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1
Li, Yang. "Geochronology and fluid evolution of the Qulong porphyry system : implications for porphyry deposit formation." Thesis, Durham University, 2016. http://etheses.dur.ac.uk/11869/.
Full textAbstract:
Understanding the metal enrichment process and rate in porphyry Cu systems (PCS) is critical to underpin the genetic model of PCS and refine the template for exploration, of which robust temporal constrain is the key. In addition, fluid evolution paths constrained by bulk analysis potentially suffer problems of contamination. Based on detailed field geology and petrographic study, this PhD thesis addresses the timescales and fluid evolution process of the world class Qulong porphyry Cu-Mo deposit, Tibet, China, by applying high precision geochronology and high spatial resolution isotope analysis. A fluid inclusion study indicates that the bulk mineralization at Qulong was deposited between 425 and 280 oC under hydrostatic pressure conditions. The depth of formation of the Qulong porphyry Cu-Mo system is estimated at ~2.7 km, which implies ~2.3 km of erosion has occurred since its formation. Zircon CA-ID-TIMS U-Pb geochronology constrains the emplacement ages of the Rongmucuola pluton, the P porphyry and quartz aplite to 17.142 ± 0.014/0.014/0.023 (analytical/plus tracer/plus decay constant uncertainty), 16.009 ± 0.016/0.017/0.024 and 15.166 ± 0.010/0.011/0.020 Ma, respectively. Molybdenite ID-NTIMS Re-Os geochronology suggests that the bulk mineralization at Qulong was deposited through multiple shorted lived pulses (~ tens of kyrs) between 16.126 ± 0.008/0.060/0.077 and 15.860 ± 0.010/0.058/0.075 Ma, with a duration of 266 ± 13 kyrs. Quartz SIMS oxygen isotope analysis indicates a periodic interplay between meteoric and magmatic fluids and continuing increase of meteoric water from ~10 to ~25 % volume percent during the ore-forming process. As a result meteoric water is invoked as the main trigger for metal deposition at Qulong. The major conclusions of this study from Qulong are supported by numerical modelling, titanium diffusion and high precision studies, and have implications for understanding porphyry systems worldwide, for example, multiple and cyclic magmatic-hydrothermal fluid pulses cooled by meteoric water are fundamental for ore formation.
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Rappé, Charles J. "Porphyry and the Platonic-Aristotelian tradition." [S.l. : s.n.], 2002. http://www.freidok.uni-freiburg.de/volltexte/599.
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McFall, Katie Anne. "Critical metals in porphyry copper deposits." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/412122/.
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Critical metals are elements essential to high-tech industry and green technology which are associated with a significant supply risk. Diversifying supplies of these elements is therefore a high priority. Porphyry copper deposits contain potentially economic enrichments of some of these elements, namely rhenium, platinum group elements (PGEs), bismuth and tellurium. This thesis investigates the source, transport mechanism and distribution of these critical elements in two post-collisional Tethyan porphyry deposits. The Muratdere Cu-Mo (Au-Re) porphyry deposit, Turkey, described here for the first time, contains two generations of molybdenite with contrasting Re concentrations. The early, Re-poor molybdenites have magmatic δ34SCDT values, while the late, vein hosted Re-rich molybdenite has δ34SCDT values matching those of the surrounding country rock suggesting that the additional Re has been sourced from hydrothermal fluid-country rock interaction. The Skouries Cu-Au porphyry deposit, Greece, is PGE, Te and Bi enriched. In contrast to Muratdere, Skouries is shown to be an orthomagmatic system hosted by a series of overprinting dykes, with the metal enrichment hypothesised to have been provided by periodic mafic recharge of a deeper source magma chamber. The mineralising fluids in Skouries are shown to have been highly oxidised and hypersaline with complex cation chemistry (Na, K, Fe, Mn and Ca), and with the overall fluid evolution progressing from an early CO2 rich fluid to a later brine. The PGEs in the deposit are located in the main hypogene mineralising veinsets, associated with potassic alteration, and are found to be hosted in bismuth and tellurium complexes. A variety of platinum group minerals are identified, including sopcheite (Ag4Pd3Te4) and sobolevskite (PdBi). LA-ICP-MS of fluid inclusions, combined with microthermometry, has shown gold, bismuth and palladium to be hydrothermally transported by high temperature ( > 500°C), high salinity ( > 65 wt% NaCl+KCl) and highly oxidised fluids, and a bismuth-tellurium collector model is proposed to allow concentration of palladium from under-saturated fluids into platinum group minerals. High semi-metal (Te and Bi) contents in porphyries are therefore proposed to be an indicator of PGE enrichment.
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Valencia, Victor A. "EVOLUTION OF LA CARIDAD PORPHYRY COPPER DEPOSIT, SONORA AND GEOCHRONOLOGY OF PORPHYRY COPPER DEPOSITS IN NORTHWEST MEXICO." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1085%5F1%5Fm.pdf&type=application/pdf.
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Wolfe, RC. "The Dinkidi Cu-Au porphyry : geology of the Didipio region and paragenesis of the Dinkidi Cu-Au porphyry deposit." Thesis, Royal Society of Tasmania, University of Tasmania Library Special and Rare Materials Collection, 2002. https://eprints.utas.edu.au/11283/2/Wolfe_-Whole.pdf.
Full textAbstract:
The Dinkidi Cu-Au porphyry deposit is located in northern Luzon, Philippines. The 110 Mt deposit is characterised by high gold grades (ave. 1.2 g/t Au and 0.5% Cu) and is one of only a few alkaline porphyry deposits to have been discovered outside British Columbia.
Alkaline magmatism in northern Luzon is related to the Late Oligocene rifting event that formed the Cagayan Valley Basin, and to the final stages of west-directed subduction along the East Luzon trench. Subalkaline andesitic and trachytic lavas and minor volcaniclastic rocks of the Mamparang Formation were emplaced along the southwest margin of the Cagayan Valley Basin, and have been intruded by a series of alkaline plutons and stocks. The Dinkidi deposit is hosted within the multi phase Dinkidi Stock, which is in turn part of a larger alkaline intrusive body, the Didipio Igneous Complex.
The Didipio Igneous Complex consists of: (I) an early composite clinopyroxene-gabbro-diorite-monzodiorite pluton; (2) the Surong clinopyroxene to biotite monzonite pluton; (3) the Cu-Au mineralised Dinkidi Stock, which comprises an early equigranular biotite-monzonite stock (Tunja Monzonite), a thin, variably-textured clinopyroxenesyenite (the Balut Dyke), and a monzosyenite porphyry (Quan Porphyry) that grades, in its core, into a crystal-crowded leucocratic quartz-syenite (Bufu Syenite); and (4) postmineralisation andesite dykes.
Whole-rock chemistry indicates that the volcanic formations in the Didipio region become progressively more alkaline up stratigraphy, indicating that Late Oligocene rifting intermittently tapped an LILE-enriched mantle source that became progressively more LILE-enriched over time. Whole rock and mineral compositions indicate that all intrusions in the Didipio region were sourced from a common magma chamber, and were related by shallow level fractional crystallisation.
Five main hydrothermal events are recognised in the Didipio region: (I) contact metamorphism and weak biotite-cordierite alteration is associated with emplacement of the early diorite phase; (2) K-silicate magnetite-biotite alteration, and subeconomic Cu-Au mineralisation associated with the emplacement of the Surong monzonite pluton; (3) intensely developed porphyry-style alteration and ore-grade Cu-Au mineralisation which is spatially and temporally associated with emplacement of the Dinkidi Stock; (4) an advanced argillic alteration assemblage, which has overprinted the Didipio Igneous Complex and is associated with subeconornic high-sulphidation style Cu-Au mineralisation; (5) late-stage unmineralised zeolite-carbonate veins, which are associated with post-mineral strike-slip faulting.
At Dinkidi, emplacement of the Tunja Monzonite was temporally and spatially associated with the formation of a pervasive biotite-magnetite K-silicate alteration assemblage in the pre-mineral diorites. Emplacement of the Balut Dyke was associated with a calc-potassic style diopside-actinolite-K-feldspar-bornite alteration assemblage and associated vein stockwork. This quartz-free mineral assemblage is associated with high gold grades (2-8 g/t Au) and is typical of alteration assemblages found in quartz-undersaturated alkaline porphyry systems. Intrusion of the Bufu Syenite led to the formation of a quartz-sericite-calcite-chalcopyrite stockwork vein and alteration assemblage, which has overprinted the calc-potassic assemblage. The quartz stock work hosts the bulk of low grade mineralisation (1-2g/t Au) at Dinkidi and is typical of silica-saturated alkaline porphyry systems. A coarse-grained assemblage of quartz-actinolite-perthite (the 'Bugoy Pegmatite') formed as an apophysis on the Bufu Syenite, and was subsequently brecciated by late-stage faulting. High-level argillic and late-stage fault-related zeolite mineral assemblages have overprinted the porphyry-style hydrothermal assemblages.
The calc-potassic assemblage is inferred to have formed at temperatures in excess of >600°C from a silica-undersaturated K-Ca-Fe brine. Fluid inclusion studies indicate that the quartz stockwork was emplaced at submagmatic temperatures (>600°C) from a quartz-saturated Na-K-Fe brine (>68 wt. % eq. NaCI) that contained up to 0.6 wt. % Cu and 4 wt. % Fe. Cooling to ~420°C and neutralisation by wall rock interaction lead to the precipitation of sulphides within the quartz stockwork. The quartz-bearing assemblage was emplacement at 2.9 to 3.5 km paleodepth, and was associated periods of overpressurisation and quartz growth disrupted by episodic depressurisation to near hydrostatic pressure conditions.
The hydrothermal mineral assemblages at Dinkidi reflect the composition and degree of fractionation of the associated intrusions. Extensive fractionation within a feldspathoid-normative dioritic magma chamber is interpreted to have ultimately caused quartz saturation and the development of the late-stage syenite intrusions and related quartz stockwork mineralisation. The calcic, silica-undersaturated Balut Dyke (associated with the calc-potassic stockwork) does not fit this fractionation trend, and is interpreted to have formed by interaction between the late-stage syenitic melt and a co-magmatic mafic melt that underplated the siliceous magma chamber prior to formation of the Balut Dyke. A reversion to fractionation-dominated magmatic processes in the silicic magma chamber then lead to the intrusion of the quartz-saturated Quan Porphyry and Bufu Syenite. Ultimately, the residual mafic melt was emplaced as a series of late-stage andesite dykes.
The Dinkidi porphyry Cu-Au deposit shows that it is possible for silica-undersaturated and silica-saturated styles of alkaline porphyry mineralisation to form in the same magmatic-hydrothermal system, given the right conjunction of geological processes. Exploration models for alkaline porphyry systems therefore need to be flexible enough to accommodate the possibility of silica-undersaturated and saturated mineralised zones forming in the same deposit. The strongly mineralised, variably textured Balut Dyke shares textural and genetic similarities with mineralised pegmatite dykes from midcrustal granitic environments. Highly Cu-Au mineralised 'pegmatitic' dykes should therefore also be considered as a viable exploration target in alkaline porphyry systems.
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Dickinson, Jenni Michelle. "Jura-triassic magmatism and porphyry Au-Cu mineralization at the Pine Deposit, Toodoggone District, North-central British Columbia." Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/3959.
Full textAbstract:
The Pine, Fin, and Mex porphyry Au-Cu ± Mo systems are all located within a 10 km² area in the
Toodoggone district, along the eastern margin of the Stikine terrane in British Columbia. Multiple
episodes of porphyry-style mineralization are associated with these three magmatic centres. The Fin
monzogranite is the oldest dated pluton in the district, with a U-Pb zircon emplacement age of 217.8 ± 0.6
Ma. A cross-cutting main-stage quartz-pyrite-chalcopyrite ± molybdenite ± sphalerite vein gives an older
Re-Os molybdenite mineralization age of 221.0 ± 1.4 Ma. Hence the vein probably cross-cuts a slightly
older, undated magmatic phase. Lead isotope values for sulphide minerals from main-stage veins indicate
that magmatic-derived fluids interacted with country rocks and possibly other fluids.
The Pine quartz monzonite (U-Pb zircon emplacement age of 197.6 ± 0.5 Ma) intrudes, alters,
and locally mineralizes Toodoggone Formation Duncan Member andesite tuff (U-Pb zircon age of 200.9
± 0.4 Ma). High-grade (0.57 g/t Au and 0.15% Cu) mineralization occurs in main-stage quartz-magnetite
chalcopyrite-pyrite veins and disseminated throughout the potassic alteration zone in the Pine quartz
monzonite stock. Late-stage anhydrite-pyrite ± specular hematite ± chalcopyrite, quartz-pyrite ±
chalcopyrite, and pyrite ± chalcopyrite veins and related phyllic alteration cross-cut earlier veins.
Propylitic alteration occurs distal to the potassic core of Pine in the Fin monzogranite and Duncan
Member andesite. Limited fluid inclusion data, in combination with S and Pb isotope values for veins and
host rocks, suggest that the main-stage fluid was magmatic-derived and deposited metals at 430 to 550 °C
and depths of about 5.5 km. Late-stage fluids were also probably derived from the Pine quartz monzonite
but interacted with Takla Group country rock prior to metal deposition. Metals were deposited at
temperatures of 330 to 430 °C and depths of about 5.0 to 5.5 km.
The final mineralization phase of the Pine porphyry system is temporally constrained by the
emplacement of weakly mineralized syenite dykes (U-Pb zircon age of 193.8 ± 0.5 Ma). The final stage
of magmatism in the Pine-Fin-Mex area is defined by the emplacement of rhyolite dykes (U-Pb zircon
age of 193.6±0.4 Ma).
7
Puig-Pichuante, R. M. "Molybdeunum mineralization with emphasis on porphyry systems genesis and exploration." Thesis, Rhodes University, 1986. http://hdl.handle.net/10962/d1006840.
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Mo became very important in the last century, because of its sophisticated properties and its use in the new technology of alloys . Porphyry systems (porphyry Cu-Mo and Mo) contribute a significant proportion (90 - 95 per cent) to the Mo world's production. This type of deposit is associated mainly with Phanerozoic orogenic belts. Above 87per cent of the world resources are in the American Circumpacific belts , both Andean and Cordilleran . Ore grade in porphyry Cu-Mo range from 0,005 to 0,04per cent Mo, whereas in porphyry Mo grades range from 0,08 to 0,75per cent Mo . These deposits are associated with a magmatism which shows an evolution from calcic in island arcs, to calc-alkaline in magmatic back arcs, with an increase of the Mo content in the same direction. Porphyry Mo deposits display several features in common with porphyry Cu deposits. hydrothermal Similarities include nature of host alteration patterns and distribution of rock intrusives, ore minerals. An interesting difference is found in the Re contents of the molybdenite mineral. This element is higher in the molybdenites of porphyry Cu, than in those of the porphyry Mo. The ore genesis process begins involves partial melting, within enriched zones of the upper mantle and magma differentation, liquid state thermogravitational diffusion, magma convection and boiling. These processes progressively concentrate Mo in the fluids, which are released at some stage, into sulphidic hydrothermal systems, under complex geologictectonic conditions involving fracturing, brecciation and hydrothermal alteration. Major concentrations of the ore mineral are always associated with potassic alteration, and with late magmatic-early hydrothermal stages (Chilean and Western North American porphyries). Geological mapping and a close understanding of alteration and mineralization patterns, and lithogeochemistry are important tools for the exploration of porphyry Mo deposits. Geochemical prospecting, using soils, vegetation and water as sampling media, and regional aeromagnetic, gravity surveys, aerial photography and remote sensing, are us.
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Nickerson, Phillip Anson. "Post-Mineral Normal Faulting in Arizona Porphyry Systems." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/242354.
Full textAbstract:
In the Basin and Range province of southwestern North America, Oligocene and Miocene normal faults are superimposed upon the Late Cretaceous-early Tertiary magmatic arc. This study examines tilted fault blocks containing dismembered pieces of porphyry systems, including pieces below and peripheral to ore bodies, that are exposed at the modern surface. Features in the magmatic-hydrothermal porphyry systems are used to place constraints on the style of extension in Arizona, and reconstructions of extension are used to examine the deep and peripheral portions of porphyry systems to provide a more complete understanding of porphyry systems as a whole. The Eagle Pass, Tea Cup, and Sheep Mountain porphyry systems of Arizona are examined in this study. In all the study areas, previous interpretations of the style of extension involved strongly listric normal faults. However, similar amounts of tilting observed in hanging wall and footwall rocks, as well as structure contour maps of fault planes, require that down dip curvature on faults was minimal (<1°/km. Instead, extension is shown here to have occurred as sets of nearly planar, "domino-style" normal faults were superimposed upon one another, including in the Pinaleño metamorphic core complex. Reconstructions of Tertiary extension reveal that sodic (-calcic) alteration is occurs 2-4 km peripheral to, and greisen alteration is found structurally below and overlapping with, potassic alteration. In addition, a preliminary reconstruction of extension across the Laramide magmatic arc reveals that the geometry, as revealed by known porphyry systems, is of similar scale to that of other magmatic arcs. These results help further the debate surrounding competing models of continental extension, and combine with previous work to provide a more complete understanding of the geometries of Arizona porphyry systems at the district and arc scale.
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Mathur, Ryan Dilip. "Rhenium-osmium isotopes of base metal porphyry deposits." Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/289216.
Full textAbstract:
This study uses Re-Os isotopes from sulfide minerals (molybdenite, pyrite, chalcopyrite, bornite, sphalerite, arsenopyrite, and galena) and magnetite from high (400-500°C) and low and low ( < 300°C) temperature mineralization assemblages associated with the intrusion of igneous rocks to trace the source of Os and by inference the other metals. The source of Os is used as a proxy for the source of copper and gold in these systems. Concentrations of Re-Os for all sulfides except molybdenite in various deposit types vary from 0.005-2 ppb Os and 0.120-500 ppb Re. Initial ¹⁸⁷Os/¹⁸⁸Os ratios derived from isochron plots ranges from 0.15-50. These data show interesting relationships among deposits of different styles within the district, region, and worldwide scales. On the district-deposit scale, Re-Os isotopes illustrate a complex behavior for the source of Os and by inference other transition and noble metals. The source of Os can be linked to one intrusive event, multiple intrusive events, and the sedimentary rocks into which the magmas intersect. On a regional scale, in the Andean Cordillera, Re-Os isotopes reveal a correspondence between the initial ¹⁸⁷Os/¹⁸⁸Os ratios from sulfides of the ore deposit and amount of copper present in porphyry copper deposits. Eleven deposits sampled from different crustal blocks and different mineralization ages form a trend in which deposits that contain large amounts of copper have less radiogenic ¹⁸⁷Os/¹⁸⁸Os initial ratios, suggesting a greater mantle component. Smaller deposits have more radiogenic Os suggesting greater crustal components. On a global scale, the significant observation for the deposits that form in arc environments is that all of the calculated initial ¹⁸⁷Os/¹⁸⁸Os ratios are greater then the chondritic mantle. This indicates that there must be a crustal source (recycled in a metasomatized mantle, lower/upper continental crust, or subducting slab) that contributes Os and by inference other metals present in porphyry coppers. Another feature of the data set is that gold-bearing systems in arc environments associated with porphyry intrusions have crustal signatures (0.5-2.5) regardless of the style of the related ore body. For instance, the low/high sulfidation epithermal gold systems in Bucaramanga Columbia (¹⁸⁷Os/¹⁸⁸Os initial 1.2), the massive sulfide ores of the Grasberg, Irian Jaya (¹⁸⁷Os/¹⁸⁸Os initial 0.7--1.2), and Cu-Au skarns in the Hedley District, British Columbia (¹⁸⁷Os/¹⁸⁸Os initial 1.7-2.5) all have large crustal components.
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Tomlinson, David Harris. "Nature and Origin of Fissure Ore at the Porphyry-Epithermal Transition Zone of the Bingham Canyon Porphyry Cu-Au-Mo Deposit, Utah." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7544.
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Late-stage fissure-filling ore at the world class Bingham Canyon, Utah, porphyry copper deposit has long been recognized, but poorly studied. Physical and chemical characterization of the Pb-Zn-Cu-Ag-Au mineralized fissures in the porphyry-epithermal transition zone provides insight into the origin, timing, and controls of ore deposition. These sheared sulfide-rich fissures are dominated by pyrite and multiple generations of quartz, with lesser amounts of other sulfides and gangue minerals. Au (0.27 to 4.61 ppm) provides the most value to the ore in the transition zone. Host rocks include Eocene monzonite and Paleozoic limestone and quartzite"”all of which can contain economic ore bodies. Associated alteration is predominantly sericitic and argillic. Mineralization into the wall rocks is restricted, not exceeding 1.5 m from the fissure margins. Mineral assemblages vary with distance from the center of the main Cu-Mo deposit and the modal abundances are dependent on host rock. The appearance of both galena and sphalerite (and tennantite to an extent) mark the transition from a porphyry to an epithermal environment. This is accompanied by an increased concentration of chalcophile trace elements in sulfides as determined by EMPA and LA-ICP-MS. Significant hosts of Ag include galena and tennantite, while Cu is hosted primarily in chalcopyrite, tennantite, and sphalerite. Gold does not appear to be hosted in solid solution, but may be focused along fractures or inclusions in pyrite. δ3434S values of fissure pyrite has a narrow range (+2.3 to 3.4‰), while δ18O of quartz is more variable and high (+11.5 to 14.0‰) relative to typical hydrothermal quartz. This can be explained by increased fractionation at lower temperatures in the magmatic fluids, which could have additionally mixed with exchanged 18O-rich meteoric water. Ore grades improve with distance from the center of the deposit; however, this is accompanied by higher concentrations of elements (Pb, As, Bi, etc.) undesirable for downstream processing. The mineralized fissures were created sequentially throughout the formation of the deposit. Initial joints probably formed as a result of the intrusion of a barren equigranular monzonite. The NE orientation of the joints was controlled by the regional stress field, which is more apparent distal to the center of the deposit. A quartz monzonite porphyry then intruded, dilating the joints to allow precipitation of quartz and then pyrite during the Cu-Au-stage of mineralization in the main ore body. After dike-like intrusions of latite porphyry and quartz latite porphyry intruded, galena, sphalerite, and pyrite precipitated to form the Pb-Zn-Ag mineralization. This was followed by late precipitation of chalcopyrite and tennantite (and likely Au mineralization).
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Diaz, Acevedo Nelson Simon. "Exotic deposits derived from porphyry copper systems in Chile." Thesis, Rhodes University, 1996. http://hdl.handle.net/10962/d1011149.
Full textAbstract:
The exotic orebodies related to cal-alkaline porphyry copper deposits. are sub-horizontal lenticular bodies of secondary copper minerals that impregnate Tertiary gravels and bedrock of different ages. They lie immediately downslope of the porphyry copper deposits, that is to say. they are related to the propylitic halo of the main deposits, and are considered to have originated with the deposition of copper minerals from solutions that overflowed during the secondary enrichment process. Supergene alteration took place between the late Oligocene and Miocene, by which time both orehodies (exotic and porphyry copper) were established. The paucity of tile denudation since the Miocene in the Andean segment from 21º to 26º latitude S. due to the dominance of a hyperarid climate explains the remarkable preservation of the shallow porphyry copper systems, supergene enriched blankets and associated deposits. This is reflected in the limonites, where the typical boxworks have been partially or totally destroyed on surface by the superleaching. As a result of the lateral migration of the copper-bearing solutions, the exotic deposits show a zonation. alteration and mineralization whose characteristics depend among other factors. on the reactivity of the bedrocks and the Cu/S ratio of the mother deposit. In these deposits three zones can be recognized: Proximal (0 to 2 km Intermediate (2 to 3) and Distal (3 to 8-14 km) with palaeodrainage control. The associations and mineralogical abundance are related to the climate (rain. temperature). In some deposits two important units are detected and they are the Cu-phosphates and Cu-lixiviable (to sulphuric acid) units. The size of tile Chilean exotic deposits varies between 100 and 3.500.000 tons of copper, with a total known resource of 8 M tons of copper. The large exotic deposits are comparable to the resources of a medium-sized porphyry copper- type deposit. The discovery of the exotic deposits is related to the exploration of porphyry copper deposits, where a mass balance of the leached column must be done. Moreover the lithology and alteration of the propylitic halo. permeability, structures, geophysics and geochemistry should be considered. The diorite model is not compatible with a supergene enrichment process, expressed by the absence of colour anomalies, exotic deposits and in the presence of secondary minerals like jarosite, which is coherent with the pyrite deficiency of the system. The projects are for exploitation of reserves by open pit methods. The projects plan to extract and to crush copper oxide ore which will he pre-treated with concentrated sulphuric acid prior to heap leaching, solvent extraction and electrowinning. The copper output varies between 10,000 and 50,000 ton per year of catilode copper. The total investment varies between 20 and 100 millions dollars. For project calculations, estimation of 65 % - 82 % copper recovery and 37 - 40 kg/ton net acid consumption can be used due to the nature of ore. The leaching time is estimated as 30 to 180 days for heaps of 4,5 to 30 metres high. As a result of this, the plant capacity is determined by an annual equivalent of 10,000 to 25,000 ton Cu per year. Pit planning has heen carried out using diverse software on the basis of 5 x 5 x 5 m and 10 x 10 x 10 m block models, evaluated using a kriging package built into the program, giving an overall waste/ore ratio (induding pre-stripping) of 0: I (in an outcrop) to 3: I. The location of the mine and plant sites are associated with the porphyry copper in production, for this the already installed facilities can be used. So there is no need to build a new mine camp or access. The environmental impact is summarized relating to the characterization of the physical, biological and socio-cuitural effects, using the framework of the Base Line study and the Impact evaluation derived from the construction and project operation phases. The conclusions and recommendations will diminish, mitigate and/or eliminate impact derived from the specific activities.
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Schumer, Benjamin Nathan, and Benjamin Nathan Schumer. "Mineralogy of Copper Sulfides in Porphyry Copper and Related Deposits." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/626163.
Full textAbstract:
Porphyry copper deposits represent one of the largest copper reserves on Earth. They typically contain large, low-grade reserves of primary ore and higher-grade, supergene enrichment blankets of sulfide and oxide ores. Understanding the mineralogy of porphyry copper ores and ores related to porphyry copper systems is exceedingly important for several reasons, foremost of which are the information provided by ore mineral parageneses, assemblages, and mineral chemistry on evolution of these magmatic-hydrothermal systems, and information on mineral processing characteristics of the ores. The focus of this work is to better understand the mineralogy of supergene copper sulfides in porphyry copper systems and hypogene base metal lodes related to porphyry copper systems, and use this mineralogical knowledge to improve our understanding of the processes responsible for ore formation.
The objectives of this study are accomplished by two means: focusing on the crystallography and crystal chemistry of minerals, and then applying this mineralogical knowledge to a supergene sulfide enrichment blanket and hypogene massive sulfides from base metal lodes in southeastern Arizona. The discovery of a new mineral, natropalermoite, NaSr2Al4(PO4)4(OH)4, provided the opportunity to use single-crystal X-ray diffraction to solve a crystal structure, and electron-probe microanalysis (EPMA) to study the crystal chemistry of natropalermoite and how the accommodation of Na in the structure changes lengthens the unit cell along [010] and shortens it along [100] and [001] compared to its lithium analogue, palermoite. Solution of the crystal structure of the mineral nickelskutterudite, (Ni,Co,Fe)As3, allowed for the investigation of anion deficiency in minerals of the skutterudite group, a problem whose solution has eluded researchers for nearly 100 years. Two skutterudite (CoAs3) and two nickelskutterudite samples were analyzed using single-crystal X-ray diffraction, EPMA, and procrystal electron density. The results showed fully-occupied anion sites and a cation surplus, which was accommodated in the icosahedral site, proving that minerals of the skutterudite group are not anion deficient.
This mineralogical knowledge was applied to the supergene enrichment blanket in the Western Copper section of the Morenci mine, Greenlee County, and hypogene massive sulfide deposits associated with a porphyry copper deposit at Bisbee, Cochise County, Arizona. This is one of very few studies of supergene sulfide blankets ever completed. One drill hole through the supergene blanket at Western Copper was examined using ore microscopy and EPMA. Results showed dominant (Cu+Fe):S ratios of 1.80 ± 0.05, 1.92 ± 0.03, and 1.10 ± 0.10, with higher (Cu+Fe):S dominant high in the blanket and low ratios dominant near the base of the blanket. These values were interpreted to be controlled by activity of Cu2+, Fe2+, and Fe3+ in solution.
Massive sulfide deposits at Bisbee were investigated using ore microscopy and EPMA in order to correct the previous conflicting reports of the mineralogy and paragenesis of this famous district and interpret constraints on conditions of ore-forming fluids. Results show four types of ore: chalcopyrite-rich with hematite and/or pyrite, bornite-rich, chalcocite-rich, and a Zn-Pb association. Chalcopyrite-rich ores formed first, followed by bornite-rich and chalcocite-rich ores. All ores were formed at relatively shallow depths from oxidized, moderately sulfur-rich fluids; early fluids were higher temperature and later fluids were lower temperature and considerably more sulfidized. Zinc-lead ores formed early and were continuously dissolved and reprecipitated distal to Cu-mineralization. These patterns are similar to many other base-metal lode districts worldwide, however Bisbee contains more Zn-Pb ore than other districts with hematite-containing ores and less than those without hematite.
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Spencer, Edward. "The transport and deposition of molybdenum in porphyry ore systems." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/27402.
Full textAbstract:
Approximately 99% of Mo is obtained from porphyry deposits (e.g. Sillitoe, 2010), representing the strongest association of any metal with a single deposit type. Despite this, the controls on the formation of Mo-rich porphyries and the spatial-temporal decoupling of Mo from Cu in these systems remain poorly understood. By combining fieldwork, Re-Os molybdenite dating and a fluid inclusion study at one of the world's largest Cu-Mo porphyries (El Teniente, Chile), this project assesses the magmatic-hydrothermal evolution of the system to help constrain the processes controlling Mo enrichment. Results indicate that deposit-wide Mo grades of < 0.06 wt.% are principally controlled by the abundance of main mineralisation-type quartz-molybdenite veins, that develop outwards and upwards into Cu-rich vein types. Parental ore fluids had low salinities (~6.5 wt.% NaCleq) and were exsolved at depth following the emplacement of multiple intrusions that acted as short-lived (< 100,000 years) conduits for mineralising fluids between 6.3 and 4.6 Ma. The decoupled deposition of Mo and Cu surrounding each temporally separate intrusion is attributed to the sequential deposition of Mo then Cu in response to decreasing temperature followed by intermittent fluid boiling and increasing fluid pH in response to sericitic alteration of the mafic host-rocks. Mo grades > 0.06 wt.% correspond to the presence of late mineralisation-type veins and breccias produced by the exsolution of Mo-rich brines ±aqueous fluids from a highly fractionated magma source. Mineralisation in this stage was short-lived and occurred in all parts of the deposit at ~4.6 Ma. The relatively Cu-poor nature of this stage is attributed to the prior preferential extraction of Cu from the underlying magma chamber in earlier mineralising events. In accordance with data from other Mo-rich porphyry systems, results indicate that Mo-Cu decoupling is controlled by both changes in magma chemistry as well as by the evolving P-T-X properties of hydrothermal fluids.
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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.
Full textAbstract:
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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Nelson, James Baird 1967. "Analysis of trace element distributions distal to porphyry copper deposits." Thesis, The University of Arizona, 1996. http://hdl.handle.net/10150/278566.
Full textAbstract:
Enrichment and depletion of trace elements occurs in host rocks distal to porphyry copper deposits as a result of hydrothermal metasomatism. Subtle geochemical distributions in weakly propylitized host rocks is sufficient to indicate proximity to a mineralized system and may be applied to porphyry copper exploration. Samples collected adjacent to four porphyry copper deposits were analyzed for a multi-element suite, then normalized to the elemental concentrations of the fresh host rocks. The probability that an element has been enriched or depleted is determined by using concentrations in the unaltered host in conjunction with a calculated standard deviation. The probabilities have distinct zoning that is related to alteration around the deposits. Contribution lateral to deposits was observed with: Ag, As, Au, Bi, Br, Ca, Cu, Hg, Mn, Mo, Pb, Sb, Se, V, and Zn. Proximal to the mineralized portion of the systems elemental removal was observed with: Ba, Br, Ca, Mg, Mn, P, Pb, Ti, V, Y, and Zn.
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Lecerf, Adrien. "Ordre et variation : essai sur le système de Jamblique." Thesis, Paris, EPHE, 2015. http://www.theses.fr/2015EPHE5071.
Full textAbstract:
Cette thèse se propose de donner une synthèse générale du système du néoplatonicien Jamblique de Chalcis, acteur important de l’évolution de la métaphysique grecque durant l’âge antique tardif. Elle reconstruit tour à tour sa doctrine psychologique, sa hiérarchie des êtres et quelques-uns de ses concepts fondamentaux, en mettant l’accent sur l’histoire des idées entre le fondateur de l’école, Plotin, et la naissance de l’école néoplatonicienne d’Athènes. L’ensemble des œuvres laissées par Jamblique est exploité, ainsi que les quelque 800 fragments et témoignages sur sa vie et sa doctrine laissés par les auteurs postérieurs. Les influences subies sont analysées et replacées en contexte : néoplatonisme de Plotin et Porphyre, qui donne à Jamblique les principaux niveaux de son ontologie, qu’il analyse et fractionne ; médio-platonisme, dont le néoplatonisme hérite des topiques philosophiques ; aristotélisme, qui lègue une conception dynamique de l’âme et une hiérarchie des puissances cognitives consacrant la transcendance de l’intellect ; pythagorisme, qui permet à Jamblique de concevoir les mathématiques comme un langage valable pour la description de toutes les parties de la philosophie. Par l’ampleur de son œuvre ainsi que l’originalité et la fermeté des solutions apportées aux problèmes traités, Jamblique crée une synthèse puissante qui sert de base doctrinale aux écoles néoplatoniciennes tardives d’Athènes et Alexandrie, et est profondément représentative d’un âge théocentrique, où l’âme humaine n’est qu’un principe dérivé, qui doit prendre sa place dans l’ordre universel des choses : une métaphysique de l’unité, reposant sur la dualité dynamique de l’ordre et de sa variationThis thesis strives to provide modern research with a synthesis of the system of Iamblichus of Chalcis, an important figure in the development of later Greek metaphysics. It reconstructs in turn his psychology, his hierarchy of being and some of his most basic concepts and philosophical laws, with a stress on the continuity between Plotinus, founder of the Neoplatonic school, and the beginnings of the school of Athens. The whole of Iamblichus’ body of work is exploited, as well as the 800 fragments and testimonia on his life and doctrine handed down to us by later authors. Influences received are analysed and set in context: Plotinus’ and Porphyry’s Neoplatonism, which provides the general levels of reality which Iamblichus tried to analyse and enrich; Middle Platonism, whose topics are debated in Neoplatonism; Aristotelianism, which accounts for a dynamic conception of the human soul and a hierarchy of cognitive powers beginning with the transcendent Intellect; Pythagoreanism, which allows Iamblichus to depict mathematics as a universal language, able to take the mark of all parts of philosophy. By the scope of his work and the originality and neatness of the solutions he provided to problems which nascent Neoplatonism had to confront, Iamblichus is able to create a powerful synthesis which acts as a doctrinal basis for the later schools of Athens and Alexandria: it is profoundly representative of a theocentric era, in which human soul is but a derived principle that has to keep its place in the grand scheme of being. It is a metaphysics of unity, founded on the dual dynamic of order and variation
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Rich, Shane Daniel. "Geochemical mapping of porphyry deposits and associated alteration through transported overburden." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58704.
Full textAbstract:
Discoveries of porphyry copper deposits (PCDs) in British Columbia have declined over the past 20 years. Undiscovered PCDs are predicted to occur in the Intermontane Belt, an assemblage of volcanic arc terranes considered important for hosting large porphyry deposits. The Deerhorn Cu-Au porphyry, located within this belt, is covered with up to 60 m of undisturbed moraine. Detailed regolith mapping based on a new classification scheme for BC, combined with aqua regia and deionised water assays, sequential leaching, physicochemical measurements and hydrocarbon analysis, was undertaken to determine the response in the till to buried mineralisation. Geochemical relationships dependent on the regolith type were identified and are particularly evident in organic rich areas. To minimise background noise, data analysis was constrained to the dominent regolith unit: the undisturbed moraine (DrM), resulting in enhanced anomaly identification. Regolith mapping in advance of a soil survey can therefore allow targeted efficient sampling. Normalisation to organic carbon (Corg) to counteract the influence of organic matter on trace element variability resulted in anomalous response for elements As, Cs, Cu, Mo, Tl, U and W by conventional aqua regia on a 180-micron fraction B-upper-horizon soil. The response for six of these elements is peripheral to mineralisation in the surface environment. Multi-element evaluation is superior for mineralisation detection than individual element evaluation. Light hydrocarbon results indicate a surface response with a distinct depletion over mineralisation. Sequential leaching on selected anomalous Cu samples indicates that an aqua regia extraction was the optimal first choice for anomalous Cu detection. Copper-Fe-oxide-bearing grains interpreted as oxidised sulphides were recovered from an anomalous Cu-bearing sample and confirm a contribution of glacial clastic transport. Visual screening for clastic fragments allows a reprioritisation of anomalous response. Copper isotope results do not support Cu-ion migration from the buried mineralisation, but instead support a clastic contribution. Anomaly formation is interpreted as a combination of clastic transport, ionic migration of H⁺, vegetation uptake and surface redistribution.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Magny, Ariane. "Porphyry in fragments : Eusebius, Jerome, Augustine and the problem of reconstruction." Thesis, University of Bristol, 2010. http://hdl.handle.net/1983/d105292c-dfd6-4210-b53c-db5d1c4003f9.
Full textAbstract:
Everyone working on Porphyry's 'Against the Christians' refers to the fragment collection compiled by Adolf von Harnack in 1916. Harnack's scholarship was impressive, but his work is difficult to use, and needs revision in the light of new approaches to the collection and interpretation of fragments. This dissertation draws mainly on the methodological work of Most et al. (1997) to argue that a fragment should not be read apart from its contextual framework. The dissertation analyses the fragments preserved in Eusebius, Jerome, and Augustine, and explains how each author's agenda, as well as their religious and intellectual contexts, influence the way in which they refer to Porphyry. Ultimately, this study aims at proposing a new fragment collection.
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Clarke, Emma Catherine. "Iamblichus' De Mysteriis : a manifesto of the miraculous." Thesis, Royal Holloway, University of London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327055.
Full text
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Miller, Owen David William. "Precious metal mineralization associated with the Coed-y-Brenin porphyry copper system, North Wales." Thesis, University of Aberdeen, 1993. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=236945.
Full textAbstract:
The Coed-y-Brenin system is a diorite-hosted porphyry copper deposit of early Ordovician age (Tremadoc) situated on the south eastern side of the Harlech Dome: a thick sequence of Cambrian and Ordovician sediments and volcaniclastics that were subject to greenschist facies metamorphism during the Caledonian Orogeny. The copper mineralization occurs as disseminations, coatings on hairline fractures and in late-stage quartz-sulphide-calcite veinlets. Pyrite and chalcopyrite are the main opaque phases but sulphosalts, tellurides and electrum are also present. The copper mineralization is largely confined to the diorite and micro-tonalite dykes and sills associated with the Rhobell Fawr Volcanic centre. This study has shown that epithermal style precious-metal mineralization is also developed in the Coed-y-Brenin area in the shales and siltstones of the Maentwrog and Ffestiniog Flags Formations. It is characterised by pyritization, sericitization and silicification. The gold and silver occur as electrum in fractures and also as tellurides in late stage quartz-pyrite veins. Both styles of mineralization share a close spatial association and are characterised by propylitic and phyllic alteration. Argillic and potassic assemblages are not developed. Geochemical analysis of mineralized and unmineralized material has shown that the diorite-hosted mineralization is enriched in Cu, Au and Ag and depleted in Zn while the epithermal mineralization displays enrichments in Au, Ag, As, Sb and the base metals. Rb:Sr ratios increase with increasing alteration in both styles of mineralization. Sulphur isotope studies have shown that both styles of mineralization have a common, probably magmatic, sulphur source. Fluid inclusion data and 0 and H isotope studies indicate that following magma emplacement and development of the porphyry copper mineralization a low temperature-low salinity meteoric hydrothermal system was established. Fluid inclusion data and 0 and H isotope studies indicate that following magma emplacement and development of the porphyry copper mineralization a low temperature-low salinity meteoric hydrothermal system was established. This was responsible for the late-stage quartzsulphide-calcite veins in the diorites and for all the sediment-hosted mineralization. The association between epithennal and porphyry deposits has become apparent in recent years but the Coed-y-Brenin system is unusual due to its Lower Palaeozoic age and because both styles of mineralization are developed at the same structural level. This study of the Coed-y-Brenin porphyry system demonstrates the potential for the development and preservation of epithermal mineralization in porphyry systems and also in older orogenic belts.
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Runyon, Simone Elizabeth, and Simone Elizabeth Runyon. "Deep Hydrothermal Alteration in Porphyry Copper Systems: Insights from the Laramide Arc." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625856.
Full textAbstract:
Multiple generations of normal faults dismembered, tilted, and exposed thicknesses of up to 15 km of the upper crust in portions of central and southern Arizona. This extension, variable in distribution and magnitude, was superimposed on the axis of the Laramide magmatic arc and dismembers many porphyry copper systems, allowing for detailed study of vertical and lateral zonation of alteration around these centers. This study examines tilted fault blocks containing portions of porphyry systems across Arizona, focusing on hydrothermal alteration deep and distal in these systems (3+ km paleodepth) to develop a more complete understanding of porphyry occurrences as larger geochemical systems.
This study focuses on Na-Ca and coarse muscovite alteration in the roots of Laramide porphyry copper systems across Arizona (Ajo, Sierrita, Kelvin-Riverside, Mt. Grayback, Granite Mountain, Charleston, Globe-Miami, Sycamore Canyon, Copper Basin, Texas Canyon, and Copper Creek), provides a detailed study of Middle Jurassic coarse muscovite alteration at Luhr Hill in the Yerington district, Nevada, and documents the structural and hydrothermal evolution of the Ajo mining district in southwestern Arizona. Most areas in this study are interpreted to be highly extended, highly eroded, or both, allowing for study of deep hydrothermal alteration. Na-Ca alteration has been previously documented extensively along the Jurassic arc of the southwestern United States but less widely known in younger plutons, notably of Laramide age in Arizona. Coarse muscovite alteration previously has rarely been documented in porphyry copper systems, and this study shows that coarse muscovite alteration is likely present in systems where root zones are exposed at surface. Na-Ca alteration also is present in many in Laramide porphyry systems, though volumetrically minor, as no Laramide system contains more than a few volume perfect Na-Ca alteration in a given hydrothermal system. Na-Ca alteration in Laramide systems can include Ca, Na-Ca and Na alteration but is dominated by Na alteration (epidote-albite-chlorite ± actinolite). At Ajo, both Na-Ca and coarse muscovite alteration are present within the district due to superposition of temporally unrelated hydrothermal alteration, coupled with complex extensional deformation.
This study shows that both Na-Ca and coarse muscovite alteration are more common in Laramide porphyry copper systems than previously recognized, that Na-Ca alteration is most commonly developed as shallower Na alteration (albite-epidote-chlorite ± actinolite), common deeper Na-Ca alteration (oligoclase-actinolite-epidote), and rare, deep Ca alteration (oligoclase-diopside-actinolite ± garnet ± epidote). Na-Ca alteration is commonly less voluminous in Laramide systems than documented in systems along the Jurassic arc.
Coarse muscovite alteration, commonly termed greisen, occurs structurally below and commonly postdates potassic alteration and likely formed from late-stage, low-temperature, magmatic-hydrothermal fluids. Coarse muscovite alteration associated with more silicic magmatic compositions is developed at shallower depths and contains muscovite with higher trace element contents, coarse muscovite alteration with more variable mineral assemblages, and coarse muscovite veins that are better mineralized. Coarse muscovite alteration (greisen) occurs as the main mineralized veins at the tops of evolved metaluminous to peraluminous granites in W-Sn systems, as well mineralized veins in the cores and tops of Mo-Cu porphyry systems, and as poorly mineralized veins in the roots of porphyry copper systems. Detailed understanding of coarse muscovite alteration in a given district can, therefore, can be an indicator of depth or petrologic affiliation of a system. These results provide a better understanding of late-stage magmatic-hydrothermal alteration and hydrothermal alteration associated with the incursion of external fluids into the root zones of porphyry copper systems.
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Greenlaw, Lauren. "Surface lithogeochemistry of the Relincho porphyry copper-molybdenum deposit, Atacama region, Chile." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50752.
Full textAbstract:
Porphyry copper deposits (PCDs) typically have large alteration haloes that extend several kilometers from economic mineralization providing a geochemical footprint potentially an order of magnitude larger than the deposit. The Paleocene (64±2 Ma) Los Morteros batholith comprises four granodiorite units and hosts four syn-mineralization porphyry units. These units are interpreted as the product of four magmatic differentiation cycles with three magmatic recharges. Alteration assemblages observed within the system include potassic, propylitic and phyllic, with intensities varying between weak to moderate for potassic and phyllic alteration, and weak to strong for propylitic.
Lithogeochemical characterization and quantification of alteration is an important exploration tool that has the potential to lead to exploration success. Two hundred and ninety-six surface rock samples were collected in a grid covering 65 km² centered over the Relincho PCD in the Atacama region, Chile to assess the suitability of surface rock lithogeochemistry as a medium for lithological and alteration characterization. Aqua regia ICP-MS, pressed pellet XRF, and fusion-ICP results, combined with shortwave infrared (SWIR) spectra, alkali feldspar staining, petrography and field observations were used to classify lithological units and identify and quantify alteration.
Data evaluation and modeling is completed through the use of exploratory data analysis, simple mass balances and molar element ratios (MER) complimented by hand and thin-section observations and SWIR analyses. Gain-loss variations are consistent with spatial element distributions indicating: the addition of SiO₂, K₂O, Ag, Cu and Mo and loss of CaO, Na₂O during potassic alteration; and the addition of Na₂O and loss of SiO₂ during propyltic alteration. Wavelengths of SWIR chlorite features indicate that chlorite is more Fe-rich proximal to mineralization and Mg-rich distally.
Simple and molar element ratios are used as proxies for the potassic, propylitic and phyllic alteration assemblages. From these ratios, alteration indices are calculated. The potassic index (K₂O/Th) and propylitic-phyllic index ((18Ca + 14Na + 25K)/(2Si + 7Al + 4(Fe + Mg)) identify and quantify potassic, phyllic and propylitic alteration. Alteration thresholds derived from probability plots indicate that these indices would identify the Relincho deposit as a potential PCD exploration target at a sample spacing of up to 2000 m. Supplementary materials: http://hdl.handle.net/2429/50971Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Hollis, Lucy. "Cretaceous porphyry magmatic-hydrothermal systems in the Tchaikazan River area, southwest B.C." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/15291.
Full textAbstract:
The Hub, Charlie and Northwest Copper are spatially related mineral showings
(Cu ± Mo) located in the Tchaikazan River area of southwest British Columbia. The
Tchaikazan River area is located on the boundary between the Intermontane Belt and
southeast Coast Belt (SECB). Evidence of magmatic-hydrothermal alteration is
preserved throughout the study area.
Multiple episodes of magmatic-hydrothermal activity are associated with these
three centres of porphyry-style mineralization. The Hub diorite is the oldest dated pluton in the area, with a U-Pb zircon emplacement age of 81.19 ± 0.78 Ma. ZFT/AFT data suggests an emplacement depth of> 4km for the Hub diorite. The Hub diorite is crosscut by a biotite ± magnetite (± quartz) matrix/cemented hydrothermal breccia. A feldspar hornblende dyke crosscuts both the diorite and hydrothermal breccia and gives a U-Pb zircon age of 79.9 ± 1.5 Ma. Copper, molybdenite ± galena occurs in quartz veining and cement to the hydrothermal breccia. ZFT/U-Pb and Ar-Ar ages for the Hub diorite are within error of each other. AFT data suggests an average erosion rate of 40 m/myr for intrusive rocks in the Taseko Lakes area. Field relationships, geophysical anomalies, geochronology, and stable isotope
data suggest that there are three centres for magmatic-hydrothermal activity in the
Tchaikazan River area: The Hub, Northwest Copper pluton, and Ravioli Ridge. The area
displays evidence for multiple, temporally-distinct intrusive, alteration and mineralizing events.
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Wareham, Christopher Desmond. "Isotopic and geochemical studies of a Pliocene porphyry-mo system, Rico, Colorado." Thesis, University of Aberdeen, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304968.
Full textAbstract:
The historic mining district of Rico in the southern Colorado Mineral Belt contains a Pliocene porphyry-Mo deposit and peripheral epithermal Pb-Zn-Ag deposits, and hot-springs. The porphyry-Mo mineralisation is confined almost exclusively to Precambrian greenstone. The epithermal mineralisation is hosted by a Palaeozoic and Mesozoic sequence dominated by carbonates, but containing evaporites. The system is geologically complex and focused on a resurgent dome which is cored by a horst of Precambrian strata, and cut by reactivated Precambrian basement shears. The shears have controlled the emplacement of the Laramide and Pliocene granitoids in area. The mineralisation is associated with more evolved members of the latter suite. Sr-Nd-Pb-O isotope and minor element data on the granitoid intrusions indicate that they are not simply differentiates of mantle magmas. However, Nd model ages indicate that they are not purely remelts of 1800Ma Precambrian crust. Realistically it is impossible to quantify the relative proportions of crust and mantle material involved in the genesis of the intrusions. Notwithstanding this, the Rico granitoids are isotopically distinct from those associated with Climax-type porphyry-Mo deposits in Colorado. Sr-Nd-Pb isotope and trace element data on a lamprophyre suite in the area suggest two episodes of mafic magmatism; a period whereby the source was predominantly subduction modified lithospheric mantle, and a period whereby the source was predominantly, OIB-type, asthenospheric mantle. δ-34S data and ore deposit paragenesis indicate that the sulphide S has an igneous origin and that the sulphate S was derived by mobilisation of Pennsylvanian evaporites. Modelling of the S isotopic data indicates a common S source for the epithermal and porphyry mineralisation. The sulphate and sulphide S reservoirs remained essentially decoupled during mineralisation. δ13C data are compatible with the hydrothermal C having been derived by the dissolution and re-precipitation of host sequence carbonate. Pb and Sr isotope analyses of ore and gangue minerals support the conclusions reached in the stable isotope study. The Sr isotope study indicates that the Sr isotopic composition of the hydrothermal fluids varies considerably. Pb isotope ratios measured on molybdenite, pyrite, and galena indicate that the mineralisation at Rico derived its Pb from source with a higher Th/U ratio than that involved in the genesis of Climax-type porphyry-Mo deposits. Sr and O isotope analyses of Laramide sills present throughout the Rico area indicate that the Sr isotopic composition of the hydrothermal fluids varied and that the Sr isotopic composition of altered sills is not solely a function of alteration temperature; the proportion of altered primary feldspar and the growth of Sr-rich secondary minerals is also important. REE data on these sills indicate that hydrothermal alteration mobilised and fractionated these elements, but that mobility is not simply a reflection of alteration temperature. [SO4]4- appears to have been an important REE complex in the near surface oxidising environment.
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de, Sousa Eudes Alves 1959. "Impact of geology on ore grade estimation of a porphyry copper deposit." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/277264.
Full textAbstract:
Accurate ore estimation processes are of crucial importance in the mining scenario. Over the last 20 years, one practical approach to improve ore grade estimation has encouraged the need to incorporate the geology of the ore deposit being estimated in the estimation process. The objective of this study is to investigate the impact of the geology on the kriging estimation of the ore grade of a portion of a porphyry copper deposit. Preliminary data analysis demonstrates the need to perform a subsequent variogram modeling and kriging estimation of the ore grade by rock type separation. Global and local estimations were done to assess the influence of the geology on the ore grade estimation at a global and local scales. The results obtained in this study demonstrated that for the portion of the deposit studied the incorporation of the geology does not produce substantial improvement on the ore grade estimation.
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Valencia-Moreno, Martin Andres 1961. "Geochemistry of Laramide granitoids and associated porphyry copper mineralization in northwest Mexico." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282731.
Full textAbstract:
The present study investigates the effects of basement variations on the geochemical composition of the Laramide plutonic belt of northwestern Mexico, and implications for the development of the associated porphyry copper mineralization. In the north part, the belt intruded rocks of the North America and Caborca terranes representing cratonic basements juxtaposed by Mid-Jurassic strike-slip faulting. The central part of the belt was emplaced in the Cortes terrane which contains Paleozoic eugeoclinal sequences accreted to North America between Mid-Permian and Late Triassic times. The southern part of the belt intruded island arc-related sequences of the Guerrero terrane, accreted to North America during the Late Cretaceous. A suite of 30 samples of granitoids were studied to characterize the geochemical composition of the belt. The samples range from 56% to 75% SiO₂ and have mid to high-K calc-alkaline and mostly metaluminous compositions. REE results show more evolved chondrite-normalized plots in the north part of the belt, characterized by higher ΣREE and La(N)/Yb(N) ratios, and more pronounced negative Eu anomalies. Southward, the samples show a progressive flattening, eventually with almost no Eu anomalies in the Guerrero terrane. ⁸⁷Sr/⁸⁶Sr initial ratios higher than 0.7062 and initial εNd below -4 characterize the granitoids from the north part of the belt. Slightly less evolved isotope signatures occur in the central part, whereas ⁸⁷Sr/⁸⁶Sr ratios below 0.7063 and more positive εNd values characterize the samples from the south. The data suggest a garnet-bearing source for the granitoids emplaced in the north and central parts of the belt, whereas much less garnet fractionation is needed in the southern part. The effect of different crustal domains on the porphyry copper mineralization is less obvious. Hypogene Cu grades do not vary much along the belt, but the associated metals such as Mo, W, and Au show a certain degree of spatial control. Higher Mo grades are associated with the North America and Caborca terranes. Tungsten deposits are not terrane-constrained, but the more conspicuous mineralization occurs in central Sonora, mainly associated to the Caborca terrane. Higher Au values seem to occur in porphyry copper and associated breccia deposits in the Guerrero terrane. In general, the associations Cu-Mo-WO₃ in terranes of North America affinity, and Cu-Au in the Guerrero terrane suggest basement control.
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Rempel, Kirsten U. "The solubility and speciation of molybdenum in aqueous liquid and vapour : an experimental study." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115874.
Full textAbstract:
We have conducted an experimental investigation of the solubility and speciation of Mo in HCl-, NaCl-, and NaOH-bearing water vapour, and of the partitioning of Mo between coexisting aqueous liquid and vapour at 300 to 370°C and up to saturated pressure. Our results indicate that Mo concentration is enhanced in HCl-bearing water vapour at fHCl > 0.1 bar, and in NaOH-saturated water vapour, but is unaffected by the presence of NaCl. This suggests that Mo speciates as MoO3·nH2O in water vapour at equilibrium with NaCl or fHCl < 0.1 bar. The dependence of SigmafMo on fHCl at higher acidity points to the formation of Mo oxychloride (MoO2Cl 2). For the system MoO3-NaOH-H2O, log Sigma fMo increases with increasing fH2O, and with log SigmafNa in a ratio of 0.28+/-0.4, but Sigma fNa does not change with increasing fH2O. This suggests the formation of a small proportion of sodium molybdate (Na 2MoO4) in addition to MoO3·nH2O. Our partitioning experiments show that at lower temperature and fluid density, Mo partitions more strongly into the liquid than the vapour, but the Mo concentration in the vapour increases as the temperature-pressure conditions approach those of the critical point of water (374°C and 221 bar), surpassing that in the liquid at ∼360°C. The results of our experiments indicate that both the liquid and vapour phases may be important for the transport of Mo in porphyry ore-forming systems, and that vapour-phase solubility is enhanced in high fHCl magmatic gases.
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Mach, Craig J. "Tectonic controls, timing and geochemistry of supergene enrichment of the Tyrone porphyry copper deposit, Grant County, New Mexico /." abstract and full text PDF (UNR users only), 2009. 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:3342621.
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Thesis (Ph. D.)--University of Nevada, Reno, 2008."December, 2008." Accompanying CD-ROM contains appendices C and D. Appendix C: AutoCAD files with drill hole log; Appendix D: excel spreadsheet with copper mass balance calculations. Includes bibliographical references (leaves 206-215). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2009]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.
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Stavast, William James Andrew. "Three-Dimensional Evolution of Magmatic Hydrothermal Systems, Schultze Granite and Ruby Star Granodiorite, Arizona." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/194841.
Full textAbstract:
The biotite bearing Schultze Granite (Globe-Miami district) and the biotite-hornblende bearing Ruby Star Granodiorite (Pima district) compose two intrusive centers that produced multiple porphyry copper deposits during the Laramide orogeny. Both magmatic-hydrothermal systems were dismembered and tilted by Tertiary extension, as indicated by tilted Tertiary sedimentary rocks, paleomagnetic data, and geobarometry, thereby producing extraordinary exposures of these magmatic-hydrothermal systems: ~ 1 to ~10 km (Globe-Miami district) and <1 to>12 km (Pima district). Ages of emplacement range from 68 to 61 Ma for the Schultze Granite and 64 to 58 Ma for the Ruby Star Granodiorite. The plutons were formed by rapid accumulation of magma within short periods of time (~1 m.y.). The Schultze Granite is a high-silica granite and did not evolve chemically with time, except during formation of late porphyry and aplite dikes. Phases of the Ruby Star pluton range from granodiorite to granite, but appear to be distinct intrusive events separated in time by several million years. Each pluton is chemically homogenous with depth, probably due to convection. The low iron contents of biotites suggest that magmas related to porphyry copper deposits have higher oxidation states than typical granitic bodies. Hydrothermal alteration was associated with most phases of each pluton, with multiple alteration types overlapping to create complex centers. Veins persist to >10 km beneath porphyry copper deposits. Deep styles of alteration differ in the two plutons. The Schultze Granite contains biotite veins and greisen veins (coarse-grained muscovite) (~10 km). The Ruby Star Granodiorite contains sodic-calcic alteration (4-8 km) and greisen veins (4-12 km). The sodic-calcic alteration is asymmetrically distributed on the eastern side of the Sierrita deposit and is interpreted to have been created by influx of external sedimentary brines from Paleozoic sedimentary rocks that only are present on the eastern side of the pluton. Greisen alteration occurs late in the hydrothermal history and may be the last fluids that were exsolved from the magma as the magma chamber completely crystallized. These deep alteration styles can be used to predict where porphyry copper deposition may have occurred, which can lead to discoveries in extended terranes.
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Gilmer, Amy K. "Petrogenesis of the Don Manuel igneous complex and porphyry copper system, central Chile." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.702924.
Full textAbstract:
Porphyry copper deposits (PCDs) are associated with shallow-level, subvolcanic intrusions. While PCDs have been studied extensively, the petrology of the host intrusions have received relatively little attention because hydrolytic alteration often destroys the primary petrologic features. However, these features are key to understanding the trans-crustal arc magmatic processes that result in PCDs. The Don Manuel porphyry copper system of the Miocene-Pliocene PCD belt of central Chile, contains significant alteration, but it is localized, allowing investigation of the primary petrology in relatively fresh portions. Fieldwork and examination of drill cores enabled characterization of the Don Manuel igneous complex (DMIC). The DMIC consists of six intrusive units ranging from 53-74 wt.% Si02. Highresolution CA-ID-TIMS U-Pb and whole-rock 40Ar/39Ar dating indicate that the intermediate to felsic units were emplaced in pulses between 4.0-3 .6 Ma, making it the youngest documented PCD system in the Andes. The episodic emplacement of this igneous complex occurred on a timescale similar to eruption and degassing events in arc volcanic systems. Petrographic, geochemical and isotopic data establish the origin and assembly of the diverse magmas that comprise the DMIC. The magmas have undergone polybaric differentiation from parents with varying initial water contents. Mineral chemistry, coupled ~ith thermobarometry, constrain the petrogenesis of the DMIC, indicating that wet magmas began differentiating in the lower to middle crust and continued to evolve in shallow crustal reservoirs. Intermediate porphyry dikes associated with copper mineralization contain diverse crystal cargos that represent mush entrained from different depths, crystals originating in different magmas, and crystals grown in-situ from hybridized magmas. The petrologic complexity and episodic timescale observed in the porphyry copperrelated magmas is analogous to the open system, trans-crustal processes indicated arid observed in arc volcanic systems. Examination of other PCDs through this framework could provide additional information about key ore ingredients such as volatiles, metals, and sulfur.
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Maher, David Joseph. "Reconstruction of Middle Tertiary Extension and Laramide Porphyry Copper Systems, East-Central Arizona." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/193922.
Full textAbstract:
In east-central Arizona, overlapping sets of Tertiary normal faults dismembered, variably extended, and exposed up to 15 km of the upper crust including portions of several Late Cretaceous to Paleocene (Laramide) igneous centers and their associated porphyry copper systems. These exposures enable both a rigorous evaluation of the nature of extension in the upper crust and systematic reconstruction of the 3-dimensional distribution of several major porphyry copper centers.Synthesis of existing geological data and new mapping provide the basis for reconstructions of district and regional scale cross sections through an area comprising about 4,000 km2 centered on the Dripping Spring Mountains of east-central Arizona. The study area is located within a highly extended portion of the Basin and Range province and encompasses the Globe-Miami, Superior, and Mineral Creek (Ray) mining districts and numerous other deposits and related occurrences.The field evidence and the reconstructions demonstrate that sequential sets of initially steeply dipping normal faults generated multiple half-grabens and associated sedimentary fill. Complex overlap of >10 sets of these half-grabens led to aggregate extension of about 100% across the study area, but the amount of extension locally varies from less than 20% to well over 400% depending on the amount of overlap and direction and amount of displacement on the various fault sets. These fault sets were not kinematically linked and do not merge into a master fault at depth, but are inferred to feather into a broader zone of mid-crustal flow, which may resemble the characteristics of nearby metamorphic core complexes.Reconstructions at regional (10's of kms) to copper deposit (a few kms) scales demonstrate that multiple deposits, prospects, and other hydrothermal features in the Globe-Miami, Superior and Ray districts are dissected portions of originally fewer, larger hydrothermal centers. These restorations delineate exposures ranging from near paleosurface to locally >10 kms paleodepth and enable comparisons of different systems and of well mineralized portions along with their roots, tops, and margins.
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Zurcher, Lukas. "Regional setting and magmatic evolution of Laramide porphyry copper systems in western Mexico." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/279937.
Full textAbstract:
This study investigates the contrasting tectonic settings in western Mexico and the controls they exert on porphyry copper deposits. Igneous rock affinities are deduced by integrating existing lithologic, geophysical, and geochemical information with new major-, trace-, rare earth-element, radiogenic isotope, and mineral phase compositional data. Regional findings are compared with theGeology of porphyry complexes in cratonic (Cuatro Hermanos) and accreted settings (Tameapa). Geochemical results identify four tectonic domains. Lower Cretaceous volcano-sedimentary successions are underlain by oceanic crust represented by the Bacurato Ophiolite. This domain is bordered on the south by the Lower Cretaceous San Pablo island arc Complex, on the west by much thicker crust (>30 km) and Jurassic and/or older sedimentary assemblages of Precambrian provenance, and on the north by the Upper Triassic Sonobari back-arc Complex. Plutonic rocks intruded the four domains. Upper Cretaceous anatectic plutons from a collisional setting have S- or I-type characteristics depending on the host rock they intrude. Combined Sr, Nd, and O isotope results from Upper Cretaceous and Laramide granodiorites show a primitive-to-evolved (εNd(I) = +4.6 to -3.8) gradient from central Sinaloa toward the north, west, and south, identifying the presence of Lower Cretaceous oceanic crust and volcanogenic materials well into southeastern Sonora. At Cuatro Hermanos, batholith (≈59 Ma) and porphyry (56 Ma) suites are broadly cogenetic and contaminated with significant radiogenic crust (εNd(I) = -3.3 to -4.0). Relative to batholith, porphyry magmas assimilated lesser sedimentary material, and are not well homogenized. At Tameapa, batholith (57 Ma) and porphyry (53 Ma) suites were derived from a mantle source, volcanogenic materials, and/or oceanic crust. Adjacent, coeval, and compositionally comparable batholithic intrusions exhibit disparate radiogenic signatures (εNd(I) = +3.1 and -2.5), indicating magma or source heterogeneity. Geochemistry of porphyries points to very high assimilation to fractionation ratios, extraction from a residual melt, heterogeneity, and magma chamber recharge. Faults have substantially rotated and dismembered both porphyry systems, as previously recognized at Cuatro Hermanos. However, Tameapa is the first deposit-scale documentation of large-magnitude extension observed in Sinaloa. Both lack of consanguinity of porphyries with well-homogenized host batholith and amount of extension have exploration significance in the region.
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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.
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Febbo, Gayle Elizabeth. "Structural evolution of the Mitchell Au-Cu-Ag-Mo porphyry deposit, northwestern British Columbia." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57001.
Full textAbstract:
The Mitchell Au-Cu-Ag-Mo porphyry deposit, hosted by Early Jurassic volcanosedimentary and intrusive rocks in the Stikine terrane of northwestern British Columbia, is considered the largest undeveloped gold resource in Canada. As of 2015 it held a resource of 1777 Mt at 0.61 g/t Au, 0.17% Cu, 3.1 g/t Ag, and 58 ppm Mo (0.5 g/t Au eqiv. cut-off; meas+ind). The calc-alkalic deposit is genetically related to multiple diorite intrusions (Sulphurets suite) that cut volcanosedimentary strata of the Stuhini Group (Upper Triassic) and Jack Formation (basal Hazelton Group, Lower Jurassic). Phase 1 plutons (U/Pb, zircon; 196 ±2.9 Ma and 192.2±2.8 Ma) host Stage 1 potassic and propylitic alteration, veins and copper-gold mineralization. A Phase 2 plug (189.9±2.8 Ma; U/Pb zircon) is central and temporally related to a molybdenum halo (190.3±0.8 Ma; Re-Os, Mo) that is accompanied by phyllic alteration (Stage 2). Phase 3 plutonism is temporally related to diatreme breccia, intrusion breccia dikes and Stage 3 massive pyrite veins and advanced argillic alteration. High-level, gold-rich veins comprise Stage 4.
Three phases of progressive deformation related to the mid-Cretaceous Skeena fold and thrust belt structurally modify the Mitchell deposit. Deformation Phase 1 is characterized by a steep, easterly striking pervasive pressure solution cleavage (S₁) and steeply west-plunging buckle folds in veins (F₁); fold geometry and flattening degree are a function of alteration type. In rheologically weak alteration types a pressure solution cleavage is associated with loss of silica, mechanical remobilization of chalcopyrite-molybdenite, and passive enrichment of chalcopyrite-molybdenite-pyrite along the cleavage planes. Strain intensity (i.e., S₁ development) is heterogeneous and this greatly affects the shape of the orebody. In Deformation Phase 2, steeply north-plunging F₂ vein folds overprint S₁ and F₁. The Mitchell thrust fault (Deformation Phase 3) offsets the Snowfield deposit ~ 1600 m to the east-southeast and the Mitchell Basal shear zone displaces the Mitchell deposit from its core zone, located ~1-2 km to the west at a depth of ~ 1 km. It is speculated the Mitchell deposit was emplaced into a structurally influenced, north-trending Jurassic basin and subsidiary east-west structures controlled the intrusion, vein geometry, alteration and metal pattern trends.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Lewis, Meghan H. "Characterisation of hypogene covellite assemblages at the Chuquicamata porphyry copper deposit, Chile, Section 4500N." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq24974.pdf.
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Lindsay, Darryl Desment. "Structural control and anisotropy of mineralization within the Chuquicamata porphyry copper deposit, northern Chile." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0025/NQ36560.pdf.
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Hezarkhani, Ardeshir. "Physicochemical controls on alteration and copper mineralization in the Sungun porphyry copper deposit, Iran." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ36982.pdf.
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Cox, Toni. "Petrological and geochemical evidence for putative ancient microfossils within the Berlins Porphyry, New Zealand." Thesis, University of Canterbury. Geological Sciences, 2013. http://hdl.handle.net/10092/7533.
Full textAbstract:
Berlins Porphyry, located on the South Island of New Zealand, is the result of granitic intrusions, brecciation and hydrothermal alteration of country rock. Exposure of the Berlins Porphyry provides an opportunity to examine high temperature hydrothermal systems at depth (~2km) and to investigate the potential of biological activity in areas of localized hydrothermal activity. All Berlins Porphyry deposits are mineralogically and geochemically similar; however, localized areas within the porphyry show increased hydrothermal activity. Locations for microbial investigations include outer porphyry alteration zones that experienced high levels of hydrothermal fluid alteration. A recently exposed and highly altered porphyry outcrop on the Denniston Plateau contains iron concretions generated during localized hydrothermal mineralization. Here we show the Fe-rich concretions are the result of biomineralization via crystal morphology observations, carbon chemistry analysis and putative microfossils. High resolution petrographic and cathodoluminescence imaging reveals a variety of ancient fossilized burrows present within the magnetite zone. Transects through the concretions demonstrate that the abundance of carbon increases in the magnetite zone and exhibits δ¹³C‰ values characteristic of organic carbon (averaging -26‰ ± 4‰). Alteration mineralogy including recrystallized quartz, muscovite, adularia and kaolinite are present within the Berlins Porphyry iron concretions and suggest a hydrothermal system with microbial activity operating at temperatures between 200-250°C. Overall, these ancient and unusually persevered microbially-mediated Fe-rich concretions potentially represent a significant temperature increase for the habitability of life.
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Jemielita, Richard Alfred. "Geochemistry and stable isotope study of porphyry-related mineralisation, central Front Range, Colorado, U.S.A." Thesis, University of Aberdeen, 1987. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU004472.
Full textAbstract:
The central part of the Front Range mineral belt, Colorado, is a Precambrian crystalline basement terrain intruded by early Tertiary porphyries and closely associated mesothermal ore deposits. The ore deposits are gold- and silver-bearing base metal sulphide-quartz veins arranged in more or less well developed concentric mineral zones centred on concealed porphyry plutons. Central areas of pyritic mineralisation are surrounded by peripheral zone of galena-sphalerite-bearing veins, often separated by a transitional zone of composite mineralisation. Molybdenite-bearing and uraninite-bearing veins are locally abundant proximal to the central pyritic zones and are closely associated spatially and temporally with highly evolved quartz bostonite intrusions. The mineral veins are enveloped in narrow selvages of sericitized and argillized wallrock and are entirely fracture controlled. A low density lithogeochemical survey of the country rocks revealed strong lithological controls on the distributions of selected trace elements and radiation emission values. Positive Rb/Sr anomalies are tentatively linked to concealed intrusions, and corresponding positive anomalies of Pb, Zn, Mo and W are associated with known molybdenite mineralisation. Sericitized rocks are characterised by low Sr and enhanced Rb, Zn, Pb, Mo and Ag values, and areas of depleted country rock Sr values may be related to vein wallrock alteration. D/H and 18 O/16 O signatures of fresh country rocks indicate variable magmatic water overprinting and similar analyses of sericitised rocks show that alteration was accomplished by magmatic hydrothermal fluids at 340o -515o C. Mineralisation and alteration in the area were caused by hydrothermal fluids evolved from highly differentiated Laramide quartz bostonite intrusions. K-Ar ages of ca. 62 Ma have been obtained from alteration sericites from the peripheral mineral zone. Similar studies in the central pyritic zone have yielded ages of ca. 59 Ma suggesting the existence of long lived hydrothermal activity in the area characterised by widespread high-temperature alteration, followed by thermal decay and collapse towards core zones. The ore deposits investigated during this study display numerous features in common with porphyry-style and other intrusive-related mineralisation characteristic of Cordilleran terrains, but also exhibit significant differences. The combination of these features contribute to the distinct and possibly unique character of these mineral deposits.
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Hosler, James. "Porphyry as neoplatonic exegete a contextual evaluation of On the Cave of the Nymphs /." Tallahassee, Fla. : Florida State University, 2008. http://purl.fcla.edu/fsu/lib/digcoll/undergraduate/honors-theses/341764.
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Thesis (Honors paper)--Florida State University, 2008.Advisor: Dr. Svetla Slaveva-Griffin, Florida State University, College of Arts and Sciences, Dept. of Classics. Includes bibliographical references.
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Allison, Antonia E. "The Geology of the Bajo El Durazno Porphyry Copper-Gold Prospect, Catamarca Province, Argentina." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/249234.
Full textAbstract:
The Bajo El Durazno prospect is a small, gold-rich porphyry copper-type prospect located in Catamarca Province, northwest Argentina. It is one of a cluster of at least fourteen porphyry copper-type occurrences and numerous younger polymetallic epithermal veins, all of which are genetically related to the waning stages of magmatism that produced the Farallon Negro volcanic complex, an isolated Upper Miocene shoshonitic andesitic volcanic center. Porphyry copper-type hydrothermal activity at the Bajo El Durazno prospect is associated with a small east-northeasterly elongated andesite porphyry stock. The stock was emplaced at 8.7 m.y. into comagmatic and petrologically similar andesitic volcanic breccias that form the highly dissected basal remnants of the main eruptive center of the volcanic complex. Intramineral, crudely radial andesite porphyry dikes accompanied the development of concentric zones of hydrothermal alteration centered on the stock. These alteration zones of potassium-silicate alteration in the stock and adjacent wallrocks surrounded by an essentially coeval, weakly developed propylitic alteration zone. The propylitic alteration assemblage, which occurs as both pervasive replacement and as veinlets, consists mainly of chlorite, epidote, calcite, and magnetite, with lesser clays and zeolites. The potassium-silicate alteration zone is character iced by the replacement of primary minerals by secondary biotite, magnetite, anhydrite, quartz, sericite, and calcite. Roughly coeval and coextensive with the earliest stages of potassium-silicate and propylitic alteration was a brief period of magnetite alteration consisting mainly of well-banded magnetite ± quartz ± biotite veins. This volume also includes the development of irregular magnetite-rich masses in the stock of probable late-magmatic origin. Major copper-gold mineralization with minor silver and molybdenum developed during later stages of potassium-silicate alteration after the magnetite alteration event, although highest grade mineralization is commonly localized in areas of most intense magnetite alteration. The bulk of the mineralization occurs as veins within the stock and its wallrocks near their mutual contact; these veins contain quartz, calcite, magnetite, pyrite, chalcopyrite, and lesser sericite, chlorite, orthoclase, biotite, siderite, molybdenite, bornite, sphalerite, galena, tetrahedrite-tennantite, and native gold. Some of the gold and silver occur in solid solution in sulfide minerals, and supergene enrichment of copper is not economically significant. Copper and gold grades are generally less than 0.4% and 1 ppm, respectively. The three early alteration assemblages were later overprinted by patchy areas of phyllic alteration consisting mainly of the assemblage sericite, quartz, pyrite, and anhydrite/gypsum in an irregular northeasterly elongated halo. Phyllic alteration is developed to its greatest extent in an irregular annular zone straddling the boundary between the potassium- silicate and propylitic alteration zones and is generally coincident with the most highly fractured rocks in the prospect. Irregular patches of weak to intense silicification are superimposed on all other alteration types, and a number of distinctive, poorly mineralized, phyllically altered and silicified fracture zones are distributed in a somewhat radial pattern around the stock. Low grade disseminated(?) gold mineralization is found over one square kilometer in phyllically and propylitically altered rocks surrounding the central mineralized zone. A fluid inclusion study has revealed the presence of two hypersaline liquid-rich fluid inclusion types having salinities of 73.0-87.0 and 50.0-79.5 weight percent NaC1 + KCl equivalent, respectively, a single low salinity liquid-rich inclusion type (6.6-8.0 weight percent NaCl equivalent), and abundant vapor-rich inclusions. Hematite, anhydrite, and a variety of unidentified opaque and nonopaque minerals occur in many inclusions. Magnetite, potassium-silicate, and phyllic-silicic alteration in silicified zones formed at temperatures between 310° C and 500° C and were the product of the less saline of the two hypersaline fluids; this fluid episodically boiled. Copper-gold mineralization in potassium-silicate rocks probably peaked at about 395° C. Fluid salinities and temperatures gradually decreased with time, and during later stages of alteration they also decreased with greater distance from the hot center of the system, perhaps as a result of dilution. Although proof is lacking, the two high salinity fluids and the low salinity vapor may be magmatic in origin, and the low salinity fluid may represent a late-stage influx of meteoric water that encroached on the waning magmatic hydrothermal system. A depth of formation of 1.6 kilometers is estimated for the presently exposed portion of the Bajo El Durazno prospect based on the fluid inclusion data.
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Enders, Merritt Stephen. "The evolution of supergene enrichment in the Morenci porphyry copper deposit, Greenlee County, Arizona." Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/289155.
Full textAbstract:
Supergene enrichment in the Morenci porphyry copper deposit was formed as a result of the coupled processes of erosion and chemical weathering that accompanied five stages of landscape evolution in the Cenozoic Era. During Stage 1 (64 to 53 Ma), low-grade primary chalcopyrite and pyrite mineralization was deposited as a result of Laramide magmatic and hydrothermal processes at about 55 Ma. During Stage 2 (53 to 30 Ma), initial unroofing and erosion removed approximately 1.8 km of rocks overlying the deposit and shed detritus to the north in the Eocene and to the south in the early Oligocene. During Stage 3 (30 to 18 Ma), the deposit was preserved under 640 to 950 meters of volcanic rocks as a result of mid-Tertiary extension and volcanism. During Stage 4 (18 to 2 Ma), most of the supergene copper enrichment at Morenci appears to have been formed as a result of Basin and Range deformation between ∼13 and ∼4 Ma. Sixteen new ⁴⁰Ar/³⁹Ar ages from alunite, jarosite, and potassium-bearing manganese oxides in the district recorded three cycles of enrichment and leaching that peaked at about 7.3 Ma. Microbiological and geological studies revealed that acidophilic iron oxidizing bacteria and dissimilatory sulfate reducing bacteria contributed to leaching and enrichment of copper in the supergene environment, at least since the late Mocene. During Stage 5 (2 Ma to present), destruction of the current enriched blanket accompanied base-level drop and stream incision as a result of progressive drainage integration in southern Arizona in the late Pliocene and Pleistocene.
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Jensen, Paul William 1967. "A structural and geochemical study of the Sierrita porphyry copper system, Pima County, Arizona." Thesis, The University of Arizona, 1998. http://hdl.handle.net/10150/291456.
Full textAbstract:
Detailed mapping of the Sierrita-Esperanza orebody has led to a revised interpretation of the Paleocene intrusive units, and a structural model for the emplacement of those units. A left-lateral wrench fault, expressed through Riedel shears, arranged in a flower structure geometry, is proposed to localize the porphyry intrusions, and control mineralization trends. Miocene extensional deformation has not tilted the orebody more than 10°. The San Xavier Thrust is interpreted to be a low angle detachment, upon which the upper plate has moved to the north-northwest approximately 10 km. When the San Xavier "Thrust" ceased movement, a set of low angle normal faults, striking nearly north-south dissected the Sierrita Range. Molybdenite dating, using the Re-Os system, shows that mineralization of the orebody began at 63.5 Ma (±300 ka, 2σ), and ended sometime after 60.0 Ma (±300 ka, 2σ). An isochron of chalcopyrite and pyrite samples with an age of 59.7 Ma (±17.1 Ma, 2σ), and an initial 187Os/188Os of.152 (±0.33, 2σ) suggests that the lower crust beneath the Sierrita Range has a low 187Os/188Os ratio.
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Wainwright, Alan John. "Volcanostratigraphic framework and magmatic evolution of the Oyu Tolgoi porphyry Cu-Au district, South Mongolia." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2760.
Full textAbstract:
The super-giant Oyu Tolgoi porphyry copper-gold deposits in the South Gobi
desert, Mongolia, consist of multiple discrete porphyry centers aligned within a north-northeast trending, >6.5 km long, arc-transverse mineralized corridor. The porphyries are linked to a tectono-magmatic event at ~372 Ma within a Devonian to Carboniferous volcanic arc, and U-Pb (zircon) geochronology records magmatic activity from ~390 Ma to ~320 Ma. The Oyu Tolgoi district underwent at least three discrete periods of syn- to post-mineral shortening and there is evidence for at least three unconformities within the Paleozoic sequence. Although the deposits were formed in an active orogenic
environment characterized by rapid uplift, their preservation is a reflection of climactic effects as well insulation from erosion by rapid burial under mass-wasted and pyroclastic material in the volcaniclastic apron of late-mineral dacitic volcanoes.
The porphyry copper-gold deposits are spatially and temporally related to
medium- to high-K calc-alkaline quartz monzodiorite (~372 Ma) and granodiorite (~366
Ma) intrusive phases that comprise the Late Devonian Oyu Tolgoi Igneous Complex
(OTIC). Adakite-like wholerock compositions as well as zircon grains with high
CeN/CeN*, EuN/EuN* and Yb/Gd in the sample populations from syn- and late-mineral
porphyry intrusions are different from younger intrusions that are not related to porphyry Cu-Au deposit formation. Moreover, mixed zircon populations within OTIC intrusions indicate that efficient assimilation of material from different host rocks by a convecting magma chamber occurred.
Mafic to intermediate volcanic units evolved from tholeiitic to calc-alkaline compositions, which is interpreted to be a reflection of marine arc maturation and
thickening. Felsic rock suites are dominantly high-K calc-alkaline, regardless of age.
Nd-isotopic geochemistry from all suites is consistent with magma derivation from
depleted mantle in an intra-oceanic volcanic arc and lead isotopic compositions indicate
that the sulfides in the porphyry Cu-Au deposits are genetically linked to the Late
Devonian magmas.
Magma mixing, adakite-like magmatism and rapid uplift and erosion in a juvenile
marine arc setting differentiate the ore-stage geologic environment at Oyu Tolgoi from other settings in active and fossil volcanic arcs.
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Maughan, Daniel T. "Contributions from Mafic Alkaline Magmas to the Bingham Porphyry Cu-Au-Mo Deposit, Utah, U.S.A." BYU ScholarsArchive, 2001. https://scholarsarchive.byu.edu/etd/6349.
Full textAbstract:
The Bingham porphyry Cu-Au-Mo deposit, Utah, may only be world-class because of substantial contributions of sulfur and metals from mafic alkaline magma to an otherwise unremarkable calc-alkaline system. Volcanic mafic alkaline rocks in the district are enriched in Cr, Ni, and Ba as well as ore-related constituents of Cu, Au, platinum group elements (PGE) and S. The bulk of the volcanic section that is comagmatic with ore-related porphyries is dacitic to trachytic in composition, but has inherited the geochemical signature of high Cr, Ni, and Ba from magma mixing with the mafic alkaline rocks. The volcanic section that most closely correlates in time with ore-related porphyries is very heterogeneous containing clasts of scoriaceous latite, latitic minette and flows of melanephelinite, shoshonite and olivine latite in addition to the volumetrically dominant dacite/trachyte.
Bingham ore-related porphyries show ample evidence of prior mixing with mafic alkaline magmas. Intrusive porphyries that have not been previously studied well have several chemical and mineralogical indications of magma mixing. These "mixed" lithologies include the hybrid quartz monzonite porphyry, biotite porphyry, and minette dikes. Even some of the more silicic latite and monzonite porphyries retain high Cr and Ba contents indicative of mixing and contain trace amounts of sapphire (
Magma mixing calculations suggest about 10% of the monzonitic/latitic ore-related magma may have been derived from mafic alkaline magma similar to the melanephelinite. If the original S content of the mafic magma was about 2000-4000 ppm, comparable to similar magmas, then the mafic magma may have been responsible for contributing more than half of the S and a significant portion of the Cu, Au, and PGE in the Bingham deposit.
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Runyon, Simone E., Matthew Steele-MacInnis, Eric Seedorff, Pilar Lecumberri-Sanchez, and Frank K. Mazdab. "Coarse muscovite veins and alteration deep in the Yerington batholith, Nevada: insights into fluid exsolution in the roots of porphyry copper systems." SPRINGER, 2017. http://hdl.handle.net/10150/623613.
Full textAbstract:
Veins and pervasive wall-rock alteration composed of coarse muscovite +/- quartz +/- pyrite are documented for the first time in a porphyritic granite at Luhr Hill in the Yerington District, Nevada. Coarse muscovite at Luhr Hill occurs at paleodepths of similar to 6-7 km in the roots of a porphyry copper system and crops out on the scale of tens to hundreds of meters, surrounded by rock that is unaltered or variably altered to sodic-calcic assemblages. Coarse muscovite veins exhibit a consistent orientation, subvertical and N-S striking, which structurally restores to subhorizontal at the time of formation. Along strike, coarse muscovite veins swell from distal, millimeter-thick muscovite-only veinlets to proximal, centimeter-thick quartz-sulfide-bearing muscovite veins. Crosscutting relationships between coarse muscovite veins, pegmatite dikes, and sodic-calcic veins indicate that muscovite veins are late-stage magmatic-hydrothermal features predating final solidification of the Luhr Hill porphyritic granite. Fluid inclusions in the muscovite-quartz veins are high-density aqueous inclusions of similar to 3-9 wt% NaCl eq. and < 1 mol% CO2 that homogenize between similar to 150 and 200 A degrees C, similar to fluid inclusions from greisen veins in Sn-W-Mo vein systems. Our results indicate that muscovite-forming fluids at Luhr Hill were mildly acidic, of low to moderate salinity and sulfur content and low CO2 content, and that muscovite in deep veins and alteration differs in texture, composition, and process of formation from sericite at shallower levels of the hydrothermal system. Although the definition of greisen is controversial, we suggest that coarse muscovite alteration is more similar to alteration in greisen-type Sn-W-Mo districts worldwide than to sericitic alteration at higher levels of porphyry copper systems. The fluids that form coarse muscovite veins and alteration in the roots of porphyry copper systems are distinct from fluids that formed copper ore or widespread, shallower, acidic alteration. We propose that this style of veins and alteration at Luhr Hill represents degassing of moderate volumes of overpressured hydrothermal fluid during late crystallization of deep levels of the Yerington batholith.
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Payette, Christine. "The melt inclusions in quartz phenocrysts of the quartz-feldspar porphyry, Harvey Station, New Brunswick /." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63383.
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Karamanolis, George E. "Plato and Aristotle in agreement? : the Platonist discussion of Aristotle's philosophy from Antiochus to Porphyry." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367464.
Full text
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Simmons, Adam Thomas. "Magmatic and hydrothermal stratigraphy of Paleocene and Eocene porphyry Cu-Mo deposits in southern Peru." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45533.
Full textAbstract:
A geological investigation of the of the Paleocene-Eocene Cu-Mo porphyry belt of southern Peru was undertaken at the Quellaveco Cu-Mo porphyry system with complimentary work completed at the Cuajone and Toquepala mines. This work adds to the understanding of the formation and evolution of igneous systems associated with Cu-Mo porphyry formation in an understudied but economically significant copper source globally.
The Quellaveco Igneous Complex is composed of at least five phases of porphyritic intrusions which were emplaced into a slightly older equigranular granodiorite batholith and Late Cretaceous Toquepala Group volcanic rocks. These intrusions were emplaced from approximately 58Ma to 53Ma. The intrusions with the closest temporal and spatial association to copper may have been emplaced in as short a timespan as approximately 1.5m.y. These time periods and time spans are almost identical to those for the emplacement of the igneous systems at Cuajone and Toquepala. At Quellaveco, zircon mineral chemistry indicates that the igneous systems associated with porphyry copper formation are different to those not associated with porphyry copper formation. Geochemical disruptions, flat to cup shaped Eu/Eu* anomalies and rapid changes in temperature of formation of the zircons with their growth are indicative of zircons from the porphyry intrusions from Quellaveco. It is postulated that these geochemical signatures may indicate that intrusions associated with the formation of the hydrothermal systems are derived from fractionating and cooling magmatic systems which remained relatively oxidized and were subject to periodic geochemical disturbance. The geochemical disturbances may reflect a dynamic deeper magmatic system where magma mixing, replenishment and scouring of wall rock took place. At Quellaveco, each of the porphyritic intrusions are temporally related with a hydrothermal system. Each hydrothermal system is an evolution of mineral assemblages in veins from biotite-magnetite-chalcopyrite rich veins to quartz-sulphide rich veins to quartz vein with quartz-sericite selvages. This sequence of vein evolution repeats itself at Quellaveco at least four times. Each hydrothermal system occurs immediately after the emplacement of at least five porphyry intrusion suites.
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Perkins, Rebecca. "Post-collisional magmatism and porphyry-epithermal style mineralisation along the Maronia Magmatic Corridor, northeastern Greece." Thesis, University of Bristol, 2018. http://hdl.handle.net/1983/12c6d2c7-5b5d-40a6-89e2-371c812d5243.
Full textAbstract:
Porphyry copper deposits are not restricted to volcanic arcs alone and have been identified in extensional tectonic settings from across the world. Post-collisional crustal extension can result in areas of elevated heat flow generating small-volume, calc-alkaline to shoshonitic magmas, some of which are associated with exotic metal-bearing porphyry – epithermal systems. The Maronia Magmatic Corridor is a NE-trending belt of post-collisional Oligocene high-K calc-alkaline to shoshonitic plutons that intrude the northern Rhodope Core Complex in northeastern Greece. It is host to several documented occurrences of post-collisional porphyry – epithermal mineralisation associated with the intrusion of co-genetic evolved porphyritic dykes and stocks. By reconstructing the tectono-magmatic evolution of post-collisional magmatism along the Maronia Magmatic Corridor, this thesis aims to explore the processes governing porphyry – epithermal mineralisation in extensional tectonic settings.