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By M. J. Gole, R. E. T. Hill, S. J. Barnes

"The Agnew (also known as the Perseverance) nickel deposit and its northern extension, the Rocky's Reward deposit, form one of the world's largest accumulations of nickel sulphides hosted by komatiites. Agnew was previously classified as an ""intrusive dunite-associated"" deposit . It has now been shown that the sulphides are hosted by komatiite flows which underlie an adcumulate-textured dunite body that crystallized in a large lava channel.The rocks of the mine area have been subjected to a metamorphic temperature of550°C and pressure of up to 3 kb. The komatiites have mostly been reconstituted to olivine-amphibole chlorite assemblages. There is a zoned sequence of enstatite-, anthophylite-, talc- and antigorite-bearing assemblages inwards from the western margin of the ultramatic reflecting variations in the CO/HP ratio of metamorphic fluids.Facing directions are determined from variations in the proportions of metamorphic minerals and in rock compositions which reflect asymmetric layering in the flows . Olivine-sulphides matrix ore is hosted in a single 50 m thick, east-facing flow that is overlain by flows containing massive sulphides. Much of the massive sulphide has been physically remobilized into fold noses, faults and shear zones. Chemical diffusion of ore components has upgraded a sulphide-rich metasedimentary unit where it is in structural contact with massive ore.To the north, the mineralized flow sequence is separated from a stratigraphically higher komatiite sequence, the Perseverance ultramafic complex, by approximately 150 m of felsic meta volcanic and meta sedimentary rocks. Southward, the Perseverance ultramafic grades laterally into an olivine adcumulate body and its lower contact cuts progressively down stratigraphy until it lies directly on top of olivine-sulphide ore of the mineralized flow sequence. This discordant contact is interpreted as the base of a thermal erosion channel formed by a voluminous komatiite lava flow. This contact greatly influenced later deformation of the mineralized flow sequence."

Jan 1, 1989

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

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

Jan 1, 1989

By John Drew Ridge

"Over the years, ore geologists have made innumerable observations as to the relationships of certain kinds of ore deposits to particular types of rocks and to the types of primary and secondary structures that these rocks contain. On the basis of these, the places in which to look for new are deposits are more clearly defined than they would be in an exploration program based largely or solely on concepts of ore genesis. This paper discusses the affinity of certain rock types and structures for such ore deposits as: (1) tin-tungsten associated with granitoid rocks; (2) lead-zinc of simple mineralogy in carbonate rocks; (3) massive base-metal sulphides in sedimentary or volcanic rocks; (4) massive base-metal sulphides and oxides at, or near, contacts with igneous rocks; (5) gold or gold-uranium in, or adjacent to, conglomerates; (6) shale- or sandstone-hosted copper; and (7) porphyry coppers. Additional varieties could be considered, but it appears that these examples are sufficient to demonstrate the validity of the suggestion that the use of observational characteristics is far more useful in mineral exploration than that of theories of ore genesis.As by-products of the theory of plate tectonics, many concepts have been put forward to explain how ore deposits of different kinds have been formed. Most, if not all, of these theories seem to be as valid as present-day information permits. However, do these ideas add to the ability of the ore geologist to find ore deposits? I doubt it, and offer reasons as to why I think so.To produce maximum results in any exploration program, the one that makes the greatest use of information produced about the geologic environment of the area being investigated is the one that will provide the greatest return in deposits found for the sponsors of the program. Such exploration is best designated as total exploration, and it certainly is the most effective way of uncovering such new deposits as may exist in the area being studied in particular and of adding to the sum total of nonfuel minerals deposits available to the industrial world in general."

Jan 1, 1983

By B. D. Pandey, D. Bagchi, Premchand

During the separation and recovery of metals from the ammoniacal leach liquor of Indian Ocean nodules by solvent extraction-electrowinning (SX-EW) in close-loop operation, the copper electrolyte containing ~40g/L Cu, 20 g/L Ni and 180 g/L sulphuric acid is bled-off to control the impurities. The recovery of copper and nickel as powders has been examined from the copper bleed solution following partial decopperisation, crystallization of mixed sulphate of the two metals and aqueous hydrogen reduction. From the dissolved sulphate solution containing 17.68 g/L Cu, 18.83 g/L Ni and 0.03 g/L Fe, the copper powder was precipitated at initial hydrogen pressure of 26 bar in an autoclave in 90 min at 140 °C. The residual copper from the spent solution was removed as sulphide and nickel powder was then recovered (99%) in two stages from a solution of pH 4.5 at 40 bar pressure and 190 °C. However, 98% nickel recovery in one stage was achieved when hydrogen reduction was carried out from an ammoniacal solution in the pH range 9-11. Copper and nickel powders were produced from the bleed solution with acceptable purity and specifications suitable for P/M applications.

Jan 1, 2004

By L. R. Plitt

A series of experiments were carried out in an effort to develop a universally applicable mathematical model of the hydrocyclone classifier. The design and operating variables studied were: cyclone diameter and height, the inlet, vortex finder and apex diameters, the feed pressure and the solids content of the feed slurry. The model consists of four basic equations which express the cut size ( dso), volumetric split between overflow and underflow, volumetric throughput, and sharpness of separation in terms of the operating and design variables. Although empirical, the model is nevertheless in general agreement with fundamentally derived models. The model clearly 1•eveals the effect of the major variables on the operation of a hydrocyclone. Because of its broad data base and the inclusion of all the major variables, the model may be used without experimental data to predict the operation of cyclones over a wide range of different operating conditions. With operating data, the equations may be modified to serve as an operational model.

Jan 1, 1976

By Dennis Hoffmann

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

Jan 1, 1994

By S. Downing, T. Grammatikopoulos, N. Hoffmann, C. Gunning

"Most deposits display a high degree of geological and mineralogical complexity that can affect metallurgical processing. Therefore, the proper characterization of the ore and gangue minerals requires a multi disciplinary approach combining geology, mineralogy, geochemistry and processing. However, mineralogy to a large extent informs the metallurgical process. Automated methods can be used throughout the mining chain from advanced exploration through to production.In this presentation we discuss actual case studies where automated mineralogy has been applied in a geometallurgical framework at a pre-feasibility to feasibility level. These include examples from a strongly serpentinized magmatic Ni deposit (Dumont) and a magmatic Cu-Ni deposit (Maturi). Mineral speciation and ratios, e.g., chalcopyrite, cubanite, and pentlandite/pyrrhotite are critical to model the Cu-Ni magmatic deposit. In the serpentinized Ni ore, automated mineralogy is used to speciate the Ni minerals into sulphides, alloys and refractory Ni in the silicate matrix.The mineralogical results are linked to the metallurgical test work in order to model the geometallurgical domains. These case studies will illustrate how mineral quantification and improved understanding of inherent mineralogical parameters in relation to metallurgy reduce technical risk in both exploration and flowsheet development.INTRODUCTIONGeometallurgy is a cross-discipline approach combining geology, metallurgy and mine planning (e.g., Dunham et al., 2011). It is aimed to improve the understanding of geological, mineralogical and metallurgical parameters of an ore. Informational gaps among the different disciplines are often apparent. Automated mineralogy is shown in many studies (e.g., Eppinger et al., 2013, Philander and Rozendaal, 2013) to constitute the link between geology and metallurgy. The geometallurgical approach can provide specific data to geology, mining and mineral processing development and plant operations. The scope of the automated mineralogy is to illustrate how mineral quantification can improve the understanding of inherent mineralogical parameters in relation to metallurgy, and reduce the technical risk in both exploration and flowsheet development."

Jan 1, 2016

By W. L. Brown

"The Normetal mine is about 7 miles east of the Ontario-Quebec boundary, and 13 miles north of the town of Dupuy on the Canadian National railway. The mine workings are largely on lots 44 and 45 in the south half of range 10, Desmeloizes township.The surface outcrop is reported to have been discovered by a trapper previous to 1925, but the details are obscure. The property was originally owned by the Canadian Exploration Company of Amos, Quebec, and was later transferred to Abana Mines, Limited. The latter Company carried out underground work from two shafts down to the 550-foot level. The property was acquired by Normetal Mining Corporation in 1931 and was reopened in 1933, when development work was carried down to the 800-foot level. The mine was closed down in 1935 because metal prices did not justify production at that time. It was reopened early in 1937 and milling commenced in September of that year. To the end of 1945, a total of 1,497,- 169 tons of ore was milled from which was produced 184,533 tons of copper concentrates containing 84,738,368 lb. copper, 2,744,100 oz. silver, 26,230 oz. gold, and 153,524 tons of zinc concentrates containing 163,752,433 lb . zinc."

Jan 1, 1954

By M. N. Pons, E. Benizri, B. Laubie, A. Bani, Université de Lorraine LRGP, P. Kidd, A. J. M. Baker

"Serpentine (i.e. ultramafic) outcrops in Europe cover more than 10,000 km2 and have a low-fertility and low-productivity, making them unattractive for traditional agriculture. In general, these areas are slowly abandoned by local farmers, affected by strong rural exodus and landscapes undergo a process of closure. However, ultramafic landscapes have the potential to provide multiple ecosystem services that can contribute to Europe’s goals towards insuring food security, production of renewable raw materials and renewable energy. Phytomining (agromining) aims at cultivating metal hyperaccumulator plants that are able to accumulate Ni and other strategic elements from metal-rich soils and transport them to the shoots (>1%), which can then be harvested as a bio-ore. Such metal-rich biomass can be used to recover highly valuable metals, e.g. nickel (Ni) and also to produce energy (heat, electricity). Nickel agromining can thus offer an eco-efficient alternative to classical pyro- or hydrometallurgical processes without disturbing the soil cover and the geology from soils and rocks that would be considered as low grade ores or sterile material for conventional mining methods.Phytomining agroecosystems can lead to better soil resource efficiency and can offer a fully integrated, new agromining agriculture that could cover thousands of km2 in Europe, benefit local communities with a sustainable rural development and provide a wide array of ecosystem services which will need to be optimised under a life cycle assessment methodology:1. Production of bio-sourced metal products2. Production of energy biomass3. Restoration of soil fertility for conventional agriculture (Ni stress)4. Limiting Ni intake by local populations and farmers5. Use and conservation of local biodiversity (plant and soil fauna and microflora) as cultivated ecosystems6. Store carbon in cultivated soils7. Enhance pollination activity at landscape level.Nickel agromining could therefore change the economical balance in historically-disadvantaged ultramaficregions of Europe"

Jan 1, 2016

By G. Van Weert, O. Wang

ABSTRACT: When exposed to microwaves, rocks containing sulphides adsorb energy preferentially over barren gangue and quickly become warmer with minimal energy consumption. This effect makes subsequent machine sorting of ore from waste rocks or overburden possible using infrared sensing. This paper reports on the 2450 MHz microwave response of a variety of sulphide minerals by mesh size and spatial distribution, as they might occur in ore rocks. The implications for infrared ore sorting are discussed.

Jan 1, 2011

By G. Van Weert

ABSTRACT When exposed to microwaves, rocks containing sulphides adsorb energy preferentially over barren gangue and quickly become warmer with minimal energy consumption. This effect makes subsequent machine sorting of ore from waste rocks or overburden possible using infrared sensing. This paper reports on the 2450 MHz microwave response of a variety of sulphide minerals by mesh size and spatial distribution, as they might occur in ore rocks. The implications for infrared ore sorting are discussed.

Aug 1, 2011

By H. J. H. Pieterse

Agitation requirements in oxidation autoclaves can vary widely depending on the mineralogy of the feed material and the specific process selected. Before selecting an agitation system it is important that the client specify the desired throughput, mineralogy, chemistry, kinetics, compartments, overall retention time, and the desired oxygen utilization. In selecting the agitation system, the factors mentioned above as well as oxygen solubility, oxygen mass transfer coefficients, and specific power are evaluated. Much research effort has been directed toward open tank systems for fermentation and oxidation processes. However, for high pressure autoclave oxidation processes little information is available. In this review the author's experience in the autoclave industry and some of the available literature are utilized to compare the installed power per unit volume with some of the methods proposed for open tank oxidation. Equations that appear to give results close to that experienced in the industry have been identified. Further work is required in this area to develop a higher degree of confidence in the ability to predict the power required for any given case.

Jan 1, 2004

By P. B. Demarsh

"Location: - Mine village of Perron, 11 miles east of Val d’Or in northwestern Quebec.Life; - Started production 1932, ceased 1951.Ore: - Flat lying quartz tourmaline veins within granodiorite. Gold values related to coarse segregations of pyrite. Specific gravity 2. 80.Capacity: - 30 tons 1932-35; 125 tons 1935-37; 350 tons 1937-51.Assay: - Heads 0.21 to 0.34 oz. per ton. Grade obtained by mining 600 tons daily, sorting belt reject 250 tons, balance to milling; tailings loss 0.003 to 0.005 oz. per ton; extraction 9 8. 5%.Grind: - 70% minus 200 mesh. Detention time 26 hours.Treatment: - Cyanidation process.Reagents: - Per ton, aero cyanide (NaCn) 0.36; unslaked lump lime 1.50; zinc 0. 03; lead acetate 0. 006; steel consumption 2. 50.Water: - Equal mixture of swamp creek water and underground seepage.Cost: - Per ton, sorting and crushing 0.21; grinding 0.31; cyanidation 0.11; filtration 0.05; precipitation 0.02; miscellaneous 0.22; total 0.92.Power: - Hydro-electric, 25 cycle, 12, 000 volts reduced to 550 volts.Labour: - 95% Maritime and European, balance Quebec and Ontario.Tailings: - Absorbed over large swampy area on barren mining claims.Personnel: - 1 7 men including supervision.Flow sheet: - Canadian Mining Manual 1947"

Jan 1, 1966

By Marcio Luis S. Godoy

The Salobo Project will be the first Vale operation to use an HPGR mill to process copper-gold ore. The mine is located in Para state, southeast of the Amazon region in Brazil. The circuit was designed to treat 12 million metric tons per year of finely disseminated sulphide ore with high hardness. The comminution circuit comprises a gyratory primary crusher, secondary crushing utilizing two cone crushers, two 2 x 1.5 m HPGR operating in closed configuration with 6 mm screens, followed by two 26 x 40 ft ball mills. The concentration circuit consists of two rougher flotation stages using mechanical cells, regrinding with vertical mills, three cleaner stages with columns and one cleaner scavenger stage in mechanical cells. The concentrate is dewatered, filtered and transported by trucks and train to the port, to be exported. The circuit was designed on the basis of data obtained from a comprehensive laboratory and pilot plant campaign. The ore variability was assessed through simulation using data from a drilling core characterization program. The start-up of the industrial plant is planned for 2011. This paper describes the main aspects of circuit design, as well as information related to the beginning of the project construction.

May 1, 2010

By T. C. Cheng, G. P. Demopoulos

It is the object of this paper to discuss various options for improving the hematite process in terms of increased throughput hence lower capital cost and production of saleable quality hematite. With reference to increasing the throughput of the process, it has now been determined via the analysis of Akita Zinc Co's continuous industrial autoclave performance data that the process kinetics is limited by the rate of the hydrolytic precipitation reaction. By correlating the hydrolytic precipitation rate to supersaturation ratio, it is shown that accelerated kinetics can be achieved via the following measures: (1) in-situ neutralization with addition of zinc calcine; (2) elevation of temperature; and (3) dilution of feed; of which, the first one was retained for further evaluation. According to presented estimates, addition of calcine, amounting to only 2.6% of the total zinc calcine processed, can allow for shortening the retention time by at least 50%. Such drastic shortening of retention time may be either used to increase the throughput of a given autoclave circuit or alternatively to release autoclave capacity for clean hematite production. Hydrothermal treatment of the crude hematite product proved effective in producing clean hematite as according to laboratory tests, hence allowing the sulphur content of hematite to be reduced from around 4% to less than 1%. A conceptual flowsheet incorporating in-situ neutralization for accelerated kinetics with hydrothermal upgrading of crude hematite without sacrificing production capacity and with minimum upset of the plant's water balance is described.

Jan 1, 2004

By W. A. Roliff

The renewed interest of the past few years in the Appalachian and Michigan oil provinces has not, as yet, created any marked increase in activity in Southwestern Ontario. During 1960 development drilling in-creased somewhat over 1959, but exploratory drilling decreased slightly. More attention was devoted to the deeper horizons, but lake drilling de-creased considerably. Oil production reached a new peak and gas production increased slightly. During 1960 an interesting oil and gas discovery was made in the Cambrian and gas discoveries six miles off-shore in the eastern part of Lake Erie were made in the Clinton-Cataract zone of the Silurian. This paper reviews activities during 1960, summarizes the discoveries made to-date and the pertinent exploration data relating to the prospects of the region and discusses some of the economic aspects of exploration and development. D URING the last few years there has •been a marked renewal of interest in the old petroleum

Jan 1, 1961

By Loris S. Russell

THE plains of southern Alberta constitute one of the classic areas of geological investigation in Canada, for it was here in 1874, and in 1881 to 1883, that George Mercer Dawson (1, 2, 3) made the pioneer observations that are basic to all subsequent work on the interior plains of Canada. Dawson's work was extended eastward by R. G. McConnell ( 4) and northward by J. B. Tyrrell( 5) , but it remained. for D. B. Dowling to re-examine Dawson's Bow and Belly River Area and to make certain necessary revisions in the stratigraphical system of his predecessor. In 1917, Dowling published his memoir, The Southern Plains of Alberta( 6) , which remained for over ten years the last word on the stratigraphy and structure of the area described. It is generally conceded that Dowling's work made known the existence of a great artesian basin beneath the semi-arid plains of southeastern Alberta. In addition, his structural studies greatly stimulated the search for natural gas and petroleum. The most recent general publications on this area by the Geological Survey are based on the field work of M. Y. Williams, E. J. Whittaker, W. S. Dyer, and P. S. Warren, between the years 1923 and 1926. Their results were embodied in the Calgary Sheet (7) and the memoir, Geology of Southern Alberta and Southwestern Saskatchewan (8). By this time, the number of geologists working in Alberta in the development of the petroleum and natural gas industries had become large, and in 1931 the Alberta Association of Petroleum Geologist~ offered the Donaldson Bogart Dowling Memorial Symposium on Stratigraphy of Southern Alberta( 9) , a most valuable series of papers descriptive both of the ,surface stratigraphy and that observed in the well records.

Jan 1, 1937

By Dale A. Sketchley

The objective of Quality Assurance and Quality Control programs on advanced exploration projects is to ensure that data from sampling, assaying, and recording of geological observations are of high integrity for the purpose of obtaining reliable mineral resource and reserve estimates. National Instrument 43-101 Standards of Disclosure for Mineral Projects states that all scientific and technical reports must be prepared and certified by a Qualified Person in accordance with professional and industry standards following Mineral Exploration Best Practices Guidelines and Definitions, and Guidelines of the CIM Standards on Mineral Resources and Reserves. Additional information is given in Companion Policy 43-101CP and Technical Report Form 43-101F1. Although the Qualified Person must discuss and describe the Sampling Method and Approach; Sample Preparation, Analyses, and Security; and Data Verification; there is little specific information in the guidelines on Quality Assurance and Quality Control programs. Examples from the Oyu Tolgoi Cu-Au Project are given for optimizing sampling protocols, following proper sample preparation procedures, safeguarding sample shipments through chain of custody, ensuring quality of assaying with Round Robin monitoring programs, verifying transcribed data, and validating data with check assays to ensure high integrity for resource and reserve estimation. Oyu Tolgoi, also known as Turquoise Hill, is in the South Gobi desert, Mongolia, about 550 km south of the capital city of Ulaanbaatar, and 875 km northwest of Beijing, China. The project covers a major copper-gold system, which consists of the South West, South, Central, and Far North deposits, comprising high sulphidation and porphyry mineralization with oxide, supergene, and hypogene ore types. Exploration is done by multiple diamond drill rigs, and samples are prepared on-site and shipped to laboratories in Mongolia, Canada, and Australia for further preparation and analysis.

May 1, 2003

By Cale J. Dubois

At Cameco Corporations' Cigar Lake Project, large excavations are developed on the 480 Level and 500 Level must remain stable for at least 15 years to host underground processing infrastructure. Following the successful dewatering of the mine in October 2009, subsequent internal rockmechanics investigations augmented by third party technical investigations; determined that to keep the back of the Water Flush Crusher/Run-of-Mine (WFC/ROMs) excavation stable; required a rehabilitation strategy to mitigate deterioration/deformation of the WFC walls and intersection pillars. The mechanism of failure propagating the movement of the excavation walls is understood to be controlled by the presence of a dominant E-W striking and steeply dipping foliation within a relatively weak and mildly altered rockmass sub-parallel in strike with 14 meters high walls and an intersection span approaching 15 meters. The application of open and resourceful communications between site mining engineers, geologists, contract mining staff, construction management experts, corporate mining and civil engineers, and third party technical experts resulted in a multi-faceted short-term ground support strategy consisting of standard bolting and screening, deep-seated modified-strand cable bolts coupled with heavy gauge mesh straps, rockmass reconditioning using low-pressure grout injection, and horizontal cable-lacing for the intersection pillars applied in lifts using a top-down methodology. The intention of the short-term strategy was to stabilize the excavation so that a long-term structural steel support installation - consisting of composite concrete walls, and arch support applied to the side walls and crown of the back - could be constructed safely. This paper summarizes the evolution of the short and long-term ground support strategy and criteria for the WFC/ROMs excavation developed using elements of civil, mining and hydrogeologic design.

Nov 1, 2011

By J. S. Fox

"Besshi-type Cu-Zn (-Ag-A u ± Co) deposits are tabular, stratiform volcanogenic sulphide bodies which are usually associated with mafic volcanic rocks of oceanic or intra-plate geochemistry, but which can also be found locally with ultramafic volcanics or subvolcanic mafic intrusions. A thick sequence of continentally-derived clastic sediment usually encloses both the mafic volcanics and the ore. Besshi-type deposits form subaqueously, in epicratonic rifting environments, more-or-less proximally, and as a result of hydrothermal convection in their subjacent mafic volcanic - clastic sedimentary piles. They belong to a rift -related metallogenic spectrum that includes sediment-hosted and Cyprus-type base metal deposits, and may diller genetically from these mainly with respect to rate and degree of crustal extension. Modern analogues to these deposits are f ound in the submarine volcanogenic sinters of the Gulf of California rift system.The associated lithologies and tectonic selling of Besshi-type deposits clearly distinguish them from Kuroko-type ores. This difference also seems to be reflected in their lead isotopic character. For example, leads from Besshi-type deposits in the Sanbagawa belt of Japan and from the Blue Ridge belt of southeastern U.S.A. lie on extended anomalous lead lines and have lowslopes in 207Pb/204 Pb - 206Pb/ 204 Pbspace (Sato and Sasaki, 1980; Leriuray, 1982), wheras those from most Kurokotype mining districts exhibit only narrow isotopic ranges and lie near or on the orogene growth curve (e.g. , Franklin et a I., 1981). More over, where Besshi- and Kuroko-type deposits are found in the same orogene, the former often occur earlier in the tectonic cycle than the tatter (e.g., Japan, the Norwegian Caledonides, the southern Appalachians and south-central Finland).Besshi-type deposits are not confined to any particular part of the world, or to any geological epoch. Moreover, in many mineralized belts, Besshi-type deposits are the predominant volcanogenic ore type. On a world-wide scale, deposits of this type therefore constitute an important base metal resource."

Jan 1, 1984