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By Gustavo Quiquia Mucha

El presente texto describe las experiencias realizadas por la Compañía Minera Milpo SAA en el marco de una gestión social basada en la consulta previa, libre e informada en la Exploración Minera Responsable. En ese sentido, es importante la cooperación entre la empresa minera y la comunidad, así como la incorporación del marco ideológico empresarial y metodológico, basado en los principios del Convenio 169 de la OIT sobre Pueblos Indígenas y Tribales en Países Independientes, las estrategias y las líneas de intervención social de la Compañía Minera Milpo SAA en los proyectos de exploración minera responsable.

Sep 12, 2011

By M. J. Shulman

The exploration geologist is frequently confronted with the problem of allocating his resources, i.e., exploration effort, among various areas. Although geologic, financial and logistic considerations influence the allocations, no objective criterion is usually given which determines the optimal allocation. Maximizing the gain in information, subject to the constraint of a limited exploration budget, is used as the objective criterion to allocate reconnaissance effort. The information function, I(x), quantifies the expected gain in information, where x is the scale of exploration. To calculate the information function the following data are necessary: 1. The probability that an area contains a target must be estimated. 2. For each scale of exploration, four probabilities must be estimated: the probability that an anomaly is produced by the target; the probability that an anomaly is not produced by the target; the probability that an anomaly is produced by a barren area (false signal); and the probability that an anomaly is not produced by a barren area. Alternatively, the barren area can be replaced by other targets. To illustrate the allocation model, the optimal number of line kilometers/line spacing per area is determined for an aeromagnetic survey for iron in Egypt.

Jan 1, 1985

By James S. Graham

Research at the University of Colorado on southern pine and Douglas-fir piling has determined that the existing building code design stress values of 1200 psi and 1250 psi, as determined by ASTM D-2899, are substantiated; but testing procedures should be revised. All full size piling tests should be standardized at 1/d ratios of 2:1, or confined tests performed. Also, it has been determined that theoretical design values for timber piling should not be based on the lumber criteria of D-245 and D-2555, but instead should follow the pattern set by engineers in the utility industry for timber poles, in accordance with ANSI 05.1.

Jan 1, 1986

By Jaeheon Lee

Gold-copper alloys are shown to form during the cementation of gold on copper in a solution containing 0.25M [S2O32-] at 25oC. The alloy composition is strongly dependent on the initial Cu:Au ratio in solution and ranges from Au3Cu to AuCu3. XPS results for Au, Cu, S, and O are reported as a function of depth through an entire deposited film with an initial solution containing 20 ppm [Au] and 30 ppm [Cu]. The deposit contained about 20 atomic % gold and was predominantly Cu3Au. Underpotential deposition (UPD) theory is discussed as a mechanism for explaining the formation of these alloys. Several other systems that produce alloys during contact reduction/cementation are also discussed.

Jan 1, 2003

By J. A. Sekhar

Solidification processing/casting is increasingly being adopted as the preferred manufacturing technique for the fabrication of net shaped complex geometry components. Modeling of solidification processes is important both for design purposes as well as for understanding the physics of morphological evolution of the solidification microstructure. A fundamental aspect of such modeling involves the precise understanding? of heat transfer through the two phase solid/liquid region. A scheme to do this will be presented where the nonlinearity of the fraction liquid with change in temperature can be incorporated into the numerical calculations. The importance of properly accounting for the non-linear mushy zone will be discussed. Typical processes like squeeze casting and electromagnetic stirring will be discussed to illustrate how precise modeling of the solid/liquid region can aid in the calculation of accurate heat transfer coefficients for these processes.

Jan 1, 1990

By S. M. McDeavitt

Waste form alloys are being developed at Argonne National Laboratory for the disposal of remnant metallic wastes from an electrometallurgical process developed to treat spent nuclear fuel. This metal waste form consists of the fuel cladding (stainless steel or Zircaloy), noble metal fission products (e.g., Ru, Pd, Mo and Tc), and other metallic wastes. The main constituents of the metal waste stream are the cladding hulls (85 to 90 wt%); using the hulls as the dominant alloying component minimizes the overall waste volume as compared to vitrification or metal encapsulation. Two nominal compositions for the waste form are being developed: (1) stainless steel-IS wt% zirconium for stainless steel-clad fuels and (2) zirconium-8 wt% stainless steel for Zircaloy-clad fuels. The noble metal fission products are the primary source of radiation in the metal waste form. However, inclusion of actinides in the metal waste form is being investigated as an option for interim or ultimate storage. Simulated waste form alloys were prepared and analyzed to determine the baseline alloy microstructures and the microstructural distribution of noble metals and actinides. Corrosion tests of the metal waste form alloys indicate that they are highly resistant to corrosion.

Jan 1, 1996

By Seong-Taek Lim

Recently, 7xxx aluminum alloys have been evolved into new variants for thick semiproducts which have low amount of 2nd phases and low quench sensitivity. Commercial 7xxx alloys, especially in the thick forgings made of big ingots, often entail microstructural inhomogeneities and concurrent poor mechanical properties due to limited heating ranges and slower quench cooling. In this study, high strength aluminum alloy 7175 and 7050 are adjusted as an attempt to control the equilibrium phases (M-, T- and S-phase) to have optimum microstructure for the thick forging applications. The effects of the relative content of (Zn, Mg, Cu) on the evolutions of the coarse equilibrium phases, hardening response and resultant mechanical properties are investigated. Equilibrium phases (M,T,S) are evolved depending on the constitutional effect, primarily the change of Zn:Mg ratio, and cooling rate following solutionizing. The formation of the T- and S-phases is effectively controlled, and M-phases are homogeneously precipitated in the adjusted (dilute and high Zn:Mg ratio) alloys. It provides extended heating range and lower quench sensitivity than conventional alloys. The attempts ensure the microstructural homogeneity and improved properties, and is expected to be uniquely applicable in 7xxx thick forgings.

Jan 1, 2004

By R. Boom, B. Kraaijveld, H. Kuntzel, Y. Meteleva-Fischer

"Alloying refining with rare earth elements followed by acid leaching was examined for the potential of upgrading of metallurgical grade silicon. Microstructure study of silicon alloyed with small additions of rare earths showed behavior relatively similar to the influence of calcium addition. After alloying with neodymium the phosphorus content was detected in various intermetallic silicides containing neodymium and iron. The content of lanthanum and neodymium in refined silicon was by several times lower than that of aluminium and calcium. Alloying with lanthanum and neodymium at smaller additions than calcium reduced the phosphorus content down to the same level. The efficiency of lanthanum and neodymium in removal of boron and phosphorus at the 1-2 wt% of their additions and their low solubility in silicon make the alloying with these metals followed by acid leaching an attractive option for the refining route of metallurgical grade silicon up to solar grade.IntroductionA striving for a cheap ""green"" energy directs the research interests in silicon solar cells towards new efficient refining routes for metallurgical grade silicon (MG-Si, -98% purity). The silicon price determines up to high extent the solar module's price, so that cheap and efficient metallurgical process is awaited. The research challenge is to fulfil the purity requirements of solar grade silicon (SoG-Si, 6N) by competing with the energy-consuming and environmentally unfriendly Siemens process. Most difficult impurities to remove are boron and phosphorus, so technologies dedicated to their efficient removal attract an attention of industry and academia.Alloying refining (also known as solvent refining) is one of the most promising refining options, which is based on a principle of solid-liquid extraction using limited solubility of impurity elements in solid silicon [ 1]. Various elements were proposed for alloying refining: aluminium [2], calcium [3], tin [4], iron [5], copper [6] etc. The attractiveness of the alloying refining is in decreasing a melting point of the metal mixture and an affinity of the alloying element to the most harmful impurities, especially to boron and phosphorus. However, the difficulties are still faced due to self-solubility of the alloying elements, their low affinity to boron and/or phosphorus, silicon losses and necessity of removal of the silicide impurity phases in an additional step, using acid leaching [7], fractional melting [ 8] etc."

Jan 1, 2013

During an eight month period, January to August 1978, nine bore holes were drilled in the Mikonui River gravels. On account of two rebores required from near bottom, the number of bores is in effect 11. Just on 1300 feet were drilled with an average depth of 120 feet. Depth varied from 102 feet to 133 feet. Penetration on average per hole value, varied from 7.4 to 16.4 feet per day. Gold values were even more erratic. Drill rig used was the Keystone churn drill manufactured locally by the Dispatch Foundary. It is skid mounted and requires a crew of two persons.

Jan 1, 1979

A substantial proportion of current and historic West Coast gold production comes from deposits situated around the margins of æice ageÆ glaciers. Gold has been eroded and transported by glacial ice then deposited in till and outwash gravel. The interplay between fluvial and glacial processes, climate, basement geology, tectonic uplift, sediment supply and sea level dictates many aspects of the development of the West Coast landscape. The way in which the external forcing factors interact is crucial in determining the gold content of placer deposits in this region. The following is an outline of some of the factors that influence the gold distribution in vicinity of glacial margins.

Jan 1, 2000

Detailed characteristics of gold from Pliocene auriferous quartz gravels from Waimumu (Southland) have been studied using a combination of optical microscopy, energy dispersive microprobe analysis and scanning electron microscopy techniques. The gold at Waimumu is classified as either: 1. detrital gold, or 2. irregular gold. A number of different morphologies a recognisable within each 'gold type'. Evidence is given for an predominently authigenic origin for some of the gold at Waimumu.

Jan 1, 1987

By P M. Hancock

The West Coast contains one of the world's giant placer gold deposits with production since the 1860s totalling some six million ounces (present day value NZ$ 3.6 billion). The deposits have been worked variously by hand, ground sluicing, hydraulicking and/or elevating, blocking out, deep leading and bucketline dredging. Since the sharp gold price rise of 1979 - 1980 gold production has increased steadily (in spite of the closure of the Kaniere dredge) to some 30 000 ounces (933 kg) in 1984. Production is primarily from some 100 medium scale mining, operations treating 50 - 200 000 m3 of auriferous late Pleistocene fluvial gravels year. In spite of their economic value the deposits remain only poorly investigated and many fundamental questions relating to the origin and formation of the deposits remain unanswered. This paper attempts to describe the geology of the deposits and outline a genetic model for their formation, and then discusses some of the economic aspects and current limitations and opportunities of the growing alluvial gold mining industry of the region.

Jan 1, 1985

By H. R. Thorpe

A floating gold dredge operating in coarse alluvial gravels of the Grey River on the west coast of the South Island, New Zealand, generated high concentrations of clay and colloidal particles in the dredge pond, which entered the groundwater system. Sampling was carried out at depths down to 20 m and it was found that variation of the length of the flow path occurred because of the movement of the dredge towards the piezometers. The alluvial gravels, the suspended sediments, the groundwater system and the water chemistry were all studied. Sediment concentrations were found to be highly variable with depth, but the relative concentrations in the depth profile were generally consistent as the flow distance shortened. The sediments were extremely fine and travelled further through the gravels than predicted. Comparison of field results with the available theory of deep filtration in clean beds of porous media gives some basis for estimating the behaviour of fine sediments in other alluvial systems

Jun 19, 1905

By D Craw

Middle and Late Cenozoic fluvial conglomerates and gravel in northeastern Southland record the transport of alluvial gold from Central Otago into Southland, and subsequent reworking and concentration of this gold into economic placer deposits. A corridor of geochemically distinctive, Hg-free gold derived ultimately from veins in Torlesse Terrane schist in Otago extends through the Caples Terrane and into Southland. The initial repository in Southland was fluvial sediment of the East Southland Group, specifically weakly auriferous, quartzose delta plain strata of the Gore Lignite Measures (GLM), a downstream equivalent of Dunstan Formation in Central Otago. Miocene uplift along the northwest trending Old Man Range beheaded the parent river system, isolating GLM from its Central Otago source area and establishing the proto-Waikaia River system. Rising topography between Otago and Southland increased fluvial gradients, and initiated erosion of cover strata and a sequence of tectonically induced gold recycling events. Auriferous GLM were recycled from the hinterland into broad braided fluvial channel and floodplain deposits of the Waikaia Group (new), specifically the highly auriferous Waikaka Quartz Gravels and equivalent Waimumu Quartz Gravels downstream (WQG), superimposing more proximal depositional environments over parts of the former GLM delta plain. WQG were deformed, and locally cannibalised during the later stages of their deposition by reverse movement on north-northeast trending faults of the Dunsdale System (NW side up). Increased tempo of uplift in the hinterland (Old Man, Garvie, Umbrella, and Blue Mountain Ranges) in the Pliocene and early Quaternary resulted in further reworking of GLM and WkQG from the hinterland as well as basement erosion. Progressively more basement-rich detritus was deposited as a locally auriferous piedmont (Gore Piedmont Gravels - GPG) over earlier channel and delta plain (GLM, WQG) strata, extending from the Blue Mountains to Waikaia, and southward through the Gore Gap to beyond Mataura. Southward propagation of the north-northeast trending ranges, local warping, and uplift of the Murihiku Terrane in Pliocene and Quaternary progressively deflected GPG fluvial systems and ultimately constrained them to the present valleys. Pre-existing auriferous strata (GLM, WQG, GPG) were reworked and deposited with or without basement detritus as these fluvial systems migrated toward their present positions. Auriferous remnants of these transitional deposits are preserved in local structural depressions on the uplifted blocks that deflected the systems (eg King Solomon Mine), and on locally abandoned floodplain segments on the lowlands (Pebbly Hills-Gore Gap). The present drainage has continued to incise and cannibalise its own and earlier deposits during late Pleistocene-Recent uplift to form confined channel placers within the present valleys.

Jan 1, 2002

The Clyde Power Project, and its Clutha Valley Development forerunner, has taken widespread investigations for various hydroelectric purposes both along the valley floors upstream from Alexandra and on the higher schist terrain. As part of this work the nature and extent of many of the alluvial deposits have been resolved and the ages established with varying precision. Gold values have been approximately appraised in some areas as an element of environmental assessment.

Jan 1, 1992

Alluvial gold mining in New Zealand and in particular on the West Coast underwent a renaissance during the early 1980's. This was based on two main factors: a) the sharp rise in the gold price b) the advent of the hydraulic excavator with which to mine the auriferous gravels. The scale of operations varies considerably. A small operation typically consisting of one or two people using an excavator to feed either a land based or pontoon mounted (floating) gold recovery unit, which will typically feature a rotary screen with or without a tailings stacker with the screened fines < 10 - 15 mm) fed over riflle tables. The largest screening plants of this type are operated by DML Resources in their Arahura and Mikonui mining operations where the plants have the capacity to screen up to 250 m3 of gravel per hour. These plants usually employ jigs and centrifugal concentrators for gold recovery. Unique amongst current operations is the Grey River Dredge, a bucket ladder dredge capable of processing 700 m3 per hour similar to those that operated earlier this century. Gold concentration is by a series of jigs. The number of plants operating in recent times peaked at around 130 in 1987 (coinciding with a nominal average gold price of $751) and since that time has steadily declined to 80 units in 1993 and about 45 - 50 units today. This cycle of rapid expansion and then steady decline has been repeated on the West Coast since the original gold discoveries in the mid nineteenth century.

Jan 1, 1996

By C L. McIntosh

The west coast of New Zealand’s south island is host to a large number of placer goldfields that stretch from the Westport area in the north to Gillespies Beach in the south and inland to the foothills of the Southern Alps. This area is host to a large number of alluvial, glacial and strand line deposits ageing in range from Recent to Tertiary. In recent years exploration models have been developed for off shore placer deposits on the continental shelf.Gold mining on the west coast has exploited placer gold resources from the 1860s to present, and with the recent surge in the gold price the industry is currently undergoing a resurgence. The current increase in mining is dominated by small-scale mechanical operations usually involving one to two people at each site; a few larger operations also exist such as the Grey River Dredge.Mining methods range from using floating bucket dredges to small diggers. Some of the mining technologies used are similar to those employed during the great gold rushes of the 19th century. Exploration and grade control techniques can be very rudimentary often relying on previous sampling programs or wide spaced bulk sample drill holes. Some bulk sample drilling is used on the larger operations as a form of grade control, most of the small operations tend not to use any ore control sampling prior to mining. Extraction techniques relying on simple gravity based designs with riffle tables or spirals are the most commonly used. Environmental standards are very high within New Zealand and require operators to return mined areas to preagreed to landforms. The high rainfall experienced on the west coast causes challenges to operators in regard to water quality. Technical issues combined with often limited capital provide for challenges to the operations.

Aug 22, 2011

By M Stewart

Alluvial gold deposits in the area studied are preserved on the valley floor and elevated terraces due to a sequence of glacial/interglacial events during Pleistocene and Recent times. Continued regional uplift has overprinted these events. Prospecting by drilling and bulk sampling has demonstrated a complex alluvial gold resource which is now being mined.

Jan 1, 1989

By T Salles, G Duclaux, E R. Ramanaidou

In a continental environment, sediment mobilisation, dispersion and deposition are mainly controlled by mass gravity and streamflow processes. Alluvial sedimentary systems have an important economic value because of their capacity to host mineral resources. In the Hamersley Province, alluvial iron deposits (including the well-known detrital iron deposits and channel iron deposits) play an increasing role on the commodity market. Alluvial deposits exploration is challenging and generally involves geomorphologic and stratigraphic field studies, as well as expensive exploratory surface sampling and drilling. We applied a new surface processes modelling technique to investigate iron rich material, ie the erosion product of bedded iron formations -dispersion in the Hamersley Province. LECODE is a 3D-parallel surface processes forward modelling code designed to compute surface flow and solve erosion, transport and sedimentation on the geological time scale. The code offers new quantitative ways to better understand how sedimentary deposits develop in intra-continental and channel environments. Here we show that our integrated forward model is capable of opening a window to the construction of sedimentary architectures, including facies distribution, deposit thickness and development of heterogeneities such as mineral traps over the modelled domain. The model results represent 1 Ma of surface evolution and are validated through comparison to published paleovalleys map and known occurrences of iron ore deposits. This numerical modelling approach allows for the first time to track alluvial materials from source to sink through time, test existing geological models and faithfully reproduce the first order distribution of alluvial iron deposits in an area of interest. This work strongly suggests the presence of iron rich alluvial deposits reserves under cover, in unexplored detrital fans in the Fortescue Valley. This method, potentially coupled with sediment geochemistry and basin analyses studies, has the potential to maximise alluvial iron deposits exploration success, while reducing exploration cost and associated environmental impact.CITATION:Duclaux, G, Salles, T and Ramanaidou, E R, 2013. Alluvial iron deposits exploration using surface processes modelling - a case study in the Hamersley Province (Western Australia), in Proceedings Iron Ore 2013 , pp 75-80 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

Outline of situations when valuations required - from capital raisings and takeovers, stamp duty, rates and capital gains tax, to probate and litigation between joint venture parties. Definition of types of exploration and mining properties as background to discussion on what methodologies to use (from grass roots to operating mine). Discussion on nature of alluvial deposits in New Zealand and how their characteristics and tonnage/grade uncertainties affect choice of methodology. Assessment of risk factors in New Zealand û technical, financial and socio-political (legislation, access, Maori land rights, environmental). Discussion of appropriate methodologies.

Jan 1, 1992