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By P. Klossek

It is estimated that China accounts for 94% of the world supply of rare earths (Roskill, 2011). This fact, together with the impact of China?s export policy, poses a substantial risk to the security of the rare earth supply as well as a rare earth price risk. This situation has motivated an increase in the number of rare earth projects under development, i.e., there are currently more than 440 worldwide (Technology Metals Research, 2012). However, economically and environmentally acceptable processing technology to produce tradable products from rare earths (e.g., separated rare earth oxides) is not freely available on the market at the moment. In this respect, a lot of research and development has been initiated on this topic, in academia as well as in industry. Using a proprietary model and scenario-based analysis, we studied the impact that the development of rare earth processing technologies would have on the rare earth market and the economic feasibility of rare earth projects mentioned before. The analysis showed that this impact varies depending on the technology type (e.g., technology can affect project production volume, cost structure or both) and the legal context of the invention (e.g., free or limited by patenting availability of a new technology). The effect of a technology which influences project production volume is not the same as of a technology which changes project cost structure. The impact of a patented processing technology differs from the impact of a processing technology which is freely available on the market. In the case of a new technology which is limited by patenting, its impact depends on the market position (?producing?, ?next-coming?, or ?not producing? project) of the patent holder. The paper contributes to existing research by studying the dependence of the expected micro- and macroeconomic impact of rare earth processing technology developments on the properties of a new technology (e.g., costs, legal framework etc.). By this means, the paper adds to existing knowledge and attempts to make the rare earths market more transparent and predictable from a perspective outside China.

Aug 1, 2013

By He De-wen

The increasing population and living standard in urban areas, have been accompanied with the growing quantity and composition complexity of rubbish, which are causing well-known social effects of pollution, while rubbish (solid waste) is a recyclable resource. To convert rubbish into useful materials, the essential measure is to carry out sorted collection of rubbish. The preconditions of implementing sorted collection are presented in the paper. 1 Characteristics of rubbish composition and amounts of recyclable contents are basic condition to implement sorted collection. 2 The existing available technologies of recycling, economic benefit from recycling, and disposal scheme of residual rubbish are restrained condition for sorted collection. 3 Public understanding and support to sorted collection are the key to success. 4 The government policies to be favorable for sorted collection is the pledge of success. 5 The establishment of a steady solid waste recycling market is also a guarantee to implement sorted collection continuously. 6 To establish management system of rubbish recycling as soon as possible. Further, the methods and procedure of sorted collection are discussed in detail and beneficial comments and theoretical basis to promote sorted collection of rubbish in urban area are presented; it will contribute reference value to municipal solid waste management.

Jan 1, 2006

By Benjamin Smith Lyman

THE importance of topography to geology is so commonly underrated as to deserve to be pointed out again and again. The relation of topography to the different branches of geology may be seen best by a glance at them all. Geology is well understood to consist of the observation of facts about rocks as materials of the earth (geognosy ), and the explanation of those facts (geogeny). The facts to observe are: I. GEOMETRICAL, as (1) structure, including the dip and strike at different points, the size, shape, and position of basins and saddles; (2) vertical section, that is, the thickness of rock groups and of their parts ; (3) horizontal or geographical position. II. PHYSICAL, such as texture, whether sedimentary or crystalline ; and, if crystalline, whether granitic, porphyritic, amygdaloidal, globular, or concretionary; whether compact or granular; coarse or fine; pervious or impervious; hard or soft; firm or tender; with cleavage or without; massive or thin; the microscopic structure; also whether magnetic or not; soluble or insoluble; fusible or infusible; and the constituent minerals. III. CHEMICAL, that is, the composition of the rocks and of their minerals and their affinities. IV. PALÆONTOLOGICAL, as what kind of fossils are in the rocks,

Jan 1, 1873

By F. J. Sotillo

Mineral processing requires good classification of particles to attain an adequate separation of minerals. This is of utmost importance in the case of sulfide minerals. An ideal classification is obtained when particles are separated at a given mesh, which is fixed according to the characteristics of each sulfide ore. Under these ideal conditions, particles coarser than the mesh of separation are recovered in the underflow, whereas particles finer than the mesh of separation are recovered in the overflow. This paper presents the results of pilot plant tests that were performed on Ag-Pb-Zn and on Ag-Au Peruvian sulfide ores using a Density Separator, and the comparison of these results with those obtained using hydrocyclones, under similar operating conditions. The results show that the ratio of circulating load is reduced by 50% by using a Density Separator with respect to that obtained by using hydrocyclones. Moreover, the effect of the improvement in the separation efficiency obtained by using the Density Separator on the kinetics of flotation is also shown. Silver recovery of the Ag-Pb-Zn ore increased by 18% whereas gold grade in the concentrate of the Ag-Au ore is doubled.

Jan 1, 1998

By A Minchinton

With blasting, all far-field phenomena including, but not limited to, stress wave propagation, fracture, vibration and muck pile formation are intrinsically and irrevocably dependent upon near-field phenomena or mechanisms that we describe using physics-based mathematics typically transcribed into computer codes. The energetics involved in such near- to far-field transitions are not fundamentally relevant as they are simply progenitors of these processes.The notion of explosive energy as a descriptor for explosive or blasting performance is a case in point. These energies, which are generally used in blasting tables, are almost exclusively based on ideal detonation theory alone and do not include the influence of the rock, charge diameter, blasthole length and the late-time dynamic expansion that can be predicted using codes based on non-ideal detonation theory.With decoupled charges in presplits for example, the pressure drop between the charge and the blasthole wall can be simply described to first order using the energy relationship associated with adiabatic expansion. However, a more realistic mechanistic solution involves interacting fluids and turbulence leading to dynamic processes such as the channel effect.CITATION:Minchinton, A, 2015. On the influence of fundamental detonics on blasting practice, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 41–54 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By Lina Lopez, Jose Sanchidrian, Manuel Lopez, Pablo Segarra

Previous work in which rock properties and blasting parameters (geometry, charging and timing) were reported together with truck filling times, is taken as a starting point for a thorough analysis of the influence of the former on the mucking velocity. The experimental set was composed by 11 blasts made in an open pit mine. Non-parametric, distribution-free statistics is applied. The mucking rates (in bank cubic meters per unit of bucket volume and per hour) appear to be clearly dependent on the explosive energy and powder factor, both magnitudes combined as energetic powder factor (energy per unit of rock volume). The mucking rate is a non-monotonic function of such factor in the range of the blasts analyzed. The determination of the function is optimum when the fraction of the explosive below grade is not considered and when the explosive energy is qualified as that delivered at a partial detonation regime. Different types of loaders seem appropriate for different energy levels. At low levels both front loaders and rope shovels obtain small productivities without a statistically significant difference in their performance. At high energy levels, front loaders qualify higher than rope shovels. Mucking velocities can be equally small at low energy powder factors and at high ones if rope shovels are involved.

Jan 1, 2008

By Jacob W. Young

A casual reading of the geological literature extant to-day would give one the impression that carbon is an element which by some chance or another always existed at or near the surface of the earth, and was never of a magmatic origin. The carbonaceous matter in shales is said to be of vegetal derivation; petroleum is stated to have been derived from vegetable matter or from marine animal bodies; if carbon or bituminous matter is found in igneous rocks or associated with metallic ores, the statement is made that deeply buried carbonaceous sedimentaries were undoubtedly the source from which such carbon or bituminous matter was derived. This, I do not consider a reasonable or common sense view of the matter. Carbon is one of the elements of which the earth is composed. In the table giving the periodicity of the elements it comes sixth in the order of increasing atomic weights. It is an element formed like all the rest were formed, and must be as common to the interior of the earth as the rest of the eighty-odd elements so far discovered. The spectroscopic analysis of light from the sun, and the stars, shows the presence of carbon in the sun and in the colder stars. Thus with carbon, an element, found throughout the universe as well as on the earth, it is entirely reasonable to consider it as present in the interior of the earth with the other elements. Such being the case, the magmatic origin for the various forms of carbon in rocks and ores is a rational and logical conclusion. If but a small fraction of thought and effort was made along these lines, which is made in fostering the idea of the organic origin of the carbon found in the earth's crust, untold advances in this phase of geological science would result.

Jan 1, 1925

By L. B. Tsymbulov

Sulphide melts formed in the course of smelting of nickel and copper-nickel feed (matte) actually are sulphide-metallic melts since sulphur contained in the melts is in deficiency with respect to metals. The level of metallization is rather relevant feature of sulphide melts and is widely used in calculating material and heat balances for pyrometallurgical processes. Despite of the above parameter? importance, the investigators have no single opinion on what should be understood under metallization level and the method of its determination. In the present study we present the results of our own experimental and theoretical researches that have allowed determination of some mechanisms of sulphide melts? crystallization. Based on the mechanisms revealed new scientifically justified approach has been offered for determining level of metallization of the components present in sulphide melts. It has been demonstrated that sulphur distribution between the melts is substantially different from generally accepted concept.

Jan 1, 2006

By K G. van den Boogaart, M Lehmann, U Mueller

Geometallurgical parameters are descriptions of the mineralogy and microstructure of the ore determining its mineralogical and microstructural characteristics. From a conditional geostatistical simulation of such properties, a processing model can compute recovery, equipment usage, processing costs, and thus the monetary value for mining and processing a block with certain processing parameters. The output can be used for optimising mining sequences or finding optimal processing parameters by solving the corresponding stochastic optimisation problem.The approach requires two properties of the simulation not provided by established geostatistical techniques:Many relevant geometallurgical parameters are from non-Euclidean statistical scales such as (mineral) compositions, (grain size) distribution, (grain) geometry, and (stratigraphic type) categorical, which might produce nonsensical values (for example, negative proportions, negative facies probablities, planar grains) when simulated with standard geostatistical techniques.Due to the nonlinearity of processing, the entire conditional distribution of the geometallurgical parameters is relevant, not only its mean and variance. The geostatistical simulation needs to reproduce the joint conditional distributions of all the geometallurgical parameters.The multipoint conditional geostatistical simulation technique discussed here allows for jointly simulating dependent spatial variables from various sample spaces. The technique combines an infill simulation, similar to the one used in multipoint geostatistics, with a new form of distributional regression to estimate conditional distributions of arbitrary scales from different information sources, including training images, training models and observed data. The distributional regression is based on a generalisation of logistic regression and is related to both Bayesian Maximum Entropy geostatistics and high order cumulants.The method ensures that simulated data reside in the set of possible values and honour the characteristics of the joint distribution to be reproduced. The computational effort is substantial, but affordable for a useful application with standard problems: from processing-aware block value prediction and block processing optimisation as shown in the test application to a mathematically completely defined simulated model situation with a complex processing model.CITATION:van den Boogaart, K G, Tolosana-Delgado, R, Lehmann, M and Mueller, U, 2014. On the joint multipoint simulation of discrete and continuous geometallurgical parameters, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014, pp 379–388 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

On the Kinetics and Equilibrium Models for Biosorption of Ni(II) onto a Gram-Positive Bacteria Strain, Rhodococcus opacus, for Environmental Applications The aim of this fundamental study was to evaluate the biosorption of Ni(II) from aqueous solution streams onto a Rhodococcus opacus strain through kinetics and equilibrium isotherms studies. The biosorption of nickel achieved its highest value in a pH around 5. The experimental data evaluation was carried out focusing three two-parameter models, as: Langmuir, Freundlich, Dubinin - Radushkevich. In order to determine the best isotherm fit, three error analysis methods were used to assess the data: correlation coefficient (R2), residual root mean square error (RMSE) and Chi-square test. The error analysis established that the Freundlich model fits better the nickel biosorption data. Maximum uptake capacity of nickel reached a value around 7.63 mg.g-1 for R. opacus. The biosorption rate was fast and achieved a removal of around 79 per cent of Ni(II) in the first 5 minutes at room temperature (25 ¦ 2¦C). The experimental kinetics data was evaluated considering two models (pseudo-second order and pseudo-first order). The error analysis established that the pseudo-second order model better fits the data.

Sep 13, 2010

By R. L. Guerguerian

Nowadays, most grinding mills driven by a wrap-around ring motor are operating successfully. Some of the earlier problems could be attributed to the lateral stiffness and stability of their bearings. As a result, modifications to the bearings included the rearrangement of the shoes, or the addition of more shoes, closer to the horizontal centerline. This technical paper reports a study of the effects of bearings on the lateral stiffness of grinding mills driven by a wrap-around ring motor. The discussions cover the design of the four shoe trunnion bearings and examine the effects of the angular location of the shoes.

Jan 1, 2000

By K. C. Corin, B. McFadzean, J. G. Wiese

The Bushveld Complex of South Africa contains almost 90% of the world’s reserves of platinum group minerals (PGMs). In the flotation of PGMs, there are significant challenges arising from the need to treat ever-decreasing grades of the relevant ore deposits. The major challenge in the flotation of these ore bodies is the control and management of the gangue minerals, particularly silicates such as orthopyroxene and plagioclase feldspar which are often rimmed with talc which makes them naturally floatable. It has been shown that various polysaccharide depressants such as CMC and guar have different properties in terms of depressing the gangue minerals. Since the PGMs are often associated with sulphides, copper sulphate is widely used as an activator in PGM flotation but can inadvertently activate the gangue minerals and reduce the recovery of PtTe2 which accounts for up to 40% of the Pt in the Platreef ore body. Depressants also reduce the mass of solids reporting to the froth and can thus destabilize the froth. This effect on the froth can be mitigated by using higher frother dosages or water of higher ionic strength. In summary due care needs to be taken to carry out site test work to develop an optimum ratio of collector, frother, activator and depressant to ensure that the highest grades and recoveries of the PGEs are obtained while reducing depressant dosage as much as possible. Chromite recoveries can be reduced through the application of gravity separation or reducing entrainment through reduced water recovery. INTRODUCTION The Bushveld Complex located in the north of South Africa contains the world’s largest deposit of Platinum Group Minerals (PGMs) (1). The so-called upper Critical Zone of the Complex hosts the largest concentration of platinum group elements (PGEs) in the world. The Zone hosts the Upper Group Chromitite No.2 (UG2) reef and Merensky Reef as well as the Platreef mineralization of the northern limb of the Bushveld Complex. The Merensky pegmatoid Zone contains the base metal sulphide grains and associated PGMs. Of particular importance to the topic of this paper is the occurrence in these reefs of various gangue minerals. The Merensky Reef consists predominantly of orthopyroxene (~60%), plagioclase feldspar (~20%), pyroxene (~15%), phlogopite (5%) and occasional olivine. Secondary minerals such as talc, serpentine, chlorite and magnetite have widespread occurrence. Of these, talc is the only mineral to show significant natural floatability (2,3). Although present in small amounts talc is closely associated with pyroxene and imparts significant floatablity to the high concentrations of pyroxene present in these ores (4). The base metal sulphides consist predominantly of pyrrohtite (~40%), pentlandite (~30%) and chalcopyrite (~15%). The major platinum group minerals are cooperite (PtS), braggite [(Pt,Pd)NiS], sperrylite (PtAs2) and PGE alloys. The UG2 consists predominantly of chromite (between 60 – 90% by volume) with lesser silicate minerals (5 – 30% pyroxene and 1 – 10% plagioclase). Other minerals present in minor concentrations, can include silicates, oxides and base metal sulphides. Total PGE varies by locality but on average range between 4 and 7 g/t. The PGMs present in the UG2 Reef are highly variable, but generally the UG2 is characterised by PGE sulphides such as laurite (RuS2), cooperite (PtS) and braggite [(Pt,Pd)NiS. The base metal sulphides consist predominantly of chalcopyrite, pentlandite and pyrrhotite. The Platreef is located in the northern limb of the Bushveld Complex. This reef consists of a complex assemblage of rock types, with pyroxenites, serpentinites and calc-silicates being the most abundant. Base metal mineralization and platinum group element (PGE) concentrations are found to be highly irregular, both in value as well as in distribution. The predominant platinum group minerals (PGM) in the mined area of the Platreef are the PGE tellurides, alloys, arsenides and sulphides. T

Jan 1, 2019

By Kirsten Corin, Belinda McFadzean, Cyril O’Connor, Jenny Wiese

As orebodies being mined globally are of ever-decreasing grades, the focus on the concentration process has moved increasingly to the challenges faced in management of the gangue minerals. This is especially so in the flotation of platinum group minerals (PGMs), where head grades are typically in the region of 4–7 g/t. Hence, in PGM operations, a typical recovery of about 80 percent requires depressing about 85 percent of the gangue minerals. In a flotation cell the main control parameters are reagent type and dosage, froth depth and air addition rate. This paper reviews research projects carried out over an extended period aimed at optimizing the depression of gangue minerals: both those that are naturally floatable and those, such as chromite, that are entrained.  This has involved comparing the two major depressants used in the industry — guar and carboxymethylcellulose (CMC) — in the depression of the relevant gangue minerals, as well as investigating their consequent effect on the behavior of the froth phase. Because most PGM flotation plants treat the ore as if all the PGMs are associated with sulfides, copper sulfate is widely used as an activator, but this can also lead to inadvertent activation of gangue minerals. Finally, chromite levels must be kept below 3–5 percent to avoid any negative effects on smelter performance, and thus it is important to reduce chromite recovery which mainly occurs due to entrainment through, for example, froth depth control.   

By Kirsten Corin, Belinda McFadzean, Cyril O’Connor, Jenny Wiese

The Bushveld Complex of South Africa contains almost 90% of the world’s reserves of platinum group minerals (PGMs). In the flotation of PGMs, there are significant challenges arising from the need to treat ever-decreasing grades of the relevant ore deposits. The major challenge in the flotation of these ore bodies is the control and management of the gangue minerals, particularly silicates such as orthopyroxene, plagioclase feldspar, and pyroxene which are often rimmed with talc which makes them naturally floatable. It has been shown that various polysaccharide depressants such as CMC and guar have different properties in terms of depressing the gangue minerals. Since the PGMs are often associated with sulphides, copper sulphate is widely used as an activator in PGM flotation but can inadvertently activate the gangue minerals as well as reduce the recovery of PtTe2 which accounts for up to 40% of the Pt in the Platreef ore body. Depressants also reduce the mass of solids reporting to the froth and can thus destabilise the froth. This effect on the froth can be mitigated by using higher frother dosages or water of higher ionic strength. Reducing chromite recovery is of critical importance since high levels may negatively affect the downstream smelting process. Chromite recoveries can however be reduced through the application of gravity separation or reducing entrainment through reduced water recovery. In summary, due care needs to be taken to carry out site test work to develop an optimum ratio of collector, frother, activator, and depressant to ensure that the highest grades and recoveries of the PGEs are obtained while reducing depressant dosage as much as possible.

By E. F. Loiseau

(Read at the Philadelphia Meeting, February, 1878.) UNTIL June, 1868, it had not been attempted, either in this country or abroad, to manufacture by mechanical means, from anthracite coal-dust, artificial fuel for domestic use. Several attempts had been made to utilize coal-waste by converting it into a fuel for manufacturing purposes, but none of the processes were original, and they were merely applications of the well-known European processes and machinery, slightly modified by American ingenuity and mechanical skill. With one exception all those attempts have been failures. The great difficulty in the application of European processes and machinery has always been the limited production, and the excessive cost of the manufactured product, as compared with the cost of mining and preparing the ordinary anthracite coal for the market. The only serious and intelligent attempt to manufacture, on a large scale, artificial fuel for manufacturing purposes, has been made by the Anthracite Fuel Company, whose works are erected at Fort Ewen, near Rondout, New York. This company, organized under the auspices of the Delaware and Hudson Canal Company, had to go through the usual course of difficulties, breakages, and disappointments, which seems to be the lot of every new industry. Thanks, however, to the energy and perseverance of Mr. L. L. Crounsse, a gentleman of means, from Washington, D. C., the enterprise succeeded, and it is to-day established on a permanent basis. In order to increase the production, and to reduce its cost, the Anthracite Fuel Company was compelled to change most of its plant, and to erect more powerful machinery, producing lumps of a larger size, almost twice the size of the lumps made previously by the same company. This increase in the size of the lumps has been resorted to in Europe as well as in this country, in order to increase

Jan 1, 1878

By F. F. Aplan, S. Chander, A. R. Alaboyun

Several aspects of the capture of hydrophobic dust particles by droplets in sprays have been studied. The particle capture depends on several sub-processes involving collision, adhesion and engulfment. The collision events between dust particles and a single droplet were observed with a high speed motion analysis system to determine the influence of a surfactant on the capture process. In the adhesive process it was observed that the dust particles are collected at the surface of the water droplet to produce a rigid film at high dust loadings. In the presence of the surfactant, however, the particles were engulfed inside the droplet keeping a fresh surface on the droplet available for capture of more particles. A theoretical analysis is presented to take into account the role of contact angle on the penetration of particles into droplets. A significant increase in collection efficiency was observed with decrease in droplet size.

Jan 1, 1991

By S. Chander

The mechanism of oxidation of sulfur in pyrite is a function of the rate and driving force for oxidation. New evidence is presented in this article to show that at moderate potentials, a sulfur-rich hydrophobic layer is formed. Under ordinary conditions, the sulfur layer is covered with a layer of iron oxides, hydroxides, sulfate or oxy-sulfide ions. Under these conditions, pyrite is hydrophilic. In the presence of iron-chelating agents or iron sequestering ions, iron layer might not form. Under these conditions, sulfur-layer is exposed and pyritic might become hydrophobic. Stronger oxidizing conditions decompose the sulfur-layer, thereby making the surface hydrophilic.

Jan 1, 1992

By D. Kosior

Influence of frothers (a-terpineol and n-octanol) concentration on kinetics of a three phase contact (TPC) formation by a bubble colliding with a hydrophobic surface (Teflon) of different roughness was studied using a high-speed camera (1040 frames per second). It was found that the Teflon surface roughness and the frother concentration strongly affected time of the TPC formation (tTPC) and time of drainage (tD) of the liquid film separating the colliding bubble from the solid surfaces. With increasing Teflon surface roughness, from ca 1 to 80 µm, the time of the TPC formation was shortened by over the order of magnitude, from ca 100 to a few milliseconds only. At low a-terpineol and n-octanol concentrations, thetTPC values were shorter than in distilled water due to lowering the bubble velocity in the frother presence and diminished bouncing of the colliding bubble. However, at high frothers concentrations the tTPC values were prolonged, despite that the bubble velocity was similar. The prolongation of the tTPC at high frother concentrations indicates that air (micro- and/or nano-bubbles) was present at the Teflon surfaces of different roughness. The mechanism of the tTPCprolongation at high frother dosage is described.

Sep 1, 2012

By N. S. Dalal, X. Shi

"With a view of elucidating the role of glutathione (GSH) in the biochemical pathways of the chromate-exposure related carcinogenesis, we carried out electron spin resonance (ESR) spectroscopic investigations of the chromate-GSH redox reactions. The ESR measurements, employing spin-traps, provide evidence for the involvement of the glutathione (GS•) radical, as well as an isolable Cr(V)-glutathione intermediate. These results indicater a new mechanism for the reduction of chromate by GSH in cellular environment and help understand the (unexpected increase in Cr(VI)-induced DNA strand breaks at elevated GSH levels.We report here indirect electron spin resonance (EGR evidence for the involvement of the glutathionyl (GS) radical and direct evidence for a Cr(V) intermediate in the reactions of glutathione ¬(GSH) with chromate for the first time.. This work was undertaken to clarify the biochemical pathway of the reduction of chromate by GSH, since this reduction process is thought to be a critical step in the pathogenesis of the chromate-exposure related carcinogenesis. This follows from the literature reports which show that (a) Cr(VI)compounds have been proven to be carcinogens in laboratory animals as well as in human studies2-4, (b) Cr(VI) and not Cr(III) compounds are mutagenic 5-7, (c) Cr(VI) and not Cr(III) compounds can penetrate cell membranes 8.9 (d) the final state of Cr(VI) in cellular reductions is Cr(III)', (e) by itself chromate (or Cr(VI)) cannot be directly mutagenic since Cr(VI) is known not to interact with isolated DNA under physiological conditions 10, suggesting the significance of Cr(VI).reduction processes. One of the major reductants in cellular environments is thought to be the GSH, both outside and inside the ce11s 11-13. Other evidence for the role of GSH in the chromate toxicity is seen from recent studies showing that exposure of hamster cells to non-toxic levels of added selenite increases the levels' of GSH as well as the Cr(VI)-induced DNA strand beaks 14, and thatsuch DNA strand breaks in hepatocytes also change in direct proportion to their GSH content 15,16. These observations wereinterpreted as implying that the reduction of chromate by GSH, to some reactive intermediate is an important step in the chromatecarcinogenicity 15,16. The following reaction steps were,suggested 15, 16"

Jan 1, 1988

By W. H. Emmons

INTRODUCTION THE deposition of metalliferous lode systems takes place at considerable depths and no one may observe the process. We see only the end results of the process and from these we seek to construct a theory that will account for them. Because there is an obvious relation between many lode systems and intrusive igneous masses, it is a natural inference that they have formed by fluids that were expelled from such masses. The metalliferous lode systems have been deposited by ascending thermal fluids that have risen mainly from great irregular bodies of intruding magmas which are called batholiths. Probably 95 per cent of such lode systems have formed in connection with acidic or "granitic" batholiths and probably less than 5 per cent have formed in connection with basic intrusives. The study of lode ores, therefore, should include the study of the intrusion and differentiation of the batholith. It was noted long ago1 that certain tin-bearing deposits are commonly associated with small stocks. That small stocks are cupolas of larger intrusive masses has generally been recognized. Butler,2 in his studies of the ore deposits of Utah, showed that the chief deposits in Utah are in and near the stocks; that is near the "apically truncated

Jan 1, 1933