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The Nena high sulphidation-type copper-gold deposit is composed of andesitic pyroclastic units with minor interstratified lava flows. Epiclastic sandstone and conglomerate, and siliciclastic rocks consisting of mudstone, shale, lithic and bioclastic sandstone and conglomerate are locally present. Pre-mineral diorite intruded and domed the volcano-siliciclastic sequence. Economic copper-gold is hosted by vuggy quartz altered lapilli tuff and tuff breccia. The early hydrothermal alteration stage involved deposition of epithermal banded quartz and chalcedonic silica in localised environments. This alteration stage was locally superimposed by a hydrothermal breccia event. Following the breccia event, magmatically-derived volatiles were channelled through a NW striking dilational fault zone and generated the high sulphidation alteration. The high sulphidation alteration is zoned from a vuggy quartz core with local massive replacement silica through a broad pyritic quartz-alunite halo and finally to a thin illite-smectite zone. This is surrounded by regional chlorite-epidote-smectite alteration. A gangue mineral phase consisting of quartz, alunite and baryte overprinted the zoned high sulphidation alteration and preceded the main copper-gold-arsenic mineralisation. Early sulphide deposition is characterised by marcasite, arsenical pyrite and melnicovenite. Main-stage copper-gold mineralisation involved sequential deposition of hypogene bladed covellite+chalcocite, enargite-luzonite and luzonite+stibioluzonite respectively. The copper sulphides are zoned from bladed covellite-chalcocite in the north (cross-sections 5000 - 5600 N) through enargite-luzonite (cross-sections 4700 - 5000 N) and to luzonite????stibioluzonite in the south (cross-sections 4400 - 4700 N). A late phase of minor acicular covellite and enargite+luzonite overprinted the zoned copper sulphides and associated gold mineralisation. Gold mineralisation commenced at the transition from enargite to luzonite, and continued through the deposition of luzonite-stibioluzonite in both stages. Most gold was deposited during the main-stage mineralisation. Yellow native sulphur was deposited in the remaining vugs and defines the waning stage of the hydrothermal system. Post-mineral dioritic intrusives and feldspar porphyries intruded the volcano-siliciclastic sequence. Finally, supergene chemical processes with associated erosion and uplift generated a 40 - 50 m thick oxide-hosted gold cap. The oxide gold cap is underlain by a 35 - 45 m thick blanket of supergene chalcocite+covellite mineralisation which overlies and occurs throughout the main hypogene copper-gold zone. Supergene gold is related to the distribution of primary gold-bearing sulphides. Therefore, remobilisation and redeposition of gold are considered to be insignificant and very localised.

Jan 1, 1999

By Moorrees C, Koh P. T, Tsambourakis G

Calcination of samples from the Savage River region of Thsmania containing varying magnesite/dolomite ratios under conditions optimized for the magnesite component, followed by carbonic acid leaching at elevated pressures, leads to leachates of varying composition. For a 3 per cent solids slurry leached at 15.5°C and 700 k Pa carbon dioxide, the leachates have magnesium concentrations in the range 0.71 - 13.2 g/litre. The corresponding magnesium extraction data are 12.5 - 86.4 per cent. The variation in leachate composition would be unacceptable in terms of continuous processing, so that a feed of "constant" composition is essential. Selective mining and physical beneficiation to remove the bulk of the dolomite do not appear to be practical. It is concluded that the most appropriate method of feed preparation is to carry out extensive blending of the magnesite/dolomite ore and the resultant calcine.

Jan 1, 1987

Your Excellency, on behalf of the Council of the Australasian Institute of Mining and Metallurgy, and, indeed, on behalf of everyone present, I extend to you a welcome, and our thanks for your gracious acceptance of the invitation to be here to-day and, later on, to present Honorary Membership Certificates. I also welcome the several official representatives of our Allies, of Great Britain and our sister Dominions.To Messrs. E. C. Driffield and E. J. Rigby, two of the original Foundation Members, who are with us to-day, I extend greetings.The present occasion is opportune to express, on behalf of a representative body of professional men, deep appreciation of the sacrifice which His Majesty the King has made, and will continue to make, by appointing His Royal Highness the Duke of Gloucester as Governor General of Australia and, therefore, His Majesty's senior personal representative in this country.I suppose, that as the primary reason for our assembly to-day is to celebrate the Fiftieth Year of the Institute's existence, I should properly on this occasion, give an account of its history and development. However, as this subject was ably covered by Mr. L. V. Waterhouse, in his Presidential Address in 1938, I trust I may be excused for selecting some other subject. I shall, therefore, exercise my privilege as President and give you a short history of the Mining and Metallurgical Industry of this country with special reference to its effect on the development of the Commonwealth and on the national economy. I apologize in advance for any statistics which I inflict upon you; some of these will be three or four years out of date, because of censorship restrictions. I shall as far as possible refer firstly to the industry prior to and including 1893, the Institute's foundation year, and then to subsequent development.Australia, is pre-eminently a pastoral and agricultural country and it leads the world in the production of wool. Nevertheless, it has an international reputation as a producer of gold and various metals and of minetal products.The development of gold mining in the decade 1840-50 was an epoch-making event in Australia's history, because, to quote one writer's apt phrase, "it precipitated Australia into nationhood." It was certainly responsible for a rapid increase in population. Thus, during the period 1841-1861 the population of Australia increased fourfold, from 221,000 to 1,170,000.The effect of the discovery of gold in Western Australia was even more striking. In 1890 the population of that State was 49,000 and in 1900 it was 180,000.Statistics in respect of gold are reasonably complete, even for the years prior to Federation, and it is interesting to note that the gold declared as...

Jan 1, 1944

By H Zhang, A Lawrence

To accommodate the fast growing need for services in Singapore’s Marina Bay downtown area, Marina South, the construction of a common services tunnel (CST) was required. The CST includes various services such as telecom cables, power lines and water pipes. A deep excavation and temporary earth retaining system (TERS) was required to facilitate the construction of the tunnels. Marina Bay is reclaimed land over thick soft marine clay which is likely to be still consolidating. The deep soft marine clay poses a big challenge for deep excavations in downtown areas where highways and sensitive structures are close by. This paper presents a case study of part of the CST Phase 1B and 2 at Marina South, in particular a 26 m deep excavation supported by a 46 m diameter temporary caisson. The construction started in late 2006 and the basic structure was completed in early 2011. The caisson was formed by 1.0 m thick overlapping diaphragm wall panels with a capping beam and three ring beams at different depths. Two-dimensional finite element analyses were conducted to predict the ground settlement, lateral displacement, bending moment and hoop stresses in the diaphragm wall and ring beams during different excavation stages. A comprehensive instrumentation and monitoring scheme was established to verify the design predictions, control excavation safety and trigger the contingency plan to protect public safety. The impact of construction activity, unbalanced temporary stockpiles and adjacent deep excavation for a mole removal will be discussed.CITATION:Zhang, H and Lawrence, A, 2014. A case history of a deep excavation in a big circular shaft in Singapore marine clay, in Proceedings 15th Australasian Tunnelling Conference 2014, pp 581–588 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

The Hill 50 Gold Mine is situated at Boogardie, 3 miles on a bearing of 295 degrees from; Mount Magnet township. Mount Magnet lies 300 miles north-north-east of Perth, Western Australia (Fig. 1).The older workings of the mine may be identified with those of Sirdar, Gold Mining Lease 696M The Sirdar had been worked before 1902 though no records remain, and irom 1903 to 1912 about a thousana tons at a grade of 6' 2 dwt. was extracted annually; by the end of 1918 6,225 oz. of gold had been obtained from the milling of 17,852 tons of ore. In view of these yields, and the length and width of the lode, this mine was early recognized as one of the most promising in the district. From 1919 to 1924 the ground,including G.M.L. 1282M, was held as Mt. Zion G.M.L. 1183M.The Hill 50 Gold Mine N.L. company took up the workings as Hill 50 G.M.L. 1282M in 1934 and have continued operations to the date of writing. To the end of 1956 the Hill 50 Gold Mine had yielded 982,106 tons of ore for a return of 448,'602 fine oz. of gold.The mine has been described by: J utson (1915), Feldtmann (1920), Johnson (1949), and Finucane (1953). Finucane (1953) details the mine structure to a depth of 414 ft. The author was able to examine the mine to a depth of 1305 ft. Detailed main level mapping to the 1060 level and a detailed surface examination have revealed aspects of the structure which were previously obscure.

Jan 1, 1960

By Blott S. F

The smelting plant and equipment at Mount Isa, as originally designed and built, was described by J. M. Callow (1) *.F. A. Forward (2) described alterations and additions to the plant and discussed the metallurgy of mixed carbonate-sulphide concentrates at Mount Isa, prior to 1933, in the Proceedings of this Institute.In 1933, A. F. McAskill (3) gave full mechanical details of the plant in a paper presented to the Institution of Engineers, Aust.FLOW SHEETSFig. No. 1 represents the present general flow sheet. Forward's (2) flow sheet is reproduced here as Fig. lA, and will serve for comparison in depicting subsequent deletions from, and alterations and additions to, the plant.Fig. No. 2 presents the daily tonnage flow sheet of 1939 practice.ALTERATIONS SINCE 1933General. Many changes in metallurgy and operation have taken place, particularly subsequent to March, 1935, when the treatment of a mixture of carbonate and sulphide ores was discontinued and the mill commenced operating on all-sulphide ore. This alteration brought about the elimination of gravity concentration-Jigs and Tables and resulted in the production of all-floatation concentrates of a very fine sizing. Refer Table No. 2, page?) Radical changes in the analyses and physical nature of concentrates also followed (see Table Nos. 1 & 2, page ?) and, similarly, radical changes in the smelting plant have been slowly brought about.

Jan 1, 1939

The literature pertaining to the electrochemical reaction at the anode during electrolytic reduction of alumina by the Hall-Heroult process is not in universal llgreement about the gaseous product. The possibility of electrochemical formation of CO at the anode was examined using existing data. Although the thermochemistry favours co-evolution of CO and CO2 with CO as the major product, the mechanism of the reaction shows this is unlikely. Since the origin of CO can be more logically explained by non-electrochemical mechanisims, it is concluded that CO2 is the only product from the electrolytic reaction at all current densities.

Jan 1, 1967

A process was developed, on a laboratory scale, for the removal of iron oxides from Weipa pisolitic bauxite. The technique involves the chemical reduction ofthe iron oxides by carbon, followed by selective removal of the iron species by acid leaching or chlorination.To remove more than 90 per cent of the iron it is necessary to reduce the iron oxides substantially to iron metal by heating the bauxite, pre-calcined at 650-800°C, with reactive carbon at 1040-1100°C. Reduction proceeds via the intermediate formation of hercynite (FeO.Al2O3) and difficulties have been encountered in reducing hercynite formed under less favourable reduction conditions.Following reduction, efficient selective removal of iron species is readily effected by acid leaching using dilute hydrochloric acid at 100°C, or chlorination at 500-750°C using Cl2, Cl2/N2, or Cl2/N2/CO mixtures.After removal of unreacted carbon, the final products contain 0·5-1.0 per cent Fe203 and 87-92 per cent Al203.

Jan 1, 1971

Drilling and blasting are an essential part of most mining operations, and are commonly major operating cost centres. The effectiveness of blasting can have a significant influence on all subsequent activities, and hence overall operating costs. Drilling and blasting systems must be compatible with the overall mining method, to minimise total costs and ensure operational efficiency. Selection of suitable equipment and techniques requires an understanding of the total operation, plus current skills in specialised technologies. This paper examines the contribution of drilling and blasting to total costs, including the balance between capital and operating costs. The use of computer modelling is discussed, to demonstrate how blast performance and costs can be predicted and alternatives analysed. Case studies illustrate how cost savings can be made in operating mines, and alternative systems evaluated to optimise new projects.

Jan 1, 1990

By C A. Locke, M Stevens, P Vidanovich, J Cassidy, J L. Mauk

The Karangahake adularia-sericite epithermal gold-silver deposit, located at the southern end of the Waitekauri Corridor, Hauraki Goldfield, occurs as quartz veins with associated alteration haloes. Integrated geophysical studies were undertaken to determine the expression, location, and extent of these alteration zones. Aeromagnetic data show an extensive, magnetic æquietÆ zone over Karangahake and the southern Rahu Ridge that represents a zone of magnetite destruction resulting from hydrothermal alteration. Analytic signal data are used to define the boundary of this zone; the resulting 6 km2 area is elongate north-south with an irregular boundary. A detailed gravity survey over the area reveals a positive residual gravity anomaly, up to 30 gu in amplitude, over the Karangahake deposit. Density measurements on near-surface rocks give low values indicating that the source of this positive gravity anomaly must be deep; possible causative bodies include an igneous intrusion or dense sulfide mineralisation. To the west and east of the host Waipupu Formation, strong gravity gradients of 100 gu/km and 65 gu/km reflect the faulted boundary of the Hauraki Rift, and the edge of the Waihi Basin respectively. High resolution airborne radiometric data define a 2.2 km2 area of potassium enrichment. This area is elongate north-south and has an irregular boundary. It coincides approximately with the centre of the magnetic quiet zone and the peak of the gravity high, and correlates with known areas of intense mineralisation. Anomalously high potassium counts and elevated K/Th ratios correlate with areas of potassic alteration that have undergone K-metasomatism. Underexplored portions of this zone may indicate areas of gold-silver prospectivity. Combined geophysical data therefore reveal the extent of hydrothermal alteration, and the central zone of Kmetasomatism that is most likely to contain orebodies.

Jan 1, 2005

In redesigning the cyanide plant at Mount Torrens, in conjunction with Mr. L. W. Grayson, the manager, several minor alterations were introduced in order to have the operations under thorough control, and these having proved serviceable may be of sufficient interest to merit a description here. The lixiviation vats, though only 8 feet in diameter, were retained, but the pipes leading away from the bottom were reduced from two inches to half-an-inch in diameter, and had a fall to the zinc boxes of about 4 feet. As these small pipes were completely filled by the solutions fiowing away from the vats, they exerted a suction equal to their fall and thus hastened the rate of flow, so that tailings containing a larger proportion of slimes could be treated than was possible where the larger pipes were used, as, there not being sufficient fiow of solution to keep the latter filled, no suction could be obtained with them. It was found that with'most of the tailings treated a sufficient flow could be obtained from the half-inch pipes when the taps on, them were only one-third to half open. The lower end of each of these pipes was connected by means on indiarubber tubing with the sille hole of 11 in aspirator bottle, and to the mouth of this bottle a few feet of similar tubing was connected, so that the solutions coming through could be directed into either of the fixed tubes leading respectively to the waste water tank the strong solution zinc boxes or the weak solution zinc boxes.In working the vats, the following method was found to give good results. While filling the vats with tailings the taps were left open, so that the water might drain off into the waste water tank the surface of the tailings was carefully levelled. When the strong solution was run in at the top, the air contained in the interstices of the tailings was forced through the half-inch pipe at the bottom as a strong blast, instead of, as I believe js usual, escaping by means of channels formed by it through the tailings, and thus tending, it would appeal, to render the disposition of the tailings less even and to make.

By L Matthews, D O’Dea, P C Hayes, J Manuel, B Monaghan, T Honeyands, D Pinson, J Leedham

Many different approaches have been used in the past to characterise iron ore sinter mineralogy to predict sinter quality and elucidate the impacts of iron ore characteristics and process variables on the mechanisms of sintering. Characterisation techniques include optical image analysis and point counting, X-ray diffraction and scanning electron microscopy. Each technique has its advantages and disadvantages depending on the objectives of the measurement. It is generally acknowledged that silicoferrite of calcium and aluminium (SFCA) is very important to the quality of the sinter produced; however, strict definitions of the phases and textures of SFCA are not generally agreed. This paper summarises the state-of-the-art in sinter characterisation applied in Australia by both academics and industrial researchers. The results from various techniques are compared and the relationships between the measurement results are discussed.CITATION:Honeyands, T, Manuel, J, Matthews, L, O’Dea, D, Pinson, D, Leedham, J, Monaghan, B, Li, H, Chen, J, Hayes, P C, Donskoi, E and Pownceby, M I, 2017. Characterising the mineralogy of iron ore sinters – state-of-the-art in Australia, in Proceedings Iron Ore 2017, pp 49–60 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By E Portes, G Noble, J Roberto, A Stabile

Iron ore beneficiation plants are facing economic pressures to treat more challenging ore types, improve efficiency and improve product quality. Better control and stability of the plant process in the face of increasing feed ore variability has been a goal for many of the operations facing these challenges.Prompt gamma neutron activation analysis (PGNAA) technology has proven to be a successful measurement technique within an iron ore beneficiation plant. PGNAA was first developed in the early 1980s for the measurement of the elemental composition of bulk materials. Today, PGNAA technology is applied for elemental analysis within the iron ore industry on both bulk materials and slurries.Traditional composite sampling throughout the wet iron ore beneficiation process provides a delayed measurement of average properties but does not capture the true variability of the process in real-time. As such this is a limiting factor towards stabilisation and optimisation of the process. A PGNAA analyser provides real-time slurry elemental analysis of feed, concentrate and tails streams within the processing plant. The analytical data from the analyser can be exploited with a control strategy to correct and stabilise the plant on a much shorter time scale, delivering significant economic benefits and greater operational flexibility. The economic benefits include more stable product quality and a reduction in composite sampling and laboratory costs.Some example results will be presented from the Vale Vargem Grande iron ore beneficiation plants, which are utilising a six stream multiplexed Thermo Scientific PGNAA Slurry Analyser.CITATION:Noble, G, Stabile, A, Portes, E and Roberto, J, 2017. Real-time slurry elemental analyser for iron ore beneficiation plant control, in Proceedings Iron Ore 2017, pp 481–486 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

In New York City, on the walls of the library of the United Engineering Societies are these words:"Engineering-the art of organising and directing men and of controlling the forces and materials of nature for the benefit of the human race," but who, reading the schedules of even our best engineering schools, would infer that engineering is an art or that it should always havejn mind the benefit of the human race? While it must be remembered that our engineering schools exemplify the British cult of the amateur, that cult which lets men who have never attended a lecture on "Education" or perhaps nevereven read a book on it, become enginering teachers by profession (and so educators by inference), the root of the matter is to be found in the fact that our educational aims, and consequently our educational practice, seem suited much better to the position engineering held in the community in 1900 than to the position it holds to-day. This civilization of ours has developed, !;loth for good and for ill, into one based largely on engineering achievement; technical progress is so continuous and so rapid that thevalue of descriptive knowledge of current practice is ever lessening; enough must be imparted to make the young graduate immediately employable, and this amount is sufficient for illustrating the principles on which practice is based and on which its advance depends, but the young graduate's technical progress depends much less on his having acquired additional knowledge than on his ability to acquire knowledge, so, paradoxically, the more useful knowledge there is availabJe the less of it the student should be taught.Less conspicuous but fully as important is the enlargement of the field of work of engineering graduates, especially its extension to the initiating of policies and to the broader problems of administration. At present the road to such positions lies normally through a considerable period of professional work, but it is by no means unlikely that the field will soon include much that requires little professional expel'ience. At all events it is safe to say that the changed. and changing position of engineering in the communitydemands the attention of the engineering schools and that profitable discussion of engineering education demands some understanding of the real nature of education and of the part which engineering plays in the life of the community.THE NATURE OF EDUCATIONUnfortunately "to educate" supplies an example of how words degenerate in meaning; most people regard it as the equivalent of "to instruct"; a small number feel they have gone to. the root of the matter when they say...

Jan 1, 1941

The principles of geometry and trigonometry are so continuously used by mining engineers for the purpose of accurately and intelligibly recording their measurements, that the writer is prompted to lay the following cursory remarks upon mine surveying before the members of this Institution in the hope of eliciting a free interchange of opinion upon details of this interesting branch of the profession. He proposes to deal with surveying only so far as it concerns the mining engineer, not to intrude upon the domain of the professional surveyor, and, in this instance, to discuss more especially that which may be termed the mechanical, rather than the mathematical side of surveying.In the latter part of the eighteenth century and the beginning of the present one, the usual underground surveying equipment in the English metalliferous mines, consisted of a magnetic needle in a fiat square wooden box of about 9-inch sides, a two-foot rule, a long cord, aud a stool, upon which to place the needle and box. The operator took his bearing by sending his assistant with the end of the cord as far in a straight line as the length of the cord would admit.On its being drawn that he held its end in one hand and placed the side of the compass-box against it with the other, and noted the bearing thus found either by a book entry, or by ticking it off with a piece of chalk on the board the compass lay in. He then measured the cord with a two-foot rule. It is needles to say that with these appliances the accuracy of the results were open to question, and mining surveying was not unduly popular.In the present day, engineers have the advantage of using instruments brought to such a state of perfection, and of employing such an exact system of underground surveying, that inaccurate work must usually be attributed either to lack of care, or lack of ability in the operator.

By Ralph B. J, Sadler W. R

Thiobacillus ferrooxidans was shown to catalyse biodegradation of chalcopyrite concentrates. The process was growth associated at normal temperatures (30°C) in dilute acid solution (pH2, H2SO4) in submerged cultures. Approximately 20% of the copper dissolved in 22 days in the presence of T ferrooxidans while less than 0.6% was released when bacteria were absent. In ore column leachates, the iron and sulphur oxidizing species T ferrooxidans, ranged from I04 to I06 cells/ml while exdusively sulphur oxidizing species ranged from I02 to 104 cells/ml. T ferrooxidans predominated below pH 3 while other sulphur oxidizing bacteria favoured higher pH. Organisms were distributed vertically in ore columns according to pH differences, resulting from gradual acid consumption by gangue, during trickle irrigation.There was a sequential development of bacteria in leachates from fresh ore irrigated with water only. High pH sulphur oxidizers were always present, low pH sulphur oxidizers appeared within a week while T ferrooxidans took 50 days to show up. Routine monitoring of bacteria in dump leachates provided a qualitative indication of events in otherwise inaccessible ore bodies.

Jan 1, 1981

he Wyalong goldfields were discovered in September, 1893, Messrs. Neeld and Sons, owners of the principal mine, being the pioneer prospectors. During the earliest days of the field the ore was sent to Barmedman, a distance of eighteen miles, for treatment at a battery there. The field rapidly increased in importance, and it was not long before a public battery was established on the spot. After some considerable quantity of ore was treated by this process, it became apparent that battery treatment was quite unsuitable for the richer ores, involving, as it did, considerable loss in the tailings. Recognition of this fact led to the erection, in 1895, of plants by the Wyalong Chlorination and Cyanide Works, owned by Mr. Walter Sully, for treatment by their processes; followed, at a later date, by Messrs. Neeld and Sons Chlorination Works. The Wyalong Chlorination and Cyanide Works, after a delay of twelve months in the erection of their plants, have since catered continuously up to the present time for the requirements of the field.Their plant consists of a No. 3 Gates' rock·breaker, a revolving dryer, a No. 5 Krupp mill, revolving roasting furnace with finishing hearth, two chlorination vats of 20 tons capacity each, "nine cyanide vats of 30 to 100 tons capacity, two Wheeler pans and three chlorine generators. The ores are purchased outright on assay at a fixed scale of charges, and treated by the owner of the works on his own account.

Jan 1, 1903

Investigation of the Classification Operation in a Coal Pulverising Vertical Spindle Mill Coal pulverisation in power plants is a major electrical energy consumer. In 2006 more than 41 per cent of world electricity generation was from coal where pulverisers use 0.5 to 1 per cent of gross generation. Therefore, pulverisers are an important target for optimisation not only for reducing costs of power generation but also for reduction of greenhouse gas emissions. A better understanding of the operation of pulverisers is an essential requirement for their optimisation. However, little information is available, other than operating experience, on the performance of pulverisers and how these react to changes in operational variables. This study investigates the effect of changes in coal and airflow feed rates on the classification performance that occurs in an industrial scale ball-and-race vertical spindle mill in which the pulverisation and classification processes are linked together due to the separator classifier being an integral component within the pulveriser. In order to decouple the breakage and classification processes, samples were cut from upward flowing streams through sampling ports drilled on the pulveriser body at different locations. Specific sampling tools were developed. Samples collected from the pulveriser were size and density fractioned to distinguish the differences in behaviour of the components, namely coal and mineral matter. The coal flow rates on dry basis within the mill and around the separator classifier were calculated by mass balancing the multi-component data. The difference in classification behaviour of components during pneumatic transport was confirmed. The response of the circulating load in the mill (~600 to ~1100 per cent) as well as the dependency of fineness of the streams to the operating variables was demonstrated. The approach taken in this study has proved that development of a classification model for a vertical spindle mill pulverising non-homogeneous materials, eg coal, requires treating these materials as multi-component/composite substances.

Sep 13, 2010

The Torington Lodes.This paper describes investigations into mineralogical, petrological and structural associations of cassiterite in occurrences of economic value. The work was carried out in three mines, during a number of years, in the hope that the, data collected might be helpfulin the search for occurrences of cassiterite in stanniferous zones and reduce unproductive exploratory work. Tin-bearing lodes at Torington, in the New England district, New South Wales, have been worked since 1880, and the locality is the most important centre of lode tin occurrence in the, State. The township of Torington is 18 miles westerly from Deepwater, a station on the Great Northern Railway, 446 miles from Sydney.The tinfield forms part of the Mole Tableland, which has an altitude between 3,000 ft. and 4,000 ft. above sea level. The country rock, in which the stanniferous lodes occur, is granite of Permian age, which has been intruded into Carboniferous claystone. An inlierof claystone is exposed to the west of the stanniferous area, 'and in it, close to' its contact with the enclosing granite, are occurrences of wolfram and bismuth. These minerals, together with chalcopyrite, pyrite, arsenopyrite, zinc blende, galena and molybdenite, in very small quantity, are associated with cassiterite in lodes traversing the granite, particularly near the claystone, but decrease in amount with distance from the contact. Their occurrence is sporadic and usually causes no trouble in dressing the cassiterite concentrate, the final product containing less than 1% of total penalisable impurity. In Curnow's mine, pyrite, galena and molybdenite have been observed at 700 ft. from surface.The granite is of the biotite type and its structure may be divided into four groups, or classifications, arising from segregation processes during cooling and consolidation. The four classes, in order of extent of distribution, are:1. Granite of normal type, in which the constituent quartz felspar and mica, have a particle size approximately 14, in.2. Porphyritic granite, in which the felspar particles are from % in. to lin. in size, that of the quartz and mica approximately % in.3. A fine-grained granite, in which the particles of all constituent minerals are % in. or less in size;4. A rock of highly siliceous ground mass containing very small particles of felspar and almost negligible biotite.Type 1 is the general type of granite in all mines of the field; types 2 and 3 may occur as large masses, or all three classes may merge rapidly one into the other, and all be disclosed in 20 ft. of driving. Usually, however, the segregations are massive, but are not associated with any special horizon. For instance, a mass of porphyiiticgranite extends from surface to a depth of 440 ft., for a distance of 350 ft. south from the New England main shaft. The upper levels of Curnow's mine, 14" mile south-east, are in normal granite, but a restricted mass 'of porphyritic granite occurred between Nos. 5 and 6 levels, or 400-500 ft. below the collar of the shaft...

Jan 1, 1950

The Morning Star diorite dyke has been subjected to two periods of mineralization. The earlier, genetically related to the dyke magma, gave rise to a weak chalcopyrite-pyrrhotite-pentlandite-gold mineralization in a narrow zone, up to 25 cm. wide, which parallelsthe nearby western (hanging) wall of the dyke. Subsequently a set of conjugate shears formed in the dyke as a result of tectonic movements. Gold-quartz veins formed in these shears giving rise to the classical "ladder veins" of the Morning Star mine. On either side of the veins ("floors") the diorite has been bleached for up to 3 ft. This involved introduction of much CO. and some K"O, and S with abstraction of SiO. and FeO, giving rise to carbonates, sericite, zoisite and pyrite. The veins consist of quartz with minor amounts of albite and carbonate, together with pyrite, arsenopyrite, pyrrhotite, chalcopyrite, sphalerite, tetrahedrite, galena, bournonite, boulangerite and gold. Spectrographic analyses of gold show that the suite of trace elements is consistent throughout the mine.INTRODUCTIONThe gold-quartz veins of the Morning Star Gold Mine, at Wood's Point, Victoria, are a classic example of the "ladder vein" type of deposit. The structure of this series of repeating quartz veins or "floors", some barren and some productive, occurring in a set of conjugate shears which transect a "dyke bulge" of diorite (Fig. 1), has been described on numerous occasions as mining has progressed and figures in the textbooks (Whitelaw, 1905; 1916; Junner, 1920; Lindgren, 1933; McKinstry, 1935; 1942; 1949; Kenny, 1949; Hills, 1952; Clappison, 1953) ; but there has been no study of the mineralization apart from that in Junner's (1920) general study of the Walhalla-Wood's Point Goldfield, made at a time when mining had not developed below the 400 ft. level,. and the mine was dormant.

Jan 1, 1958