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1
Whitfield, Derek. "The genesis and controls of gold mineralization south of Rehoboth, Namibia." Thesis, Rhodes University, 1991. http://hdl.handle.net/10962/d1005560.
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Gold mineralization is hosted within gossanous quartz-haematite veins in volcano-sedimentary lithologies of the Klein Aub - Rehoboth basin of the Irumide Belt, Namibia. Mineralization and hydrothermal alteration are restricted to deformed lithologies particularly the metasediments. Lithological relationships, geochemistry and metallogenic characteristics of the Irumide Belt suggest an intra-continental rift setting. Copper mineralization is well known along the length of the belt, from Klein Aub in the southwest to Ghanzi in the northeast, whereas gold mineralization appears restricted to the Klein Aub Rehoboth basin. The gold is envisaged as having being leached initially from graben fill sequences during rift closure and basin dewatering. Location of the mineralization is strongly controlled by structure and lithological contact zones. Such zones are percieved as having acted as conduit zones for escaping mineralized fluids during basin closure and deformation. Apart from the lack of an effective mineralizing trap, all features consistent with the development of an ore deposit are present. The largest mineralization traps within the area studied are shear zones followed by lithological contact zones. The Mebi and Blanks gold mines are developed over large shear zones while the Swartmodder and Neuras gold mines are situated over mineralized lithological contacts. The Swartmodder copper mine yielded ore from a mineralized schist enclave within granite. Copper and gold occurrences are attributed to two contrasting styles of mineralization. Copper mineralization is suggested to have developed during initial rifting of the belt (ie. stratabound sedimentary exhalative type), while the gold and minor copper resulted from rift closure and basin dewatering. Although no economical orebody was realized during the course of this study a model is proposed for the development of mineralization within the Irumide basement lithologies as a working hypothesis for future exploration.
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Morasse, Suzanne. "Geology, structure and timing of gold mineralization at the Kiena deposit, Val d'Or, Québec." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0005/NQ31942.pdf.
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Gendall, Ian Richard. "The porphyry copper system and the precious metal-gold potential." Thesis, Rhodes University, 1994. http://hdl.handle.net/10962/d1005604.
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It has been established that porphyry copper/copper-gold deposits have formed from I Ma to 2 Ga ago. Generally, they are related to the Mesozoic-Cenozoic interval with few reported occurrences from the Palaeozoic or Precambrian. A reason cited is the erosion of these deposits which are often related to convergent plate margins and orogenic belts. Observations of the alteration and mineralisation within and around porphyry copper/copper-gold systems have been included in numerous idealised models. These alteration and mineralisation patterns are dependent on the phases of intrusion, the tectonic setting and rock type, depth of emplacement and relationship to coeval volcanics, physiochemical conditions operative within and surrounding the intrusive and many other mechanical and geochemical conditions. Island arc and cratonic arc/margin deposits are generally considered to be richer in gold than their molybdenum-rich, intra-cratonic counterparts. Metal zonation may occur around these copper/copper-gold deposits, e.g. copper in the core moving out to silver, lead, zinc and gold. This zonation is not always present and gold may occur in the core, intermediate or distal zones. Examples of gold-rich porphyry deposits from British Columbia, Chile and the SW Pacific Island regions suggest gold is closely associated with the potassic-rich zones. Generally these gold-rich zones have greater than 2% magnetite and a high oxygen fugacity is considered to be an important control for gold deposition. High Cl contents within the magma are necessary for gold mobility within the host intrusive centres. Beyond this zone HS₂ becomes an important transporting ligand. Exploration for porphyry copper-gold deposits includes an integrated geological, geophysical and geochemical approach. Petrographic work through to Landsat imagery may be used to determine the chemical conditions of the system, ore association, favourable structural zones and alteration patterns, in order to focus exploration activities.
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Hastings, Matthew H. "Relationship of base-metal skarn mineralization to Carlin-type gold mineralization at the Archimedes gold deposit, Eureka, Nevada." abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1460760.
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Skead, Michael Bethel. "Geological characteristics of selected disseminated sediment-hosted gold deposits in Nevada, U.S.A. : in search of an exploration model." Thesis, Rhodes University, 1995. http://hdl.handle.net/10962/d1007414.
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Sediment-hosted disseminated gold deposits in Nevada, western United States are major gold sources and contain reserves in excess of 1 500 metric tons of gold (Percival et aI., 1988). Discovery of these deposit types continues at a pace, with Placer Dome announcing a mojor discovery, Pipeline, to the south of the Gold Acres Mine, along the Battle Mountain - Eureka Trend in 1994 (The Northern Miner, 1994). Host sediments favoured for disseminated gold mineralisation are thinly bedded silty limestones , carbonate debris flows and to a lesser extent shale, chert and sandstone. The distribution of mineralisation is controlled essentially by the intersection of high-angle faults, which acted as conduits for hydrothermal fluids, with favourable host lithologies, anticlines, low-angle faults and other high-angle faults. Geochemical signature for these deposits is simple being Au, Ag, As, Sb, Hg, Tl, Te, F and Ba, but individual element concentrations vary greatly between and within deposits. Age of mineralisation is cause for considerable debate, and ages ranging between isotopic dates of approximately 117 Ma to early to mid-Tertiary (30-40 Ma) are proposed. Most of these deposits are situated along three major trends namely the Carlin, Battle Mountain - Eureka and Getchell trends. The Battle Mountain - Eureka trend and, to a lesser extent the Carlin trend, are defined by major linear aeromagnetic and gravity anomalies , which are believed to reflect deep-seated structures. Most deposits are hosted in autochthonous Devonian, thinly bedded, silty limestones that occur as windows through what is believed to be allochthonous Ordovician siliciclastic sediments, which were transported from west to east along the Roberts Mountains thrust during the late-Devonian Antler Orogeny. However, recent fossil dating of what were thought to be Ordivician siliciclastic sediments, gives a Devonian age. This questions the age of Ordivician sediments at the other deposits and the interpretation of the structural windows in which deposits are located. Fault-bounded, proximal, carbonate debris-flow breccias are now recognised as a major host to mineralisation. These debris flow breccias, together with interbedded carbonate and siliciclastic sediments, carbonaceous sediments and soft sediment deformation are all characteristics of lithologies in pull-apart basins which develop along a major strike slip faults. It is proposed that sediment-hosted disseminated gold mineralisation is controlled by the distribution of deep-seated long-lived, predominantly right-lateral strike-slip faults. It is along these strike-slip faults that syn-sedimentary pull-apart basins developed, within which sediments favoured by epigenetic gold mineralisation were deposited. These pull-apart basins were then overprinted by post-depositional extensional structures, such as negative flower structures. Igneous intrusions and hydrothermal cells have exploited these extensional structures in both compressional and extensional regional tectonic regimes. This model explains the characteristics of the host sediment at many of the deposits, the spatial relationship between igneous intrusion and mineralisation, spanning the period Cretaceous through to mid-Tertiary, the distribution of deposits as districts along major regional trends and why hydrothermal activity is noted between deposit districts but with no complementary mineralisation. Mineralisation is controlled predominantly by high angle structures and although the recent age for mineralisation at the Betze/Post deposit is ~ 117 Ma (Arehart et aI., 1993a), placing it in the compressional Sevier Orogeny, these high-angle structures would be developed within local extensional tectonic domains as described above. This model can, and should, be applied to other areas of the world where similar geological features exist. In exploring for these deposits in Nevada the distribution of Ordovician siliciclastic sediments should be reviewed, especially where spatially associated with deep regional structures. Ordovician sediments have historically been regarded as unfavourable, hence large areas for potential exploration have been ignored but with new ages for these sediments this opens large areas for potential discoveries.KMBT_363
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Veselinović, Milica. "Genetic models for epithermal gold deposits and applications to exploration." Thesis, Rhodes University, 1992. http://hdl.handle.net/10962/d1005562.
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Epithermal gold deposits are the product of large-scale hydrothermal systems in tectonically active regions. They form at shallow crustal levels where the physico-chemical conditions change abruptly. Two major groups of epithermal gold deposits can be distinguished based on their genetic connection with: A) Copper-molybdenum porphyry systems and B) Geothermal systems related to volcanic centres and calderas. Epithermal gold deposits connected with geothermal systems encompass three major types: adularia-sericite, acid-sulphate and disseminated replacement (the Carlin-type). Their essential ingredients are: high heat source which leads to convection of groundwater in the upper crust; source of hydrothermal fluid, metals and reduced sulphur; and high-permeability structures which allow fluid convection and metal deposition. Mixing of these ingredients leads to the formation of epithermal gold deposits throughout crustal history, without any restriction on age. The ores were deposited from near-neutral (adularia-sericite type and some of the Carlin-type) to acidic (acid-sulphate type and porphyry-related epithermal gold deposits), low-salinity, high C0₂ and high H₂S fluids, which were predominantly meteoritic in origin. The transport capability of deep fluids in epithermal hydrothermal systems may be shown to be dependent largely on their H₂S content and, through a series of fluid mineral equilibria, on temperature and on C0₂ content. The most common mechanisms of ore deposition are boiling (phase separation), mixing of fluids of different temperatures and salinities, reaction between them and wall rocks, dilution and cooling. An understanding of genetic models for epithermal gold deposits provides the basis for the selection of favourable areas for regional to prospect-scale exploration.
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Mann, P. L. "Surficial placer gold deposits." Thesis, Rhodes University, 1994. http://hdl.handle.net/10962/d1018245.
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This review summarises the factors which control the formation and distribution of surficial gold placer deposits. Regional tectonic and climatic conditions as well as gold source are considered. The characteristics of eluvial, alluvial, marine, glacial and fluvioglacial gold placer deposits are described. Particular attention is paid to the gold grains within these placers. These gold grains have a distinctive morphology and chemical composition which reflect the manner in which they were transported, deposited and concentrated within the placers. The knowledge of the processes which lead to the formation and location of surficial gold placers is then used to guide exploration and target potential deposits, which can then be evaluated.
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Campbell, Keith Bryan. "The geology, alteration, and mineralization of the True North gold deposit, Fairbanks, Alaska." abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3239880.
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Breedt, Machiel Christoffel. "Gold exploration in tropical and sub-tropical terrains with special emphasis on Central and Western Africa." Thesis, Rhodes University, 1996. http://hdl.handle.net/10962/d1005578.
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The aim of this dissertation is an attempt to' provide a general guide for future gold exploration in tropical and sub-tropical terrains. The dissertation includes a brief discussion of the various exploration techniques used in regional and local exploration. This provide the necessary background knowledge to discriminate between the constraints and applications and to be able to select the techniques which are more suitable for gold exploration in tropical and sub-tropical terrains. Weathering, gold geochemistry and soil formation, fields often neglected, are emphasized to illustrate the importance of the mobility and dispersion of gold in the weathering of the lateritic soil profile. A sound knowledge and experience in regolith mapping is to the advantage of the explorationist. Case studies with special emphasis on Central- and Western Africa are included to illustrate the effectiveness of some of the gold exploration techniques in tropical and sub-tropical terrains. Gold exploration is a highly complex and demanding science and to be successfull involves the full intergration of all geological, geochemical and geophysical information available. An intergrated exploration method and strategy would enhance the possibility of making viable discoveries in this highly competative environment where our mineral resources become more depleted every day. Where applicable, the reader is refered to various recommended literature sources to provide the necessary background knowledge which form an integral part of gold exploration.
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Sener, A. K. "Characteristics, distribution and timing of gold mineralisation in the Pine Creek Orogen, Northern Territory, Australia /." Connect to this title, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0102.
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Harlap, Ariel. "Alteration and ammonium enrichment vectors to low-sulphidation epithermal mineralization : insights from the Banderas gold-silver prospect." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112633.
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The alteration at the low-sulphidation epithermal Banderas Au-Ag prospect, Guatemala, was characterized using a portable infrared mineral analyzer (PIMA) spectrometer and shown to comprise illite, buddingtonite and, on surface, kaolinite associated with gold mineralization. The Spextract python program, developed by the author, was used to measure variations in the short-wave infrared spectra (SWIR) which were then mapped as equal-area-of-influence or voronoi diagrams. Voronoi maps of the 2200 and 2350 nm absorption features, position and depth, respectively, for illite and 1560 and 2120 nm feature depths for buddingtonite indicate that illite crystallinity and ammonium alteration intensity increase towards gold mineralization. The latter observation suggests that gold transport and deposition may have been controlled by ammonia complexation. At conditions likely to have prevailed during mineralization, i.e., temperatures between 150° and 250°C, a pH between 5 and 8.5, an oxygen fugacity ( fO2 ) near the hematite-magnetite buffer, a chlorinity of 0.5 m, a total sulfur activity of 0.001 m, and a total nitrogen activity of 0.004 m, AuNH3 +2 is the dominant ammonia complex and gold solubility at optimal pH- fO2 conditions reaches ∼65 ppm at 250°C. In contrast, the maximum solubility of gold as AuHS -2 , the species normally assumed to control gold transport in epithermal systems, is approximately four orders lower at 250°C; at 150°C the solubility of AuNH3 +2 and AuHS -2 are essentially the same, i.e., ∼9 ppb. A model for Au-Ag mineralization is proposed in which hydrothermal fluids were focused along NW-SE extensional faults and at the contacts of rhyolite domes and tuffs, and gold transport and deposition were controlled mainly by ammonia-dominated complexation and boiling-induced temperature decrease, respectively.
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Coxon, Brian Duncan. "Lateritisation and secondary gold distribution with particular reference to Western Australia." Thesis, Rhodes University, 1993. http://hdl.handle.net/10962/d1005586.
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Lateritisation is associated with tropical climates and geomorphic conditions of peneplanation where hydromorphic processes of weathering predominate. Laterites are products of relative (residual) and absolute(chemical) accumulation after leaching of mobile constituents. Their major element chemistry is controlled by the aluminous character of bedrock and drainage. Bauxitisation is characterised by residual gibbsite neoformation and lateritisation, by both residual accumulation and hydromorphic precipitation of goethite controlled by the redox front at the water table. The laterite forms part of a weathering profile that is underlain by saprock, saprolite, the mottled zone and overlain by a soil horizon. The secondary gold in laterites has its source invariably with mineralised bedrock. The distribution of secondary gold is controlled by mechanical eluviation and hydromorphic processes governed by organic, thiosulphate and chloride complexing. The precipitation of secondary gold is controlled by pH conditions, stability of the complexing agent and ferrolysis. Gold-bearing laterites are Cainozoic in age and are best developed on stable Archean and Proterozoic cratons that have suffered epeirogenesis since lateritisation. Mechanical eluviation increases in influence at the expense of hydromorphic processes as a positive function of topographic slope and degradation rate. Gradients greater than 10⁰ are not conducive for lateritisation, with latosols forming instead. High vertical degradation rates may lead to the development of stone lines. In the Western Australian case, post-laterite aridification has controlled the redistribution of secondary gold at levels marked by stabilisation of the receding palaeowater table. Mineable reserves of lateritic ore are located at Boddington, Westonia and Gibson toward the south-west of the Yilgarn Block. A significant controlling variable appears to be the concentration of chloride in the regolith. Based on the Boddington model, the laterite concentrates the following elements from bedrock gold lodes: i) Mo, Sb, W, Hg, Bi and Au as mobile constituents. ii) As and Pb as immobile constituents. Geochemical sampling of ferruginous lag after bedrock and laterite has provided dispersed anomalies that are easily identifiable. "Chalcophile corridors" up to 150 km in length are defined broadly by As and Sb but contain more discrete anomalies of Bi, Mo, Ag, Sn, W, Se or Au, in the Yilgarn Block. The nature of the weathered bedrock, the tabular distribution of secondary gold ore deposition and the infrastructural environment lends the lateritic regolith to low cost, open-cut mining. The western Australian lateritic-gold model perhaps can be adapted and modified for use elsewhere in the world.
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Sapiie, Benyamin. "Strike-slip faulting, breccia formation and porphyry Cu-Au mineralization in the Gunung Bijih (Ertsberg) mining district, Irian Jaya, Indonesia /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Thesis (Ph. D.)--University of Texas at Austin, 1998.Vita. Four folded plates in pocket. Includes bibliographical references (leaves 285-303). Available also in a digital version from Dissertation Abstracts.
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Ruiz, Párraga Juan Antonio. "Geology of the Chukar Footwall Mine, Maggie Creek District, Carlin Trend, Nevada /." abstract and full text PDF (UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1447807.
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Thesis (M.S.)--University of Nevada, Reno, 2007."May, 2007." Geological maps on eleven folded leaves in pocket. Includes bibliographical references (leaves 143-154). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2008]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.
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Hart, Craig Joseph Ronald. "Mid-Cretaceous magmatic evolution and intrusion-related metallogeny of the Tintina Gold Province, Yukon and Alaska." Connect to this title online, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0062/.
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Salier, Brock Peter. "The timing and source of gold-bearing fluids in the Laverton Greenstone Belt, Yilgarn Craton, with emphasis on the Wallaby gold deposit." University of Western Australia. School of Earth and Geographical Sciences, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0013.
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[Truncated abstract] The Laverton Greenstone Belt (LGB), located in the northeastern part of the Eastern Goldfields Province (EGP) of the Yilgarn Craton, Western Australia, has a total contained gold endowment of over 690t. An important feature of the gold deposits in the LGB is their close spatial association with granitoids, with many gold deposits located adjacent to, or hosted by, granitoids. Recently-proposed genetic models for Archaean orogenic gold deposits have emphasised the role of granitoids in the formation of ore-deposits, but differ significantly in the nature of that role. Some models suggest that the granitoids are a source of ore-fluids and solutes, whereas others suggest that granitoids exert an important structural control on gold mineralisation. Such competing genetic models for gold mineralisation variably propose either a proximal-magmatic or distal-metamorphic, or less commonly distal-magmatic, source for goldbearing fluids, or mixing of fluids from multiple sources. Isotope geochemistry and geochronological studies are used to constrain the source and timing of auriferous fluids at nine gold deposits in the LGB in an attempt to differentiate between conflicting genetic models. To overcome the lack of detailed deposit-scale geological constraints inherent to any regional study, hypotheses generated from regional datasets are tested in a detailed case-study of the Wallaby gold deposit. The Pb-isotope compositions of ore-related sulphides from deposits in the LGB plot along the line representing crustal-Pb in the Norseman-Wiluna Belt of the EGP, with individual deposits clustering with other nearby deposits based on their geographic location. This trend is similar to that recorded in the Kalgoorlie-Norseman region in the southern EGP, and is consistent with a basement Pb reservoir for gold-bearing fluids. As such, data are consistent with a similar fluid source for all gold deposits. The Nd and Sr isotopic composition of goldrelated scheelite in the LGB clusters very tightly. The inferred ore-fluid composition has a slightly positive εNd, similar to ore fluids at other gold deposits in the EGP for which a proximal magmatic source is highly improbable. As such, Sr and Nd data are consistent with a similar fluid source for the gold deposits analysed in the LGB, but cannot unequivocally define that source. The median S, C and O isotopic compositions of ore minerals from all nine different gold deposits studied in the LGB fall in a very narrow range
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Rankine, Graham M. "Gold metallogeny of Australia." Thesis, Rhodes University, 1987. http://hdl.handle.net/10962/d1004676.
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The gold metallogeny of Australia is predominantly confined to the Archaean and Palaeozoic Provinces. The Archaean gold occurrences are predominantly hosted in ultramafic-mafic dominated greenstone belts, with less associated tofelsic-volcanic and sedimentary sequences. Most gold occurrences are confined to shear zones or faults, and adjacent discoveries of economic laterite-hosted deposits, host rocks. Recent are presently under investigation and will supply a significant proportion of production in the future. The Proterozoic gold deposits of Australia , are confined to geosyncinal sequences, commonly turbidites (eg: Telfer), with other hydrothermal deposits associated directly to granites. An important feature of the North Australian Craton deposits, is the spatial association of most deposits to granite bodies, although a genetic link has not been established conclusively. The Roxby Downs deposit in South Australia is a unique occurrence of gold in association to copper, uranium and R.E.E. This deposit is tentatively related to intraplate alkaline-magmatism, with further work necessary. The most significant recent discovery of gold mineralization in Australia is in the Drummond Basin in Queensland. This epithermal is tentatively related to mineralization within the Georgetown Inlier. The latter mineralization is Permo-Carboniferous, in a Proterozoic (and possibly Archaean) sequence of schists. It is tentatively suggested that all the gold mineralization in northern Queensland may be related to single tectonic event, a feature which requires further study . Other mineralization in the Phanerozoic includes the turbidite-hosted metamorphogenic deposits of Victoria, the rift related deposits in New South Wales and magmatic related deposits in Queensland. The gold deposits in Australia may in the future be classified in a tectonogeological framework, similiar to the layout of this dissertation, particularly once further data becomes available on recent discoveries.
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Pelly, Frederick Douglas Peter. "Guidelines to the evaluation of selectively mined, open pit gold deposits during the exploration stage of mine creation." Thesis, Rhodes University, 1992. http://hdl.handle.net/10962/d1005582.
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This dissertation studies the evaluation of selectively mined, open pit gold deposits during the exploration stage of the mine's life. Since 1970 a large number of selectively mined, open pit gold mines have come into operation. The most common deposits include epithermal vein, mesothermal lode and laterite gold deposits. In general the deposits are characterized by small tonnages (1-20 million tonnes), relatively high grades (2-10 grams per tonne gold), submicroscopic to coarse gold, inexpensive mining, and both free milling and refractory ores.The key components that require evaluating during the exploration period are the deposit's geology, ore reserves, pit design, ore metallurgy and environmental impact. Feasibility studies are the main vehicle by which to report and guide the exploration programme. During the exploration period a company may undertake an initial (geological feasibility), second (preliminary mine feasibility) and third (final feasibility) delineation programme in order to gather sufficient data to justify a mine development decision. The responsibility of evaluating the mineral prospect lies primarily with the exploration geologist and mining engineer. Broad experience, a professional attitude, a thorough understanding of mining economics, and a high level of geological, engineering and technical skills are traits required by the evaluators. In order for mining companies to make sound investment decisions the geographical, geological, mining, metallurgical, environmental, marketing, political and financial aspects affecting the economic potential of the venture must be integrated so that the likely costs, risks and returns of the investment alternative are quantified. Ultimately, it is the economic analysis of these three items that determine whether the mineral prospect is developed into a mine I delineated further I retained until economic circumstances improve, or abandoned. To assess the costs, risks and returns, extensive use of the risk analysis is advocated throughout the exploration period . When combined with intelligent judgement of the intangible risk elements, the probabilistic distribution of discounted cash flows are invaluable in making sound investment decisions. However, the economic analysis is only as good as the information on which it is founded. Accurate and representative field data is the most important prerequisite to successfully evaluating and developing a new mine.
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Doyle, Jessica B. "Geology and structure of Winters Creek, Jerritt Canyon District, Elko County, Nevada." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1447627.
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Gaspar, Luis Miguel Guerreiro Galla. "The Crown Jewel gold skarn deposit." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Dissertations/Summer2005/l%5Fgaspar%5F072805.pdf.
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Buckman, Solomon. "Tectonics and mineralization of West Junggar, NW China." Thesis, Click to view the E-thesis via HKUTO, 2000. http://sunzi.lib.hku.hk/hkuto/record/B43894306.
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Day, Stephen John. "Sampling stream sediments for gold in mineral exploration, southern British Columbia." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/27869.
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The problems encountered by mineral explorationists when sampling stream sediments for gold were investigated by considering the sparsity of free gold particles and their tendency to form small placers at certain locations in the stream bed.
Fourteen 20-kg samples of -5-mm sediment were collected from contrasting energy and geochemical environments in five streams draining gold occurrences in southern British Columbia. The samples were sieved to six size fractions (420 µm to 52 µm) and gold content was determined by neutron activation analysis following preparation of two density fractions using methylene iodide. Gold concentrations were converted to estimated number of free gold particles and the Poisson probability distribution was used to show that much larger field samples (>100 kg of -1 mm screened sediment) would be required to reduce random variability due to nugget effects to acceptable levels. However, in a comparison of conventional sampling methods, the lowest probability of failing to detect a stream sediment gold anomaly is obtained using the sampling method described in this study.
Small-scale placer formation was investigated by collecting twenty 60-kg samples of -2-mm sediment from ten locations along five kilometres of Harris Creek in the Okanagan region, east of Vernon. Samples were prepared and analysed as described above though heavy-mineral concentrates were only prepared for two size fractions. Gold was found to be considerably enriched in sandy-gravel deposits compared to sand deposits, with the effect decreasing as sediment size decreased. The level of enrichment varies on the stream in response to changing channel slope and local hydraulic conditions. Gold anomaly dilution is apparent in sand deposits but not apparent in sandy-gravel deposits since gold is preferentially deposited in gravels as channel slope decreases. These results are presented in the framework of H.A. Einstein's sediment transport model.
Sediment collected from gravels may represent the best geochemical sample since placer-forming processes produce high gold concentrations, however in very high energy streams, the small quantities of fine sediment in gravels may lead to unacceptable nugget effects. In the latter case, a sample collected from a sand deposit is a satisfactory alternative.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Sibbick, Steven John Norman. "The distribution and behaviour of gold in soils in the vicinity of gold mineralization, Nickel Plate mine, southern British Columbia." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28862.
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Sampling of soils and till are conventional methods of gold exploration in glaciated regions. However, the exact nature of the residence sites and behaviour of gold within soil and till are poorly known. A gold dispersion train extending from the Nickel Plate mine, Hedley, southwest British Columbia, was investigated in order to determine the distribution and behaviour of gold within soils developed from till.
Three hundred and twelve soil, till and humus samples (representing LFH, A, B and C horizons) were collected from fifty-two soil pits and thirty-four roadcut locations within the dispersion train. Soil and till samples were sieved into four size fractions; the resultant -212 micron (-70 mesh) fraction of each sample was analysed for Au by FA-AAS. Humus samples were ground to -100 micron powder and analysed for Au by INAA. Based on the analytical results, each LFH, A, B and C horizon was subdivided into anomalous and background populations.
Detailed size and density fraction analysis was carried out on soil profiles reflecting anomalous and background populations, and a mixed group of samples representing the overlap between both populations. Samples were sieved to six size fractions; three of the size fractions (-420+212, -212+106, -106+53 microns) were separated into two density fractions using methylene iodide and analysed for Au by FA-AAS. The Au content of the -53 micron fraction was analysed by FA-AAS and cyanide extraction - AAS.
Results indicate that the Au content of soil profiles increase with depth while decreasing with distance from the minesite. Heavy mineral concentrates and the light mineral fraction Au abundances reveal that dilution by a factor of 3.5 occurs within the till over a distance of 800 metres. However, free gold within the heavy mineral fraction is both diluted and comminuted with distance. Recombination of size and density fractions indicate that the Au contents of each size fraction are equivalent; variation in Au abundance is not observed with a change in grain size. Seventy percent of the Au in the -53 micron fraction occurs as free gold.
Chemical activity has not altered the composition of gold grains within the soil profiles. Compositional and morphological differences between gold grains are not indicative of glacial transport distance or location within the soil profile. Relative abundances of gold grains between sample locations can be used as an indicator of proximity to the minesite. The sampling medium with the best sample representivity and contrast between anomalous and background populations is the -53 micron (-270 mesh) fraction of the C horizon. Geochemical soil sampling programs in the vicinity of the Nickel Plate mine should collect a minimum mass of 370 grams of -2000 micron (-2 mm) soil fraction in order to obtain 30 grams of the -53 micron fraction.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Linklater, Michael Anthony Leonard Flanders. "The exploration for and possible genesis of, some Archaean granite/gneiss-hosted gold deposits in the Pietersburg granite-greenstone terrane." Thesis, Rhodes University, 1992. http://hdl.handle.net/10962/d1005557.
Full textAbstract:
Abstract The gold mineralization event within Archaean granite-greenstone terranes occurred during the late Archaean, and followed the intrusion of syn- to late-tectonic granitic plutons into previously deformed greenstone belts. An Archaean granite/gneiss-hosted gold deposit, in terms of this project, is classified as having a gold-assay cutoff of 1g/metric ton over widths of at least several metres, or higher grades over narrower widths and/or verbal descriptions that indicate such values. Fluid inclusion studies and isotopic data identify two possible origins for the auriferous fluids; namely magmatic and metamorphic. The exploration target according to the magmatic model, is a late-Archaean, hydrothermally altered, mineralized and fractured granitic intrusion preferably with a granodioritic or quartz-dioritic composition. The exploration target according to the metamorphic replacement model is a granitic stock that has intruded a zone of crustal weakness such as a shear zone, active during the late Archaean. Alternatively, the granitic intrusion should be affected by regionally extensive late-Archaean shearing. It should be hydrothermally altered, deformed and mineralized. Five areas within the Pietersburg granite-greenstone terrane were selected for the 'Regional Area Selection' phase of exploration for Archaean granite/gneiss-hosted gold deposits; namely Roodepoort, Waterval, Ramagoep, Moletsie and Matlala. Roodepoort contains a known granodiorite-hosted gold deposit; the Knight's Pluton, and served as an orientation survey for this project. The use and interpretation of LANDSAT images formed an integral part of exploration techniques; to assess their usefulness in the exploration of Archaean granite/gneiss-hosted gold deposits. Area selection criteria for granite/gneiss-hosted gold mineralization at Roodepoort are the major ENE-trending shear zone, the NNW-trending lineament and hydrothermal alteration, shearing, quartz-stockworks and sulphide mineralization within the Knight's Pluton. The origin of the gold within the Knight's Pluton is uncertain; both magmatic and metamorphic models are possibilities. Ongoing exploration is in progress at Roodepoort. The only area selection criterion for granite/gneiss-hosted gold mineralization at Waterval is the sericitized, subcropping granites located within trenches. Gold mineralization is insignificant. No area selection criteria for Archaean granite/gneiss-hosted gold mineralization were located at Ramagoep, Matlala and Moletsie. No further exploration is recommended for all these areas. The MES image interpretations were successful in identifying lineaments, granitic outcrops, greenstones, vegetation and soil cover. The Clay-iron images adequately differentiated betweeen iron-rich and clay-bearing areas. However, not all clay-bearing areas were associated with hydrothermal alteratian; field checks were necessary to discriminate between weathered granites and hydrothermally altered granites. The Wallis images served to locally enhance the contrasts of the MES and Clay-iron images.
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Miller, Lance Davison. "Tectonic evolution and structural control of auriferous veins in the Juneau gold belt, southeastern Alaska." Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186623.
Full textAbstract:
A portion of northern southeastern Alaska known as the Juneau gold belt is composed of a disparate assemblage of lithotectonic terranes which range in age from Paleozoic and perhaps older to Cretaceous. Five progressive deformational events associated with contractional tectonism began in the mid-Cretaceous time and continued well into the Tertiary. Widespread plutonism occurred in the region from Cretaceous through Tertiary time. Gold-bearing quartz vein systems in the Juneau gold belt formed within a 160-km-long by 5- to 8-km-wide zone along the western margin of the Coast Mountains, Alaska. The vein systems are localized in second and third order shear zones spatially associated with terrane-bounding, mid-Cretaceous thrust faults. Mesoscopic structures integrated with ⁴⁰Ar/ ³⁹Ar ages from vein sericite are interpreted to indicate that a fluid cycling event along the entire belt occurred between 56.5 and >52.8 Ma. Structural analysis of the vein orientations and geometries are interpreted to indicate that mineralization developed under a near-field stress regime of subhorizontal contraction along a west-southwest to east-northeast trending axis. The axis of extension plunged steeply to the southeast. Slight variations in the interpreted stress axes may have been the result of variations in fluid pressure. Post-mineralization deformation was associated with a dextral transpressive regime along the Denali-Chatham Strait fault system. Gold vein mineralization occurred during the latter stages of orogenesis. Fluid flow and subsequent vein development was temporally associated with changes in plate motion during Eocene time. Veining was also synchronous with exhumation and voluminous plutonism immediately inboard of the gold belt. These interacting tectonic events likely facilitated fault-valve action and vein development along now exhumed shear zones.
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Simango, Robert Zulu. "Gold exploration northeast of Ngundu Halt, northern marginal zone of the Limpopo Belt, Zimbabwe." Thesis, Rhodes University, 2004. http://hdl.handle.net/10962/d1005844.
Full textAbstract:
Gold exploration was conducted in northern margin, granulite-facies rocks of the Limpopo Belt. Methods used in the prospecting include drainage, soil and rock geochemistry, geophysical surveys, geological mapping, trenching and diamond drilling. These techniques successfully led to the discovery of two medium size, mesothermal gold deposits (Grid 2s and Grid 4). Objectives of this study were to (a) document the exploration methodology used; (b) describe the regional geology; (c) establish a mineral deposit model; (d) outline the methods and results of various exploration techniques; (e) outline follow-up procedures and evaluation of anomalies; and (f) discuss results of the exploration exercise and conclusions. The granulite-facies terrain comprises Charno-enderbites, mafic and felsic to intermediate metavolcanic rocks and meta-sediments. Renco Mine situated immediately east of the study area, was selected as the ore deposit model for the exploration program. Gold mineralization occurs in shear and thrust zones within an enderbite. The gold deposits are structurally controlled by a first-order, Sinistral transcrustal Mauch Shear Zone, which is parallel to a regional east-northeast penetrative foliation. The deposits are in dilation zones where the Mauch Shear (a) is intersected by a dextral east-west shear (Grid 2s), or (b) has a sinistral splay (Grid 4 and Renco). Close to these deposits, the Mauch Shear is in contact with a "greenstone belt", which is a possible source of crustal metamorphic ore fluids and gold. The Grid 2s deposit contains fine-grained, disseminated free gold, and small amounts of pyrrhotite, pyrite and chalcopyrite in quartz veins within third-order shears in K-feldspar granite. K-feldspar, sericitic, silicic, sulphidation and carbonate alteration characterizes the deposit, which has a proposed mantle-degassing model. The Grid 4 deposit is magmatic porphyry-type, with CuMo and Au in third- and fourth-order shears respectively. Mineralization comprises disseminated to semi-massive pyrrhotite, pyrite, chalcopyrite, sphalerite, bismuth, molybdenite and gold. Wall rock alteration includes biotitic, chloritic, silicic, sulphidation and carbonate. In Grid 2s, Grid 4 and Renco deposits, the alteration mineral assemblages are in three facies, which are granulite, amphibolte and greenschist. In the three deposits, the mineralization occurs with the amphibolite-facies, indicating post-peak, retrograde metamorphic conditions.Illustrations (maps) only available in print form at Cory Library
KMBT_363
Adobe Acrobat 9.54 Paper Capture Plug-in
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Dwyer, Gordon Bransby. "The geology of the Welkom Goldfield with special reference to the "A", "B" and Beatrix Reefs." Thesis, Rhodes University, 1993. http://hdl.handle.net/10962/d1005575.
Full textAbstract:
The first Witwatersrand gold deposits in the Orange Free State were discovered under younger cover rocks in the 1930's with the aid of drilling and geophysics. The Welkom gold deposits are found in the sedimentary rock sequences of the Central Rand Group, which represent unconformity bounded genetic packages. The structural configuration of the goldfield is one of a north to south trending synform that is split near it's axis by the De Bron and Homestead faults. The "B" Reef is a highly variable, erratically mineralised reef that lies on an unconformity at the base of the Spes Bona Formation. The "A" Reef Zone consists of several placers 1 including the "Reworked BPM" 1 the Witpan, the Uitsig, the Hanging Wall Grits and the Upper "A" Reef. The Beatrix Reef lies at the base of the Eldorado Formation on an unconformity surface overlying the Virginia Formation in the southern part of the Welkom Goldfield. The origin of gold in the Witwatersrand basin can be classified into the modified placer theory, the syngenetic theory and the epigenetic theory. From the distribution of basin edge unconformities it can be deduced that the Welkom fan depository was tectonically active on the western, southern and eastern margins during sedimentation. Palaeocurrent studies indicate that sediment was transported predominantly from the south and west. It is thought that the "B", "A" and Beatrix Reefs were all deposited in a braided stream environment. A multidisciplinary approach to ore evaluation of Witwatersrand deposits is considered to be the best method, where sedimentology, geostatistics and structural geology are used.
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Franey, N. J. "A geological model of shear zone gold deposits in the Pietersburg Greenstone Belt, South Africa." Thesis, Rhodes University, 1987. http://hdl.handle.net/10962/d1007190.
Full textAbstract:
The Pletersburg greenstone belt Is located In South Africa, about 300 km northeast of Johannesburg. It hosts a significant amount of gold mineralization and just over 1000 kg of gold have been produced from Its various reefs and secondary deposits. The greenstone belt is interpreted as an Archean ophiolite complex. It comprlses a volcano-sedimentary succession (the Pletersburg Group) which Is subdivided Into a basal greenstone sequence, interpreted as oceanic crust, and an upper sedimentary cover sequence. A number of major shear zones, which are thought to represent thrusts that developed during the subduction of the greenstone sequence, form an integral part of the stratigraphy . Four stages of deformation (D₁-D₄) and four phases of metamorphism (H₁-H₄) (three of which are correlatable with the peak stages of deformation) are recognized. The primary gold deposits are all shear zones related. but they are subdivided into greenstone, sedimentation and granIte-hosted types. Geographically, they occur In three distinct goldfields: Eerstellng, Roodepoort and Marbastad. The greenstone-hosted · Plenaar-Doreen shear complex Is In the Eersteiing goldfield and hosts eight gold occurrences. Within the complex, Girlie North Reef is the 640m-long "pay" section of the Girlie North shear zone. This reef is characterized, macroscopically, by a Quartz-carbonate-chlorite-sulphlde assemblage and, mlcroscoplcally, by the presence of tourmaline, arsenopyrlte and Au. Geochemical evidence Indicates that mineralizing fluids were H₂O and CO₂-bearing and rich In S, K and Al. The wall rock alteratlon was Isochemlcal but Is manifest as a change In mineralogy from a hornblende + plagioclase assemblage to an actlnollte/tremollte + Quartz + clay assemblage. This Is best developed In the hangIng wall of the reef and is thought to have been caused by hydrogen ion metasomatism. The Arsenopyrite Reef was one of the main sediment-hosted shear zone gold producers In the Harabastad goldfield. This reef Is Interpreted as the basal margin of a shear zone whose top contact Is probably represented by the Quartz Vein Reef. The shear zone consists predomonantly of quartz and carbonate, and the two "pay" reefs are characterized by tourmallne. arsenopyrite and Au. No wall rock alteration was identified In this study, Based on the mineralogy and geochemical signature of the Girlie Nortn Reef and the Arsenopyrite Reef, It Is proposed that both were formed at the $The Pletersburg greenstone belt Is located In South Africa, about 300 km northeast of Johannesburg. It hosts a significant amount of gold mineralization and just over 1000 kg of gold have been produced from Its various reefs and secondary deposits. The greenstone belt is interpreted as an Archean ophiolite complex. It comprlses a volcano-sedimentary succession (the Pletersburg Group) which Is subdivided Into a basal greenstone sequence, interpreted as oceanic crust, and an upper sedimentary cover sequence. A number of major shear zones, which are thought to represent thrusts that developed during the subduction of the greenstone sequence, form an integral part of the stratigraphy . Four stages of deformation (D₁-D₄) and four phases of metamorphism (H₁-H₄) (three of which are correlatable with the peak stages of deformation) are recognized. The primary gold deposits are all shear zones related. but they are subdivided into greenstone, sedimentation and granIte-hosted types. Geographically, they occur In three distinct goldfields: Eerstellng, Roodepoort and Marbastad. The greenstone-hosted · Plenaar-Doreen shear complex Is In the Eersteiing goldfield and hosts eight gold occurrences. Within the complex, Girlie North Reef is the 640m-long "pay" section of the Girlie North shear zone. This reef is characterized, macroscopically, by a Quartz-carbonate-chlorite-sulphlde assemblage and, mlcroscoplcally, by the presence of tourmaline, arsenopyrlte and Au. Geochemical evidence Indicates that mineralizing fluids were H₂O and CO₂-bearing and rich In S, K and Al. The wall rock alteratlon was Isochemlcal but Is manifest as a change In mineralogy from a hornblende + plagioclase assemblage to an actlnollte/tremollte + Quartz + clay assemblage. This Is best developed In the hangIng wall of the reef and is thought to have been caused by hydrogen ion metasomatism. The Arsenopyrite Reef was one of the main sediment-hosted shear zone gold producers In the Harabastad goldfield. This reef Is Interpreted as the basal margin of a shear zone whose top contact Is probably represented by the Quartz Vein Reef. The shear zone consists predomonantly of quartz and carbonate, and the two "pay" reefs are characterized by tourmallne. arsenopyrite and Au. No wall rock alteration was identified In this study, Based on the mineralogy and geochemical signature of the Girlie Nortn Reef and the Arsenopyrite Reef, It Is proposed that both were formed at the same time. Textural evidence Indicates that tourmaline, arsenopyrite and Au were all very late In the paragenesis of minerallzatlon. The presence of tourmaline also Indicates a probable granite association. It Is proposed that the maln gold mineralizing event was synchronous with the Intrusion of granitoids (and therefore also with (D₁-D₄) and (H₁-H₄) and that most of the Au was derived from felsic magma. Gold was partitioned Into a magmatic hydrothermal fluid and then transported into the greenstone belt as a chlorIde complex. These magmatiC fluids were channelled up shear zones whIch had already been mineralized with a quartz-carbonate-chlorlte - sulphide assemblage by previous metamorphic fluidS. generated during the dynamic (D₂-related) H₂-phase of metamorphism. The Au was then deposIted as the result of a change In a fluid variable, such as temperature, pH, f0₂, or the activity of Cl (some Au may have been transported In a sulphur complex and so the activity of reduced 5 could also have been Important).
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Mujdrica, Stefan. "Gold-bearing volcanic breccia complexes related to carboniferous-permian magmatism, North Queensland, Australia." Thesis, Rhodes University, 1994. http://hdl.handle.net/10962/d1005577.
Full textAbstract:
Gold-bearing volcanic breccia complexes are the major sources of gold in the Tasman Fold Belt System in north Queensland. The Tasman Fold Belt System represents the site of continental accretion as a series of island-arcs and intra-arc basins with accompanying thick sedimentation, volcanism, plutonism, tectonism and mineralisation. In north Queensland, the fold belt system comprises the Hodgkinson-Broken River Fold Belt, Thomson Fold Belt, New England Fold Belt and the Georgetown Inlier. The most numerous ore deposits are associated with calc-alkaline volcanics and granitoid intrusivesof the transitional tectonic stage of the fold belt system. The formation and subsequent gold mineralisation of volcanic breccia complexes are related to Permo-Carboniferous magmatism within the Thomson Fold Belt and Georgetown Inlier. The two most important producing areas are at Mount Leyshon and Kidston mines, which are high tonnage, low-grade gold deposits. The Mount Leyshon breccia complex was emplaced along the contact between CambroOrdovician metasedimentary and metavolcanic rocks, and Ordovician-Devonian I-type granitoids of the Lolworth-Ravenswood Block. The Kidston breccia complex is located on a major lithological contact between the Early to Middle Proterozoic . Einasleigh Metamorphics and the Silurian-Devonian Oak River Granodiorite. The principal hosts to the gold mineralisation at the Mount Leyshon and Kidston deposits, are breccia pipes associated with several episodes of porphyry intrusives. The goldbearing magmatic-hydrothermal and phreatomagmatic breccias post-date the development of a porphyry-type protore. The magmatic-hydrothermal breccias were initially emplaced without the involvement of meteoric-hydrothermal fluids, within a closed system. Later magma impulses reached higher levels in the cooled upper magma chamber, where meteoric water invaded the fracture system. This produced an explosive emplacement of phreatomagmatic breccias, as seen at Mount Leyshon. Widespread sericitisation and pyrite mineralisation are common, with cavity fill, disseminated and fracturelveincontrolled gold and base metal sulphides. The Kidston and Mount Leyshon breccia complexes have hydrothermal alteration and mineralisation characteristics of the 'Lowell-Guilbert Model'. However, the argillic zone is generally not well defined. The gold travelled as chloride complexes with the hydrothermal fluids before being deposited into cavities and fractures of the breccias. Later stage epithermal deposits formed at the top of the breccia complexes that were dominantly quartz-adularia-sericite-type. The erosion, collapse and further intrusion of later porphyry phases allowed the upper parts of the breccia complexes to mix with the lower hydrothermal systems. Exploration for gold-related volcanic breccia complexes is directed at identifying hydrothermal alteration. This is followed by detailed ground studies including geological, mineralogical, petrological and geochemical work, with the idea of constructing a 'model' that can be tested with subsequent subsurface work (e.g. drilling). Geomorphology, remote sensing, geochemistry, geophysics, petrology, isotopes and fluid inclusions are recommended exploration techniques for the search of gold-bearing volcanic breccia complexes. Spectral remote sensing has especially become an important tool for the detection of hydrothermal alteration. Clay and iron minerals of the altered rock, within the breccia complexes, have distinctive spectral characteristics that can be recognisable in multispectral images from the Landsat thematic mapper. The best combination of bands, when using TM remote sensing for hydrothermally altered rock, are 3/5/7 or 4/5/7. The breccia complexes have exploration signatures represented as topographic highs, emplaced within major structural weaknesses, associated I-type granitic batholiths, early potassic alteration with overprint of sericitic alteration, and an associated radiometric high and magnetic low. The exploration for gold-bearing volcanic breccia complex deposits cannot be disregarded, because of the numerous occurrences that are now the major gold producers in north Queensland.
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De, Klerk Ian Duncan. "The nature and origin of gold mineralization in the Tugela valley, Natal Structural and Metamorphic Province." Thesis, Rhodes University, 1991. http://hdl.handle.net/10962/d1005591.
Full textAbstract:
The project area is situated within the Tugela Valley, located in the Northern Marginal Zone of the Natal Structural and Metamorphic Province, and this work outlines the different styles of gold mineralization found in the Tugela Valley. Two different styles have been recognized and both have economic significance:- 1) Epigenetic shear zone-hosted gold occurs in late-stage relatively undeformed thin quartz veins confined to shear zones, and is present in both the greenschist facies Natal Thrust Belt and the amphibolite facies Natal Nappe Complex. However the vast majority of these occurrences are concentrated within the thrust front (i.e. the Natal Thrust Belt). The gold grades (up to 7 g/t) and the hydrothermal alteration assemblages associated with the epigenetic deposits have been documented. 2) An as yet unrecognized occurrence of syngenetic gold mineralization is found associated with the sediment-hosted exhalative massive, to semi-massive, sulphides of the iThuma prospect, located within the amphibolite facies Natal Nappe Complex. Here gold (up to 3 g/t) is concentrated together with the main sulphide are, as well as some gold enrichment (230ppb) in the hydrothermally altered footwall feeder pipe. It is proposed that the epigenetic mineralization was formed as a consequence of the northward directed abduction of the major thrust slices of the Natal Nappe Complex. This increased the permeability of the rocks and provided channelways for the focussing of fluids. Deposition took place at the thrust front where metamorphic hydrothermal fluids interacted with meteoric water.
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Scott, John G., and n/a. "Structural controls on gold - quartz vein mineralisation in the Otago schist, New Zealand." University of Otago. Department of Geology, 2006. http://adt.otago.ac.nz./public/adt-NZDU20070412.160816.
Full textAbstract:
Hydrothermal fluid flow is spatially and genetically associated with deformation in the earth�s crust. In the Otago Schist, New Zealand, the circulation of hydrothermal fluids in the Cretaceous formed numerous mesothermal gold-quartz vein deposits. Otago schist rocks are largely L-S tectonites in which the penetrative fabric is the product of more than one deformation phase/transposition cycle. Regional correlation of deformation events allowed mineralised deposits to be related to the structural evolution of the Otago Schist. Compilation of a detailed tectonostratigraphy of New Zealand basement rocks reveals that extensional mineralisation correlates with the onset of localised terrestrial fanglomerate deposition, thermal perturbation and granitic intrusion that mark the beginning of New Zealand rifting from the Antarctic portion of Gondwana.
Laminated and breccia textures in mineralised veins suggest that host structures have experienced repeated episodes of incremental slip and hydrothermal fluid flow. However, analysis of vein orientation data in terms of fault reactivation theory (Amontons Law) shows that most deposits contain veins that are unfavourably oriented for frictional reactivation. Repeated movement on unfavourably oriented structures may involve dynamic processes of strain refraction due to competency contrasts, the effect of anisotropy in the schist, or localised stress field rotation.
Deposits have been classified on the basis of host structure kinematics at the time of mineralisation into low angle thrust faults, and high angle extensional fault - fracture arrays. Low angle deposits have a mapped internal geometry that is very different from conventional imbricate thrust systems. This study applied ⁴⁰Ar/�⁹Ar geochronology to selected deposits and has identified at least three distinct mineralisation events have occurred within the central axial belt during the Cretaceous. Relationships between radiometric apparent age and inferred crustal depth reveal that after metamorphism, the onset of cooling and rapid exhumation of the schist belt coincides temporally and spatially with the age of mineralisation and structural position of a regional scale low angle shear zone in Otago.
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Blamey, Nigel John Frederick. "The geology and evaluation of the "A"-reef at No.3 shaft, Western Holdings Mine, Welkom goldfield." Thesis, Rhodes University, 1992. http://hdl.handle.net/10962/d1005569.
Full textAbstract:
The "A" -Reef occurs within the Aandenk Formation of the Central Rand Group, Witwatersrand Supergroup, in the Welkom Goldfield. It comprises the Witpan and Uitsig Reefs which are both oligomictic conglomerates, and are exploited for their gold content by Anglo American Corporation. The main Witpan channel complex is orientated in a NW-SE direction and occurs close to No.3 Shaft of Western Holdings Mine where it is currently being mined. The Witpan Reef varies in thickness from 7-220cm, with lateral facies changes controlling the thickness. Within the reef, gold is associated with degradation surfaces, carbonaceous material, increase in pebble sphericity, and channel edges. Two channel edges have yielded the best gold values on No.3 Shaft although the potential for further payable gold lies in the recognition of sieve conditions. The potential also exists for extensions of the "carbon"-bearing Uitsig channel currently being mined on President Steyn Mine. The palaeo-environment proposed for formation of the Witpan Reef is a braidplain that was partly reworked by a brief transgression. Ore evaluation using geostatistics was considered a valid technique as the dataset is sufficiently well structured. Semi-variograms in the channel and across-channel directions differ markedly. It was found that variograms of gold in cmg/t lacked sufficient structure for modelling, however, log semi-variogram modelling followed by simple log-kriging and back-transformation, proved to be the most successful method. Owing to the morphology and distribution of gold within the reef, a geologically based geostatistical valuation method is proposed. The potential for further exploration of "A" -Reef depends on a substantially higher gold price. In this event, exploration of Uitsig Reef to the southwest of the current mining area is recommended as well as a new exploration strategy for Witpan Reef.
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Hodkiewicz, Paul. "The interplay between physical and chemical processes in the formation of world-class orogenic gold deposits in the Eastern Goldfields Province, Western Australia." University of Western Australia. Centre for Global Metallogeny, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0057.
Full textAbstract:
[Formulae and special characters can only be approximated here. Please see the pdf version of the abstract for an accurate reproduction.] The formation of world-class Archean orogenic gold deposits in the Eastern Goldfields Province of Western Australia was the result of a critical combination of physical and chemical processes that modified a single and widespread ore-fluid along fluid pathways and at the sites of gold deposition. Increased gold endowment in these deposits is associated with efficient regional-scale fluid focusing mechanisms and the influence of multiple ore-depositional processes at the deposit-scale. Measurement of the complexity of geologic features, as displayed in high-quality geologic maps of uniform data density, can be used to highlight areas that influence regional-scale hydrothermal fluid flow. Useful measurements of geological complexity include fractal dimensions of map patterns, density and orientation of faults and lithologic contacts, and proportions of rock types. Fractal dimensions of map patterns of lithologic contacts and faults highlight complexity gradients. Steep complexity gradients, between domains of high and low fractal dimensions within a greenstone belt, correspond to district-scale regions that have the potential to focus the flow of large volumes of hydrothermal fluid, which is critical for the formation of significant orogenic gold mineralization. Steep complexity gradients commonly occur in greenstone belts where thick sedimentary units overly more complex patterns of lithologic contacts, associated with mafic intrusive and mafic volcanic units. The sedimentary units in these areas potentially acted as seals to the hydrothermal Mineral Systems, which resulted in fluid-pressure gradients and increased fluid flow. The largest gold deposits in the Kalgoorlie Terrane and the Laverton Tectonic Zone occur at steep complexity gradients adjacent to thick sedimentary units, indicating the significance of these structural settings to gold endowment. Complexity gradients, as displayed in surface map patterns, are an indication of three-dimensional connectivity along fluid pathways, between fluid source areas and deposit locations. Systematic changes in the orientation of crustal-scale shear zones are also significant and measurable map features. The largest gold deposits along the Bardoc Tectonic Zone and Boulder-Lefroy Shear Zone, in the Eastern Goldfields Province, occur where there are counter-clockwise changes in shear zone orientation, compared to the average orientation of the shear zone along its entire length. Sinistral movement along these shear zones resulted in the formation of district-scale dilational jogs and focused hydrothermal fluid-flow at the Golden Mile, New Celebration and Victory-Defiance deposits. Faults and lithologic contacts are the dominant fluid pathways in orogenic gold Mineral Systems, and measurements of the density of faults and contacts are also a method of quantifying the complexity of geologic map patterns on high-quality maps. Significantly higher densities of pathways in areas surrounding larger gold deposits are measurable within 20- and 5-kilometer search radii around them. Large variations in the sulfur isotopic composition of ore-related pyrites in orogenic gold deposits in the Eastern Goldfields Province are the result of different golddepositional mechanisms and the in-situ oxidation of a primary ore fluid in specific structural settings. Phase separation and wall-rock carbonation are potentially the most common mechanisms of ore-fluid oxidation and gold precipitation. The influence of multiple gold-depositional mechanisms increases the potential for significant ore-fluid oxidation, and more importantly, provides an effective means of increasing gold endowment. This explains the occurrence of negative δ34S values in ore-related pyrites in some world-class orogenic gold deposits. Sulfur isotopic compositions alone cannot uniquely define potential gold endowment. However, in combination with structural, hydrothermal alteration and fluid inclusion studies that also seek to identify multiple ore-forming processes, they can be a useful indicator. The structural setting of a deposit is also a potentially important factor controlling ore-fluid oxidation and the distribution of δ34S values in ore-related pyrites. At Victory-Defiance, the occurrence of negative δ34S(py) values in gently-dipping dilational structures, compared to more positive δ34S(py) values in steeply-dipping compressional structures, is potentially associated with different gold-depositional mechanisms that developed as a result of fluid-pressure fluctuations during different stages of the fault-valve cycle. During the pre-failure stage, when fluids are discharging from faults, fluid-rock interaction is the dominant gold-depositional mechanism. Phase separation and back-mixing of modified ore-fluid components are dominant during and immediately after faulting. Under appropriate conditions, any, or all, of these three mechanisms can oxidize orogenic gold fluids and cause gold deposition. The influence of multiple gold-depositional mechanisms during fault-valve cycles at dilational jogs, where fluid pressure fluctuations are interpreted to be most severe, can potentially explain both the large gold endowment of the giant to world-class Golden Mile, New Celebration and Victory-Defiance deposits along the Boulder-Lefroy Shear Zone, and the presence of gold-related pyrites with negative δ34S values in these deposits. This study highlights the interplay that exists between physical and chemical processes in orogenic gold Mineral Systems, during the transport of ore fluids in pathways from original fluid reservoirs to deposit sites. Potentially, a single and widespread orogenic ore-fluid could become oxidized, and lead to the formation of ore-related sulfides with variable sulfur isotopic compositions, depending on the nature and orientation of major fluid pathways, the nature of wall-rocks through which it circulates, and the precise ore-depositional processes that develop during fault-valve cycles.
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Voicu, Gabriel. "Géologie, géochimie et métallogénie du gisement d'or Omai, Bouclier Guyanais, Amérique du Sud = Geology, geochemistry and metallogeny of the Omai Gold Deposit, Guiana Shield, South America /." Thèse, Montréal : Chicoutimi : Université du Québec à Montréal ;. Université du Québec à Chicoutimi, 1999. http://theses.uqac.ca.
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Hart, Craig J. R. "Mid-Cretaceous magmatic evolution and intrusion-related metallogeny of the Tintina Gold Province, Yukon and Alaska." University of Western Australia. Centre for Global Metallogeny, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0062.
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[Truncated abstract] The Tintina Gold Province (TGP) comprises numerous (<15) gold belts and districts throughout interior Alaska and Yukon that are associated with Cretaceous plutonic rocks. With a gold endowment of ∼70Moz, most districts are defined by their placer gold contributions, which comprise greater than 30 Moz, but four districts have experience significant increases in gold exploration with notable discoveries at Fort Knox (5.4 Moz), Donlin Creek (12.3 Moz), Pogo (5.8 Moz), True North (0.79 Moz), and Brewery Creek (0.85 Moz). All significant TGP gold deposits are spatially and temporally related to reduced (ilmenite-series) and radiogenic Cretaceous intrusive rocks that intrude (meta-) sedimentary strata. The similar characteristics that these deposits share are the foundation for the development of a reduced intrusion-related gold deposit model. Associated gold deposits have a wide variety of geological and geochemical features and are categorized as intrusion-centered (includes intrusion-hosted, skarns and replacements), shear-related, and epizonal. The TGP is characterized by vast, remote under-explored areas, unglaciated regions with variable oxidation depths and discontinuous permafrost, which, in combination with a still-evolving geological model, create significant exploration challenges. Twenty-five Early and mid-Cretaceous (145-90 Ma) plutonic suites and belts are defined across Alaska and Yukon on the basis of lithological, geochemical, isotopic, and geochronometric similarities. These features, when combined with aeromagnetic characteristics, magnetic susceptibility measurements, and whole-rock ferric:ferrous ratios define the distribution of magnetite- and ilmenite-series plutonic belts. Magnetite-series plutonic belts are dominantly associated with the older parts of the plutonic episode and comprise subduction-generated metaluminous plutons that are distributed preferentially in the more seaward localities dominated by primitive tectonic elements. Ilmenite-series plutonic belts comprise slightly-younger, slightly-peraluminous plutons in more landward localities in pericratonic to continental margin settings. They were likely initiated in response to crustal thickening following terrane collision. The youngest plutonic belt forms a small, but significant, magnetite-series belt in the farthest inboard position, associated with alkalic plutons that were emplaced during weak extension. Intrusion-related metallogenic provinces with distinctive metal associations are distributed, largely in accord with classical redox-sensitive granite-series. Copper, Au and Fe mineralisation are associated with magnetite-series plutons and tungsten mineralisation associated with ilmenite-series plutons. However, there are some notable deviations from expected associations, as intrusion-related Ag-Pb-Zn deposits are few, and significant tin mineralisation is rare. Most significantly, many gold deposits and occurrences are associated with ilmenite-series plutons which form the basis for the reduced intrusion-related gold deposit model
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Guo, Dijiang. "Caractéristiques structurales de la zone de cisaillement de Wulong et de la minéralisation relative d'or dans le camp d'or de Wulong, Province du Sud-Est de Liaoning, Chine = [Structural characteristics of the Wulong shear zone and related gold mineralization in the Wulong Gold Camp, southeastern Liaoning Province, China] /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2001. http://theses.uqac.ca.
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Murphy, Daniel M. K. "Regolith expression of hydrothermal alteration : a study of the Groundrush and Vera Nancy gold deposits of Northern Australia." University of Western Australia. School of Earth and Environment, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0186.
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[Truncated abstract] Mineralogical and geochemical characteristics were identified for regolith overlying two Australian Au deposits that discriminate mineralized and associated hydrothermally-altered rock from weathered rock that was not hydrothermally-altered. Mineralization was lithologically controlled within a previously unrecognized diorite dyke at the lower Proterozoic mesozonal Groundrush deposit, Tanami region, Northern Territory. Although hydrothermal alteration effects within the dyke were subtle and obliterated by weathering, Ti/Zr ratios clearly discriminated the diorite dyke from visually indistinguishable but generally unmineralized dolerite. In contrast, the Carboniferous Vera Nancy low-sulphidation epithermal Au deposit, located in the Drummond Basin, northeast Queensland, comprises structurally-controlled quartz veins within a relatively chemically homogenous suite of andesitic lavas and subvolcanic intrusions. A zoned hydrothermal alteration system in the hangingwall of the main vein grades from a proximal silica-pyrite alteration zone through an argillic zone into regionally extensive propylitic 'background'. Deep chemical weathering has destroyed the minerals diagnostic of the different alteration zones in bedrock to leave a kaolinitic regolith overlying all alteration zones. However, the silica-pyrite alteration zone is identified in regolith by retention of the anomalous concentrations of Au, As, Sb and Mo present in bedrock, and mineralogical characteristics, determined from X-ray diffraction investigations, discriminated weathered argillic from propylitic alteration zones. ... Metasomatic reactions, including weathering reactions, are typically difficult to specify, as some reactants and products may be removed by fluids, and thus evidence for their involvement is absent from the observed assemblages. In addition, the range of possible reactions even for relatively simple systems is such that identifying the real reaction may be intractable without additional information. Linear algebra provides an approach to this problem. If minerals and aqueous phases are represented as columns in a matrix with elements as rows, any vectors in the null space of this matrix (if it is greater than 0-dimensional) provide coefficients to balance reactions between the phases. The 'Gale' vectors for a set of phase are the row vectors of any basis for this null space. The relationships between phases are clarified through examination of these vectors in d-dimensional Gale vector space, where d is the dimension of the null space. The hyperplane normal to any vector in Gale vector space separates the space into reactant and product half-spaces. The geometric relationships between the Gale phase vectors describe all the possible reactions. Because changes to parameters (e.g. volume, mass, density) can be determined for each possible reaction, Gale analysis can be used to identify reactions consistent with these constraints. Gale analysis of weathering at the Vera deposit indicated that all the possible weathering reactions producing kaolinite, goethite and quartz from illite, pyrite and siderite resulted in minor reductions in volume and mass only, whereas acid-neutral weathering of propylitic rocks exhibited greater mass losses, consistent with observation and geochemical interpretation.
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Allen, George B. "Economic Geology of the Big Horn Mountains of West-Central Arizona." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/244099.
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The Big Horn Mountains are a geologically complex range that extends over 500 square km in west-central Arizona. Three major lithologic terranes outcrop: (1) Proterozoic amphibolite, phyllite, schists, gneiss, and granite; (2) Mesozoic monzonite to diorite intrusives; and (3) Cenozoic mafic to silicic volcanic rocks and clastic rocks. The entire area is in the upper plate of a detachment fault and, consequently, contains many low- to high-angle normal faults. Each lithologic terrane has its associated mineral occurrences. The Big Horn district is exclusively hosted in the pre- Tertiary terrane. Most of its mineral occurrences are spatially related to the Late Cretaceous intrusive rocks. One occurrence, the Pump Mine, may be a metamorphic secretion deposit, and therefore, would be middle Proterozoic. The vast majority of the mineral occurrences in the Big Horn Mountains are middle Tertiary in age and occur in three districts: the Tiger Wash barite - fluorite district; the Aguila manganese district; and the Osborne base and precious metal district. Fluid inclusions from Tiger Wash fluorite (T(h) 120 to 210° C, NaCl wt. equivalent 17 to 18 percent not corrected for CO₂) and nearby detachment - fault- hosted Harquahala district fluorite (T(h) 150 to 230° C., NaC1 wt. equivalent 15.5 to 20 percent not corrected for CO₂) suggest cooling and dilution of fluids as they are presumed to evolve from the detachment fault into the upper plate. Mass-balance calculations suggest that the proposed evolution of fluids is sufficient to account for the observed tonnage of barite and fluorite. The Tiger Wash occurrences grade directly into calcite- gangue-dominated manganese oxides of the Aguila district. A wide range of homogenization temperatures (T(h) 200 to 370° C.), an absence of CO₂ and low salinities (NaC1 wt. equivalent 1 to 2 percent) in the Aguila district calcite-hosted fluid inclusions argue for distillation of fluids during boiling or boiling of non saline-meteoric waters. Mass - balance calculations modeling the evolution of Ca and Mn during potassium metasomatism of plagioclase in basalt suggest that little if any influx of these cations is necessary to form the calcite –dominated manganese oxide tonnage observed. The Aguila district grades directly to the east into the base-metal and precious-metal occurrences of the Osborne district. Preliminary data describing geological settings, fluid inclusions, and geochemistry suggest that the Osborne district has a continuum between gold-rich to silver-rich epithermal occurrences. The gold-rich systems have dominantly quartz gangue, with or without fluorite, and are hosted in a variety of rocks, but are proximal to Precambrian phyllite or mid-Tertiary rhyolite. Fluid inclusions from two occurrences representative of the gold -rich systems spread across a minor range (T(h) 190 to 230° C., NaC1 wt. equivalent 17 to 23 percent not corrected for CO₂). Dilution of highly saline fluids is the inferred mechanism for precipitation of gold in the gold-quartz systems. The silver-rich systems have dominantly calcite gangue with or without quartz, and are hosted in mid-Tertiary basalt. Calcite fluid inclusions from a representative high-silver occurrence display a wide range of homogenization temperatures and salinities (T(h) 120 to 370° C., NaC1 wt. equivalent 7 to 23 percent). Boiling and consequent neutralization of acidic solutions is the inferred mechanism for the silver-rich, calcite gangue systems. A model inferring a regional fluid-flow regime and local sources of metals is proposed. Four possible regional and local causes of fluid flow in upper-plate detachment regimes are proposed: (1) regional elevation of geothermal gradients as a result of middle-crustal, lower-plate rocks rising to upper crustal levels; (2) meteoric water recharge along the southeast flank of the Harquahala antiform and consequent displacement of connate waters in the upper-plate of the Big Horn Mountains; (3) local emplacement of feeder stocks to rhyolitic flows; (4) and tilting of major upper-plate structural blocks.
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Bullen, Warwick David. "Gold mineralization in an archaean granite-greenstone remnant west of Melmoth, Natal ore genesis and implications for exploration." Thesis, Rhodes University, 1991. http://hdl.handle.net/10962/d1005579.
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The previously undifferentiated, "Melmoth Granite-Greenstone Remnant" (MGGR¹) crops out over an area of about 360 km² in northern Natal, South Africa. The greenstone sequence is comprised mainly of mafic metalavas with lesser serpentinite, talc schist, dacitic tuff, quartz-muscovite schist, quartzite and calc-silicate rocks. The greenstones are intruded by syntectonic trondhjemitic gneisses, late-tectonic granodioritic gneisses and post-tectonic granite dykes. Four phases of deformation and metamorphism are recognized. Epigenetic, disseminated and quartz vein-hosted gold mineralization is associated with D₂ shearing - a positive correlation existing between the intensity of the shearing, the thickness of the shear zone and the grade of ore it contains. Auriferous quartz veins are distinguished from an earlier generation of barren vein quartz on the basis of mineralogy, texture and relationship to the s-fabric. The mineralization occurs in zones of dilation associated with shear zone refraction. Associated wall rock alteration includes sericitization, argillization and chloritization. An ore genesis model based on the aforementioned parameters, is proposed. Finally, an exploration programme has been devised in order to locate undiscovered gold deposits in the MGGR. The programme could probably be applied, with minor modifications, to shear zone-hosted gold deposits in other granite-greenstone remnants in northern Natal. ¹- Name suggested by writer.
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Brisson, Harold. "Caractéristiques, chronologie et typologie des minéralisations aurifères de la région du Lac Shortt (Québec), sous-province archéenne de l'Abitibi /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1998. http://theses.uqac.ca.
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Dubé, Benoît. "Métallogénie aurifère du filon-couche de Bourbeau : région de Chibougamau, Quebec /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1990. http://theses.uqac.ca.
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Sener, A. K. "Characteristics, distribution and timing of gold mineralisation in the Pine Creek Orogen, Northern Territory, Australia." University of Western Australia. Centre for Global Metallogeny, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0102.
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Over the last two decades, gold occurrences in the Palaeoproterozoic Pine Creek Orogen (PCO) have been cited as type-examples of high-temperature contact-metamorphic or thermal-aureole deposits associated with granitoid magmatism. Furthermore, spatial relationships between these gold occurrences and the granitoids have led to inclusion of these deposits in the intrusion-related gold deposit group. Research on the characteristics, distribution and timing of these gold deposits tests these classifications and supports an alternative interpretation. The deposits display many similarities to well-described ‘turbidite-hosted’ orogenic gold deposits described from several Palaeozoic orogens. As in most ‘turbidite-hosted’ orogenic deposits, the gold mineralisation is dominantly epigenetic, sediment-hosted (typically greywacke and siltstone) and fold-controlled. Most gold is hosted by concordant or discordant veins, with limited alteration halos in host rocks, except where they occur in silicate-facies BIF or other Fe-rich rocks. The domal culminations of major doubly-plunging anticlines, and/or fold-limb thrust-faults, are important structural controls at the camp- and deposit-scales. Many deposits are sited in parts of the lithostratigraphy where there is significant competency and/or chemical contrast between units or sequences. In particular, the complex interdigitated stratigraphy of euxinic and transitional high-energy sedimentary rocks of the c.1900-1880Ma South Alligator Group is important for the localisation of gold deposits. The distribution of deposits is influenced further by the location and shape of granitoids and their associated contact-metamorphic aureole. Approximately 90% of gold deposits lie within the ∼2.5km wide contact-aureole, and most of these are concentrated in, and just beyond, the biotite-albite-epidote zone (0.5-1.0km from granitoid), with few deposits located in the inner hornblende-hornfels zone. At the deposit scale, gold is commonly associated with arsenopyrite-loellengite and pyrite, native-Bi and Bi-bearing minerals, and is confined to a variety of extensional quartz-sulphide ± carbonate veins. Such veins formed typically at 180-320°?C and ∼1kbar from low- to moderate salinity, two-phase aqueous fluids. Isotopic studies of the deposits are equivocal in terms of the source of hydrothermal fluid. Most δD and δ18O values fall within the range defined for contact-metamorphic and magmatic fluids, and sulphur isotopes indicate that the fluids are within the range of most regional sources. Significantly, lead isotope ratios show that the goldbearing fluid does not have a felsic magmatic-source signature, but instead suggest a homogenous regional-scale lead source. Excluding a few outliers, the relative uniformity of deposit characteristics, including host rocks, structural style, alteration, sulphide paragenesis and fluid P-T-X conditions, suggests that most deposits represent a continuum of broadly coeval mineralisation that formed under similar geological conditions
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Dopavogui, Joseph Siba. "Structural assessment of the Koulekoun Gold Deposit, Guinea, West Africa." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1018201.
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The Koulekoun Gold project is the most important prospect of Avocet Mining plc. It is one of the projects within the TriK-block in Guinea (West Africa) for which an exploration permit has been granted. The Koulekoun deposit is located within the Siguiri basin of Birimian age in the Eastern Guinea region; where most Guinea’s gold mines are situated. The present study involves the investigation of structural elements (S₀, S₁, S₂, intrusive contacts, faults and veins) from selected drill cores from drill sections that intersect the Koulekoun orebody in four parts of the deposit; characterizes the principal orientations of measured structures and determines their relationships using stereonet; in order to predict important intersections to focus on in exploration programs within the TriK-block and suggests a possible structural model of the Koulekoun deposit. Raw data used for the present research was collected from half-core samples due to the absence of surface outcrop from which direct measurements could have been made. Measured data were interpreted using stereographic projection. Often no preferred orientations of structural elements exist in the area, suggesting a complex structural situation, particularly with regard to hydrothermal vein attitudes. Thus, it has been illustrated from structural data analysis and S₀ data 3d interpolation of the four sub-structural domains (North-East, North-West, Central and South) that NE-SW structures (S₂, intrusive contact, fault and vein) have controlled the occurrency of gold mineralization in the Koulekoun deposit area. Geometrical relationships between structure main cluster orientation from stereonet analysis show the majority of S₀ moderately E-dipping; intrusive contacts dip at moderate angle to the SE in all zones, except in the North-East zone where they are sub-vertical and SE-dipping. Fault planes show variable orientation of NE-SW, NW-SE and E-W, and steeply SE-dipping. Vein planes correspond to fault systems and show high variability in their orientation with numerous orders of vein direction in each domain. The cross-cutting relationships suggest two principal generations of faults: the NE-SW fault (F1) and the NW-SE fault (F2). These two fault systems and their associated vein intersection areas preferably define the ore shoot zones within the Koulekoun deposit. The proposed structural model of the Koulekoun deposit suggests the intersection and interference of major NW-SE and minor NE-SW structures. The interference of folds formed basin-dome structures with oval shape geometries striking NW-SE and that dominantly occur in North-East, North-West and Central zones. The South Zone is characterized by NE-SW gently plunging and moderately inclined folds with NW-SE striking axial surface. Gold mineralization occurs at the edges of basin-dome structures in North-East, North-West and Central zones. Mineralized porphyry intrusions are likely located within the axial surface of the South zone folds and extend toward the Central zone. The proposed model is compliant with the earlier model of the Koulekoun deposit presented by Tenova (2013); Fahey et al. (2013) describing the Koulekoun deposit as an auriferous NE-SW trending fault zone, intersecting a major NW-striking and steeply E-dipping porphyry units. The model also fits within the regional structural context suggested by Lahondere et al. (1999a) related to the E-W vein structures attributed to NW-SE fractures and to the conjugated fault of NE-SW direction. Comparatively to the three industrial gold deposits (Siguiri, Lero, Kiniero) being currently mined in the Siguiri Basin, and defined as mesothermal vein and lode mineralization hosted in Birimian meta-sedimentary rocks (Lalande, 2005), the Koulekoun gold deposit appears to be a porphyry hosted orogenic disseminated style mineralization system (Fahey et al., 2013). Although, similarities between the Koulekoun gold deposit and these three industrial deposits (Siguiri, Lero, Kiniero) constitute of the intensive extends of the weathering profile and at some stages, by the existence of numerous ring-shaped and curved lineaments enhanced by drag folding (Lero deposit for instance). It is therefore recommended that targets selection around the Koulekoun deposit and within the TriK-block for further exploration programs be concentrated along NW-SE structures, in objective to determine possible intersection zones with NE-SW structures.
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Branson, Thomas Keegan. "A review of archean orogenic gold deposits in greenstone belts and the Slave Province : exploration in the Yellowknife domain, NWT, Canada." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1012142.
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A review of Archean granite-greenstone terranes, orogenic gold deposits, the Slave Province and modern exploration tools, techniques and methods was conducted to identify prospective areas in the Yellowknife domain for hosting orogenic gold deposits and illustrate the best exploration methods for delineating this deposit type. This study identifies Archean granite-greenstone terranes as economically important hosts to quartz-carbonate vein-hosted orogenic gold deposits. These deposits occur at convergent plate margins, but can also be related to local extensional tectonics within a convergent setting. Heat generated from tectonic processes can trigger hydrothermal fluid movement along first-order faults and shear zones. Precipitation of gold-bearing quartz-carbonate veins from the hydrothermal fluids occurs in second- and third-order faults and shear zones related to the first-order structures. This study also identifies the Archean Slave Province in northern Canada as a well-endowed craton with numerous orogenic gold deposits, diamondiferous kimberlites, VMS deposits and several other mineralization styles. In particular, three greenstone belts (Yellowknife, Cameron River and Beaulieu River) associated with likely first-order structures are comprised of prospective rocks for hosting orogenic gold and VMS mineralization. The Yellowknife greenstone belt hosts the past-producing and former world-class Con and Giant orogenic gold deposits, but has been little explored with modern exploration techniques. The Cameron River and Beaulieu River greenstone belts host numerous base and precious metal VMS and BIF-hosted orogenic gold prospects and deposits, indicating mineralization is present. There is considerable potential for significant discoveries to be made using modern exploration techniques in the greenstone belts; however, exploration in the region has been hindered over the past decade by ongoing political negotiations. Once the political negotiations are finalized, application of modern exploration methods and techniques in the prospective greenstone belts should be carried out. Regional scale methodologies should be applied to generate targets using predictive modelling, implicit 3D modelling, 3D geochemistry and exploration targeting so decisions defining a businesses strategy for ground acquisition of high priority targets are made using quantitative analysis. Once ground is acquired, field-based exploration for orogenic gold and VMS deposits should include geological mapping with a focus on structural geology, geochemical sampling and airborne magnetic, radiometric and EM geophysical surveys. Prior to reconnaissance drilling, integration of all data layers and interpretation within a common 3D earth model should be conducted. Following successful reconnaissance drilling, definition drilling along strike and down dip of intersected mineralization, combined with borehole geophysics, should be carried out to delineate the extent of mineralization.
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Tremblay, François. "Étude de reconnaissance en géochimie isotopique de l'oxygene et de l'hydrogène : application à quelques minéralisations de la région de Chibougamau, Québec, Canada /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1986. http://theses.uqac.ca.
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Mémoire (M.Sc.A.)-- Université du Québec à Chicoutimi, 1986."Mémoire présenté en vue de l'obtention d'un diplôme de M.Sc.A." CaQCU Document électronique également accessible en format PDF. CaQCU
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Gao, Sanmei. "Etude de la geologie et des inclusions fluides des gisements auriferes de Francoeur et de Lac Fortune : Study of geology and fluid inclusions in the Francoeur and Lac Fortune gold deposits, Québec /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1994. http://theses.uqac.ca.
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See, Jeannette. "L'analyse des inclusions fluides et magmatiques des dépôts aurifères dans la région du Lac Shortt, Abitibi, Québec : l'interprétation thermodynamique et métallogénétique du rôle des fluides minéralisants à l'Archéen /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1994. http://theses.uqac.ca.
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Oré, Sánchez Carlos. "Caractérisation et rôle des failles (E-W) sécantes dans le contrôle de la minéralisation aurifère à la mine Poderosa, Pataz, Pérou = Caracterización y rol de las fallas (E-W) secantes en la mineralización aurifera filoniana del Batolito de Pataz, Peru /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2006. http://theses.uqac.ca.
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Zhou, Yongzhang. "Géochimie et mécanisme métallogénique du district aurifère de Hetai, sud de la Chine = Geochimistry and metallogenetic mechanism of the Hetai gold field, southern China /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1992. http://theses.uqac.ca.
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Thèse (D.R.Min.) -- Université du Québec à Chicoutimi, 1992.These présentée en collaboration de l'Université du Québec à Chicoutimi et Institute of geochemistry, Academia Sinica. CaQCU Document électronique également accessible en format PDF. CaQCU
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Hammond, Napoleon Quaye. "The geochemistry of ore fluids and control of gold mineralization in banded iron-formation at the Kalahari Goldridge deposit, Kraaipan greenstone belt, South Africa." Thesis, Rhodes University, 2003. http://hdl.handle.net/10962/d1008370.
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The Kalahari Goldridge mine is located within the Archaean Kraaipan Greenstone Belt about 60 km SW of Mafikeng in the Northwestern Province, South Africa. Several gold deposits are located within approximately north - south-striking banded iron-formation (BIF). Current opencast mining operations are focused on the largest of these (D Zone). The orebody is stratabound and hosted primarily in the BIF, which consists of alternating chert and magnetite-chloritestilpnomelane-sulphide-carbonate bands ranging from mm to cm scale. The ore body varies in thickness from 15 to 45 m along a strike length of about 1.5 km. The BlF is sandwiched between a sericite-carbonate-chlorite schist at the immediate footwall and carbonaceous meta-pelites in the hanging-wall. Further west in the footwall, the schists are underlain by mafic meta-volcanic amphibolite. Overlying the hanging-wall carbonaceous metapeiites are schist units and meta-greywackes that become increasingly conglomeratic up the stratigraphy. Stilpnomelane-, chlorite- and minnesotaite-bearing assemblages in the BlFs indicate metamorphic temperatures of 300 - 450°C and pressures of less than 5 kbars. The BIF generally strikes approximately 3400 and dips from 60 to 75°E. Brittle-ductile deformation is evidenced by small-scale isoclinal folds, brecciation, extension fractures and boudinaging of cherty BIF units. Fold axial planes are sub-parallel to the foliation orientation with sub-vertical plunges parallel to prominent rodding and mineral lineation in the footwall. Gold mineralization at the Kalahari Goldridge deposit is associated with two generations of subhorizontal quartz-carbonate veins dips approximately 20 to 40°W. The first generation consists of ladder vein sets (Group lIA) preferentially developed in Fe-rich meso bands, whilst the second generation consists of large quartz-carbonate veins (Group lIB), which crosscut the entire ore body extending into the footwall and hanging-wall in places. Major structures that control the ore body are related to meso-scale isoclinal folds with fold axes subparallel to mineral elongation lineations, which plunge approximately 067°E. These linear structures form orthogonal orientation with the plane of the mineralized shallowdipping veins indicating stretching and development of fluid - focusing conduits. A second-order controlling feature corresponds to the intersection of the mineralized veins and foliation planes of host rock, plunging approximately 008°N and trending 341°. G0ld is closely associated with sulphides, mainly pyrite and pyrrhotite and to a lesser extent with bismuth tellurides, and carbonate gangue. The ore fluid responsible for the gold deposition is in the C-O-H system with increased CH₄ contents attributed to localized hydrolysis reaction between interbedded carbonaceous sediment and ore fluid. The fluid is characterized by significant C0₂ contents and low salinities below 7.0 wt % NaCl equivalent (averages of 3.5 and 3.0 wt % NaCl equivalent for the first and second episodes of the mineralization respectively) . Calculated values of f0₂. ranging from 10⁻²⁹·⁹⁸ to 10⁻³²·⁹⁶ bars, bracket the C0₂-CH₄ and pyrite-pyrrhotite-magnetite buffer boundaries and reveal the reducing nature of the ore fluid at deposition. Calculated total sulphur content in the ore fluid (mΣs), ranges from 0.011 to 0.018M and is consistent with the range (10⁻³·⁵ to 10⁻¹M) reported for subamphibolite facies ore fluids. The close association of sulphides with the Au and nature of the fluid also give credence that the Au was carried in solution by the Au(HS)₂ - complex. Extensive epigenetic replacement of magnetite and chlorite in BIF and other meta-pelitic sediments in the deposit by sulphides and carbonates, both on meso scopic and microscopic scales gives evidence of an interaction by a CO₂- and H₂S-bearing fluid with the Fe-rich host rocks in the deposit. This facilitated Au precipitation due to changes in the physico-chemical conditions of the ore fluid such as a decrease in the mΣs and pH leading to the destabilization of the reduced sulphur complexes. Local gradients in f0₂ may account for gold precipitation in places within carbonaceous sediments. The fineness of the gold grams (1000*Au/(Au + Ag) ranges from 823 to 921. This compares favourably with the fineness reported for some Archaean BIFhosced deposits (851 - 970). Mass balance transfer calculations indicate that major chemical changes associated with the hydrothermal alteration of BIF include enrichment of Au, Ag, Bi, Te, volatiles (S and CO₂), MgO, Ba, K and Rb but significant depletion of SiO₂ and minor losses of Fe₂O₃. In addition, anomalous enrichment of Sc (average, 1247%) suggests its possible use as an exploration tool in the ferruginous sediments in the Kraaipan greenstone terrane. Evidence from light stable isotopes and fluid inclusions suggests that the mineralized veins crystallized from a single homogeneous fluid source during the two episodes of mineralization under the similar physicochemical conditions. Deposition occurred at temperatures rangmg from 350 to 400°C and fluid pressures ranging from 0.7 to 2.0kbars. Stable isotope constraints indicate the following range for the hydrothermal fluid; θ¹⁸H₂O = 6.65 to 10.48%0, 8¹³CΣc = -6.0 to -8.0 %0 and 8³⁴SΣs = + 1.69 to + 4.0%0 . These data do not offer conclusive evidence for the source of fluid associated with the mineralization at the Kalahari Goldridge deposit as they overlap the range prescribed for fluid derived from devolatization of deep-seated volcano-sedimentary piles near the brittle-ductile transition in greenstone belts during prograde metamorphism, and magmatic hydrothermal fluids.KMBT_363
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