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By Sabina Brady

Nearly a decade and a half after the US and China established formal diplomatic relations, and two decades after the two countries signed the Shanghai Communique and established commercial ties, the world, and perhaps China itself, has discovered that a wealth of natural mineral and energy resources lie beneath China's soil and directly off its coast. The country's coal reserves and oil and gas potential are well known. Its ferrous and nonferrous metal reserves are respectable and in a number of instances pre-eminent. According to 1981 Minerals Yearbook estimates - more often than not below those now being claimed by China - the country's aluminous metal reserves are about 907 Mt (1 billion st); iron ore reserves are 40 Gt (44 billion st); and copper reserves are about 46 Mt (54.4 million st) of contained metal. In addition, the country has about 10.7 Gt (11.8 billion st) of phosphate reserves, the fourth largest in the world, and 3 Gt (3.3 billion st) of pyrite. China's national Sixth Five Year Plan promulgated in late 1982 ended a stringent three-year retrenchment or readjustment period in which a number of major development projects involving foreign participation initiated in the late 1970s were shelved. The new Five Year Plan is a signal both within and outside of China that things are now moving again, and that major industrial and service sectors are receiving the kind of funding and flexibility they need for expansion, construction and modernization. The new plan's strategy for growth is measured and much less grandiose and frenetic than it was five years ago when China flung open its doors to foreign companies and invited participation in large-scale development projects. Now, the country's reticence to spend foreign exchange to purchase key equipment, technology, and services -a reaction to these projects and the spending they entailed - is clearly on the wane. In China's effort to quadruple its GNP by the year 2000, there is a new willingness to use some of its substantial foreign reserves. In fact, it is projected that 1983 will witness a $1.9 billion deficit, with a $2-3 billion deficit in 1984 and 1985. The following article discusses implications the Sixth Five-Year Plan has for nonferrous metal development in China. It is the first in a series of three articles on Chinese mineral resource development to be published in Mining Engineering over the next few months. The second article will identify specific nonferrous projects underway, while the third in the series will focus on trade and development opportunities for phosphate and potash producers in China. China's Ambitious Plans In the last few months, the exploitation of China's nonferrous resources and development of its industrial processing capabilities have begun to receive increasing attention on both provincial and central levels. Unlike the earlier modernization drive of 1978 when China's ferrous sector - best typified in the Baoshan iron and steel project - got the lion's share of the Ministry of Metallurgical Industry's (MMI) energy and resources, it now appears that in some respects the nonferrous and industrial sectors are finally moving out from beneath the dominating shadow of ferrous and getting their own day in the sun. Separation of Nonferrous from Ferrous One clear demonstration of this is the establishment in April 1983 of the China Nonferrous Metals Industry Corporation (CNFMIC). The corporation is composed of 819 enterprises with over a million workers, and also includes 12 nonferrous metal construction companies, eight design institutes, and three prospecting companies. Of ministerial rank, CNFMIC is responsible for the development of both the country's nonferrous resources and its processing facilities. Although closely tied to the parent ministry from which it sprang (i.e. MMI), CNFMIC, at least theoretically, is separate and independent from it. One strong indication that this independence is, or soon will become a reality, can be seen from the fact that the new corporation is not headed by the former MMI officials, not even those who made up the ministry's now defunct nonferrous bureau. Instead, its president Qiu Chunfu is formerly of the State Economic Commission and the China International Trust and Investment Corp. Its general manager Fei Ziwen, an engineer in his early 50s, is from the Jiangxi Province Copper Corp. The new nonferrous corporation appears to be powerful

Jan 7, 1983

By Yi Luo

In a shearer longwall mining operation, the longwall bits are responsible for breaking into and chip-ping the broken coal blocks away from the coal face. However, underground observations have found that a large number of longwall bits are always working under various degrees of wear. Reduction of the bit wear could be realized by using better designed longwall bits and properly selected shearer operating parameters. A computer program has been developed to simulate the performance of the longwall bits. The shape of the bit head, the installation of the bits on the drum and the operation parameters are the information required by the program. Through the simulations, the main factors affecting the bit wearing process are identified. Suggestions are also made for improving the design of the longwall bits.

Jan 1, 1996

By Earle Faig

Along with other transportation modes, the barge industry will be greatly effected by trends in domestic coal production. Traditionally, coal has been one of the major commodities moved by barge. Now, because of events in the international energy market, coal is finally getting the recognition it deserves as a major component of the country's energy program. Perhaps even more significantly, a series of events have caused other countries to turn to the United States as a source of coal. Although the outlook for coal demand is optimistic, it will be greatly influenced by the ability of the transportation sector to handle the additional traffic. Because of our long experience in moving large quantifies of coal, the barging industry is in an excellent position to capitalize on coal's increased popularity. A brief description of the barging industry should facilitate the discussion of coal as it relates to the barging industry. Barge companies operate on a 40.23-Mm (25 000 mile) river system which includes the East and West Coasts and the Mississippi River System. Included in the Mississippi River System are the Allegheny, Monongahela, Kanawha, Ohio, Illinois, Missouri, Tennessee, Cumberland, Arkansas, Warrior - Tombigbee and Mobile Rivers as well as some smaller tributaries. The Gulf Intracoastal Waterway, which stretches along the Gulf Coast from Brownsville, Texas to Apalachicola, Florida, is also considered part of the inland waterway system.

Jan 1, 1981

By H. V. Fairbanks

It is estimated that millions of tons of coal fines are unsaleable each year due to difficulty of drying them economically with conventional mechanical dewatering and thermal drying equipment. The difficulty is due to the fact that coal of small particle size presents a large surface area with polar groups which have a great affinity for water. In order to remove this water thermally, a high temperature is necessary which oxidizes the surface of the coal. This substantially reduces the heating value of the coal. If drying could be satisfactorily carried out at a lower temperature, much more of the heating value of the coal fines could be retained. It was conjectured that acoustic energy applied during the drying process might prove to be of value since acoustic energy has the property of producing cavitation at a liquid-solid interface when the intensity is sufficiently great. This cavitation process produces water at room temperature which can be carried away from the solid surface by a flow of relatively cool air. Hence, moisture removal is made possible at a lower temperature.

Jan 1, 1966

By Y. C. Kim

The strongly skewed grade distributions and the need to estimate the local recoverable reserves in a selective mining environment are the two problems that Ordinary Kriging (OK) cannot easily handle. With the recent introduction of the nonparametric, distribution-free technique of Indicator Kriging (IK), the above problems can be solved. This paper describes the results of performance evaluation of IK in an open-pit gold-silver deposit. For performance evaluation, the predictions of local recoverable reserves using IK were compared with the actual reserves based on blast hole information. The IK estimator, although a bit optimistic, performed very well in predicting the total recoverable ounces of gold from each panel on a test bench. The OK estimator was also used to try to predict local recoverable reserves, by treating each panel as either waste or ore, depending on the panel's average grade. Under this criterion. OK was found to be very biased and pessimistic.

Jan 1, 1986

By Robert E. Kirby

The potash mine and refinery of AMAX Chemical Corporation is located 26 miles east of Carlsbad on the north end of the potash producing areas. This property was developed between 1949-1952 and production of muriate began in August 1952. Two shafts, located 400 feet apart, were sunk to the ore zone 900 feet below the surface. A 15-foot diameter ore hoisting shaft equipped with a 1000-ton ore pocket, crusher and automatic skip loading equipment plus a 20-foot diameter service shaft with a curtain wall for exhausting air were provided. Sylvinite production to date has been from the first ore zone, stratigraphically, the lowest of ten identified mineralized zones in the salt section. This first ore zone has been the top producer of Muriate of Potash over the years. In our area we do have some very marginal mineralization in the third ore zone some 35 feet above the first. We have not mined from this seam as yet but we are investigating the economics very closely with access slopes and an experimental mining panel. Our ore seam is generally flat lying but does have local gentle rolling with grades from 2% to 5%. The mine was designed and developed from the beginning with conventional mining practices and rail haulage from the mining section to the ore pocket. As mining progressed in the early years, production increased from less than one million tons annually to a maximum of 3,935,000 tons in 1964. Efficiency also kept pace with the increasing production and continually improved until the efficiency of the production crews reached an average of 100.3 tons per manshift in 1964.

Jan 1, 1974

By Alan D. Randolph

A size-continuous breakage kinetics model is postulated and supported with industrial grinding mill data. It is shown that the kinetics parameters include the effects of possible classification at the mill discharge. The estimated parameters were then used in the kinetics model to simulate the behavior of a grinding mill in open and closed circuit operation. While material transport and kinetics are equally important in open loop operation, heavy recycle in a closed circuit make a detailed material transport model for grinding unnecessary. In effect, the mill can be considered as backmixed. This suggests that more emphasis should be placed on modeling the classifier than the development of detailed material transport models for the grinding mill.

Jan 1, 1975

By Edwin B. Wilson

Over the past several years, state governments have been vigorously refurbishing old health department agencies and smoke control laws in anticipation of pending federal developments. Many states now possess a mature air pollution control administrative organization and a fairly sophisticated set of regulations on air pollution, This developing network of state control legislation and regulation is the machinery which will be called upon to implement federal standards, In order to prevent the wasted effort and resources which inevitably result from hasty action, industry should be in con- tact with local and state control agencies and be familiar with lines of communication to agency representatives. Thorough knowledge of applicable laws and regulations, both current and pending, is required. Moreover, federal law and future federal air pollution control plans, should be well known. Industrial air pollution control should be geared to a long range plan which utilizes existing technology while at the same the recognizing that today's technology will be improved upon with time, Regulation, too, can be expected to become more stringent. The implications of air pollution control in the Appalachian region of the United States will be felt most strongly by the coal industry of this area. Either directly or indirectly most regulations in these states have a significant bearing on coal mining, processing, utilization or waste disposal. The extent of coal-related activity in the Appalachian States of West Virginia, Pennsylvania, Maryland, Virginia, Kentucky, and Tennessee can be observed from the data provided in Table I. This data indicates that 86 percent of active bituminous coal mines and 69 percent of bituminous coal production were accounted for by these states. The purpose of this paper is to provide information on current and proposed legislation and regulations on air pollution in the Appalachian states, The information should prove valuable not only to the coal industry but also to industry in general as a means of evaluating both pollution control action that has been taken to date and the course of future control measures. Reference information in the forms of addresses of appropriate agencies and citations to specific state laws and regulations is provided. All information is current as of February, 1969.

Jan 1, 1969

By Nawal Kishore, Nilesh Pratap Singh, Amit Kumar Verma, Vikram Seervi

In India, demand for coal exceeds its countrywide supply, despite its natural abundance, due to failure to achieve high production targets, especially in opencast mines, which are responsible for 94.98% of total raw coal production within the country. Employment of technological solutions, such as surface miners, is key to achieving higher coal production and productivity in an eco-friendly manner, especially in the populated areas adjacent to the mining zone and, hence, require restricted blasting operations. It eliminates blast hole drilling, blasting, and primary crushing units, thus reducing related environmental hazards like ground vibration and fly rocks. This paper encompasses the applicability, advantages, constructional features, and performance assessment models for each working mode of a surface miner. The current paper discusses the correlation between coal production and key productivity indicators, namely, machine shift-time, pick, and diesel consumption of surface miner in three different geo-mining conditions. Furthermore, relationships between machine shift-time, pick, and diesel consumption of surface miner and coal production were evaluated through bivariate regression analyses along with their coefficient of determination. These key productivity indicators of surface miner follow polynomial relationships with coal production on a daily and monthly basis, having Pearson correlation values from 0.774 to 0.907 and coefficient of determination, from 0.664 to 0.909 in opencast coal mines.

Jan 20, 2023

By Michael Clar

Total suspended solids (TSS), generally referred to simply as sediment, is one of the four major parameters of water pollution associated with surface mining activities. The other three para¬meters are iron, manganese and pH. Currently the Environmental Protection Agency (EPA) is in the process of developing and implement¬ing effluent limitations for these pollutants pursuant to section 301 of the Federal Water Pollution Control Act Amendments of 1972, 33 USC 1811.1 To date, effluent guidelines for existing point sources have been published, and guidelines for new sources are forthcoming. The effluent limits which have already been developed for TSS have been subjected to some controversy.1 Some industry spokesmen have indicated that they may be unable to meet these effluent limitation guidelines for TSS. The industry claims that in certain areas the suggested limit is unattainable since high suspended solid loads already exist in streams due to numerous and various sources of nonpoint pollution which include agriculture, silviculture and urban construction for which no TSS effluent limits have been set. An opposite viewpoint asserts that the TSS limitations are too lenient since permit data from the Regions (U.S. EPA Regions) indicates present compliance for several companies under more stringent TSS limits. The experience at the Centralia mine in Washington is one example.2

Jan 1, 1977

By Robert C. Ellman

Lignite and subbituminous coals are utilized essentially as mined without beneficiation. Most of the present production is used to generate electric power and the major problem in this use is ash deposition on fireside surfaces. The preparation at existing mines involves principally crushing and screening operations. Blending of production from different locations within the mine is practiced in several mines to control ash composition. Drying and oil treatment for freezeproofing, of lignite are used to a limited extent during winter. Future processing may involve both washing and drying operations to alter ash composition by ion exchange and upgrade the low-rank fuels to higher heating values. Research has been initiated to determine the feasibility of such processing.

Jan 1, 1969

By Z. R. Llanos

The petroleum refining industry makes extensive use of catalysts for the conversion of crude oils into more usable products such as gasoline, fuel oil and gas, aromatics, and others. Catalysts used for hydraprocessing contain cobalt-molybdenum or nickel -molybdenum, although there are catalysts that also contain tungsten. During hydroprocessing, nickel and vanadium are deposited on the catalysts, eventually rendering them inactive. The refiners are then confronted with the problem of disposing the spent catalysts. In the past, landfilling was a common method of disposal and it is still practiced in some countries. Other refiners prefer to stockpile the spent catalysts at the refineries until the price of metals warrants their sale to metal reclaimers. This practice, however, poses environmental problems to the refineries for storage and disposal of spent catalysts. Other types of catalysts are amenable to regeneration. The purpose of this paper is to focus attention on the recovery of nickel, cobalt, molybdenum, vanadium, and alumina from spent hydroprocessing catalysts by Gulf Chemical and Metallurgical Corporation and to review the use of sodium hydroxide and sodium carbonate for pressure leaching of spent catalysts.

Jan 1, 1986

By D. L. Whiting

Dump leaching and ,in-situ solution mining have received considerable attention during the past few years due to their apparent economic viability and minimal environmental impact. Solution mining actually dates back to the 17th century when leaching of copper ore was first reported. However-, modern day leaching didn't begin on a wide scale until the mid-1900's. In-situ mining for copper, nickel, salts, and oil shale is currently looking more attractive as the technology advances. Presently, about 15 percent of the copper production in the United States is from leaching operations at approximately 14 active sites, the largest of which are the waste dumps near the Bingham Copper Mine, Utah. To establish a common background, the discussion is centered around state-of-the-art conditions. For dump leaching, complications inherent to the physical conditions and chemical reactions such as channeling, porosity and permeability, sorption, air flow, rock alteration and pH control are discussed. Emphasis is made on those conditions which render solution recovery rates and solution mineral concentrations unpredictable. By illustrating typical and actual field conditions, the generally accepted flow theories for both dump leaching and in-situ solution mining, including rubblization, are presented. For in-situ mining, hydrogeologic techniques such as geophysical well logging, aquifer testing and digital computer modeling are also discussed. The importance of artificial fracturing and well stimulating to solution injection and recovery is made with regard to project development. Finally, the subject of water pollution control techniques and the potential impact of the

Jan 1, 1977

By M. E. Ryan, C. L. Hoebbel, E. J. Haas

DISCLAIMER The findings and conclusions in this paper are those of the authors and do not necessarily represent the official position of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. Mention of any company or product does not imply endorsement does not constitute endorsement by NIOSH. ABSTRACT It has been suggested that effective disaster prevention and response in mining requires that elements of emergency management be incorporated into everyday operations, planning, and decision-making, much in the same way that the industry approaches routine risk management. Since Congress passed the MINER Act in 2006, the newly mandated structural and technological advancements in mine emergency response preparation have been made and are apparent, but measureable improvement in mineworker emergency preparedness is difficult to ascertain. To begin exploring whether measurable indicators of mine workforce preparedness can or should be addressed within a risk management framework, NIOSH researchers examined the datasets from two separate research efforts—one which measured the organizational safety climate and self-reported safety performance, and the other which measured individuals’ perceptions of their own self-escape competency. INTRODUCTION In response to the mine disasters in 2006, the United States Congress passed the Mine Improvement and New Emergency Response Act (MINER Act), which strengthened existing regulations [30 CFR, Part 48] and introduced new provisions to improve mine emergency response. Since that time, new technological and structural features, such as mandated redundant communication systems, personnel tracking systems, and lifelines in primary and secondary escapeways, have been installed in underground coal mines across the country. Additionally, mine operators are required to develop emergency response plans, provide adequate supplies of breathable air throughout the mine, provide more frequent and realistic expectations training, and are required to immediately notify the Mine Safety and Health Administration (MSHA) in the event of an accident. While the structural and technological advancements in emergency preparedness are readily observable and easily measured, levels of individual mineworker preparedness remain difficult to assess. There is a general consensus that deficiencies in competence in the non-routine tasks required for individual miners to effectively respond to a mine emergency likely remain (e.g., National Research Council [NRC], 2013), and NIOSH research continues address this concern (Haas, et al., 2015; Hoebbel et al., 2018). To maximize an operation’s capacity to effectively prevent disasters and/or respond to emergency events, it has been suggested that individual and emergency management efforts be incorporated into everyday operations, planning, and decision-making in much the same way organizations manage routine risks to health and safety (Haddow et al., 2017). To the authors’ knowledge, the mindful intersection of routine risk management policies and practices and emergency prevention and response readiness have yet to be empirically studied within the mining industry.

Jan 1, 2019

By H. Murray

Introduction Industrial minerals are key ingredients in a large majority of domestic and industrial products that are used in our daily lives. In the 7th edition of Industrial Minerals and Rocks, fifty three industrial mineral commodities are described. A precise definition of industrial minerals and rocks is difficult. Bates (1975) proposed a definition which is widely used and is as follows: "any rock, mineral, or other naturally occurring substance of economic value, exclusive of metal ores, mineral fuels, and gemstones: one of the non-metallics". They can be igneous, metamorphic, or sedimentary and range in price from a few dollars per ton to a very high price of hundreds of dollars per ton. The growth in their production and use is closely allied with population growth particularly in countries that maintain a high standard of living. The United States just passed 300 million in population and it is predicted that by 2040 the population will be 400 million. This will result in large increases in the need for Industrial minerals. Other factors that relate to increased use of industrial minerals are increased research and development by the producing companies and better quality control. Many industrial minerals such as kaolin, barite, nepheline syenite, fluorspar, lithium carbonate, phosphate rock, potash, talc, and several others are exported from the producing countries to many users around the world which has significantly increased their use. Also, government agencies, State Geological Surveys, and Universities have contributed to their growth by their research and development activities.

Jan 1, 2007

By Emmanuel V. Manlapig

The variables involved in a complex process like flotation can be classified as follows: a. Disturbance variables - which are undesired properties of the process input which affect the value of the process output but which are not subject to adjustment. They are the result of changes in the properties of the feed, like changes in head grade, flow rate, fineness of grind, etc. b. Manipulated variables (sometimes referred to as process variables or control variables) -which are those that are adjusted - reagent addition, aeration, pulp level - in order to compensate for the disturbances in the properties of feed. c. Performance variables (sometimes referred to as controlled variables) -which are those whose values measure the performance of the process. They are properties of the process output such as grade and recovery. The function of a control system is to maintain the process performance equal to the control objective in spite of the disturbances by adjusting the manipulated variables. Attempts at developing automatic control systems for mineral processing operations date back to the thirties and in many of these attempts the results were not surprisingly poor and un-stable. The poor results brought indifference and suspicion towards automatic control on the part of operators and management. The reasons for the apparent failure of these attempts were two-fold: a. the lack of adequate understanding of the behavioural responses of the process from the control point of view, and b. the lack of reliable control instrumentation which could withstand the harsh environment in mineral dressing plants. Many operators had accepted the fact that control of mineral dressing could be best conducted manually. In the case of flotation circuits, control had been virtually based on the skill and experience of operators particularly their ability to identify and rectify poor flotation performance aided by results from the laboratory (chemical) analysis of regularly collected samples from strategic points in the circuit which are at best, hourly collected samples.

Jan 1, 1978

By J. Bilant, B. Carlson, N. Gow

"High-pressure grinding roll (HPGR) technology was evaluated to replace tertiary cone crushing at Coeur Rochester operations (Coeur Rochester Inc.) as an opportunity to improve silver recovery. In 2016 and 2017, onsite and third-party pilot programs were initiated to evaluate the impact on metallurgical recovery and heap leach performance of crushed product generated by an HPGR. In 2018, Forte Dynamics evaluated the HPGR laboratory metallurgical data from Coeur Rochester and all third parties to develop field-scale leach curves based on new crushing scenarios. The laboratory recovery test work data were consolidated and scaled to field conditions to determine projected heap leach performance. Based on the metallurgical testing conducted, the replacement of current tertiary cone crushers with HPGR technology has the potential to increase Coeur Rochester’s silver recovery rate by 8 percentage points, from 61 percent to 69 percent, and shorten the overall timing of silver recoveries from 20 years to just more than two years.The Rochester Mine, and associated valley fill heap leach facilities is an openpit silver and gold mine located in Pershing County, NV, approximately 42 km (26 miles) northeast of the city of Lovelock. In 2017, Rochester produced approximately 4.7 million oz silver (Ag) and 51,000 troy oz gold (Au). Ore mined at Rochester is either fed directly to the primary X-Pit crusher, crushed at an in-pit crusher system, or placed directly onto a heap leach pad as run-of-mine (ROM). Both crushing circuits are comprised of three stages of crushing to produce a nominal 3/8 in. ore. Primary crushing consists of jaw crushing while secondary and tertiary crushing are composed of varying cone crushers.Historical recovery rates of crushed Rochester ore averaged 61.4 percent Ag and 95.9 percent Au over a period of 20 years (Robinson et al., 2018). These rates were derived from third-party verification of in-house metallurgical test results, crusher production and heap leach production results from 1986 through 2004 in a private report for Rochester produced by KD Engineering Co., Inc. Recovery rates are regularly verified by compositing daily samples of ore delivered to each leach pad from the X-pit crusher, in-pit crusher and/ or ROM. A proportionate split of each sample is used to generate monthly composites for metallurgical analysis utilizing column leaching and bottle roll leaching. These tests are run in a manner analogous with production conditions and deliver test results that provide expected heap leach performance. As the Rochester oxide deposit has been mineralogically and metallurgically consistent, the gold and silver recovery trends have also been consistent over the life of the project."

Sep 1, 2019

By Thomas P. Meloy

Comminution is an old art. Unfortunately the analysis of the unit operations has been handicapped by the lack of both theoretical and experimental information. Two types of infor¬mation are needed, one an understanding of what happens when a particle breaks in a brittle manner; and two, an understanding of what happens when the daughter fragments pass through the mill. This paper is concerned with the former, the catastrophic fracture of a brittle solid. Recently, successful theoretical attacks on the frac¬ture of brittle solids have yielded significant-results. New experimental techniques are yielding insight into the physical phenomenon occurring during brittle fracture. Many of the re¬doubtable shiboliths of the last century are either being laid to rest or verified.

Jan 1, 1965

By Kallam V. K. Reddy, VADAPALLI SANJANA, Veerendra Singh, Gajanan Kapure

This work describes a leaching process for the conversion of high-magnesium peridotite rock, which is a chromite ore overburden, into two valuable products: magnesium salts and micro silica. Under normal leaching conditions, residue remaining after leaching is of a gelatinous nature and thus hinders the filtration process. To address this issue, oxidative leaching with the addition of H2O2 was employed, and it significantly improved the filtration kinetics. Four different approaches for H2O2 addition were tried, and they all proved effective in controlling gelation. The optimum oxidative leaching condition was 70 °C, 2 h time, 2 M H2SO4, 0.5MH2O2 and 400 RPM; under these conditions, 92% magnesium leaching efficiency was achieved. After leaching, the leach liquor obtained was purified and dried into Mg(OH)2 and MgSO4 salts. The leach residue contained mainly silica particles, with size in the 10–30 μm range. This material thus represents an attractive candidate for the production of highperformance concrete for the construction industry. The oxidative leaching process described here enabled the complete conversion of peridotite into valuable products, magnesium salts and micro silica.

May 5, 2020

By Kim Appleby

Epithermal gold-silver (lead-zinc-copper-manganese) mineralization on Misima Island is confined to steep and reactivated flat-lying normal faults in the upper plate of a major, shallowly dipping detachment fault. The hangingwall comprises an Eocene metavolcano-sedimentary sequence that has been extensively intruded byMiocene calc-alkaline granodiorite. It is unconformably overlain by Pliocene sedimentary and volcanic rocks. High-pressure amphibolite facies rocks dominate the footwall and have many characteristics of a metamorphic core complex. Mafic-alkalic lamprophyre dike swarms intrude the hangingwall and footwall sequences. Previous workers attributed the gold-silver mineralization on Misima to the intrusion of the porphyritic granodiorite (Williamson, 1984). This has been proposed for many tertiary gold deposits of the southwest Pacific(Sillitoe, 1989; Leach and Corbett, 1994).

Jan 1, 1996