Search Documents

By Balint F

The Izok massive sulphide deposits are located in the Northwest Territories of the remote western Canadian Arctic. Together they represent one of the highest grade undeveloped zinc-copper resources in North America. Metall Mining Corporation is presently engaged in a feasibility study on developing the Izok property as well as actively exploring for additional reserves. The Izok deposits are Archean-aged, volcanogenic massive sulphide (VMS) bodies hosted within and near the top of a thick sequence of predominantly felsic pyroclastic rocks. The hangingwall package includes additional felsic volcanoclastics, dacitic and basaltic flows, thin sulphide-rich iron formations, and turbiditic sediments. The felsic volcanics are intruded by syn- to late-hydrothermal dacitic dykes and sills and post-hydrothermal gabbroic dykes and sills. Both intrusives are interpreted to be volcanic feeders to overlying flows. All lithologies are cut by much later irregular granitic pegmatite dykes and regionally metamorphosed to pyroxene homfels grade. The deposits occur within a large kilometre-scale soda-depleted alteration zone. The immediate footwall and hangingwall rocks to the deposits are characterised by zones of muscovite-biotite (with or without sillimanite), lesser chlorite-biotite-cordierite (with or without anthophyllite), and locally intense silicificified and albitised zones. All lithologies have been affected by a later calcic metasomatic alteration. As currently defined, the Izok Zn-Cu-Pb-Ag deposits comprise a cluster of four complexly-zoned composite lenses: the Northwest, North, Central, and newly discovered Inukshuk deposits. The first three deposits are amenable to open pit mining while development of the Inukshuk deposit will require underground methods. The combined mineral inventory of the Northwest, North, Central and Inukshuk deposits at present totals 15.6 million tonnes with a grade of 2.4 per cent Cu, 13.8 per cent Zn, 1.4 per cent Pb, and 74.6 g/t Ag.

Jan 1, 1993

By Ballantyne GH

The Ladolam gold deposit on Lihir Island, in Papua New Guinea, is a large disseminated gold deposit hosted by hydrothermal breccias. The deposit occurs in the cupola zone of a 350,000 year old monzonite stock which is emplaced in the collapsed caldera of a shosho- nitic stratovolcano.

Jan 1, 1987

By Townsend IJ

The Upper Triassic Leigh Creek Coal Measures which include a number of seams of sub-bituminous black coal are preserved in four small intramontane basins. The largest is Telford Basin, 1,000 m in thickness. The coals, of variable thickness and quality, are mined by open cast mining methods and utilised for generation of electricity at Port Augusta. The combined proven and indicated reserves are about 100 million tonnes.

Jan 1, 1975

By Perring CS, Hill RE, Barnes SJ, Vallance SA

The Maggie Hays nickel sulphide deposit is located at latitude 32¦ 15 'S, longitude 120¦ 30' E on the Lake Johnston (SI 51-1) 1:250 000 map sheet. The deposit occurs in the Lake Johnston greenstone belt, in the Southern Cross Province of the Archaean Yilgarn Block, 500 kilometres east of Perth, Western Australia (Figure 1). The remoteness of the Lake Johnston greenstone belt and its poor access, restricted previous exploration activities and the full appreciation of the geology and its Ni-sulphide potential. It was not until 1991, when Forrestania Gold NL commenced exploration activities, that the geology of the ultramafic units and their potential to host significant concentrations of Ni sulphides were clearly established. This paper, which describes the geology and the characteristics of the Maggie Hays deposit, is based on the results of exploration by Forrestania Gold NL and a collaborative research agreement between CSIRO Division of Exploration and Mining and Forrestania Gold as reported by Perring, Barnes and Hill (1994), Perring and Hill (1995), Perring (1995 a and b) and Barnes, Perring and Reilly (1995). A comprehensive description of the geology, petrology and geochemistry of the deposit is being prepared for publication by CSIRO (Pemng, Hill and Barnes, in press).

Jan 1, 1996

The Ravensworth-Liddell area is part of the Muswellbrook- Singleton Coal District of the Northern Coalfield. It lies in the Parishes of Liddell, Ravensworth, Vane and Howick, in the County of Durham, midway between Singleton and Muswellbrook, and is traversed by the Great Northern Railway, and the New England Highway.Ravensworth and Liddell railway stations are 57 miles arid 61 miles, respectively, north from Newcastle (Fig. 1).The area has been the centre of an intensive search for open cut coal during the past few years. More than 1,200 bores, of which about 10% were cored diamond drill holes, were drilled to depths of about 200ft. Portions with thicker cover have been explored by 10 diamond drill holes to depths of over 400ft. but core recovery from these deeper holes was poor, and the lack of detail in the recorded logs limits geological interpretation. The drilling has proved about 34,000,000 tons of open cut coal, and about 246,000,000 tons under deeper cover.GEOLOGYThe Ravensworth-Liddell area lies on the eastern flank and southern extremity of the Muswellbrook Dome, extending from Hebden in the north, to Jerry's Plains in the south, and the rocks under consideration belong to the Tomago Stage of the Upper Coal Measures. On the north they are truncated by the Hebden Thrust fault, which has a throw of about 4,500ft. (Raggatt, 1929). On the west they are bounded by outcrops of the Upper Marine Series, which conformably underlies the Upper Coal Measures, and...

Jan 1, 1953

In the Renison Bell area of western Tas mania, a series of Lower Cambrian quartzites, shales, carbonate beds ("dolomites"), cong- lomerates, tuffs and argillites have been folded into a broad monocline whose general strike is NW-SE, plunging slightly north and dipping NE. The downwarped eastern side of the monocline is disrupted by a steep (50-800) east dipping normal fault, known as the Bassett Structure, whose throw is in excess of 500 m. A series of flat north dipping normal faults, each with a throw of approximately 50 m, further disrupts the sequence. All major faulting was pre-mineralization. A cassiterite- bearing Devonian quartz porphyry body intrudes this Cambrian sequence 2 km south of the currently operating mine. Of economic importance is the presence of three carbonate beds in the sequence. These carbonates consist of a mixture of calcite, dolomite and siderite. The No. 1 (youngest) and No. 2 carbonate beds are each approximately 15 m thick and are separated by 20 m of hematitic conglomerates and tuffs. The No. 3 (oldest) carbonate bed is approximately 5 m thick and is separated from the No. 2 horizon by 50 m of dark grey, finely laminated shales and quart- zites. Whilst the carbonates are remarkably persistent over at least 30 km2, facies changes are common and as a result of these changes, the carbonates vary considerably in

Jan 1, 1973

By Silver EA

The Finisterre Range on the north coast of Papua New Guinea is the uplifted forearc riagio.n. of a modern arc-continent collision. The core of the range is composed of the P- nisterre Volcanics, an Oligocene''-arc terrane. The southern flank of the range consists of a clastic sedimentary sequence which is an uplifted accretionary wedge and collision complex. This clastic sequence can be subdivided into three distinct units. To the south of aiid structurally below the Finisterre Valcanics are the Mebu beds, an Oligocene- $arly Miocene sequence of volcanolithic turbidites. The Erap Structural Complex is south of, and structurally below the Mebu 43eds. , It consists of three subunits; the 3rly Pliocene micaceous turbidites of the Sukurum unit, contemporaneous pillow basalts AF{ the Basalt unit, and Late Pliocene to Pleistocene volcanolithic turbidites of the -Nariawang unit. The Quaternary Leron Formation, a fluvial to shallow marine 'clastic unit, is the southernmdst. and structurally lowest unit of the clastic -sequence The Finisterre Range is dominated by a fold-and-thrust belt with most thrusts "dipping steeply N. Melange fabric _ is developed in the vicinity of major thrusts. "ffle thrust belt strikes NW, oblique to the regional convergence direction, but no strike-slip motion is observed along NW striking faults.

Jan 1, 1991

The discovery of copper and nickel sulphides in the Riwaka Complex in 1967 led to considerable exploration activity by a number of companies. Various exploration techniques used by these companies are summarised and discussed. Activity of these companies shows that mineralisation is mainly confined to the southern, ultramafic section of the Riwaka Complex where geological mapping recognised sixteen units within, or associated with the Riwaka Complex. Significant pyrrhotite, pentlandite chalcopyrite mineralisation is restricted to biotite feldspar pyroxenites and to clinopyroxenite units. Lesser and more erratically distributed pyrite chalcopyrite pyrrhotite mineralisation occurs in poikilitic pyroxene hornblendites, melanocratic gabbros, and in marginal diorite lenses. It is suggested that a linear belt of layered ultramafic and mafic rocks described in Fiordland by Williams (1974) may be a southern extension of the Riwaka Complex. The Riwaka Complex has been classified as belonging to the Picritic subtype, (Tholeiitic suite), of Naldrett and Cabri, (1976), and as such it is concluded that it exhibits substantial potential for the discovery of economic copper and nickel deposits. It is considered that the complex is a multiphase differentiated intrusion emplaced in a major tensional fracture zone that developed in a relatively stable tectonic environment, namely a succession of middle Paleozoic shallow water shelf sediments. Based on sparse available evidence it is suggested that the Riwaka Complex was intruded in the lower to middle Permian. It is further suggested that the tensional fracturing was initiated by the onset of subduction process which were responsible for the development of the Permian volcanic arcs and ophiolite belt in the north west Nelson area.

Jan 1, 1977

CONTENTSSummaryIntroductionGeographical and Geological Outline of the RegionGrowth of the Mining IndustryTable 1: Production StatisticsGeneral GeologyRecent Alluvium and River GravelsSambeto SeriesMudstone and Basalt ContactVatukoula SeriesIntrusivesStructureGeologic HistoryLodesTable 2: Principal Lodes and Their OrebodiesMineral Assemblage and ParagenesisOre Shoots and Their ControlEmperor MineLoloma MineDolphin MineExplorationConclusionAcknowledgmentReferencesSUMMARYThe Tavua Goldfield was found in 1932 within a basin, both topographical and structural, near the sea on the north side of Viti Levu, Fiji, and has produced over £13,000,000 (Fijian) worth of gold and silver from the three mines...

Jan 1, 1953

By Collings P. S, Adair D. L

The Upper Robe (Robe Gorge) deposits occur in Kumina Creek and the Robe River, some 20-40 km upstream from mining operations at Pannawonica. The Gorge Deposits were rec- ognised, mapped and sampled in 1962-3 and re- examined in detail in 1971. Approximately 180 mineralized occurrences were mapped in 1971 on 1:4800 scale and 50 of these were remapped in detail at 1:1200 scale. Eighty cross sections were measured and sampled and 300 geological maps prepared. In addition 88 holes totalling 7388 feet were drilled in three occurrences considered to have the greatest potential. The Gorge Deposits occur in the Robe Pisolite unit which forms thin remnant crusts, bay fillings and occasional cut-off meanders along the edge of the present streams. Less than 50 of the deposits have tonnage potential of one million or more. Consequently exploit- ation of the Gorge reserves must be considered as a very uncertain, long range possibility because the deposits are small and scattered throughout the gorges in the area, thereby necessitating costly railroad spur lines to gain mining access. Grade of the occurrences is extremely variable over short distances both vertically

Jan 1, 1973

The main iron ore deposits of Western Australia fall into three very different geological classes, which are, in order of importance: hematite enrichment ore, pisolitic limonite ore, and sedimentary ore. These are presently (1973) being mined in the approximate proportions 20 : 2 : 1, while the equivalent proportions for reserves are, very approximately, 200 : 70 : 1. Two minor categories which mar- ginally qualify as ore are detrital material variously referred to as scree ore or canga, and potentially beneficiable iron formation. These two latter types are dealt with very briefly, and the three main categories are dis- cussed in order of economic significance. Hematite enrichment ore results from the selective replacement of a pre-existing host rock by hematite. Almost without exception, this host is cherty banded iron formation (BIF); but certain exceptions have great genetic inter- est. Ore bodies of this kind occur both in the Archaean BIFs of the Pilbara and Yilgarn Blocks and in the Proterozoic BIFs of'the Hamersley Basin. It follows from their virtual restriction to a single kind of sedimentary host that there is strong stratigraphic control over the shape of ore bodies: these may be almost flat, of dyke-like form, or of complex configuration, according to the pre-enrichment structure of the host bed. This structure was an important control over the position in which ore formed:

Jan 1, 1973

Western Australian tin deposits are similar to those of other Precam- brian terrains in that they are mainly associated with rare-metal pegmatites, in which cassiterite is found with minerals containing any or all of the elements Ta, Nb, Be, Li, Cs, Rb and the rare earths.. They differ from Phanerozoic deposits where cassiterite occurs in quartz veins, greisens, dis- seminations in granite or sulphide lodes, and is associated with minerals containing W, Mo, Bi, Sb, As, Ag, or Cu. The main tin production in Western Australia has come from the Pilbara Block where the more important tin- bearing pegmatites are related to a younger granite phase, and from Green- bushes where large albite pegmatites intrude ?Proterozoic metamorphic rocks. The more important tin deposits in the Pilbara Block, and those in the Halls Creek and Murchison Provinces, are related to granites which are richer in Si and K and poorer in Ca, Mg, Fe and Ti than 'average granite'. The tin granites tend to have higher than average contents of Sn, Rb and Li.

Jan 1, 1973

By D Kepert

It is the role of the exploration geologist to create wealth through the discovery, delineation and characterisation of economic mineralisation. This requires a critical depth of geological understanding.Unfortunately, the resource industry is well known for its cyclic nature. Many of the current generation of workers have only ever experienced the boom of the ‘super-cycle’ and are only just discovering the negative side to the business. For the case of the geologist and especially the exploration geologist, the magnitude of peaks and troughs are usually amplified and may become destructive to all parties. During the uptime a healthy stream of exploration good news becomes the staple diet of company releases, in particular those of junior companies attempting to bolster the share price. The geological knowledge and experience gained thus forms a significant and integral part of the value and therefore, future of a company. On the downturn it is often viewed that geologists are a luxury, an optional extra and a burden on the bottom line with companies entering a period of memory loss and myopia.Retention of geological knowledge however remains critical as projects, companies and cycles mature. Beyond exploration per se, this knowledge becomes both fundamental in de-risking and commercialising an asset (through development or divestment) and in positioning the company for cyclic or counter-cyclic opportunities.The growth and retention of this knowledge base is difficult to quantify in terms of direct value but becomes one of a successful resource companies greatest assets. At worst, its loss can lead to millions of investors’ funds wasted on missed opportunities, drilling, or poorly designed plant and mine.But the rocks are around for the longer haul and pay little notice to the vagaries of the scurrying of Man.This paper reflects on some of the authors own observations through 25 years of iron ore exploration, in why it is critical to always rigorously question the prevailing geological (mis)understanding and the technical and commercial benefits which that may bring, and looks forward to the future.CITATION:Kepert, D, 2015. Geology – the affirmative case, in Proceedings Iron Ore 2015, pp 285–298 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By A Madera, R Watt

The Tampakan deposit is a strongly telescoped high-sulphidation-epithermal/ porphyry deposit pair which is hosted by a sequence of probable Pliocene age subaerial andesite flows. These host units lie on the western flank of a deeply dissected andesitic stratovolcano within the northernmost portion of the Sangihe Arc in southern Mindanao. The deposit was discovered by WMC geologists in 1992 and is currently undergoing resource evaluation. Preliminary resource estimations indicate a total inferred metal content of 12 million tonnes of copper metal and 16 million ounces of gold. Using a 0.2 per cent Cu cut-off grade, the deposit has a current mineral resource of approximately 2.5 billion tonnes with an estimated grade of 0.48 per cent copper. At a higher cut-off grade of 0.5 per cent Cu, the mineral resource is approximately 900 million tonnes with an estimated grade of 0.75 per cent copper. Mineralisation is open both to the west and at depth. The Tampakan district is centrally located with respect to a 100 km wide zone of left-lateral strike-slip deformation represented by the trans-Mindanao Cotabato Fault Zone. The district is transected by several WNW-striking wrench faults which represent strands of the regional Cotabato Fault Zone. High-sulphidation epithermal mineralisation within the Tampakan deposit is strongly controlled by NNE-trending faults which lie along a dilational orientation within the Pliocene stress field associated with the Cotabato strike-slip fault zone. The mineralisation is broadly hosted by a gently-dipping, tabular zone of partial to massive silicification which displays multi-phase brecciation, acid-leaching, related vuggy porosity and which is developed within a district-scale advanced-argillic and argillic lithocap exceeding 90 km 2 in area. High-sulphidation epithermal mineralisation is associated with a silica-pyrophyllite-dickite-alunite-diaspore¦sericite alteration assemblage which is transitional downward to sericite-chlorite alteration and relict potassic biotite-chlorite-magnetite-anhydrite alteration associated with pervasively developed but weakly mineralised porphyry quartz stockwork veins. The high-sulphidation mineralisation is dominated by disseminated, vein and vug-filling enargite-bornite-digenite-chalcocite-covellite ¦ molybdenite which has overprinted an earlier phase of porphyry copper stockwork veins associated with high-level porphyritic hornblende diorite stocks. The distribution of high-sulphidation alteration and mineralisation reflects strong stratigraphic and structural controls. The high-sulphidation mineralisation covers a surface area of approximately 1.6 km by 2.0 km and forms a tabular, flat-lying to gently-dipping body between 200 and 500 metres thick. It is intersected at RL-1200 m ASL (at surface) in the northern portion of the deposit and extends down to RL-600 m ASL at the southern end. The deposit has been diamond-drill tested to a depth of 400 - 500 metres where low-grade chalcopyrite-bornite-pyrite mineralisation is hosted by pervasive quartz stockwork veins. This deep-level mineralisation represents the outer portion of a porphyry Cu system hosted by both andesite flows and the uppermost portions of high-level hornblende diorite stocks. Deep drilling to test for higher tenor porphyry Cu mineralisation is planned.

Jan 1, 1999

By Z S Chang, T F. Zhou, G X. Zhong

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Yaojialing zinc-gold polymetallic deposit is a newly discovered, large skarn deposit in the Middle-Lower Yangtze metallogenic belt, East China. It is located in the transitional zone between the Tongling uplift block and the Fanchang faulted basin. It is mainly hosted in the contact zone between early Cretaceous granodiorite porphyry and Carboniferous-Triassic limestone, or occurs in limestone xenoliths within the intrusion. Skarn and stratabound massive sulfide orebodies are the primary ore styles. Sulfide ?34SV-CDT values indicate a magmatic sulfur source, in common with most deposits in the Tongling block. Calcite d13CV-PDB and d18OV-SMOW ratios reveal that marine carbonates were the major source of carbon in late-stage hydrothermal fluids. The calcite probably formed during interaction between magmatic fluids and carbonate wall rock.CITATION:Zhong, G X, Zhou, T F and Chang, Z S, 2015. Geology, chronology and isotope geochemistry of the Yaojialing zinc-gold deposit, Tongling ore district, Anhui Province, China, in Proceedings PACRIM 2015 Congress, pp 457–462 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By AMIRA P588 Research Team

This contribution summarises new knowledge and data, obtained during a three year ARCAMIRA funded research project, on the mineralogical and geochemical characteristics of hydrothermal alteration associated with low sulfidation, gold-silver epithermal deposits. These data are used to develop exploration vectors for use at both deposit and district scales, plus techniques have been established to distinguish ore grade epithermal systems from barren or low grade systems. Deposits investigated were Ladolam, Papua New Guinea, Gosowong and Mt Muro, Indonesia, Cerro Vaguardia, Argentina and Bimurra and Twin Hills, Australia.

Jan 1, 2005

By G B. Arehart

The Midas epithermal system is one of the larger low-sulfidation epithermal vein systems discovered in the western US in recent years, containing in excess of 3 Moz of gold (premining). The deposit is spatially and temporally related to bimodal volcanism in the Northern Nevada Rift; dates on igneous rocks (16 - 14.7 Ma) bracket the age of high grade veins (15.3 Ma). Hydrothermal alteration at Midas is typical of epithermal systems, comprising proximal potassic through distal propylitic assemblages; in contrast to many epithermal systems, Midas has minimal development of wallrock illite/sericite. Mineral assemblages are clearly zoned on the vein structures that acted as focal planes for fluid upflow. Geochemical zoning patterns also show this zoning. Metals were deposited in open-space veins as the result of boiling of hydrothermal fluids; multiple episodes of crustiform mineral deposition are documented in the vein textures. The major vein minerals include quartz, adularia, calcite, selenides and sulfides, with electrum as the primary ore mineral. REE patterns for vein material are similar to patterns for coeval rhyolites, but distinctly different from patterns of the host rocks. Stable isotope data are consistent with meteoric water as the dominant ore fluid. Combined REE and stable isotope data suggest that fluid from which the main ore-bearing stage of the veins was deposited was slightly lower pH than other stages.

Jan 1, 2005

The Douglas mineral sands deposit is located 75 km north of Hamilton in western Victoria, Australia. The deposit was discovered in the late 1990s by Basin Minerals Limited and purchased by Iluka Resources Ltd in 2002. Prestrip mining commenced in December 2004, with ore mining commencing in August 2005. Douglas is the first of several projects being implemented by Iluka Resources Ltd in the Murray Basin, with all heavy mineral concentrate planned to be treated at the companyÆs mineral separation plant in Hamilton. The mineralisation at Douglas lies along the south-eastern margin of the Murray Basin. It is hosted by marine Pliocene Loxton-Parilla Sands and consists of three discrete deposits; Bondi Main, Bondi West and Bondi East. The mineralised sediments dip at a low angle to the west and lie unconformably beneath a veneer of top soil (50 - 100 mm) and subsoil (up to 600 mm) and between three to 12 m of overburden. The barren overburden, characterised by high clay content (<53 ¦m material) generally provides a stark contrast to the sandy ore, which is between 1 m (parts of Bondi East) and 15 m (Bondi Main) thick. Both overburden and ore are removed utilising standard dry mining techniques using both scraper-bulldozer and truck-excavator combinations. All ore is delivered to run-of-mine (ROM) stockpiles before being reclaimed by front end loader into the processing plant. Grade control at Douglas is based around visual dig control aided by high precision survey, which enables accurate reference to the resource drilling and block model data. Vertical excavator faces, inclined scraper faces plus regular test pits and trenches provide opportunities for in pit mapping and sampling. This data is used to refine not only the resource estimate for Douglas but also the drilling, interpretation and resource modelling methods used for similar deposits across the basin. The foundations of the geological reconciliation process at Douglas are the in pit surveys undertaken each time the mining fleet has completed building a ROM stockpile. These surveys and the subsequent interrogation of resource models enable robust estimations of the heavy mineral content of the stockpiles, which are subsequently used to predict the daily input grades into the plant during their reclamation. Reconciliation of this daily data is then undertaken at the end of each month against metallurgical production data and plant balances. Learnings and results from the reconciliation process are used to further refine subsequent resource models and modelling methods.

Jan 1, 2009

Recent well-publicised problems with the start-up of new mining projects have continued to feed the perception that the mining business in general and Ore Reserves in particular are a poor risk. New mines commonly experience difficulties when the true variability of ore characteristics becomes apparent during commissioning. At this critical stage, the impact of lower metal recovery, reduced throughput or increased consumption of reagents and energy can have a catastrophic effect on economic returns, as illustrated by the premature closure of some operations. There appear to be several common reasons contributing to the poor performance of mining projects, of which three are examined here: lack of early risk assessment before feasibility studies are started, inadequate sampling for metallurgical test work and variability of the run-of-mine (ROM) ore. An underlying feature of these issues is the lack of effective interaction between geologists, mining engineers and metallurgists/ process engineers. Geologists need to be more aware of ore processing issues and the range of characteristics that need to be considered as part of the resource estimate. Metallurgists need a greater understanding of the variability of the run of mine ore in terms of all the characteristics that influence the design and operation of the plant. Mining engineers need to determine the short-term variability of the ore in the mine schedule, so that there is confidence that the quality of the run-of-mine ore will be within the design specifications of the plant. A substantial overlap between these disciplines and sharing of areas of responsibility is necessary if these and other technical problems are to be better understood, production estimates are to be improved and commercial risks are to be reduced. Although the JORC Code (1999) provides guidelines for reporting all the issues that are material to an Ore Reserve estimate, some issues are rarely fully addressed in Ore Reserve reports. In particular there is no formal requirement for a metallurgist to assure his or herself of the appropriateness of the Ore Reserve classification. Consequently the level of uncertainty related to recovered grade and ore processing characteristics may be understated. It is suggested that to meet the concerns of bodies funding new mineral developments a stronger multi-disciplinary approach to the analysis of mineral deposits and reporting of Ore Reserves is required. The culmination of this approach would be the formal requirement for a geologist, mining engineer and a metallurgist to co-sign Ore Reserve reports.

Jan 1, 2002

By B Xiao, J Yang, H Chen

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Tuwu-Yandong Cu deposit, located in the East Tianshan mountains in the eastern section of the Central Asian Orogenic Belt, is the largest and economically most important porphyry Cu deposit in Xinjiang, China. It contains ~3 Mt of copper at an average grade of 0.46 per cent Cu and 0.2 g/t Au, with significant amounts of Mo and Ag. The deposit is mainly hosted in the Carboniferous Qi’eshan Group and plagiogranite porphyry, and is controlled by faults that are east–west-, north-west- and north-east-trending. Ore minerals in the Tuwu-Yandong deposit are dominated by pyrite, chalcopyrite and molybdenite, with minor bornite, chalcocite, magnetite, sphalerite and galena. Gangue minerals are mainly composed of quartz, sericite, chlorite, epidote, anhydrite, gypsum, muscovite, biotite, phosphorite, sphene, dolomite, actinolite, barite, albite and calcite. Based on the megascopic and microscopic textural relationships and mineral assemblages, five stages of hydrothermal alteration and hypogene mineralisation are recognized in the Tuwu-Yandong Cu deposit: the potassic stage, propylitic stage, phyllic stage, late veins stage and supergene stage. Most of the copper was deposited during the phyllic stage, along with less molybdenite.CITATION:Xiao, B, Chen, H, Wang, Y and Yang, J, 2015. Geology, mineralisation and alteration of the Tuwu-Yandong porphyry Cu deposit, north-west China, in Proceedings PACRIM 2015 Congress, pp 641–644 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015