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The Tennant Creek goldfield is situated in the Northern Territory, 360 miles north of Alice Springs, or a tot~l distance of 1,300 miles north of Adelaide, and 600 miles south of Darwin. The auriferous area extends 20 miles north and south by 50 miles east and west. The overland telegraph line and the AIice Springs-Darwin road pass through the centre of the field.HISTORY, PRODUCTIONThe country comprising the goldfield was traversed by J. MacDouall Stuart between 1859 and 1861 in the course of his last three exploring expeditions, which terminated respectively at Attack Creek, Newcastle Waters and at the mouth of the Adelaide River. The explorer named Tennant Creek and also Mount Samuel, on which mining operations are now in progress. The overland telegraph line was completed in 1872 and a relaying station established eight miles north of the site of the present township. There was no other settlement in the adjacent country prior to the opening up of the goldfield.Gold was discovered in 1926 on what is known as the Great Northern lease, three miles north of the township. The field was remote; the nearest plant at which gold ore could be treated was at Peterborough, in South Australia, 1,186 miles distant, and it was not until 1932 that the development of the field actively commenced.The production of the field from its inception to December 31, 1939, was 57,895 QZ. of gold, valued at £522,000, recovered from 61,793 long tons of ore, won from 98 mines. In 1940 seven of these mines had reached depths between 100 ft. and 230 ft., the workings of the majority being less than 60 ft. below surface.TOPOGRAPHY, WATERThe country is traversed by parallel and sub-parallel lines of hills trending east and west and rising to altitudes varying from 50 ft. to 100 ft. above the intervening valleys. The low ranges and isolated hills owe their survival to the resistance offered by their indurated, harder rocks to erosion which has removed the softer intervening formations. Their elevation and area depend to a considerable extent upon the presence of; and, the size of, the more or less exposed haematite formations, or are due to the influence of extensive siliceous dykes which traverse the locality.Watercourses head from the hills and either flood out on the flats within a short distance, or in a few cases follow longer courses to the northward. In the channels of the larger creeks billaoongs, which form important water storages for a considerable part of the year, -are to be found. Tennant...

Jan 1, 1942

This paper deals with the application of table flotation to two unusual mineral dressing problems. Both problems involved the removal of interfering minerals at sizes too coarse to normal froth flotation.The first problem was the removal of arsenical minerals from Broken Hill gravity concentrates without further size reduction. Table flotation without grinding of the original concentrates gave almost complete rejection of the arsenic from the concentrates. A typical test result was a reduction of arsenic in jig concentrate from 0.75% arsenic to 0.007% arsenic.The second problem was to develop a method to produce a high grade calcium carbonate concentrate from coastal dune sands containing about 10% silica and about 80% calcium carbonate. The sands were about 30 mesh British Standard Screen (B.S.S.), and for economic and other reasons it was stipulated that the separation be made without grinding. Again, table flotation gave excellent results. A concentrate was produced containing 99.62% acid soluble material, representing a recovery of 98.69% of the calcium carbonate in the feed with a rejection of 96.44% of the silica.The investigations' were carried out at the Kalgoorlie Metallurgical Laboratory, under the Department of Mines...

Jan 1, 1954

By G J. Corbett, P Magner, M McKenzie

Structures formed during ductile deformation have been reactivated during the later brittle mineralisation process. Two generations of folding are classified as: early recumbent megascopic FI folds and FI shears which transpose the hinge regions, and later upright F2 folds. S1 is folded about F2 folds which contain axial planar S2 crenulation cleavage. Vergence relationships between S1 and bedding indicate that many of the mineralised structures occupy sites of FI folds which have acted as plumbing systems for later gold mineralisation (eg Blackwater mine). The Globe-Progress gold mineralisation is localised by a major jog formed by sinistral strike-slip movement on two FI fault segments and mineralisation also occurs in smaller jogs along strike (eg Sir Francis Drake, Happy Valley-Merrijigs, Cumberland).   The lodes of ribbon quartz which exploit the FI shears and local bedding planes, are inferred to have mostly formed after the peak of metamorphism, possibly related to the emplacement of Carboniferous granites. This was followed by a sequence of vein deposition and wallrock alteration which consists of quartz-As/Fe sulphides ? carbonate - stibnite ¦ trace base metal sulphides and Bi-sulphosalts ? illitic clay/sericite-chlorite. Gold at Globe-Progress is mainly encapsulated in arsenopyrite. At Blackwater, free high fineness gold occurs in partings in lode quartz with late sericite-chlorite. The above sequence of events is comparable to that encountered in many intrusion-related gold systems throughout the Southwest Pacific region. There is a spatial relationship between gold mineralisation and dykes variably described as diabase, dolerite or lamprophyre. Alkaline rocks occur in many Pacific rim and older goldfields and may possibly be related to a magmatic source for gold mineralisation.

Jan 1, 1997

A combined reflection seismic and magnetic survey off the south coast of New South Wales has revealed six distinct reflection horizons within the Lower Triassic-Upper Permian sequence, and has enabled the upper part of the lllawarra Coal Measures to be mapped in considerable detail. Large magnetic anomalies in the eastern half of the survey area appear to originate in the Gerringong Volcanic Sequence which forms the magnetic basement in the survey. Small residual anomalies in the western half of the area can be correlated with small scale faulting and folding in the upper part of the llawarra Coal Measures, as revealed by the seismic reflection survey.A synclinal axis striking at approximately 55° has been mapped near the western margin of the survey area, and areas of faulting and folding have been outlined by combined analysis of seismic and magnetic results.

Jan 1, 1970

THE present article makes no claim to be exhaustive, since it cannot contain all the knowledge which scientists and manufacturers of the compounds of the rare earths have gained. The following notes are, therefore, simply an attempt to ascertain andclearly record the occurrence, properties, and uses of the more important of the rare earths, with a special reference to their commercial values and the industries based upon them.HISTORYIt was the mine manager, Gcyer, of Stockholm, who, in 1788, first drew attention to a black mineral which had been found in a quarry near Roslagen, in Sweden. In 1805 Klapproth received some specimens of this mineral, which he declared to be a newmineral. Subsequently Gadolin, professor of chemistry at Abo, analyzed the same mineral, and determined the presence of an unknown earth resembling alumina and lime. He named the mineral ytterbite, and afterwards gadolinite. Klapproth has alsothe merit of having detected (1804) another rare earth, which he named ochroit-earth, found in the Bastnas mine, near Riddarhyttan, in Wcstmannland, Sweden. Curiously enough, Hisinger and Berzelius simultaneously ascertained the existence of the same...

Jan 1, 1909

By A Paz, H Lehto, M +stholm, I Roitto

Nowadays, the demand for a finer grind in minerals processing has set new challenges within the industry, particularly for grinding technology. Apart from a finer grind, energy efficiency is also a key driver in optimising comminution technology.Stirred milling technology, already proven in many other industries, delivers a modern, sophisticated, flexible and energy efficient grinding solution for fine and ultra fine grinding in minerals processing. Fine grinding technology is utilised particularly in concentrate regrinding to complete the liberation of valuable minerals after the first stage of concentration. Maintaining the correct particle and particle size distribution of the regrind product is crucial for downstream process performance. Stirred milling technology offers the unique possibility for online control and optimisation of the regrind product particle size. This paper describes the basis of this online control possibility and discusses the implementation of stirred milling technology in minerals processing, particularly in regrinding applications. The paper will also outline management and control of fluctuations in feed rate tonnages as well as particle size fluctuations in concentrate regrinding.CITATION:Roitto, I, Lehto, H, Paz, A and +stholm, M, 2013. Stirred milling technology - A new concept in fine grinding, in Proceedings MetPlant 2013 , pp 190-201 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By G F. Brent, R D. Hart, C Carr, F Felipe

In underground operations, where copper, gold and other metals are mined, the open stopes can be backfilled to stabilise surrounding workings. This fill may consist of tailings from the processing plant, usually mixed in slurry with a binder such as ordinary Portland cement (OPC). Extensive use is made of tailings in OPC-based paste fill, cemented hydraulic fill or cemented aggregate fill applications. A large underground operation such as the Mount Isa Copper Operations utilises over three million tonnes of backfill per annum. Geopolymers offer an alternative binder system with significant environmental advantages over OPC. Geopolymers are formed by polymerisation of aluminosilicate precursors in an alkali medium. They generally form products with superior strength characteristics as well as increased resistance to degradation, particularly under acidic conditions. Geopolymers have lower carbon dioxide emissions associated with their manufacture than OPC and offer further potential advantages, such as the use of less water and more waste materials. The application of geopolymers to weak material systems such as mine backfill has not been widely studied. The aims of this investigation were to assess a range of Australian mine process wastes for suitability as feedstocks in fill applications and to construct a range of these cemented minefills using a geopolymer binder. The physicochemical characteristics of each of the wastes are discussed as well as how they ultimately contribute to the geopolymer cement through direct replacement of OPC. Results from various tests on the candidate geopolymer fill formulations are presented and the potential of such fill formulations to replace OPC in mine backfilling operations is highlighted. The significant potential contribution to reducing greenhouse gas emissions from the use of geopolymer-based mine backfill across the industry is noted. Conversion of a single mine, such as the Mount Isa Copper Operations, is shown to match the reductions in greenhouse gas emissions due to the current total installed photovoltaic electricity generation capacity of Australia. A similar examination of wastes available to a gold mine could potentially yield new binders for use in established or new fill systems.

Jan 1, 2007

This study explores two evolving 3D surveying technologies, photogrammetry and laser scanning, and applies them to deformation monitoring of rock faces and mine highwalls. A quantitative analysis focused on 3D coordinate determination is performed. Furthermore, a qualitative assessment directed at the practicality and viability of each system operating near a rock face or in a mining operation is undertaken to reveal one systemÆs deficiencies over the other. Two photogrammetric and four laser scanning surveys aimed at optimising accuracy and precision within a short period of data acquisition are conducted on the rock face at Organ Pipes National Park, Keilor, Victoria. The accuracy and repeatability of each survey is determined using a combination of iWitness photogrammetric, and Cyclone laser scanning software. The 3D coordinates of targets placed on the rock face are determined by triangulation and resection principles within a bundle adjustment. The coordinates determined by each system are then compared in a 3D transformation. Controlled deformation conditions are established to determine the precision to which each system can detect movement in the rock face. An object of known dimensions is placed on the rock face to simulate deformation. The relative orientation of images taken for the pre- and post-deformation photogrammetric surveys provide an overall 3D point accuracy of 1.255 mm and 1.804 mm respectively. A 3D transformation shows discrepancies of less than ¦22 mm (RMS) between the geometry of the photogrammetric and laser scanning models. Both systems are able to detect the simulated deformation to a precision of 50 mm. This work also identifies how to obtain millimetre accuracy for 3D coordinate determination of rock faces, thereby providing a quality data set for surveyors, geotechnical engineers and mine geologists. Photogrammetry is shown to be a mobile, time and cost-effective technique that is more amenable to mining operations than terrestrial laser scanning. However, both systems demonstrate that they are capable of detecting movements that may lead to failures in the rock face, and possibly endangering human life. The implications are significant for surveyors, geotechnical engineers and mine geologists working in mining operations where enhanced safety conditions, increased productivity and lower operational costs are important considerations.

Jan 1, 2009

By Carlos G. C

Geological mapping in various parts of Australia is revealing a number of regional associations of mineralizations with particular persistent stratigraphic horizons. Such associations have been found in the Broken Hill district of New South Wales, in the Nairne district of South Australia, in the Mount Isa district of Queensland, and in the Cloncurry district of Queensland. The question has arisen as to whether such mineralizations are of sedimentary origin, syngenetic with the enclosing formation, or whether they are of epigenetic origin, and reflect the selective hydrothermal mineralization of favourable beds on a regional scale.The purpose of this investigation is to test the use of sulphur-selenium ratios as an objective method of distinguishing between suphide deposits or sedimentary or supergene origin, and sulphide deposits of hydrothermal origin, with particular application to the districts mentioned. At the same time much data has been accumulated as to the selenium content of Australian sulphide ores. The possible use of sulphur-selenium ratios for this purpose was first demonstrated by Goldschmidt and his coworkers (1933; 1935), and later by Carstens (1941). Goldschmidt and Strock (1935) found that pyrite of sedimentary origin had a sulphur : selenium ratio of the order of 200,000 or more, whereas pyrite of hydrothermal origin had a sulphur: selenium ratio of 10,000 to 20,000. Carstensfound that sedimentary pyrite deposits in Norway contained less than 1 g. Se per ton, whereas hydrothermal pyrite deposits contained 20 to 30 g. per ton.

Jan 1, 1954

By I F. Bell, K P. Hammerschmid

Well planned and executed environmental management plans can reduce life-of-mine operating costs and the need to deal with major environmental issues at the time of mine closure. With proper planning during the exploration, feasibility and execution phases of a project, final closure costs can be reduced. The reduction of closure costs should be considered during exploration and initial feasibility studies and when process facilities, waste rock dumps and tailings impoundments are designed. During the mining of the resource, closure cost reduction will depend on effective and efficient environmental management plans for ongoing land clearance, segregation of mine waste materials, management of mine site water and workshop wastewaters, and the establishment of progressive rehabilitation strategies. These issues are the responsibility of planning, production, technical support and maintenance personnel at an operating site. The successful implementation of environmental plans will ensure that all impacts are reduced and that closure issues with major cost implications are addressed prior to closure of the mine.

Jan 1, 1995

The smelting of the Broken Hill lead concentrates at the Broken Hill Asso,ciated Smelters produced, among other products, approximately 4,900 ounces of gold and 8,800,000 ounces of silver during the year ending June 30th, 1938. The following table shows the actual amounts of gold per ton of lead concentrate produced during this period at the important mines. The total gold in the period is calculated from the number of tons of lead concentrates produced, and by comparison with the production' of silver, shows thatthere is no constant relation between the amounts of gold and silver.The fact that no gold is seen during milling, even when gravity concentrating tables are employed, signifies that the gold does not occur as occasional coarse particles.Further, as the values increase considerably in the flotation slime, it can be inferred that the gold occurs as minute inclusions in one or more of the minerals in the lead concentrates.The four most abundant minerals in the lead concentrate are galena, zinc blende, chalcopyrite, and...

Jan 1, 1940

The Fraser Range is composed dominantly of basic pyroxene granulites derived from basalts, many of which appear to have been vesicular and pillowed. Acidic and basic garnet-bearing granulites are important in the west, and acidic granulites and narrow anorthosite layers are dominant in some regions east of the Fraser Range. An extensive flat-lying olivine gabbro sheet cuts the granulites, and in places has been converted to spineI-bearingmeta-gabbros and pyroxene granulites. The granulites of the Fraser Range (Proterozoic) are separated from the gneisses and schists of the goldfields regions (Archaean) by the Fraser Fault, over which there is a large gravity anomaly (gradient 20 milligals per mile). Some of the problems associated with the concentration of Cu, and Ni liberated from mineral lattices during metamorphism, and other principles of metal concentration in granulite terranes, are discussed. The recognition of vesicular and pillowed zones, even though highly metamorphosed, is of fundamental importance.

Jan 1, 1969

The need for the hydraulic transportation of coal in the New South Wales coal industry, both from the coal face to the surface and from the coal mine to the consumer or the port for export, is explained. Details of research projects currently in'progress and involving the hydraulic transportation of New South Wales coals are given together with information on the hydraulic transportation of coal in the United States of America.The potential of hydraulic transportation as a viable alternative to the proposed expansion and upgrading of the New South Wales railway system to meet the projected New South Wales coal production to the year 2000 is described.

Jan 1, 1980

By D Caley

During the response to the Moura No 4 disaster, use was made of the New South Wales Mines Rescue Service’s ‘Mineshield’ inertisation equipment. The equipment had to be transported from Newcastle, approximately 1400 kms, and the liquid nitrogen a similar distance. The time taken, and therefore availability of the liquid nitrogen, became a significant problem. Operational issues were also experienced during use. Typically the liquid nitrogen is converted to a gas (vaporised) before being injected into the mine. However, as the propane gas tanker used for the vapourising unit was delayed, an attempt was made to inject the liquid nitrogen directly down uncased boreholes. This proved unsuccessful.Following the Moura No 4 disaster and the Moura No 2 disaster, recommendations were made relating to having inertisation capacity for the Queensland coal mining industry. Today the Queensland industry has multiple options available for inertisation, including the high-volume GAG and smaller volume units such as boilers and membrane separation units. Although it ultimately aided re-entry into Moura No 4, most likely due to the issues associated with supply to Central Queensland, liquid nitrogen has not found favour within the Queensland industry as an inertisation tool.Coregas has commissioned an air separation plant in Mackay, improving the availability of liquid nitrogen to Central Queensland. Based on the availability of this nitrogen, recent sealing operations at Kestrel have trialled using liquid nitrogen and associated vapourising units. This paper details the practical application and findings of using liquid nitrogen during routine longwall panel sealing.CITATION:Caley, D, 2017. Using liquid nitrogen for the inertisation of goafs, in Proceedings Australian Mine Vent Conference 2017, pp 35–40 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

By Pupazzoni P. D, Meissner D. C

Incorporating an iron ore pelletising plant, a MIDREX'"' Direct Reduction Plant, and a mini mill, the conversion of iron ore fines to high- quality steel slabs in Western Australia is among the lowest cost routes in the world. The cost and availability of iron ore and natural gas, government support, and proximity to the growing Southeast Asian market all contribute to the competitive position of the area. Owing to the lead-time required, this is an ideal time to develop a new project to supply semi-finished steel to Asia for rolling to a finished product. A project contracted now will start up in about three years, when the market should have recovered.

Jan 1, 1999

Triboelectric Charge and Separation Characteristics of Industrial Minerals The basic principles of triboelectric charge and separation of minerals and the factors affecting the entity of the charges developed on mineral surfaces are discussed and the surface pretreatment methods by which the electrophysical properties and thereby triboelectric charging and separation of minerals can be artificially altered/modified are reviewed. Furthermore, the triboelectricfication theory of materials is envisaged from the chemical concept of acid-base donor-acceptor and an attempt is made to correlate the physical concept of triboelectrification with the donor-acceptor properties. The triboelectric charge characteristics of the quartz, calcite and wollastonite mineral samples for different size classes were defined using different tribocharging medium. Based on the triboelectric charges acquired by mineral samples their energetic work function values are estimated. In addition, the main electrophysical properties, ie dielectric constant and electrical conductivity, of different size fractions of the mineral samples are measured and their donor-acceptor chemical properties were defined. A series of triboelectric separation tests were conducted to explore the possibilities for separation these mineral from each others. The results from the triboelectric charge and separation of the single mineral systems showed promising prospect in separating quartz, calcite, and wollastonite from each others. Finally, attempts were made to explore the possibilities to implement triboelectric charge and separation process to real ores. Promising results achieved when separation of calcite from silicate impurity was sought from a carbonate ore. A very high purity (99 per cent) calcite product was obtained at a recovery of 80 per cent. Interesting results were also achieved to concentrate wollastonite from a complex silicate ore containing quartz, different feldspars, wollastonite and other Mg-Fe silicates. In this case conditioning of the ore with salicylic acid at defined temperature and relative humidity was found to be essential to concentrate wollastonite. The outcomes indicate despite the fact that triboelectric charge and separation process has not been completely perceived, it pronounced to be an environmentally friendly and economically viable technique for minerals and wastes beneficiation. Being a dry beneficiation technique the process has special appeal, which must be explored further in particular for treating industrial minerals.

Sep 13, 2010

My selection of the Australian coal industry as the theme of this Presidential Address arose from the fact that it is one of our most important mineral industries. The industry is presently prospering.M.ore coal, mostly of better quality (except for certarn power-house types), is being produced more cheaply in terms of real money than at any time in the past, and exports overseas are currently at a highlevel.In. spite of this, concern has been expressed in certam quarters about the future of some phases of the industry; for example, there has been some public comment on the selling price of our coking coal to Japan, the possible over-export of our coking coals from New South Wales, the introduction of foreign capital to develop large-scale mining ventures in Queensland, and the proposed export of substantial quantities of coking coal from the same State.Furthermore, proposals for the introduction of atomic power plants into several States well endowed with reserves of coal have given rise to comment, and recently the Department of National Development(1968) warned that insufficient attention is being paid to "orderly development and careful husbanding of the nation's coal.To reach a balanced judgment on whether these views are well founded it is essential to make a broad survey of the present position of the coal industry in the Australian economy. I therefore propose to deal briefly with several aspects, and to comment, in particular, on the important subjects of exploration and research in progress at present on Australian coals.Detailed descriptions of the Australian coalfields are to be found in existing technical publications (e.g.. Andrew, 1965; McLeod, 1965) and the data on coal reserves have been progressively revised as more accurate information has become available. In New South Wales detailed knowledge of the coal reserVes is limited to under 20 per cent of the sur...

Jan 1, 1969

By Tumilty JA, Schmidt CG

Sulphide ion is a powerful poison in gold cyanidation, however, the detrimental effect is less severe in plant practice. This is thought to be due to the presence of depassivating elements in the ore, mainly lead. Trace amounts of lead can counteract the poisonous effect of considerable amounts of sulphide. The reaction is instantaneous and is likely to be a direct involvement in the electrochemical surface reaction. Lead addition cannot be regarded as an all-round cure when experiencing poor leach efficiencies. A possible beneficial effect depends on the mineralogy of the ore and has to be determined individually for every material.

Jan 1, 1989

By J Williamson, M Griessmann

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Watershed tungsten deposit is located in the Hodgkinson Province of north Queensland, Australia. The deposit is hosted by Siluro-Devonian flysch-type meta-sediments of the Hodgkinson Formation, which were subjected to four major deformation events. Mineralisation has occurred syn- to post-D4 and is related to the intrusion of S-type granitoids of the Permian Whypalla Supersuite.Watershed is located within a regional NW–SE-striking melange zone composed of brecciated and intermixed arenites and shales. The major NW–SE-striking Tullah fault zone is situated in close proximity to the east of the deposit.The Watershed deposit occurs within a tightly folded upright anticline with NW-plunging fold axis. The anticline contains a major package of coarse-grained to conglomeratic arenite, which harbours the Watershed mineralisation. Several alteration styles occur within the arenites, of which Fe-poor calc-silicate alteration dominated by clinozoisite/epidote is the most significant. Less widespread but locally important alteration styles comprise garnet-dominated calc-silicate alteration, albitisation and sericitisation. The arenites are enveloped by unmineralised carbonaceous shales and shale breccias.Tungsten mineralisation occurs solely as molybdenum-poor scheelite and can be found as three styles: disseminated mineralisation in calc-silicate altered arenites, vein-style mineralisation with quartz-albite-scheelite veins and minor but high-grade mineralisation in albitised felsic dykes.Contact metamorphic rocks and geophysical data indicate the proximity of an underlying granitic body. It is believed that this granitic body was the main driver of the hydrothermal system generating the Watershed deposit. An early mineralisation stage caused the selective calc-silicate alteration of the arenites, while a second stage caused the vein-style high-grade mineralisation. The folded shales enveloping the arenites worked as an effective barrier that kept the mineralising fluids in a confined rock volume.The scheelite mineralisation at Watershed is open to depth, with a granite-hosted porphyry or greisen-style mineralisation anticipated below the current resource.CITATION:Griessmann, M and Williamson, J, 2015. The calc-silicate-hosted Watershed tungsten deposit, far north Queensland, Australia , in Proceedings PACRIM 2015 Congress, pp 545–550 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By Grynberg H, Lindon P, Wardrop J

The Gippsland Basin is unique in Australia in that it is a major resource based industry centre within a sensitive and special environmental context supplying Melbourne, a major urban/industrial environment with most of its energy 'on-line'. The environmental effects of the supply systems are generally local and mostly affect only those who are directly or indirectly dependent on the upstream systems. The major urban metropolis which is served remains largely unaware of the environmental impacts of the system upon which it is dependent, except when specific attention is drawn to them as in the case of the Latrobe Valley Outfall, algal blooms in the Gippsland Lakes, etc. This paper discusses the environmental context within which the energy industries operate, the environmental legislative framework which applies, the likely environmental impacts and some solutions. The energy resources of the Gippsland Basin occur in an area where the physical environment exhibits a wide variety of inherent energy states in its physical and biological regimes. The off-shore regions of the oil and gas platforms has to be able to withstand the wind and wave energy generated in a shallow sea in a confined waterway lying athwart the main current and climatic stream. The coastline includes the delicately balanced quiescent environments of Corner Inlet with its 'wilderness' tourism industry and the powerful surf and long shore drift and dunes of Ninety Mile Beach.

Jan 1, 1992