Search Documents

By Dale R. Ralston, Roy E. Williams, Gerry V. Winter, George L. Bloomsburg

It is imperative that the hydrogeologic frame- work and the ground water flow systems of a Potential mine area be investigated prior to initiation of mining. Such investigations are necessary so that potential mine water inflow problems can be anticipated and controlled. Obvious difficulties can arise if large inflows of ground water occur in underground workings. Costs of water removal and disposal, if not foreseen and included in economic planning, can severely limit or eliminate profit from a mining operation. Safety problems associated with large inflows are an additional potential problem. The inflow of water into a mine necessarily alters the associated ground water system. The inflow also may impact nearby surface water regimes, depending upon the interaction of the surface water and ground water systems. The inflow of water into a mine inevitably causes a decline in the ground water levels in the vicinity of the mine. This decline may be restricted to a small area or it may extend a considerable distance, depending upon the hydrogeologic properties of the associated hydrostratigraphic units. A decrease in surface flow will result if the area of ground water level decline intersects a stream or spring that is hydraulically connected to the ground water system. Mine inflow problems historically have been evaluated after-the-fact. Premining hydrologic investigations only recently have been initiated. Brown's (1977)* report on anticipated hydrologic impacts of oil shale mining in the Piceance Basin of Colorado is an example of premining hydrologic planning. Observed difficulties inherent in designing a data collection network and then utilizing the data to predict mine inflow have led us to the preparation of this manuscript. This manuscript reflects a two-phase effort. The first phase describes and develops analytical and numerical techniques for mine inflow prediction. Emphasis in this section is placed on the selection and application of data collection techniques and data analysis procedures. The second phase applies the prediction technique(s) developed during phase 1 to two existing mines. The objective of phase 1 efforts is to evaluate the hydrologic variables associated with surface water systems and ground water systems that can affect the inflow of water into an underground mine. Subsequently these variables are incorporated into predictive techniques for estimating underground mine water inflow and its effect on associated ground water and surface water systems. The specific objectives of phases 1 and 2 are to: 1) Determine the hydrologic parameters required for predicting underground mine water in- flow and the potential effects of the inflow on surface and ground water systems. The hydrologic parameters represent both premining and past initiation conditions. 2) Outline methods for obtaining the necessary input data for the predictive techniques in pre- mining and post initiation periods. 3) Present existing numerical techniques for predicting underground mine water inflow including assumptions Ad required input. 4) Evaluate existing numerical techniques previously tabulated based on their applicability to mine water inflow prediction. 5) Attempt to develop analytical techniques for predicting underground mine water inflow. 6) Develop, through modification of existing models, a general mathematical model as a numerical technique for predicting underground mine water inflow and the resultant effects on surface and ground water systems. 7) Apply the predictive techniques to two existing mines selected for this purpose. 8) Compare the predicted inflow rates to measured inflow rates at both mines. 9) Compare predicted impact on district hydrology to observed impacts where possible. 10) Evaluate the predictive technique.

Jan 1, 1986

By Christopher J. Bise

PRINCIPLES OF MINE PLANNING During the initial planning stages, all mining operations are analyzed and evaluated in a similar fashion. This similarity holds true because the mine-planning procedure can be reduced to a network of interrelated systems that are tied together by a common philosophy of mine planning: namely, that the resource is to be extracted in a manner which is safe, efficient, and profitable. The success of the mining operation cannot be guaranteed unless each of these three requirements is met. Fig. 1 shows a flowchart for the initial planning of any mining operation. Notice that there is a preplanning stage that leads to the planning of four interrelated systems. The preplanning stage includes property exploration, estimation of production and manpower requirements, and the establishment of construction timetables. The four systems, evaluated after the pre-planning stage, are broken down into the following: (1) Excavation and handling system, (2) Strata control system, (3) Operating support system, and (4) Service support system. The Excavation and handling system includes the selection of all the equipment for the removal of the resource from its in-place deposit (e.g., draglines, continuous miners, rock drills, etc.) and for the transportation of the mined material from the face (e.g., belt conveyors, trucks, etc.). The Strata control system incorporates all those considerations which maintain the integrity of the roof, ribs, floor, and overburden both during and after the extraction phase; typical considerations in this area include pillar sizing, artificial support of the immediate roof in mine entries, and subsidence protection. The Operating support system contains the "necessary evils" of mine planning; the system consumes a large percentage of the mining engineer's planning time but does not contribute to the actual extraction of the resource. However, if proper attention is not paid to the various components of the system, such as ventilation, drainage, and power, then the mining operation will not perform to its capabilities. Finally, the Service support system is composed of those operations which keep the mine running efficiently; typical examples of these include maintenance and sup- ply. One important concept that Fig. 1 is designed to emphasize is that the four systems are interrelated; typically, a slight alteration of one can affect the performance of another. If these interrelationships are ignored, the effects on the system can be disastrous. The mine preplanning stage and the four subsequent system evaluations constitute the Analysis portion of the mine planning flowchart. After this portion of the study is completed, the overall projected operation can be evaluated by techniques such as financial analysis. This last step in the study is referred to as the Synthesis of the previously calculated parameters into an overall plan. Much has been written about the overall evaluation of mining properties, but, over the past thirty years, very little has been written about the analysis of mine- planning systems in a coordinated manner. Further, those texts which attempted this topic have failed to give sufficient examples for successful implementation, thus supporting the operating engineers' lament that it is easy to discuss theories but difficult to show applications. This text is intended to bridge this gap. Examples of the various stages of the analysis portion of the mine planning flowchart shown in Fig. 1 will be covered in this text, with the exception of the Service support system, since this system is oriented more toward day-to-day planning than long-term mine planning. INTERNATIONAL STANDARDIZATION The benefits that can be derived from an international standardization of the units used in mining engineering calculations are numerous. The interchange- ability of equipment parts and the ability to analyze and compare performance and design specifications on an equal basis are just two of the goals desired by both manufacturers and mine operators. Unfortunately, conversion to an international standard has not been rapidly achieved by engineers in the United States, due to their training under the English system. The Society of Mining Engineers of AIME has made the commitment for the adoption of the Systeme International d'Unites (SI) in all mining engineering calculations. Since many practicing mining engineers and students in undergraduate programs still find difficulty in relating to SI units, the calculations in this textbook will use the English system, with Table 1 available for conversion into SI units.

Jan 1, 1986

Ever since A Decade of Digital Computing in the Minerals Industry was published in 1969, mining men have expressed the need for an additional reference on computer methods. It was felt such a volume should spell out the "how to" of computer applications in the solution of their problems. Computers in the minerals industry will be 20 years old when the 1979 SME Fall Meeting and the 16th International Symposium on the Application of Computers and Operations Research in the Mineral Industry (APCOM) take place jointly in Tucson, AZ. On such an occasion it was thought appropriate to publish an anniversary volume which reviewed current practices and projected what might prevail as computer methods for the future. Thus was born the idea to publish Computer Methods for the 80's. The first planning meeting for this volume took place in Las Vegas, NV, during the 1976 annual meeting of the American Institute of Mining, Metallurgical, and Petroleum Engineers. It quickly became evident that no single computer method existed to solve most mining problems; rather, mining computer methods are generally tailored to fit unique geologic, mining, and organizational conditions. Hence a format which included both the theory and practice for each of the computer applications was adopted for this volume.

Jan 1, 1979

By George S. Koch

Today, after about 30 years of development, computer-based analysis of geoscience data has reached a mature phase. From the tentative early beginnings recorded in the proceedings of the APCOM meetings, geoscientists are now able to emphasize the need for both pertinent mathematical/statistical models and computer hardware and software. From those models that are well understood in the disciplines of statistics and mathematics and for which effective computational methods are available, practitioners select and develop methodology for their particular purposes. Computer hardware is typically assembled from off-the- shelf components now readily available, with particular emphasis, whenever feasible, on microcomputers for reasons of economy and control by the scientific or engineering user rather than by a bureaucratic computer center. Computer software may be written by the user in high level languages such as Pascal, FORTRAN, or LISP. However, more often today geoscientists use routines available in spreadsheets, data bases, or statistical packages. In so doing, they save time and, programming costs and take advantage of routines written and maintained by large, well- established organizations, while losing the flexibility in specifying exact input/output afforded by writing in a high level language.

Jan 1, 1989

By Kunio Hashimoto

The conventional troughed belt conveyor system is the most widely used form of equipment for transporting bulk materials in the world today. The reason is not only because it is possible to transport a great deal over a long distance when compare to other types of equipment but also due to its greater economic efficiency and low initial and running costs. When dry, powdery materials and liquid materials are being conveyed, there are enclosed transport methods such as flow, case, air-slider and pipe line. In addition to features of the belt conveyor, a system employing a pipe line to transport dry powdery and liquid materials has always been considered an ideal method. This has been brought into reality through the Pipe Conveyor Sys tem.

Jan 1, 1984

By Justin Jensen, Luis Moya, Jose Carlos Durazo, William Szolga, Tyler McCallum, Tim Doubleday

Sulfuric acid mist is an undesired by-product of the copper electrowinning process, caused by oxygen evolution at the anode which entrains droplets of the acidic copper electrolyte solution. As the oxygen moves to the surface of the cell, these droplets become aerosolized resulting in acid mist. The addition of chemical anti-misting agents to the copper electrolyte is a common mitigation technique. This paper details Syensqo’s laboratory development of a new environmentally friendly acid mist suppressant, ACORGA® EW98. The product exhibits excellent acid mist suppression and it is fully compatible with the adjacent solvent extraction process. Lab and pilot test results are reviewed ahead of future planned industrial trial testing.

Feb 1, 2025

By J. Ramirez-Castro

The abstract and text of this chapter were not received in time for printing.

Jan 1, 1982

By R. O. Burt

The Tanco pegmatite is located in the Bird River greenstone belt of south-eastern Manitoba approximately 160 km northeast of Winnipeg (Figure 1). The orebody was discovered in 1929 and subsequently attempts were made to exploit it for tin by Jack Nutt Mines Ltd. and later in the middle 1950's by Montgary Oil Ltd., who extensively developed but did not produce from its lithium deposits. In 1966 systematic investigation of the pegmatite as a potential source of tantalum led to the founding of Tantalum Mining Corporation of Canada Ltd. (TANCO), and production of tantalum concentrates from the Bernie Lake mine commenced in 1969. Tanco's currently jointly owned by Hudson Bay Mining and Smelting Co., Cabot Corporation, and the Province of Manitoba.

Jan 1, 1988

By Ray W. Ballmer

Historically, Bingham is a rail pit, starting with steam locomotives in 1906 and converting to electric locomotives in 1923. Ore production was maintained through an effective utilization of available rail equipment. From time to time as it became necessary to deepen the pit and as stripping ratios increased, various studies were made on alternate material haulage systems. Utilization of diesel locomotives, conveyor belts, and trucks have all been subjects of study, however, conversion from rail haulage utilizing electric locomotives could not be justified. Because of the gradual decline in ore grade, a program was approved in 1963 to raise ore production to 108,000 tons per day. This was designed to return copper production to the 1950 level. Attainment of this production level by expansion of the rail system had definite limitations and built-in inflexibility. Track and trolley wire relocation causes shovel down time in excess of that required for normal maintenance. Instability of the dumps and the resulting additional track maintenance increases greatly as the volume of waste material to be handled daily expands.

Jan 1, 1965

By A. K. Snelgrove

At a time when water resource planning is proceeding on a continental scale, such as the proposed $100 billion North American Water and Power Alliance, which would redistribute water among three nations, including seven provinces of Canada, 35 of the United States, and three States of Mexico, the selection of a single river basin for study may seem to require an apologia. None is offered because of ( 1) the magnitude of the Indus , itself a part of the great Indo-Gangetic Plain drainage system, with Himalayan sources, upon which the thickly populated northern sub-continent of Indo-Pakistan depends for agriculture and hydroelectic power; (2) the extraordinary problems created by dismemberment of the world?s largest irrigation system through legal beheading of the Eastern Waters under the Indus Waters Treaty of 1960; and (3) the herculean effort to contain the twin encroachments of waterlogging and salinization in a basin which faces a shortage of fresh water. The British irrigation system of barrages and canals on the Indus was a venture admirable in conception. Unfortunately, it is now a legacy burdened with unwanted consequences, due to interference with the hydrological regimen, particularly the rise of water table occasioned by leakage.

Jan 1, 1967

By Betty L. Gibbs

The ultimate objective of mine design is to determine the development and untilization of mining resources. Computer Aided Design (CAD) and automated mapping are becoming very popular in engineering and in mining. Any computer program which produces a design or model with the interaction of an engineer can be considered computer-aided design (CAD), but' the term CAD is often associated with interactive graphic design and mapping capabilities. Graphics can be effectively used to describe and model two-or-three dimensional mine workings, orebodies, and geologic structures. Interactive computer graphics is applied to mine design with a combination of deposit modeling techniques and the use of AutoCAD for interactive graphics and mapping. The combined system can perform a large part of the calculations and drafting work for geologic and mining design. Using computer calculation and graphics techniques, comparisons of alternatives, can be made quickly.

Jan 1, 1989

By James W. Babcock

Introduction Geologic ore deposit models are key to any exploration program. In the search for ore deposits, the geologist first tries to understand the genesis of known ore bodies. During reconnaissance and evaluation of a prospect, a valid exploration model of a known ore body can help the explorationist focus on critical geologic attributes of the target area. Exploration models can conserve exploration funds that might otherwise be spent collecting data not critical to delineating an ore body. This article examines the benefits of using models, factors to be considered in developing models, and examples of the way recent models have evolved. New exploration concepts and techniques are developed in response to increased competition in the mining industry. New techniques can give an exploration group a slight edge that may translate into a discovery. Mine geology staffs may find previously unlooked for extensions to the ore body by applying new genetic concepts. When all appropriate techniques are applied to exploration and mining efforts, greater efficiency and increased profits may result. Before the 1950s, scientists speculated on the genesis of ore deposits and other natural phenomena. But they presented their results as if universal and final, even though they applied to only a few deposits. Because it did not provide sufficient criteria to distinguish the genetic processes, the classic conflict between hydrothermalists, epitomized by Lindgren, and nonhydrothermalists did not help the minerals explorationist much. Important information about individual ore deposits, such as age of the host rocks and mineralization, composition of the mineralizing fluids, and separation of mineralizing and nonmineralizing events in the paragenetic sequence, could not be gathered with past equipment and methods. But these early concepts of ore genesis contained excellent empirical observations, perhaps the most useful parts of these hypotheses. Through the years, prospectors have found most of the ore deposits in the world using direct observations and their collective empirical wisdom - an empirical model. The geologist's contribution becomes increasingly important after the more obvious surficial ore deposits have been discovered. In Europe and North America that time has arrived. With the introduction of sophisticated equipment and matching techniques in the 1950s in geochronology, geochemistry, geophysics, remote sensing, and computers, many previously equivocal genetic questions can be resolved. This proliferation of highly technical data has allowed the construction of many well-founded genetic models.

Jan 12, 1984

By Betty L. Gibbs

Mine planning and scheduling done with computer programs is possible only after extensive work has been completed to define the geologic extent of an ore body and an overall mine design. Mine planning methodology on computer can vary from computerized engineering tasks through systems which completely optimize a plan with little input from an engineer during the actual scheduling process. However, a strong emphasis is placed on producing practical mining sequences which may be "best" rather than "optimum". This section offers several viewpoints on the planning process using computers. Interactive planning and scheduling systems are attractive for many companies because they are easy for engineers to understand, and the results are acceptable. The engineer develops an open pit mine sequence by trial and error using interactive graphics. The results of this approach can usually be improved. A computer program can help an engineer make many trials in a short time period and provide a higher level of confidence that a "best" plan has been generated.

Jan 1, 1989

Contributions made by mining have played a much more significant role in the development of civilization than is generally conceded by historians or recognized by ordinary citizens. In modern society, mined products pervade all industry and the lives of all civilized people. Early man relied largely on stone and ceramics, and eventually metals, to fashion tools and weapons. Civilization was advanced by discoveries such as abundant supplies of high-quality flint in northern France and southern England and firesetting to break rock. Middle Eastern cultures flourished not only because of agriculture and trade, but also because of mineral-rich deposits nearby. The earliest miners date back perhaps to 300,000 BC; their quest was for nonmetallic minerals (chert, flint, obsidian) suitable for utensils and eventually for weapons. Other rocks and minerals (ceramics, clay, salt, meteoric iron) attracted the miners for jewelry, cosmetics, construction materials, food seasoning, and coinage. At first, their excavations were confined to the surface, either pits or placers. But by about 40,000 BC, mine workings had been extended underground as short adits or shafts, and by 8000 BC as elaborate interconnected openings 300 ft (90 m) in depth. Metallurgical separation of metals from their ores and their subsequent fabrication evolved gradually over the centuries, copper being the first liberated (c. 7000 BC) followed by lead, silver, gold, and iron. Man enhanced both the sophistication of his

Jan 1, 2008

By Peter Kreisman

This paper and four other papers on the MEQB Regional Copper-Nickel Study, presented today at the 1980 SME-AIME Fall Meeting are based on four years of extensive inter-disciplinary research and impact analysis supported largely by the Legislative Commission on Minnesota Resources. This study produced over 180 technical reports, the results of which are summarized in an Executive Summary available from the Minnesota State Planning Agency, St. Paul, Minnesota. Those wishing to examine the many scientific, engineering, environmental, social or economic issues addressed by the study are encouraged to obtain a copy of the executive summary. The executive summary includes a bibliography of all technical reports produced by the Regional Copper-Nickel Study and describes the five-volume, 26 chapter Regional Copper-Nickel Study Report.

Jan 1, 1980

By Kenneth P. Katen, Robert H. Trent

GENERAL DESCRIPTION Shortwall mining is one of the newest mining meth¬ods to be introduced into the world coal industry. The technique of shortwalling seems to have a number of origins, but it is generally agreed that it is an outgrowth of pillar-and-stall mining where timbering was employed as the primary means of roof support. In early opera¬tions the face was undercut by a shortwall cutter, hand¬bored, and blasted. The coal was loaded by hand or gathering arm loader. Australia, having experienced success with this method, advanced the technique through the use of mechanized roof supports in 1968. Although there were several attempts at shortwalling in the US, it was not until 1973 that Eastern Associated Coal Corp.'s Federal No. 1 mine successfully extracted a shortwall panel. Table 1 is a list of shortwall opera¬tions in the US as of April 1976. Shortwall mining is a method of mining in which a continuous miner cuts and loads from the short end of a rectangular pillar of coal while hydraulically powered self-advancing roof supports provide protective cover. Characteristics of a shortwall system include panel di¬mensions (Fig. 1) of 610 to 1219 m (2000 to 4000 ft) in length, face widths of 30 to 61 m (100 to 200 ft), straight-line ventilation, and production machinery, with the exception of roof supports, commonly used on con¬tinuous miner units. GENERAL REQUIREMENTS AND LIMITATIONS The justification for shortwalling is primarily eco¬nomic, i.e., increased production and recovery concur¬rent with savings in material and labor. The method also has a number of secondary benefits including the much needed progress it has stimulated in deep mine technology, the alternatives it presents to some of the problems resulting from the 1969 Coal Mine Health and Safety Act, and is perhaps a key to the solution of the enigmatic labor problems which plague the industry. The advantages of shortwall mining over continuous miner units include the following: a highly effective method of ventilation and dust control; a greater per¬centage of extraction (approximately 85%) ; fewer equipment moves, hence more efficient operating time; cost savings on materials such as roof bolts, rock dust, ventilation curtains, timbering materials, and the labor needed to supply, load, and transport these materials; a cyclical pattern of mining, each phase of which, i.e., development and retreat, lasts for approximately three months and appears to be psychologically motivating as well as highly productive; and improved safety. In addition to these positive aspects, a shortwall sys¬tem also has advantages over a longwall system, and these are listed as follows: the capital outlay for a shortwall system is one-third to one-fourth that for a longwall (1976 prices); the shortwall system utilizes equipment that is used on a continuous miner section, with the ex¬ception of the roof support system; there is a great deal of flexibility in areas with numerous gas wells and in areas where surface subsidence cannot be tolerated; the shortwall has reduced tailgate problems, since the tail¬gate entry serves as a return airway only; and the cyclical pattern of mining insures that the mining machinery pro¬duces coal even while the roof support system is being moved to another panel. There are several parameters which govern the se¬lection and use of a shortwall system. They are all of equal importance, and hence are not listed in any par¬ticular order. These are deposit size, seam height, seam inclination, roof and floor conditions, depth of over¬burden, subsidence and chain pillar extraction, man¬power, ventilation, and materials handling. Deposit Size Reserves available for shortwalling should be suffi¬cient for at least an eight to ten-year period, since this seems to be the effective life, without rebuilding, of a hydraulic roof support under average conditions. Of

Jan 1, 1982

By Jorgen Elbrond

Before and in the early stages of industrialization, mining was the undisputed leader in technology. It represented the high-tech of the time. Early mechanization bears witness to that. Hoisting and rock breaking driven by waterpower are such examples. The mines' use of the steam engine was a major incentive to its development. By these means new mines could be opened and more metal supplied. Understanding of systems was essential for miners when shaping the infrastructure of the mines for the transportation of ore, material and men and for the evacuation of water and for ventilation. The irrigation systems of ancient mines are such examples. However, with the industrial revolution other more specialized branches of industry advanced further, and the mines became users of other industrial branches technologies. The mining industry had, however, always been quick to recognize a good thing and use it, when time was right. But, compared with other branches of industry, the mining industry has the disadvantage of working in a rugged environment with (and actually inside) a raw material which is abrasive and highly variable with respect to mechanical properties. This determines the rather high unpredictability of mining machines' performances and their low availabilities and explains a part of the delays in introducing technological advances.

Jan 1, 1989

By Y. J. Wang

Along with the inexpensive availability of computing hardware, a proliferation of powerful personal computers is being realized throughout the mining industry. People from every arena within the industry are designing, developing, and/or applying mining specific software, which is increasing at a rapid rate. In this section applications (or potential applications) that are being made in the analysis and design of mine systems are discussed, including the design of compressed air networks, the simulation of hoisting operations, analysis of longwall face maintenance, and a summary of computer and software applications for analysis and design of coal operations. In "Computer Aided Design of Mine Compressed Air Networks" the authors describe software, called CompAir, and the underlying theoretical and mathematical foundations of it that can be used to make accurate, cost-effective designs of compressed air systems for mines. It includes algorithms for network analysis and the optimization of pipe diameters. The techniques embodied in the software replace traditional rule-of-thumb approximations which have been used in the past and avoid the operating problems that often result from using average, steady-state parameter values, estimated for ideal operating conditions. CompAir, coded in Turbo Pascal for personal computer use, bases calculations on compressible fluid theory, which gives more accurate results than incompressible fluid theory whenever high flow rates or long line distances are involved. The net- work and pipe diameter analysis is formulated as a nonlinear programming problem. The solution technique requires a trial and error approach that iteratively applies the unconstrained optimal pipe diameter algorithm to successive solutions of the constrained network problem until the diameters become "fixed." The authors conclude by recommending the use of a mine-wide monitoring system to improve cost control and provide a better understanding of flow regimes in compressed air networks.

Jan 1, 1989

By Y. C. Kim

One-quarter of a century has passed since the "theory of regionalized variables" (geostatistics) was introduced by G. Matheron (1962, 1963) in France. Yet, only during the past decade has geostatistics found broad acceptance in the mining industry. Foremost among the reasons for this time lag was ignorance. The first English treatise on geostatistics was not written until Matheron (1971), and the first published text accessible to mining professionals did not appear until David (1977). Other significant reasons for the slow acceptance of geostatistics included the conservative nature of management in the 1970s minerals industry, and the fact that conventional ore reserve estimation performs reasonably well when confined to massive deposits of base metal and iron deposits having relatively low coefficients of variation in grades. In short, mine engineers and geologists were not willing to accept a new set of tools for problems that they did not see.

Jan 1, 1989

By Charles Banks Belt

In 1925, Niggli (1925, pp, 1-69), formulated a physico-chemical, explanation for the origin of hydrothermal ore deposits, from a concept that had appeared earlier in the literature in the writings of Von Groddeck, Stelzner, Beck, de Launay, Kemp, and Lindgren. Niggli proposed that pressure at depth could force volatiles from deep-seated magmas. The volatiles would In turn form pegmatites and then ore deposits as the fluids cooled. This is one view of a general theory of ore genesis that gained secondancy for years among such prominent geologists as Fenner (1926, p, 697) and Emmons (1936, pp. 29-70). It was, proposed that ore deposits were precipitated from solutions or fluids that had escaped or been separated from a deep-seated magma by means of liquid immiscibility or crystallization or gas transfer. This theory is based on the presence of igneous rocks close in space and age to hydrothermal ore deposits in many mining districts of the world. As is well known, there are many ore deposits apparently of hydrothermal origin that are neither spatially nor chronologically related to igneous rocks, In still other localities where there are no hydrothermal ore deposits, igneous rocks occur that are similar in composition to those in mining districts. In view of such facts, the applicability of the Niggli theory to all hydrothermal ore deposits may well be questioned. The chief purpose of this paper is to test the Niggli theory by studying the primary petrology, hydrothermal alteration, and distribution of copper and zinc in silicic igneous plutons supposedly genetically related (in the Niggli sense) to nearby hydrothermal ore deposits, Silicic Tertiary plutons in three New Mexico mining districts were chosen, the Hanover-Fierro intrusive at Hanover and Fierro, the Granite Mountain pluton at Magdalena, and the four outliers of the Lordsburg stock at Lordsburg. First, it had to be established whether the observed plutons were or were not the source of the adjacent ore deposits. This was done by studying the relation between the copper or zinc distribution-and the primary or secondary features in the plutons studied, and the time relations between instrusion and ore deposition. Primary igneous features of a pluton are defined as the minerals, texture, shape, and character of the pluton which were formed prior to the complete solidification of the rock, secondary features include all changes that took place in a pluton after solidification. They are identified by their cross cutting nature or as replacing primary minerals, Under the Niggli concept, it is proved that the ore ions did not originate from the parts of the pluton now visible as immediately adjacent to the ore deposits; it must then be established, if possible', that the ore ions were separated from deeper parts of the intrusive, Some idea as to whether the copper or zinc ions originated from a related magma at depth may be gained by a comparison between the primary (that is, pre-alteration) zinc and copper abundances found in ore localizing intrusive studied and the average abundances for copper and zinc in silicic igneous rocks most recently given in the literature. Finally, the relation between ore deposition and hydrothermal alteration was studied on a regional as well as on a local scale.

Jan 1, 1958