing complexity of the mineralogy, and increasingly demanding environmental constraints. In addition, higher cost producers seek to optimize their process t o reduce operating costs.This paper presents some highlights of three case studies on optimization of gold leaching strategies that improved the economics of brownfield projects. Processing of sulphide-bearing ores was optimized by using the synergy between cyanide, lead nitrate, and oxygen. The outcomes were significant reduction of retention times while maintaining or increasing gold extraction and reducing cyanide addition and effluent treatment costs. A stirred tank reactor experimental programme led to direct implementation of reliable leaching strategies from laboratory scale to production. This approach resulted in savings of $2.2 million to $15.2 million on the three brownfield projects discussed in this paper."

Jan 1, 2016

By G. M. Card, K. D. Card, B. V. Sanford

The Canadian Shield and its extensions are traversed by an orthogonal system of north-west and northeast trending arch-style uplifts. These basement arches were formed by repeated vertical movements along pre-existing structures during compressional and extensional tectonism connected with events in surrounding Proterozoic and Phanerozoic orogens and ocean basins. The arches in?uenced patterns of sedimentation and tectonism in the intervening epicratonic basins andmarginal platforms throughout the Proterozoic and Phanerozoic. Movements on the arch structuresalso triggered minor magmatism and controlled the location and timing of alkalic rock-carbonatite, kimberlite, and related intrusions in the Canadian Shield, the Western Canada Sedimentary Basin, and West Greenland.

Jan 1, 1997

By André Chagnon, Michel Malo, Benoît Dubé, Chantal Pelchat

"Abstract- In the southern Gaspé Appalachians, gold mineralization is spatially associated with the Acadian dextral strike-slip Grand Pabos-Restigouche fault system. Two different structurally-controlled gold prospects, the Lac Arsenault and the Saint-André-de-Ristigouche, are described to unravel the genesis of gold mineralization in this part of the Canadian Appalachians.At the Lac Arsenault gold prospect, gold mineralization consists of Au-As-Pb-Zn-Cu-(Ag) polymetallic fault-filled quartz veins with laminated textures emplaced in brittle-ductile sinistral X shear fractures. Mineralized veins are hosted by Middle Ordovician graywacke of the Arsenault Formation, belonging to the Dunnage Zone, the Early Paleozoic oceanic domain of the Appalachians. Terrigeneous rocks of the Arsenault are regionally metamorphosed at the lower greenshist facies and the mineralized veins are included in a zone of Fe-carbonate alteration.The Sb-Au-As mineralization of the Saint-André-de-Ristigouche gold prospect, in the southwestern Gaspé area, comprises extension veins in the extension direction emplaced in brittle conditions. Mineralized veins are hosted by calcilutite and laminated silty and argillaceous limestone of the Early Silurian part of the White Head Formation, which belongs to the Gaspé Belt, the Middle Paleozoic successor basin in the Gaspé Appalachians. Metamorphic grade of the White Head Formation in the southwestern Gaspé area is very low, but the gold mineralization is included in a zone of hydrothermal propylitic alteration which includes two Cu-skarn mineral occurrences. The Lac Arsenault gold prospect has many characteristics of "greenstone-hosted quartz-carbonate vein" deposits whereas the southwestern Gaspé area, which includes the Saint-André-de- Ristigouche gold prospect, shows affinities with the geological setting of sediment-hosted gold deposits (Carlin-like deposits). The two gold prospects are controlled by the Grand Pabos- Restigouche fault system but they were not emplaced at the same level in the crust. Acadian strikeslip fauting played a major role in their respective genesis in providing channelways for ore-bearing fluids. The recognition of the analogy of the geological setting of the southwestern Gaspé area with that of Carlin-like mineralization gives new ideas for exploration in the area and elsewhere in the Appalachians.Résumé - Dans le sud des Appalaches de la Gaspésie, on trouve des minéralisations aurifères spatialement associées au système de failles de coulissage dextre acadien de Grand Pabos-Restigouche. Deux indices très différents, Lac Arsenault et Saint-André-de-Ristigouche, sont décrits pour évaluer la genèse des minéralisations aurifères à contrôle structural de cette partie des Appalaches canadiennes. Au Lac Arsenault, la minéralisation aurifère comprend des veines polymétalliques à Au-As-Pb- Zn-Cu-(Ag) en remplissage de failles. Ces veines à texture laminaire se retrouvent dans des zones de cisaillement fragiles-ductiles senestres de type X. Les veines minéralisées sont encaissées dans les grauwackes d’âge Ordovicien moyen de la Formation d’Arsenault appartenant à la zone de Dunnage, le domaine océanique du Paléozoïque précoce des Appalaches canadiennes. Les roches terrigènes de l’Arsenault sont métamorphisées régionalement au faciès inférieur des schistes verts et les veines aurifères sont dans de larges zones d’altération dolomitique (Fe-carbonate).Dans le sud-ouest de la Gaspésie, la minéralisation à Sb-Au-As de Saint-André-de-Ristigouche est dans des veines d’extension comprises dans la direction d’extension et mises en place dans des conditions de déformation fragile. Les veines minéralisées sont encaissées dans les calcaires argileux et les calcilutites de la partie silurienne de la Formation de White Head qui appartient à la ceinture de Gaspé, le bassin successeur du Paléozoïque moyen des Appalaches de la Gaspésie. Le degré métamorphique des roches du White Head est très bas, mais"

Jan 1, 1998

By G. Gu, B. Fang, R. W. Revie, M. Elboujdaini

Electrochemical behavior of an X-80 pipeline steel, including frequency-sweep electrochemical-impedance spectroscopy (EIS), time-sweep EIS at a constant frequency and open-circuit potential (OCP) monitor, was investigated using four-point bending specimens subjected to a stress-corrosion cracking (SCC) test in a near-neutral pH environment. The capacitive loop became smaller with test duration, revealing an increase in the corrosion rate. The resistance obtained in the constant-frequency EIS test showed two regions, of which the region with a remarkable decrease in resistance transformed into a region of slow decrease, whereas the capacitance increased with test time indicating that iron dissolution was fast at first, and then a corrosion product or film formed and covered the surface, leading to the pitting formation.

Jan 1, 2005

By László Guczi1

Nanosize model gold particles with varying size were fabricated by deposition of a 10 nm thick gold film onto SiO2/Si(100) substrate by electron beam evaporation followed by modification using low energy Ar+ ion bombardment. The change in particle size were monitored by the Au 5d valence band states determined by ultraviolet photoelectron spectroscopy (UPS). The gold/iron oxide interface was studied by iron oxide deposition on gold. It was found that the energy profile of Au 5d valence band states are strongly redistributed with decreasing the gold particle size mostly affecting at the lowest and at the highest binding energies. The size effect in the UPS spectra can be interpreted by the energy redistribution rather, than by narrowing the 5d states. The iron oxide deposition increases the catalytic activity in CO oxidation whether it is on gold nanoparticles or on a continuous 80 nm thick gold film. The activity enhancement is significantly larger in case of gold nanoparticles. The interface interaction is operative in enlargement of the catalytic activity even if gold particles are not exposed to the surface, but they are located below the iron oxide layer.

Oct 1, 2003

By Denni Hoffmann

"Banded iron formation rocks associated with massive sulfide lenses in the Broken Hill Pb-Zn-Cu-Ag deposit in the Namaqualand Metamorphic Complex, South Africa, were investigated with respect to the geochemistry of manganiferous silicate-rich bands. Two common varieties of these are: amphibole- and garnet-rich iron formation bands. The results reveal that the former are enriched in Fe, Mg, Cu, Co and S. The garnet-rich bands are enriched in Mn, Ca, P, Pb and Ba with significant detrital contamination of Ti, AI, Zr, Cr, Y, V, Ni and Nd.The silicate-rich bands have compositions, in terms of, Si/AI, SilFe, FelMn, LalCe and Co/Zn, comparable to submarine chemical sediments which precipitated from hydrothermal fluids. The garnetand amphibole-rich bands are interpreted as ""evolved"" and ""immature"" hydrothermal sediments, respectively. The latter resulted from rapid precipitation after exhalation, whereas the former had a longer residence within sea water. The silicate-rich bands both exhibit increasing Mn/(Mn+Fe) fractions, which are consistent with a variation expected from proximal to distal depositional settings. The prevalence of garnet-rich bands over amphibole-rich bands is interpreted as the result of injection of hydrothermal fluids from a single vent situated along the northwest margin of the Broken Hill deposit."

Jan 1, 1994

By A. Dolatmoradi

Nanocrystalline structure formations produced by severe plastic deformation in Fe-0.15C with initial ferritic-pearlitic and IF steel with ferritic microstructures have been studied through microstructural observation and microhardness measurements. It was found that the nanocrystalline region first forms near the surface of samples due to localized severe deformation. It was also observed that the nanocrystallization rate of Fe-0.15C and IF steels and the deformed layer thickness in these two materials are different with similar milling conditions. The crystallite size and structural evolution of the samples during milling was studied by employing XRD and SEM.

Jan 1, 2010

By Elaine Ellingham, Francis T. Manns

"The Orostar and Scadding were two small gold mines owned and operated by Orofino Resources Limited. Conventional statistical treatment indicates an identical arithmetic mean grade of 0.22 oz/T Au for both mineable reserves. Further, the deposits are both shown to have cut weighted average reserve grade of 0.21 oz/T. Orostar mined out at 0.206 oz/T and Scadding at 0.156 oz/T Au. The combined exploration and development database contained 1394 fire assays, more than enough for statistical confidence in a normal distribution. Therefore this study was initiated to determine, if possible, why the mill head grades were lower than the averages and to experiment with several methods to determine whether a reliable statistical mill head grade estimation method would emerge. Despite the identical reserve grades, distinct differences in the grade distribution histograms are present. By studying the arithmetic and log-normal grade distributions, with some attention to South African practices, this paper reports on those differences which may account for the considerable divergence in the mill head grades. Furthermore, this study casts considerable doubt on the industry standard method of cut weighted averages.The global mill head grades of the two deposits have been derived from the arithmetic average grades by graphic means. This precise method of mill head grade prediction, if applied to complex orebodies, could permit selective grade control and result in direct cost savings by allowing the operator to detect false value stopes, benches or levels and emphasize reliable regions of not only gold mines, but also uranium or base metal deposits."

Jan 1, 1992

By T. Ivankina, T. Lokajícek, H. Kern, T. Svitek

The knowledge of 3D velocity distribution of P- and S-waves in rocks is very important parameter for interpretation and understanding the nature of seismic anisotropy observed in the earth’s crust and upper mantle. A new high-pressure measuring head was designed and constructed to enable ultrasonic sounding of spherical rock samples in 132 independent directions under up to 60 MPa of acting hydrostatic pressure by means of simultaneous longitudinal and transversal sounding. New measuring system enables ultrasonic sounding of spherical rock samples by using a pair of P-wave sensors and two pairs of perpendicularly polarized S-wave sensors (TV and TH) see Fig.1. Shear wave sensors polarization is oriented according to rotation axis of the sample. Special shear wave gel was used to transfer shear waves between the sample and sensors under acting hydrostatic pressure. An isotropic glass sphere was used to check and calibrate the new measuring setup. A spherical sample of a biotite gneiss from the Outokumpu scientific drill hole was used for testing measurement. There is shown that both, P- and S-wave velocities, can be measured simultaneously up to 70 MPa, respectively. We report data of the 3D velocity distribution of P- and Swaves measured for the first time on a sample sphere of biotite gneiss. We rely, in particular, on the directional dependence of compressional and shear wave propagation and their relationship to the crystallographic (CPO) and shape preferred orientation (SPO) of major rock-forming minerals. The 3D seismic measurements revealed a strong foliation-related directional dependence (anisotropy) of P- and Swave velocities. Ultrasonic measurements were compared with 3D velocity calculations based on neutron diffraction measurements of crystallographic preferred orientation (CPO) of major minerals. Comparison of 3-D velocity distribution (P, S1, S2 and S1-S2) determined by two completely different methods ultrasonic sounding and neutron diffraction is presented. Measurements showed that the intrinsic bulk anisotropy is basically caused by the CPO of biotite constituting about 23 vol.% of the rock.

Jan 1, 2015