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1
Schoeman, Philo. "Overview and comparison of Besshi-type deposits ancient and recent". Thesis, Rhodes University, 1996. http://hdl.handle.net/10962/d1005595.
Testo completoAbstract (sommario):
Besshi-type deposits range in age from early Proterozoic to early Tertiary, of which the largest number are late Proterozoic, early Palaeozoic or Mesozoic in age. No Archaean examples of Besshi-type deposits are known, probably due to insufficient availability of sialic crust for erosion and clastic marine sedimentation before the start of the Proterozoic. All Besshi-type deposits are contained within sequences of clastic sedimentary rock and intercalated basalts in a marine environment. The basalts and amphibolites are principally tholeiitic in composition. Besshi-type deposits characteristically form stratiform 1enses and sheet-like accumulations of semi-massive to massive sulphide. The main ore assemblage consists dominantly of pyrite and/or pyrrhotite with variable amounts of chalcopyrite, sphalerite and trace galena, arsenopyrite, gold and e1ectrum, barite being absent in general. The median Besshi-type deposit (n=75) contains 1.3 million tonnes (Mt) of massive sulphide with a Cu grade running at 1.43%. It is suggested that Besshi-type deposits form by both exhalative and synsedimentary replacement processes when considering geological features and comparisons with modern analogues in the Guaymas Basin, Middle Valley and Escanaba Trough. The currently forming metalliferous sediments in the Red Sea provide for a brine pool model explaining the lack of footwall feeder zones below sheet-like deposits. Where thick sulphide lenses are contained in some Besshi-type deposits, combinations of exhalative precipitation and sub-sea-floor replacement of permeable sediments and/or volcanic rocks, take place in the upper parts of submarine hydrothermal systems.
2
Unger, Derick Lee Saunders James A. Hames W. "Geochronology and geochemistry of Mid-Miocene Bonanza low-sulfidation epithermal ores of the northern Great Basin, USA". Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SPRING/Geology_and_Geography/Thesis/Unger_Derick_6.pdf.
Testo completo
3
Ash, Philip John. "A review of the sediment-hosted, disseminated precious metal deposits of Nevada : geological setting, classification, genesis and exploration". Thesis, Rhodes University, 1986. http://hdl.handle.net/10962/d1001566.
Testo completoAbstract (sommario):
Carlin-type, fine-grained, "invisible" or Disseminated Replacement Type gold-silver deposits are all different names for a major new type of ore deposit that is currently being extensively developed in the Western United States. This type of deposit is now being found elsewhere. Thus a descriptive empirical model that emphasizes the geological and geochemical environment of formation is needed to assist the mining industry in the search for similar deposits. These deposits are typically formed in carbonaceous, silty dolomites and Iimestones or mineralization calcareous siltstones rocks and is exceedingly fine-grained is disseminated in the and claystones. host sedimentary Gold-silver , ore. Primary alteration usually less than one micron in size in unoxidized types include decalcification, argillitization, silicification resulting in the and pyritization. Silicification is commonly intense formation of jasperoid bodies which may be the host to higher grade ore. Supergene alteration is dominated by oxidation resulting in the formation of numerous oxides and sulphates and the release of gold from its association with sulphides and organic carbon. elements are As, Ba, Hg, Sb, and TI. Commonly associated trace Available geological, geochemical, fluid inclusion and stable-isotope studies lead to the conclusion that a circulating hydrothermal system is the important factor necessary for gold-silver concentration and deposition. A direct genetic or only casual relation between are deposition and discrete igneous formations remains unclear. However, it is considered that volcanism provided the source of heat necessary for the generation of a circulating hydrothermal system. High angle faults and fold structures facilitate transport and are of prime importance in directing are fluids to favourable host lithologies. The host rocks, overwhelmingly carbonate - rich, include those whose original and/or altered compositions and resulting permeability provide favourable sites for the precipitation of disseminated gold. The processes specialized. resulting Any th ick in the formation of these deposits are section of carbonate rocks has the potential not to produce Disseminated Replacement Type deposits wherever underlying igneous activity has developed a hydrothermal system
4
Osterholt, Volker. "Simulation of ore deposit geology and an application at the Yandicoogina iron ore deposit, Western Australia / y Volker Osterholt". [St. Lucia, Qld.], 2006. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19175.pdf.
Testo completo
5
Slabbert, W. L. "Ore distribution controls of the Navachab Gold Mine, Damara Belt, Karibib District, Namibia". Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1016364.
Testo completoAbstract (sommario):
The Navachab Gold mine, an orogenic lode gold deposit, is located in the Karibib region of the Pan-African (ca. 550-500) Damara belt of central Namibia. Gold mineralisation is developed within the steeply NW dipping limb of the Karibib dome. Here, ore envelopes trend along three main orientations: a) trends shallowly towards the NE (the down plunge extent), b) trends sub-vertically in and along the down plunge extent and c) trends sub-horizontally across the down plunge extent. The down plunge extent represents the bulk of the gold mineralisation, hosting the only high grade ores mined at Navachab. As such, past work primarily focused on establishing the controls to the mineralisation observed here. The sub-vertical and sub–horizontal ore trends are seen as secondary, lower grade, being hosted in the footwall. By cutting pushbacks into the footwall, in an effort to regain access to high grade pit bottom, future gold production almost exclusively relies upon optimally mining these ores. This underlines the importance to investigate and outline the mineralising controls to the secondary ore trends. This study identified the following prevailing quartz vein sets developed within the footwall, set (1) dips shallowly towards the NE (conjugate vein set), (2) steeply towards the NW (bedding parallel veins) and (3) steeply towards the SE (S2 foliation parallel). The NW and SE dipping sets contain high average gold grades, occurring at an infrequent vein density. The NE dipping veins, as a result of occurrence density alone, was highlighted as the dominant gold hosting set. Veining occurred during the late stages of the NW-SE directed, sub-horizontal shortening (D2) event and is associated with top-to-the-NW thrusting and NW-verging folds. Re-Os molybdenite dating from auriferous quartz veins indicates mineralisation occurred at 525-520 Ma. As crustal shortening amplified the Karibib dome, flexural flow developed fractures along bedding planes, providing the control to bedding parallel veins (NW dipping). With continued crustal compression the dome later experienced fold lock up associated with reduced mean rock stress and sub-horizontal extension occurred along the steeply NW dipping limb. Horizontal extensional gashes sucked in fluids to form the shallowly NE dipping conjugate vein set. These features suggest the regional D2 strain as the first-order control to quartz vein development, down plunge and within the footwall ores. To further define the secondary ores, lithological and structural controls were evaluated on a more detailed local scale. With equal amounts of biotite schist and calc-silicate host rock (bulk of the footwall lithology) material analysed, the biotite schist units were found to contain a larger volume amount of quartz veins. The mineralisation incurred is also developed at higher average gold grades compared to that of the calc-silicates, demonstrating biotite schist having the optimal rheology for quartz vein emplacement. Normal faulting and thrusting occurs widespread, at all scale levels, across the footwall. These were primarily observed along bedding foliations and secondly at higher angles cutting across foliation. The study did not constrain the extent of these, but can conclude faulting plays a very prominent role in re-distributing the secondary ores parallel to bedding along sub-vertical trend planes. Great care should be placed in properly modelling these with 3D software such as Leapfrog. The Navachab gold mineralisation came about as a result of convergent and collisional tectonics activating metamorphic dehydration of the crustal metapelites. As these fluids ascended they absorbed gold from the crust, emplaced by either a magmatic or paleo-placer source. The gold enriched hydrothermal fluids amalgamated in large scale 1ste order structures (shearing of the steep NW limb of the Karibib Dome, the Mon Repos Thrust Zone) that acted as primary active fluid path ways. In the case of Navachab the gold enriched fluid fluxed along these pathways while interacting with fluid sinks related to a physical throttle (brittle schist, folding, bedding parallel shears) and/or a chemical trap (marbles). By summarising and detailing the fluid sinks and active fluid pathways identified by this and previous works, it is strongly recommended that a mineral approach system be designed and implemented as targeting model to lead future exploration endeavours.
6
Thomson, Brian. "Geology of silver mineralisation at Candelaria, Nevada, USA". Thesis, University of Aberdeen, 1990. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=238078.
Testo completoAbstract (sommario):
Candelaria, situated in central western Nevada, along the western margin of the Great Basin, is a large and predominantly low grade, epigenetic disseminated- and vein-type Ag deposit, of Early Cretaceous age. It represents the eroded, deeply oxidised and fault-disrupted root of extensive stratiform quartz-dolomite stockworked and sericite-dolomite-altered zones of medium temperature pyrite-dominated Ag(-Pb-Zn-Sb-As±Cu±Au) sulphide-sulphosalt mineralisation, which is hosted by receptive sedimentary and igneous rocks within structurally favourable zones in a district-scale tectonic pinchout, and which is genetically associated with Cordilleran granodiorite porphyry hypabyssal magmatism (diking), of high K calc-alkaline affinity. The mineralisation occurs along and directly beneath the Pickhandle allochthon, a serpentinite-sheathed volcanic-sedimentary tectonic méange which forms a local 'sole' plate to the regionally extensive Golconda allochthon, which was emplaced onto the edge of continental North America during the Early Triassic Sonoma orogeny. Mineralisation occurred where an irregularity in the Pickhandle thrust plane, caused by thickening of the méange, effected locally deeper truncation of the parautochthonous foreland sequence in its footwall - chiefly marine sediments of the Lower Triassic Candelaria Formation - against the deformed cherts of the Ordovician basement (Palmetto complex), to form a structural trap. Within this trap, mineralisation is hosted mainly by carbonaceous, carbonate- and phosphate-rich (and trace metal-rich) black shales at the base of the Candelaria Formation and by dolomite-quartz-altered serpentinites at the base of the Pickhandle allochthon. Stable isotope data (O, H, S) point to a predominantly magmatic source for the hydrothermal fluids and ore sulphur, a source most likely to be the parent pluton to the granodiorite porphyry dikes. More ore metals were also of igneous origin (mass balance calculations rule out Candelaria member 1 as the chief metal source).
7
Becker, Stephen Paul. "Fluid Inclusion Characteristics in Magmatic-Hydrothermal Ore Deposits". Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28318.
Testo completoAbstract (sommario):
Magmatic-hydrothermal ore deposits are formed in association with aqueous fluids that exsolve from hydrous silicate melts during ascent and crystallization. These fluids are invariably trapped as inclusions in vein-filling minerals associated with hydrothermal fluid flow, and their composition may be modeled based on the H₂O-NaCl system. Thus, if we know the pressure-volume-temperature-composition (PVTX) properties of H₂O-NaCl solutions, it is possible to interpret the PTX trapping conditions, which is important for understanding the processes leading to the generation of the hydrothermal system and ore mineralization.
High salinity (> 26 wt. % NaCl) fluid inclusions contain liquid, vapor, and halite at room temperature, and are common in magmatic-hydrothermal ore deposits. These inclusions homogenize in one of three ways: A) halite disappearance (Tmhalite) followed by liquid-vapor homogenization (ThL-V), B) simultaneous ThL-V and Tmhalite, or C) ThL-V followed by Tmhalite. The PVTX properties of H₂O-NaCl solutions three phase (L+V+H) and liquid-vapor (L+V) phase boundaries are well constrained, allowing researchers to interpret the minimum trapping pressure of inclusion types A and B. However, data that describe the pressure at Tmhalite for inclusion type C are limited to a composition of 40 wt. % NaCl. To resolve this problem, the synthetic fluid inclusion technique was used to determine the relationship between homogenization temperature and minimum trapping pressure for inclusions that homogenize by mode C. These results allow researchers to interpret the minimum trapping pressure of these inclusions, and by extension the depth at which the inclusions formed.
The temporal and spatial distribution of fluid inclusions formed in associated with porphyry copper mineralization has been predicted using a computer model. A simple geologic model of an epizonal intrusion was developed based on a Burnham-style model for porphyry systems and thermal models of the evolution of epizonal intrusions. The phase stability fields and fluid inclusion characteristics at any location and time were predicted based on PVTX properties of H₂O-NaCl solutions. These results provide vectors towards the center of a magmatic-hydrothermal system that allow explorationists to use fluid inclusion petrography to predict position with the overall porphyry environment when other indicators of position are absent.Ph. D.
8
Kasmaeeyazdi, Sara <1983>. "Geostatistical Modeling of Ore Deposits with Transitional Boundaries". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amsdottorato.unibo.it/7983/1/PhD-Thesis-KASMAEEYAZDI-SARA.pdf.
Testo completoAbstract (sommario):
In mineral resources and ore reserves estimation, a crucial point is the geological domains that will be used for the modelling, as well as the type of boundaries between these domains. The most common geostatistical techniques are based on the assumptions of stationarity of the variable within estimation domains considered hard boundaries (sharp contact between geological units). However, in most cases, the geological mechanisms that generate a deposit are transitional -overlapping in geological units- in nature. In transitional boundary deposits, each geological zone has its own mineral grade distributions and spatial variability, but with an overlapping between geological zones. Hence, any method for estimation models, affects the mine planning with a significant sensitivity particularly in transition areas. Due to this point, the identification of the exact boundaries of mineralization is essential for an accurate estimate of resources. The objective of this dissertation is to develop a methodological framework to be used in presence of transitional boundaries. The methodological framework is introduced and then explained through a case study with transitional boundaries. Moreover, through a mining case study, it will be shown how choosing appropriate methodology for modelling variables and for interpreting the deposit geology will help to optimize parameters identification. The methodological framework in general allows decreasing the uncertainty in resources estimation and reserves selection. The method is general and can be used in other field of geoscience that incorporate numerical modelling, such as environmental modelling, petroleum or mining industry where complex geology deposits should be characterized
9
Shellnutt, John Gregory. "A-type granites of the Permian Emeishan large igneous province (SW China) implications for the formation of the giant magmatic oxide deposits /". Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B39634498.
Testo completo
10
Roditis, Ioannis Stavros 1960. "A PERFORMANCE EVALUATION OF THE INDICATOR KRIGING METHOD ON A GOLD DEPOSIT: A COMPARISON WITH THE ORDINARY KRIGING METHOD". Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/275482.
Testo completo
11
Lecumberri, Sanchez Pilar. "Spatial and temporal evolution of fluids in hydrothermal ore deposits". Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/50960.
Testo completoAbstract (sommario):
Magmatic-hydrothermal systems typically have vertical extents of several hundredmeters and their geochemical characteristics (e.g. mineral assemblages) vary considerably
over that vertical extent. As a consequence the expression in outcrop varies depending on
the level of erosion. Therefore understanding the geochemical zonation of magmatic-hydrothermal
ore deposits opens the possibility to detect deep magmatic-hydrothermal
systems, and to assess qualitatively the degree of erosion that has taken place in the area
and at which level the mineralization may occur. This dissertation presents the
characterization of two shallow hydrothermal systems and their potential relations with
deeper magmatic-hydrothermal systems. In addition, this dissertation develops the
equations to directly interpret thermometric data from the fluid inclusion type dominant in
one of those deposits (fluid inclusions that homogenize by halite disappearance).
Red Mountain, AZ is a porphyry copper system with a well-preserved lithocap
providing an ideal candidate to characterize the shallow expression of porphyry copper
systems in the southwestern US. The distribution of fluid inclusions, alteration mineralogy
and grade indicate that the intrusive responsible for the mineralization was only partially
intercepted during the exploration program and that one single magmatic event was likely
responsible for the mineralization detected. Fluid inclusion types and clay minerals are
systematically distributed within the deposit. The fluid responsible for the shallow
hypogene mineralization was a low pH-intermediate temperature-low density fluid while a
high salinity fluid was responsible for deep mineralization.
Wutong is a Pb-Zn-Ag deposit in the Nanling belt (southeast China). The combination
of fluid inclusion and mineral thermometry indicates that the Wutong deposit formed at
relatively low pressures. The age and isotopic composition of the mineralization indicates
that the deposit formed during the Cretaceous from crustal derived fluids. The occurrence
of a shallow magmatic-hydrothermal system of Cretaceous age in this region suggests that
Cretaceous intrusions, despite not outcropping very commonly in this particular region may
occur at deeper levels.
Ph. D.
12
Chikochi, Christopher. "Ore breakage characterisation of UG2 deposits using the JK RBT". Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/27300.
Testo completoAbstract (sommario):
Ore breakage characterisation is a methodology that is used to determine the ore hardness, or resistance to breakage which can be compared across a database of different rock types. It thus develops a relationship between specific energy input and degree of breakage which can be applied to impact breakage in comminution devices. The present study is focussed on investigating the breakage properties of UG2 chromitite, pyroxenite, spotted anorthosite and mottled anorthosite grab samples from run-of-mine (RoM) ore stockpile (particle selection method) and cut drill core particles (cut core method). A mineralogical analysis of UG2 chromitite, pyroxenite, spotted anorthosite and mottled anorthosite was performed using Leica EZ4D optical microscope and QEMSCAN 650F to determine their mineral composition and texture. The presence of cracks in chromitite stockpile and cut drill core samples was also explored using a Nikon XTH 225 ST micro-focus X-ray system. RoM ore stockpile and cut drill core particles of each of these rock types were subjected to impact breakage in the JK Rotary Breakage Tester (RBT). The progeny particle size distributions and degrees of breakage of UG2 rock types obtained via the particle selection and cut core methods were compared. Standard breakage characterization models were fitted to the breakage data of different rock types and the relative hardness parameters compared. It was found that UG2 chromitite comprised mainly fine, isolated, round chromite grains in a plagioclase matrix. Pyroxenite samples were found to be made up of granular orthopyroxene, interstitial plagioclase and clinopyroxene. The mineralogical analysis also revealed that spotted anorthosite primarily contains plagioclase with orthopyroxene crystals forming isolated "spots" creating a poikilitic texture. Mottled anorthosite is made up of mainly plagioclase. Results from breakage tests showed that the progeny particle size distributions and the degrees of breakage for particles sourced from the RoM ore stockpile breaks into a finer product compared to cut drill core samples. This was attributed to the presence of cracks in the RoM ore particles as revealed by the tomographic scans. No visible cracks were found in the cut core particle. The ore hardness parameters were determined from fitting the breakage data to standard impact breakage characterisation models (t10 breakage and size dependent breakage model). Samples obtained via the particle selection method were consistently found to offer less resistance to impact breakage as shown by the higher Axb values compared to the cut drill core samples. Using the ore hardness classes presented by Napier-Munn et al (1999), UG2 chromitite, spotted anorthosite, mottled anorthosite and pyroxenite were thus classified as very soft, soft to very soft, soft to very soft and medium to soft respectively. The hardness indicator, 3600.M.fmat.x, for each size class determined using the parameters obtained from the size dependent breakage model decrease with an increase in the parent particle size. This shows that particles become more resistant to impact breakage as the initial particle size increases. However, for pyroxenite, spotted and mottled anorthosite, the indicator decreases between the particle sizes 14 to 28.6 mm but then increases for 41.1 mm.
13
Haggan, Titus. "Paragenesis, fluid flow and structural controls on bitumen vein deposits and bitumen-hosted ore deposits, Andean Cordillera". Thesis, University of Aberdeen, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395068.
Testo completoAbstract (sommario):
Three bitumen-hosted ore deposits from Peru, Argentina and Chile are described. These deposits (now abandoned) contain diverse mineral assemblages and were mined for vanadium (Minasragra, Peru), uranium (Cerro Huemul, Argentina) and copper (Copiapó, Chile). Highly integrated geological and geochemical studies have enabled the construction of paragenetic sequences and genetic models for these deposits. The Minasragra deposit was a bitumen-hosted vanadium orebody located within the Central Peruvian Andes. It was characterised by a highly unusual and world-unique mineral assemblage which included the vanadium sulphide mineral, patronite. Paragenesis is divided into four distinct phases and deposit genesis is linked to the extreme alteration of an in situ vanadium and sulphur-rich bitumen vein catalyzed by the intrusion of a high-level dyke suite. Cerro Huemul is a bitumen-hosted sandstone-type U-Cu deposit located within continental facies in the Neuquén Basin. Petrographic studies of bitumens and ore species coupled with fluid inclusion analysis enable reconstruction of fluid flow through this sandstone unit. Mineralization is divided into three paragenetic stages and is integrated into a regional and deposit-specific genetic model for ore deposition. The Copiapó study focuses on an extensive andesite lava horizon of Lower Cretaceous age which contains a diverse suite of copper sulphide minerals in intimate association with solid bitumen. Petrographic studies of ore and bitumen species enable the construction of paragenetic sequence which is divided into three mineralizing stages. All three bitumen-ore deposits formed due to the presence of solid bitumen and each case study investigates the role that bitumen played in the mineralizing process. Collectively these studies provide detailed insight into mineralization processes at bitumen-hosted ore deposits and highlight the versatility of bitumens to economically-concentrate a wide range of metals and minerals. A synopsis of the formation of all bitumen-type deposits (solid bitumen veins and bitumen-hosted ore bodies) is presented and ideas regarding the potential of mineral exploration for organo-metallic deposits within the Andean Cordillera are outlined.
14
Harris, Anthony Charles. "The genesis of a porphyry Cu-Au deposit, farallon negro volcanic complex, NW Argentina /". St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17494.pdf.
Testo completo
15
Botha, André Erasmus. "Towards modelling the formation of ore bodies initial results dealing with the fluid mechanical aspects of magma chamber convection". Thesis, Rhodes University, 1999. http://hdl.handle.net/10962/d1005278.
Testo completoAbstract (sommario):
This thesis forms part of a larger effort which aims to establish the means of assessing the fluid mechanical behaviour of magma 1 as it cools inside a magma chamber surrounded by porous country rock. The reason for doing so is to advance the understanding of some types of mineral deposits; for example,the Platinum Group Elements (PGEs). The magma is modelled with the governing equations for a single-phase incompressible Newtonian fluid with variable viscosity and density. In this thesis, thermal conductivity and specific heat are approximated as constants and the country rock is treated as a conducting solid so as to save on computational time in the initial phases of the project. A basic review of the relevant literature is presented as background material and three basic models of magma chambers are discussed: crystal settling, compositional convection and double diffusive convection.The results presented in this thesis are from finite element calculations by a commercial computer code: ANSYS 5.4. This code has been employed in industry for over 26 years and has a long and successful benchmark history. In this context, finite element methods that are applicable to the code are discussed in chapter 5. In chapter 6, results that were obtained in the course of this research are presented. The thesis concludes with an indication of the possible geological significance of the results and various refinements that should be made to future models.
16
Couture, Jean-François. "Géologie et gitologie du gisement de la rivière Eastmain, Ungava, Québec /". Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1993. http://theses.uqac.ca.
Testo completo
17
Alldrick, Dani James. "Geology and ore deposits of the Stewart Mining Camp, British Columbia". Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30795.
Testo completoAbstract (sommario):
The Stewart mining camp in northwestern British Columbia is abundantly mineralized with widely distributed, texturally and mineralogically varied, precious and base metal deposits. This report documents the geologic setting of the mining camp and the geologic features of the major mineral deposit types.
The Stewart camp is underlain by a 5-kilometre-thick Upper Triassic to Lower Jurassic (Norian? to Toarcian) island arc complex of calc-alkaline basalts, andesites and dacites with interbedded sedimentary rocks. Coeval (211-189 Ma) hornblende granodiorite plutons intruded the arc at two to five kilometres depth. Rocks were deformed during mid-Cretaceous (110 ± 5 Ma) tectonism that produced north-northwest-trending folds, penetrative fabric and lower greenschist facies regional metamorphism (290°±20°C, 4.5 ±1.5 kb). Mid-Eocene (54.8-44.8 Ma) biotite granodiorite of the Coast Plutonic Complex intruded the deformed Mesozoic arc complex.
Two mineralizing events formed over 200 mineral occurrences in the district. These two metallogenic epochs were brief (< 5 million years), regional-scale phenomena characterized by different base and precious metal suites. The Early Jurassic ore-forming episode produced Au and Au-Ag-Zn-Pb-Cu deposits. The mid-Eocene episode produced Ag-Pb-Zn ± W ± Mo deposits.
Early Jurassic deposits have a characteristic lead isotope signature (²⁰⁶Pb/²⁰⁴Pb = 18.816; ²⁰⁷Pb/²⁰⁴Pb = 15.617) and include gold-pyrrhotite veins, gold-silver-base metal veins, and stratabound pyritic dacites. All Early Jurassic mineral occurrences are late- to post-intrusive deposits that were emplaced in andesitic to dacitic host rocks at the close of volcanic activity, about 190-185 million years ago.
Transitional gold-pyrrhotite veins (Scottie Gold mine) formed in en echelon tension gashes developed in country rock around Early Jurassic plutons during late magma movement. Epithermal gold-silver-base metal veins and breccia veins (Big Missouri and Silbak Premier mines) were deposited along shallower sub-volcanic faults and in hydrothermal breccia zones formed along dyke contacts. Stratabound pyritic dacite tuffs (Mount Dilworth and Iron Cap prospects) formed where venting fumarolic fluids and hotspring pools deposited abundant fine pyrite in local areas on a cooling ignimbrite sheet.
Eocene deposits also have a characteristic lead isotope signature (²⁰⁶Pb/²⁰⁴Pb = 19.147; ²⁰⁷Pb/²⁰⁴Pd = 15.627) and include silver-rich galena-sphalerite veins, gold-silver skarns and, beyond the study area, porphyry molybdenum deposits. These mineral occurrences are related to Middle Eocene plutons of the Coast Plutonic Complex. All are late- to post-intrusive deposits emplaced about 50-45 million years ago.
Mesothermal silver-lead-zinc veins (Prosperity/Porter Idaho and Riverside mines) were deposited in brittle zones along major fault structures. Skarns (Oral M and Red Reef prospects) developed where plutons cut limestone or limy siltstone units within minor turbidite sequences. Major porphyry molybdenum deposits (Kitsault mine and Ajax) developed where mid-Eocene stocks were emplaced in thick turbidite sequences.
Diagnostic features such as lead isotope ratios, stratigraphic and plutonic associations, alteration assemblages, sulphide mineralogy and textures, and precious metal ratios allow discrimination amoung these different deposit types. Using these criteria, the most prospective areas for each deposit type have been targetted for exploration.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
18
Whiteley, Robert School of Mines UNSW. "Electrical and seismic responses of shallow, volcanogenic, massive sulphide ore deposits". Awarded by:University of New South Wales. School of Mines, 1986. http://handle.unsw.edu.au/1959.4/28078.
Testo completoAbstract (sommario):
SP, resistivity/IP and seismic refraction responses of the Woodlawn Orebody and Mt.Bulga Deposit are examined and compared. Both exhibit similar responses produced mainly by uneconomic and disseminated sulphide mineralization and host rock features, demonstrating that the magnitude and character of electrical and seismic responses are not reliable indicators of size and economic sulphide content of volcanogenic sulphide ores. SP, soil geochemistry and electrogeochemistry are found to be the most effective exploration methods followed by resistivity/IP and seismic refraction. The large SP responses over both ore zones are simulated using new methods which allowed the width and depth of oxidation to be computed. Conventional and compensation array resistivity responses best define the deposits. Computer simulation shows that dipole- dipole and Unipole arrays are most useful. First order IP responses are large and similar, but the ore zones are not easily distinguished from polarizable host rocks. Second order responses, at Woodlawn, better define these lithologies and cross-plots of EM coupling removed first order parameters prove useful. The supergene and gossan zones are defined as sources of electrical anomalies and correlate with interpreted SP sources. Seismic velocities of fresh Woodlawn ore samples indicate only small contrasts with host rocks. Refraction travel-time data are highly complex but host rocks are clearly distinguished by their seismic velocities. Both deposits appear as low velocity zones at the general bedrock level which are shallower and narrower than the electrical sources associated with the ore zones. Extensive model simulation shows that the Reciprocal interpretation method is most useful when compared to other time- term methods for refraction interpretation but has some limitations. Computer simulation shows the significance of non- critical refractions, diffractions and laterally hidden zones which define the lateral resolution of the refraction method. The results of this study and the interpretative techniques developed will assist the exploration for similar and deeper massive volcanogenic orebodies in comparable geological environments.
19
Townley, Brian K. "Ore deposits, tectonics and metallogenesis of the continental Aysen region, Chile". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq20591.pdf.
Testo completo
20
Apostolopoulos, D. G. "The manganese oxide ore deposits of the Nevrokopi district, Macedonia, Greece". Thesis, University of Reading, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374035.
Testo completo
21
Del, Rio Salas Rafael Eduardo. "METALLOGENESIS FOR THE BOLÉO AND CANANEA COPPER MINING DISTRICTS: A CONTRIBUTION TO THE UNDERSTANDING OF COPPER ORE DEPOSITS IN NORTHWESTERN MÉXICO". Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/145742.
Testo completoAbstract (sommario):
Northwestern Mexico is characterized by different metallogenic provinces that are included along the Basin and Range, the Sierra Madre Occidental, and the Baja California geological provinces. With the purpose of contribute to the current understanding of the mineralizing processes, the present study focused on two important copper metallogenic provinces: the Cananea Porphyry District in Sonora, and the Sediment-hosted Stratiform Copper- and Mn-deposits in Baja California Sur. The U-Pb zircon ages from the mineralizing porphyries from Cananea district suggest a continued magmatic activity period of ~6 Ma. Also suggests a period of ~20 Ma for the entire magmatic activity in the district. The Re-Os molybdenite ages demonstrate five well-constrained mineralization events in the district; the main mineralization is constrained over a short period of time (~4 Ma). The new molybdenite age from the Pilar deposit documents the oldest mineralizing pulse, suggesting possibly the initiation of the Laramide mineralization in northern Sonora. A detailed study of Mariquita porphyry Cu and Lucy Cu-Mo deposits in the Cananea district was performed. Four hydrothermal stages were defined in Mariquita, whereas a single hydrothermal pulse characterizes Lucy. Emplacement depths between 1-1.2 km, and temperatures between 430-380ºC characterized the mineralization from Mariquita, whereas deeper emplacement depths and higher mineralization temperatures characterized Lucy. The stable isotope systematic and fluid inclusion data determined that the mineralizing fluids in Mariquita deposit are essentially magmatic during the earlier hydrothermal stages, whereas the last stage is the mixing between magmatic and winter meteoric-waters. The mineralizing fluids from Lucy deposit are magmatic in origin. A comprehensive study was performed in the Cu-Co-Zn-Mn ineralization of the Boléo District, and Mn-oxide mineralization along the eastern coast Baja California Sur. The REE and trace element in the Mn-oxides demonstrated the exhalative nature of the mineralizing hydrothermal fluids, and exclude the hydrogenous nature. The stable isotope systematic in ore and gangue minerals, along with the Cu-isotope data helped to decipher the nature of mineralizing and non-mineralizing fluids. The application of Pb, Sr and Re-Os isotope systems was applied to constrain the nature of the fluids involved during the mineralization processes and that the metal sources.
22
Gungor, Kazim. "Production Of Heavy-media-quality Magnetite Concentrate From Kesikkopru Iron Ore Tailings". Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611830/index.pdf.
Testo completoAbstract (sommario):
ABSTRACT
PRODUCTION OF HEAVY-MEDIA-QUALITY MAGNETITE CONCENTRATE FROM KESiKKÖPRÜ
IRON ORE TAILINGS Gü
ngö
r, Kazim M. Sc. Department of Mining Engineering Supervisor: Prof. Dr. M. Ü
mit Atalay May 2010, 91 pages The aim of this research was to investigate the possibility of the production of a magnetite concentrate which is suitable for preparation of heavy media from iron ore tailings of Gü
ncem Mining Company magnetic separation facility. During the study, three different tailings named as low grade, medium grade and high grade with 5.91 % Fe3O4, 19.06 % Fe3O4 and 37.06 % Fe3O4, respectively, were used. Mineralogical analyses of test samples showed that magnetite and hematite were the major ore minerals while pyrite and chalcopyrite were found in trace amounts. Actimolite, tremolite, epidote, chlorite, quartz, calcite, and dolomite were the gangue minerals. The effects of feed particle size and applied magnetic field intensity on the Fe3O4 grade and recovery of concentrate were examined throughout magnetic concentration tests. The highest grade magnetite concentrate with 79.98% Fe3O4 content was obtained with 65.42% recovery from 100% -75 micron size feed at 1000 Gauss magnetic field intensity from high grade tailing.
23
Gabell, Andrew R. "High-resolution remote sensing applied to mineral exploration in Australia /". Title page, and contents only, 1986. http://web4.library.adelaide.edu.au/theses/09PH/09phg1123.pdf.
Testo completo
24
Carroll, Sandy. "The viability of the Kaplats Platinum group element deposit". Access, 2006. http://upetd.up.ac.za/thesis/available/etd-07102008-080330/.
Testo completo
25
Edfelt, Åsa. "The Tjårrojåkka apatite-iron and Cu (-Au) deposits, northern Sweden : products of one ore forming event /". Luleå : Department of chemical engineering and geosciences, Luleå University of Technology, 2007. http://epubl.ltu.se/1402-1544/2007/17/.
Testo completo
26
Goodman, Sally. "The relationship between light hydrocarbons, carbonate diagenesis, and base metal ore deposits". Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38017.
Testo completo
27
Dhu, Trevor. "Geophysical signatures of iron ore deposits in the Middleback Ranges, South Australia /". Title page, contents and abstract only, 1996. http://web4.library.adelaide.edu.au/theses/09S.B/09s.bd535.pdf.
Testo completo
28
Adams, Garry J. "Structural evolution and ore genesis of the granites gold deposits, Northern Territory /". Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09pha2128.pdf.
Testo completo
29
Way, Bryan C. "Geology and Geochemistry of Sedimentary Ferromanganese Ore Deposits, Woodstock, New Brunswick, Canada". Thesis, Fredericton: University of New Brunswick, 2012. http://hdl.handle.net/1882/44600.
Testo completoAbstract (sommario):
The Early-Silurian Woodstock Fe-Mn Deposits are a series of six, northeasttrending,
low grade manganiferous-iron deposits in western New Brunswick that
collectively represent the largest Mn resource in North America (194,000,000
tonnes; 13% Fe and 9% Mn). Recent expansion of Route 95 has allowed a more
detailed local stratigraphy, mineralogy, and geochemistry of the Fe-Mn deposits
within the context of the regional stratigraphy to ascertain the genesis of these
deposits. Geological mapping during the field seasons of 2008 and 2009 has
revealed six Lithofacies Associations (O, I, II, III, IV, V) within the area, that,
generally, are lying conformably on top of each other. However complications due
to folding and interbedding have resulting in juxtaposition of the lithofacies
associations so they are not always in stratigraphic order. These lithofacies
associations are composed of a turbidite-rich section of blue grey calcareous
sandstone (O) overlain by black pyritic mudstone (I), associated mineralized and
nonmineralized green (II) and red siltstone (III), and laminated to massive grey
green calcareous sandstone (IV and V).
Na/Mg ratios, chondrite-normalized REE patterns, and mineralogical
evidence of rapid changes in ocean redox conditions suggest the Fe-Mn mineralized
lithofacies were formed in the offshore zone of a continental shelf on a stable
cratonic margin. Al-Fe-Mn ternary and SiO2/Al2O3 binary plots developed from
archived drill core data indicate the Fe-Mn mineralization was initially derived from
hydrogenous-detrital sources without any indication of a hydrothermal input as a
source of Fe and Mn.
30
Tatiya, Ratan Raj. "Ore estimation and selection of underground mining methods for some copper deposits". Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/46738.
Testo completo
31
Anderson, Kelvin Frederick Esebewa. "Geometallurgical evaluation of the Nkout (Cameroon) and Putu (Liberia) iron ore deposits". Thesis, University of Exeter, 2014. http://hdl.handle.net/10871/15019.
Testo completoAbstract (sommario):
The Nkout (Cameroon) and Putu (Liberia) oxide facies iron ore deposits comprise fresh magnetite banded iron formation (BIF) at depth, which weathers towards the surface, forming high grade martite–goethite ores. This study aimed to improve the mineralogical understanding of these deposits in order to predict their metallurgical responses. It concentrated on developing the QEMSCAN® technique and testing its application to these ore types, but also used a variety of other analysis methods. The QEMSCAN® species identification protocol was developed to include three goethite entries: goethite/limonite, phosphorus-bearing and aluminium-bearing goethite. QEMSCAN® was also used to distinguish between the iron oxides using their backscattered electron signals. To test the correlation between the mineralogy and metallurgical characteristics, magnetic separations were carried out. The samples were divided into 4 main groups based on their whole rock Fe content, determined by XRF analysis, and their degree of weathering: enriched material, weathered magnetite itabirite, transitional magnetite itabirite and magnetite itabirite. Quartz and Al oxide and hydroxide minerals such as gibbsite are the major gangue minerals in the magnetite BIF and martite–goethite ores respectively. From the QEMSCAN® analysis it was concluded that the iron oxides are closely associated and liberation of them individually is poor. Liberation increases when they are grouped together as iron oxide. Chamosite concentrations > 6 wt. % significantly lower liberation of the iron oxides. From the metallurgical testing, it was concluded that iron oxide modal mineralogy gives an indication of iron recovery but other QEMSCAN® data such as mineral association and liberation could be important especially if the iron oxide minerals are not liberated. Grain size and instrument characteristics also affect recovery of iron minerals. There is no evidence to show that there is any structural control on the BIF mineralisation at Nkout because metamorphism has significantly affected the lithological characteristics. The BIF mineralised zones occur as stacks with no particular stratigraphic relationship. Alteration and stratigraphy are the main controls on the martite–goethite ores. These results are applicable to most other BIFs so that as direct shipping ores are exhausted, the approach used here can help to develop the lower grade portions of the deposits.
32
Gapara, Cornwell Sine. "A review of the deposition of iron-formation and genesis of the related iron ore deposits as a guide to exploration for Precambrian iron ore deposits in southern Africa". Thesis, Rhodes University, 1993. http://hdl.handle.net/10962/d1005610.
Testo completoAbstract (sommario):
Iron-formations are ferruginous sedimentary rocks which have their source from fumarolic activity associated with submarine volcanism, with deposition of iron as oxides, hydroxides, and hydrous oxide-silicate minerals in shallow and/or deep marine sedimentary systems. The Precambrian ironformations of southern Africa have a wide age range, but are more prominently developed before 1.SGa. These iron formations occur in greenstone belts of the Kaapvaal and Zimbabwean cratons, in the Limpopo mobile belt, in cratonic basins and in the Damara mobile belt. The Archaean-Proterozoic sedimentary basins and greenstone belts host iron ore deposits in iron-formation. Iron formations have a lengthy geological history. Most were subjected to intense, and on occasions repeated, tectonic and metamorphic episodes which also included metasomatic processes at times to produce supergene/hypogene high grade iron ores. Iron-formations may be enriched by diagenetic, and metamorphic processes to produce concentrating-grade ironformations. Uplift, weathering and denudation, have influenced the mineral association and composition of the ores, within which magnetite, haematite and goethite constitute the major ore minerals. The iron resources of the southern Africa region include the Sishen deposits, hosting to about 1200 Mt of high grade direct shipping ore, at >63% Fe. Deposits of Zimbabwe have more than 33 000 Mt of beneficiable iron-formation. The evaluation of an iron ore prospect involves many factors which must be individually assessed in order to arrive at an estimate of the probable profitability of the deposit. Many of these are geological and are inherent in the deposit itself. Other factors are inherent aspects of the environment in which the ore is formed. Although the geological character of the ore does not change, technological advances in the processing techniques may have a great effect on the cost of putting the ore into marketable form. Geochemical, geophysical and remote sensing methods would be used for regional exploration. Chip sampling and drilling are useful for detailed exploration. Purely geological exploration techniques are applicable on a prospect scale in the exploration of iron ore deposits. Regional exploration targeting should choose late Archaean greenstone belts containing oxide facies iron-formation or Early Proterozoic basins located at craton margins as they are both known to host high-grade haematite orebodies formed by supergene/hypogene enrichment. Most types of iron ore deposits in southern Africa are described and classified. An attempt is made to emphasize the major controls on mineralisation, in the hope that these may be applicable to exploration both in the southern African region and within analogous settings around the world.
33
Muwanguzi, Abraham Judah Bumalirivu, Andrey Karasev, Byaruhanga K. Joseph e Jönsson G. Pär. "Characterization of chemical composition and microstructure of natural iron ore from Muko deposits". KTH, Tillämpad processmetallurgi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-123054.
Testo completoAbstract (sommario):
The study aimed at investigating the chemical composition and microstructure of raw iron ore from the deposits in Muko area (south-western Uganda). The quality of this iron ore was evaluated to establish its suitability to serve as a raw material for iron production. Samples were taken from the six hills of Muko ore deposits and tests carried out to establish their composition and properties. X-ray diffraction and scanning electron microscopy were employed in the investigation and chemical analysis performed to determine the compounds constituting the ore. The quality of this ore was compared to generalized world market standards and ores from other nations. It was found that Muko ore is a rich hematite grade with Fe content above 65%. It has little gangue (<6% SiO2 and 3-4% Al2O3) and low contents of the deleterious elements (P ~ 0.02% and S < 0.006%), which correspond to acceptable levels for commercial iron ores.QC 20130531
Sustainable Technology Development in the Lake Victoria Region
34
Ahmed, Ayesha Doris. "Beyond the confines of the ore deposit : mapping low temperature hydrothermal alteration above, within, and beneath Carlin-type Gold deposits". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/29423.
Testo completoAbstract (sommario):
Multiple analytical techniques were employed to investigate distal patterns in low temperature hydrothermal fluid flow into and out of Carlin-type gold deposits in two study areas: the Leeville deposit and the Shoshone range including the Pipeline, Gold Acres and Elder Creek deposits. Previous studies indicate that gold is hosted in lower Paleozoic carbonate rocks overlain by thick sequences of similarly aged siliciclastic rocks. Patterns in δ¹⁸O depletion (<20‰VSMOW), and Au, As, Sb, Hg, Tl, and Te concentrations in lower Paleozoic carbonate rock identified three disconnected lateral fluid pathways into the Pipeline deposit: a main conduit providing gold-bearing fluid to the main ore body, the Abyss fault located ~300m below the main ore zone, and the RMT located underneath the Abyss fault. Following gold precipitation in the Pipeline deposit, gold-depleted fluids were likely exhausted laterally, at least initially, along the same structures as those that allowed fluid to enter the deposit. Upon intersecting the RMT fault, fluid either exploited the fault to reach surface, or transgressed overlying siliciclastic rocks via small scale faults and fractures. δ¹⁸O and δD values of H₂O in equilibrium clay minerals, and the concentration and crystallinity of illite outlined multiple zones of hydrothermal alteration in surface rocks from both the Shoshone Range and Leeville study areas, however no genetic link was established to Carlin-type gold mineralization at depth. Similarities in trace element geochemistry, ore assemblage, and alteration assemblages however, suggest that the Elder Creek deposit may represent low temperature (200°C) gold mineralization resulting from the exhaust of Carlin-type ore forming fluid. The region above the surface projection of the Leeville deposit exhibits multiple zones of hydrothermal fluid upflow resulting in pervasive illitization of surface siliciclastic rocks. The Pipeline/ Gold Acres also contain abundant crystalline illite. The presence of highly crystalline illite highlights zones of focused fluid upflow, typically along faults and other secondary permeability structures such as breccias.
35
Warlo, Mathis. "Improving trace metal characterisation of ore deposits – a crucial step towards sustainable mining". Licentiate thesis, Luleå tekniska universitet, Geovetenskap och miljöteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-73865.
Testo completoAbstract (sommario):
Sustainable mining, including the utilisation of an ore body to its full potential, is becoming increasingly important for human society as the demand for metals increases. In order to maximise the recovery of useful metals, detailed characterisation of the ore prior to processing is vital. Characterisation should include major and minor ore minerals, gangue minerals, and also trace metals. Trace metals despite their low abundance are often particularly important, either due to their high economic value and criticality for society, or their negative impact on the quality of the main commodity recovered and/or the environment. To properly characterise trace metals in an ore deposit the use of micro-analytical techniques is necessary. Nowadays, a plethora of techniques exist, each with their own strengths and weaknesses. In the mining industry, automated scanning electron microscopy systems are widely used. These systems allow for rapid mineralogical characterisation and quantification of a sample and are commonly used to quantify the mineralogy of the ore feed and subsequent products. Operators of these systems benefit from prior knowledge of the mineralogy of a sample/deposit to fine-tune their processing software to deliver data of highest quality. In this study, a method to improve trace metal characterisation in ore deposits with automated scanning electron microscopy systems is presented. It is implemented as a case study on the Liikavaara Cu-(W-Au) deposit in northern Sweden. The deposit is enriched in several trace metals including Au, Ag, Bi and Sn, and is planned for production in 2023. The mine will produce Cu as the main product and Au and Ag as by-products, and the processing of the ore will be performed in the nearby Aitik plant. For this study, a detailed geological and mineralogical investigation of the deposit was performed prior to analysis with the automated scanning electron microscopy system. A good understanding of the mineralogy is necessary to be able to select a representative sample for the subsequent automated analysis and to guarantee optimal data quality produced by the automated system, and to judge the performance of the automated system, to improve the method of analysis. Manuscript 1 deals with the geological description and genetic aspects of the Liikavaara ore deposit. Results indicate that Liikavaara is an intrusion-related vein-style deposit. Mineralisation is hosted by quartz-tourmaline and calcite veins in a metadiabase that is partly metamorphosed to biotite schist. A 1.87 Ga granodiorite intrudes the footwall. Aplite dikes, genetically related to the intrusion, crosscut the metadiabase host rock. Mineralised veins are concentrated in and around these dikes. Manuscript 2 deals with method development of automated mineralogical analysis. A sample from a mineralised quartz-tourmaline vein at Liikavaara was analysed in great detail with the QEMSCAN® system. Apart from ore minerals in major and minor abundance the sample also contains ore minerals in trace quantities, e.g. Au and Ag minerals. The sample was analysed using two different analytical settings, at two different laboratories, one typical of a production-focused industrial approach and one quality-focused scientific approach. A first analysis using the industrial approach was unable to detect any Au and Ag minerals in the sample. By modification of the QEMSCAN® mineral reference library, through iterative use of the data from both the industrial- and the scientific approach, detection and quantification of Au and Ag minerals was successful. This method can be implemented as an add-on for routine industrial analysis by automated scanning electron microscopy systems to gain information on trace metal occurrence and distribution. This information can then be used for targeted sample selection for further in-depth analysis of the trace metal content and occurrence in the deposit.
36
Schuh, Wolfram Dieter, e Wolfram Dieter Schuh. "Geology, geochemistry, and ore deposits of the Bau gold mining district, Sarawak, Malaysia". Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/187561.
Testo completoAbstract (sommario):
District-scale zoning of ore deposits and structural-tectonic setting of Bau was investigated. Regional tectonic studies, structural analysis, and field mapping complemented by aeromagnetic interpretation were integrated to a structural model of Bau. Ores were studied with optical and electron microscopy, followed by major and trace element, fluid inclusion, and lead and sulfur isotope analyses. In the Late Triassic, Bau was in an island arc - back-arc basin environment Following Early Jurassic deformation and uplift, an active margin developed. Subduction of the West Pacific oceanic plate under the NW Kalimantan block began. Erosion of the Triassic Serian Volcanics produced extensive turbidite flows of the Pedawan Formation since the Latest Jurassic. Coeval development of rudist patch reefs on an unstable shelf edge of the overriding plate lasted until Cenomanian. Accretion of the turbidites ended in the Latest Cretaceous. Early Tertiary molasse deposition ended with a Mid-Eocene event. A 200-km-Iong, crustal-scale complex fault system involving dextral strike-slip and wrench faulting, termed the Bau Trend, developed during Mid-Miocene post-subduction regional extension. The principal mineralization event at Bau took place at 12-10 m.a., when I-type, calc-alkaline, reduced granodiorites intruded along the Bau Trend and its intersection with seven parallel, ENE fracture zones, providing channel ways to distribute hydrothermal fluids laterally away from the Bau Trend. Deformation preceding mineralization produced high structural permeability of the host rocks. Central Bau is underlain by an ENE trending, 5x12 km broad plutonic body at depth, inferred from aeromagnetic data. Bau displays district-scale zoning, from proximal porphyry-copper and skarn deposits, via intennediate Cordilleran-Vein base metal mineralization, sediment-hosted precious metal deposits, to distal disseminated Au-As and Ba-Hg-TI deposits. The deposits are hosted in, from proximal to distal, porphyritic granodiorites, limestones, and turbiditic shales. Gradual changes in geochemical, mineralogical, and isotopic compositions across the district indicate consanguinity between them.
Epithermal gold mineralization at Bau is most similar to disseminated, sediment-hosted gold deposits of Nevada, except for higher grades, visible occurrence of gold, both base and precious metal signatures, purely structural controls, less radiogenic lead, and magmatic sulfur isotope signatures.
37
Painter, Matthew Graham Morgan. "The geochemical and mineralogical haloes around the Mount Isa base metal orebodies /". [St. Lucia, Qld.], 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17242.pdf.
Testo completo
38
Collings, Matthew David. "Complexation of Ba and Cu in hydrothermal NaCl brines : insights from EXAFS spectroscopy and molecular dynamics". Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326719.
Testo completo
39
Kiracofe, Zachary Aaron. "Assessing the geologic sources of manganese in the Roanoke River watershed". Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/52890.
Testo completoAbstract (sommario):
Elevated manganese (Mn) concentrations have been measured in groundwater within the Roanoke River watershed, Virginia. Concentrations of Mn often exceed the secondary drinking water standard. A historic belt of Mn ores, the James River-Roanoke River Manganese District (JRRRMD), occurs in the eastern part of the watershed. The project objectives were to 1) evaluate the formation of the JRRRMD ore deposits and 2) analyze existing groundwater chemistry data to evaluate sources and processes that control groundwater Mn.
Analysis of ore minerals, morphologies, and chemistry provides support that the ore deposits are supergene in origin, consistent with previous work. Spatial correlations between Mn ore locations and stream terrace deposits support a model of ore formation in which Mn-oxides were precipitated near discharge zones as anoxic groundwater mixed with oxic groundwater. Terrace deposits present at elevations higher than modern streams suggests that topography has been inverted, allowing ores to be found at higher elevations than what is typically associated with ores formed in discharge zones.
Analysis of groundwater chemistry data shows positive correlations between Mn, calcium and bicarbonate concentrations in groundwater, suggesting that carbonate-bearing lithologies are probable sources of Mn to groundwater. Regionally, groundwater flows toward the Roanoke River where the flowpath terminus is marked by elevated Mn. The inverse correlation of Mn with dissolved oxygen suggests that reducing conditions that develop along flowpaths allow for Mn to persist in groundwater. Overall, results suggest that the same processes that allowed for formation of the JRRRM ore deposits continue to occur today.Master of Science
40
Dünkel, Ines. "The genesis of east Elba iron ore deposits and their interrelation with Messinian tectonics /". Tübingen : Institut und Museum für Geologie und Paläontologie, 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=967986257.
Testo completo
41
Malehmir, Alireza. "3D Geophysical and Geological Modeling in the Skellefte District: Implications for Targeting Ore Deposits". Doctoral thesis, Uppsala University, Department of Earth Sciences, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8188.
Testo completoAbstract (sommario):
With the advancements in acquisition and processing of seismic reflection data recorded over crystalline rocks, building three-dimensional geologic models becomes increasingly favorable. Because of little available petrophysical data, interpretations of seismic reflection data in hardrock terrains are often speculative. Potential field data modeling are sometimes performed in order to reduce the ambiguity of seismic reflection interpretations. The Kristineberg mining area in the western part of the Paleoproterozoic Skellefte Ore District was chosen to construct a pilot three-dimensional geologic model in an attempt to understand the crustal architecture in the region and how the major mineral systems operated in this architecture. To contribute to this aim, two parallel seismic reflection profiles were acquired in 2003 and processed to 20 sec with special attention to the top 4 sec of data. Several reflections were imaged and interpreted by the aid of reflector modeling, borehole data, 2.5D and 3D potential field modeling, and geological observations. Interpretations are informative at the crustal scale and help to construct a three-dimensional geologic model of the Kristineberg mining area. The three-dimensional geologic model covers an area of 30×30 km2 down to a depth of 12 km. The integrations help to interpret a structural basement to the Skellefte volcanic rocks, possibly with Bothnian Basin metasedimentary affinity. The contact is a shear-zone that separates the two units, generating large fold structures, which can be observed in the region. The interpretations help to divide the Revsund granitic rocks into two major groups based on their present shape and thickness. A large gravity low in the south is best represented by the intrusion of thick dome of Revsund granite. In the north, the low-gravity corresponds to the intrusion of sheet-like Revsund granites. In general, the structure associated with the Skellefte volcanics and the overlying metasedimentary rocks are two thrusts exposing the Skellefte volcanic rocks in the cores of hanging wall anticlinal structures. Lack of coherent reflectivity in the seismic reflection data may be due to complex faulting and folding systems observed in the Skellefte volcanics. Ultramafic sills within the metasedimentary rocks are interpreted to extend down to depths of about 5-6 km. The interpretations are helpful for targeting new VHMS deposits and areas with gold potential. For VHMS deposits, these are situated in the southern limb of a local synformal structure south of the Kristineberg mine, on the contact between the Revsund granite and the Skellefte volcanic rocks. A combination of metasedimentary and mafic-ultramafic rocks are highly gold prospective in the west, similar to observations elsewhere in the region. There are still questions that remain unanswered and need more work. New data in the study area will help to answer questions related to e.g., an enigmatic diffraction seismic signal in Profile 5 and the structural relationship between the Skellefte volcanic rocks and the Malå volcanics. Although the derived 3D geologic model is preliminary and constructed at the crustal scale, it provides useful information to better understand the tectonic evolution of the Kristineberg mining area.
42
Smith, Stephen Findley. "Structural stability, support and excavation aspects of mine openings in stratified iron ore deposits". Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283587.
Testo completo
43
Jiang, Shao-Yong. "Chemical and boron isotopic compositions of tourmaline from sedex-type and metaevaporite ore deposits". Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294950.
Testo completo
44
Robison, Lori Carol 1955. "Geology and geochemistry of Proterozoic volcanic rocks bearing massive sulfide ore deposits, Bagdad, Arizona". Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/558078.
Testo completo
45
Dünkel, Ines. "The genesis of East Elba iron ore deposits and their interrelation with Messinian tectonics". [S.l. : s.n.], 2003. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10405671.
Testo completo
46
Knorsch, Manuel. "The mechanisms and implications of hydrothermal mineral replacement reactions in carbonate-hosted ore deposits". Thesis, Knorsch, Manuel (2021) The mechanisms and implications of hydrothermal mineral replacement reactions in carbonate-hosted ore deposits. PhD thesis, Murdoch University, 2021. https://researchrepository.murdoch.edu.au/id/eprint/64693/.
Testo completoAbstract (sommario):
Mineral replacement reactions commonly occur during the formation and alteration of ore deposits. In such settings, primary minerals are often dissolved, with new phases forming as products in the presence of a fluid phase. Particularly within carbonate-hosted epigenetic ore deposits, mineral replacement reactions represent a fundamental ore-forming mechanism whereby primary carbonates are replaced by secondary minerals. These replacement processes generate porosity and facilitate ore mineral precipitation. This study compares observations of natural, ore-forming mineral replacement reactions with laboratory-derived hydrothermal replacement experiments to decipher the metasomatic processes of ore formation from the deposit scale to the nanoscale. This thesis presents insights on (i) the ore-forming mechanisms and post-ore alteration of the Artemis Zn-Cu-Au prospect (Chapters 2 and 3), (ii) the pseudomorphic replacement of calcite by siderite (Chapter 4), and (iii) the replacement of bastnaesite by rhabdophane and monazite (Chapter 5). These chapters focus on the mechanisms, porosity formation, and element redistribution of mineral replacement reactions, typically observed in carbonate-hosted mineral deposits.
Chapter 2 details the importance of mineral replacement reactions during the formation and post-depositional alteration of a carbonate replacement deposit. The study was carried out on the Artemis Zn-Cu-Au prospect, which is located in the Cloncurry district, NW Queensland, Australia. The high-grade polymetallic mineralization displays a complex association of massive sulfides and carbonates hosted in a vertical marble lens. Petrographic analyses suggested three major stages: (i) pre-ore stage marble; (ii) ore stage mineralization involving the dissolution of calcite from the marble and precipitation of sulfides and secondary carbonates; and (iii) a post-ore alteration stage involving the replacement of sulfides by calcite and garnet. The replacement of Co-rich arsenopyrite (Fe0.75Co0.26As1.13S0.83) by relatively Co-poor arsenopyrite (Fe0.86Co0.15As0.99S0.99) revealed formation temperatures of 650 ± 50 and 450 ± 70 °C, respectively. In the post-ore stage, pyrrhotite Fe(1-x)S, (x = 0.091–0.119) was pervasively replaced by an almandine-spessartine-rich garnet. The microscale investigations of the mineralization processes in the Artemis orebody document the impact of hydrothermal mineral replacement reactions on metal sequestration. Mineral replacement reactions facilitate the formation of ore deposits and subsequent alteration processes, which may lead to the late-stage loss of economic value of the deposit.
Chapter 3 discusses the importance of conducting nanoscale investigations of mineral replacement reactions to constrain their physicochemical conditions, exemplified by the suggested replacement of pyrrhotite by garnet at the Zn-Cu-Au Artemis prospect. Nanoscale examinations by transmission electron microscopy (TEM) of the grain boundary between pyrrhotite and garnet reveal textural and compositional complexity at the reaction front. The single crystal of pyrrhotite has a <100 nm thick Bi-rich rim (~2.7 at.% of Bi). The pyrrhotite rim is bounded by a 5–20 nm wide hematite layer, while pores (<10 nm thick) are present between the two phases. The garnet single crystal and the hematite layer are separated by a gap (10–30 nm). These observations indicate that the replacement of pyrrhotite by hematite proceeded via the coupled dissolution reprecipitation (CDR) mechanism, while Bi precipitated from the hydrothermal solution. The newly formed porosity was occupied by subsequent precipitation of garnet. This study highlights the importance of nanoscale characterization for revealing detailed mechanisms of sulfide alteration.
Chapter 4 details experiments on the replacement of calcite by siderite in Fe-rich hydrothermal fluids, investigating the effects of temperature (60–200 °C), solution pH (1.8–10), time (2–1680 h), and calcite precursor (marble and Iceland spar). Two contrasting replacement processes were identified: At 60 °C, the replacement was slow at a transformation of 89% after 1680 h for Iceland spar experiments. Siderite precipitated preferentially along the twin boundaries of calcite, and porosity developed in-between the twins. At 200 °C, the reaction was much quicker at a transformation of 94 % after 8 h. Several concentric 5–15 μm thick epitaxial siderite layers, separated by gaps (<15 μm) that were partly occupied by akaganeite [Fe3+O(OH,Cl)], replaced the calcite grains. Two siderite populations were identified: (i) metastable, pristine and Ca-rich siderite-1 and (ii) microporous, Ca-poor siderite-2. With time, siderite-1 equilibrated with the Fe-rich bulk fluid and transformed into siderite-2, marking the second replacement step. The formation of microporosity created permeability as a result of molar volume change between siderite-1 and -2 (-4.8%). The concentric layer formation is interpreted as an “oscillatory” CDR mechanism, which forms due to the interplay of passivation, fluid with nonequilibrium composition at the reaction front, and secondary porosity formation. Both textures may be used to interpret reaction conditions in natural mineral replacement reactions, especially within carbonate-replacement deposits.
Chapter 5 focuses on the replacement of the rare earth element (REE) fluorocarbonate mineral bastnaesite (REECO3F), which is frequently affected by fluid-induced alteration processes throughout all crustal levels. The experiments studied the effect of epithermal phosphate-bearing solutions on bastnaesite, which led to its replacement by monazite (REEPO4) and rhabdophane (REEPO4∙nH2O). At 90 °C, fibrous metastable rhabdophane replaced bastnaesite, which was then gradually replaced by monazite. At 220 °C, only monazite formed, and the reaction initiation was much quicker. Spot analyses showed that REE patterns were similar between bastnaesite and monazite. However, rhabdophane preferentially scavenged Nd to Ho. The presented results provide new insights into the formation conditions of rhabdophane and monazite and detail contrasting REE fractionation processes in the epithermal environment, which are critical to our understanding of the genesis of REE deposits.
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Williams, Richard James. "Karst-associated bauxite deposits of Parnassos-Ghiona, Central Greece : ore genesis and structural evolution". Thesis, University of Brighton, 2014. https://research.brighton.ac.uk/en/studentTheses/2b04d019-0696-4544-a13d-b2de8971a69b.
Testo completoAbstract (sommario):
The karst-associated bauxites of the Parnassos-Ghiona zone in Central Greece are part of the large Mesozoic age Mediterranean Karst Bauxite belt. Greece is responsible for around 50% of European bauxite production, and has an estimated 600 million tonnes of bauxite reserves. This investigation focuses on the bauxites of Mount Iti and Mount Ghiona, two mountains in the west of the Parnassos-Ghiona zone that are currently being explored and mined by Greek bauxite producer, Elmin S.A. The aim was to develop a better geological understanding of the ore genetic history and regional structural evolution to aid ore deposit science and bauxite exploration. Within the Parnassos-Ghiona zone the bauxites were deposited as three separate ore horizons intercalated with thick limestone layers during the early Jurassic, late Jurassic and late Cretaceous. Only the upper two bauxite horizons are economic and therefore formed the focus of this investigation.
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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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Shellnutt, John Gregory. "A-type granites of the Permian Emeishan large igneous province (SW China): implications for the formation of thegiant magmatic oxide deposits". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39634498.
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Piché, Mathieu. "Synthèse géologique et métallogenique du camp minier de Matagami, Québec /". Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1991. http://theses.uqac.ca.
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