Calcic-iron skarns are one of the characteristic part of the regional metamorphic complexes of the Bohemian Massif. Their mineral assemblages, structures and significant enrichment of Ca, Al and Fe were previously interpreted to be primary (exhalation sediment) or secondary (metasomatic carbonates). In this project, which consists of three sub-studies will focus on the geochemical composition of skarn as the main arguments for the discussion of their origin. Malešov deposit belongs to the typical calcic-iron skarns whose mineral assemblages are not very different from similar skarns associations in the Bohemian massif. It consists of lenticular body that is stored in gneiss and migmatites of the Kutná Hora crystalline complex. On the deposit prevails garnet-pyroxen skarn, less abundantly represented garnet and magnetite skarns and skarns replacement by amphibole or epidote. Fine-grained garnet skarns are formed by isotropic dark red garnet (Adr78-88Prp0-0.3), while in massive garnet rocks garnet grains form the core (Adr13-38Prp2.5), which envelop newly formed garnet (Adr28-66Prp1.6). In association with them is often pyroxene (Hd60-90) which can be replaced by hastingsite amphibole composition. Other minerals present are magnetite, Fe-epidote, calcite and albite. Magnetite and pyroxene skarns are...

Thesis submitted for the degree MAGISTER SCIENTIAE to the Faculty of Science, Department of Geology, University of the Witwatersrand, Johannesburg / The Koperberg Suite intrusion at Jubilee, Namaqualand varies in composition from anorthosite, through mica diorite to pyroxene leucodiorite and pyroxene diorite. Detailed mapping and petrological studies of these rocks indicate that they were sequentially emplaced into the Concordia Granite country rocks, and that each of the rock types represent discrete magmatic events. The sequence of intrusion is from more acidic to more basic. Whole-rock geochemical analyses indicate that these rocks represent cumulates involving variable proportions of plagioclase, orthopyroxene, mica, quartz, oxides and immiscible sulphides. These cumulate phases intruded into the Concordia Granite at the time of peak of metamorphism and deformation in the Okiep Copper District, i.e, about 1030Ma ago, At the time of intrusion, the country rocks were under going partial melting under high grade (granulite facies) metamorphic conditions. and granitic anatects were present in the crust. Hybridisation of basic magma and granitic melts occurred within the shear zones along which the basic magmas ascended. The En content of orthopyroxene in the Koperberg Suite exceeds the An content of plagioclase. This is atypical of basic intrusions and is a consequence of this mixing. Mixing calculations based on the initial 87Sr/86Srratio (Ru) of the Jubilee samples at 1030Ma, imply high levels of assimilation (as much as 80% assimilation in the case of anorthositic rocks) between a granitic component, similar in composition to the Nababeep Gneiss and a mantle-derived basic magma. Sulphide mineralisation was initiated by the assimilation process, which caused the separation of immiscible sulphides from the hybridised magma. Subsequent oxidation of the original sulphide assemblage produced bornite, chalcopyrite and Ti-poor magnetite. / Andrew Chakane 2019

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2016. / The Jacomynspan Ni-Cu sulphide mineralisation is hosted within a 100m thick steeply dipping tabular, differentiated, sill of mafic to ultramafic composition intruded into country gneissic rocks of the Namaqualand Metamorphic complex. This sill is predominantly composed of tremolite schist (metamorphosed pyroxenite) containing lenticular bodies of harzburgite. The harzburgite generally hosts net-textured mineralisation with up to 50% by volume of the rock. Massive sulphide veins and stringers are occasionally present within the harzburgite. The sulphide minerals are a typical magmatic assemblage of pyrrhotite, chalcopyrite and pentlandite. The sill covers an approximate strike length of about 5km but only a small portion covering 1km x 1km was selected for this study. Physical property studies carried out on the drill core (magnetic susceptibility and conductivity) indicate that the country gneissic rocks are not conductive and neither are they magnetically susceptible. However, the mineralized sill has elevated values of both magnetic susceptibility and relative conductivity compared to its host making it a suitable target for both magnetic and electromagnetic inversion. Drilling done so far on the study area has shown that the well-mineralised harzburgite (hosted within the poorly mineralised ultramafic sill) is not a continuous body but occurs in ‘pockets’. There is therefore need to use the available geophysical and geological datasets to derive a model of these well mineralised pods. This study is therefore intended to assess the feasibility of using electromagnetic (EM) methods together with other geophysical methods and geology in obtaining a model of the harzburgite pods hosted within the less conductive poorly mineralised ultramafic sill in order to guide further drilling. Geosoft’s VOXI Earth Modelling software was used to model the high resolution airborne magnetic data for this study. Cooper’s Mag2dc (www.wits.ac.za) and Stettler’s Magmodintrp software (personal communication, 2015) was also used during modelling of the magnetic data to compliment the modelling from VOXI. The mineralised ultramafic sill was clearly mapped in both the 3D model representation from Mag2dc modelling and VOXI’s 3D unconstrained smooth model inversion for the study area. Based on the physical properties studies carried out on the study area, EM data (both ground and downhole EM) were modelled using Maxwell software. The poorly mineralised tremolite schist was clearly modelled. In order to better constrain the targets, an assumption was made that at late decay times the currents would be focused in the centre of the large EM plate probably giving an indication of the most conductive part of the intrusion. Smaller ‘Resultant EM plates’ of dimensions, 300mx300m that coincide with the centre of the large EM plates (with a conductance above 100S) were constructed in iv Maxwell software and integrated with the DXF file of the Micromine geology model of the well mineralised harzburgite clearly mapping the well-mineralised harzburgite and showing its possible extensions. 2D inversion modelling was conducted on all audio-frequency magnetotelluric (AMT) data for this study area. The modelling results clearly mapped the mineralised intrusion.

Este trabalho propõe a geração e fechamento de um proto-oceano e consequente formação de um arco de ilhas durante o Neoproterozóico no Complexo Metamórfico Passo Feio na região de Caçapava do Sul, RS. O Complexo Metamórfico Passo Feio, constituinte do Terreno São Gabriel, consiste em uma sequência metavulcanossedimentar supracrustal neoproterozóica intrudida pelo Granito Caçapava. O estudo utiliza petrografia, química de rocha total e química mineral por microssonda para classificar e identificar a afinidade geoquímica e ambiente tectônico de geração de anfibolitos contidos na sequência metavulcanossedimentar do Complexo Metamórfico Passo Feio. Os resultados são comparados com basaltos e pillow lavas da Formação Arroio Mudador, além de diques intermediários, básicos e ultrabásicos, intrudidos em rochas vulcanogênicas da Formação Hilário. A petrografia com auxílio da geotermometria da clorita, composição dos anfibólios e sua relação núcleo-borda permitiu a classificação da fácies metamórfica em prehnita-pumpeleíta para os basaltos e pillow lavas, xisto verde para os diques e fácies anfibolito inferior para os anfibolitos Os diagramas discriminantes de geoquímica de rocha total e de química mineral indicam afinidade desde toleítica a alcalina para os diques da Formação Hilário. Os basaltos, pillow lavas e anfibolitos possuem composição basáltica a basáltico-andesítica e afinidade toleítica, por vezes transicionando para calci-alcalina, interpretados como derivados de um mesmo protólito basáltico. As diferenças mineralógicas devem-se aos diferentes graus metamórficos. Os diagramas discriminantes de ambientes geotectônicos indicam em sua maioria basaltos de arco vulcânico (e toleítos de arco de ilha que se incluem nessa classificação). Os dados obtidos combinados com dados da literatura permitiram a interpretação de um modelo de evolução onde há uma abertura de um proto-oceano através do rifteamento do Arco da Bossoroca em cerca de 760 Ma, onde houve a formação de um arco de ilha (rochas do Complexo Passo Feio), a precipitação de carbonatos e margas neste proto-oceano, subsequente fechamento, dois eventos de metamorfismo e por fim a intrusão do Granito Caçapava a 562 Ma. / This paper proposes the generation and closure of a proto-ocean and consequently formation of an island arc in the Neoproterozoic Passo Feio Metamorphic Complex, Caçapava do Sul region, southern Brazil. The Passo Feio Metamorphic Complex, São Gabriel Terrane, consists of a Neoproterozoic supracrustal metavolcano-sedimentary sequence intruded by the Caçapava Granite. The study uses petrography, whole-rock geochemistry and mineral chemistry by microprobe to classify and identify the geochemical affinity and tectonic environment of the amphibolites contained in the metavolcano-sedimentary sequence of Passo Feio Metamorphic Complex. The results are compared with the basalts and pillow lavas of Arroio Mudador Formation, besides intermediate, basic and ultrabasic dykes, intruded in nearby volcanogenic rocks of Hilário Formation The petrography with aid of chlorite geothermometry, amphibole composition and its core-rim relation allow the metamorphic facies classification of prehnite-pumpellyite for the basalts and pillow lavas, greenschist for the dykes and lower amphibolite facies for the amphibolites. The whole-rock geochemistry and mineral chemistry discriminant diagrams indicate from tholeiitic to alkaline affinities for the Hilário Formation dykes. The basalts, pillow lavas and amphibolites have basaltic to basaltic-andesite composition and tholeiitic affinity, occasionally transitioning to calc-alkaline, and are interpreted as derived by the same basaltic protolith. The mineralogical differences are due to the different metamorphic grades. The geotectonic environment discriminant diagrams mostly indicate volcanic arc basalts (and island arc tholeiites, included in this classification). The present results combined with literature data allow an interpretation and propose a geotectonic evolution model for the region, starting with a proto-ocean opening through the Bossoroca Arc rifting in about 760 Ma, where occurred the formation of an island arc (Passo Feio Complex rocks), the precipitation of carbonates and marls in this proto-ocean, subsequent closure, two metamorphism events and at last the Caçapava Granite intrusion at ca. 562 Ma.

Orogenic gold deposits occur within metamorphic belts throughout the world and have through time represented the source for over 25% of the world’s gold production. Although orogenic gold deposits are of great economic importance, controversies exist on the subject of fluid and metal sources and there have been few studies of gold´s distribution and mobility outside of large economic deposits. Research made by Pitcairn et al. (2006), on the Mesozoic Otago and Alpine schists of New Zealand, observed systematic depletion of Au and a suite of 6 associated elements with increasing metamorphic grade. This depletion was identical to the suite of elements enriched in the Otago gold deposits and provided strong evidence that orogenic gold deposits form due to metamorphic processes. The mobilization of metals was attributed to the recrystallization of sulfide minerals during prograde metamorphism causing dehydration and release of metal-rich metamorphic fluids.  This thesis is part of a larger project aimed at testing the “Otago model” in a classic metamorphic terrain: The Dalradian metamorphic belt of Scotland. Rocks in the study are from the southern higlands group and the Appin and Argyll group which range in metamorphic grade from chlorite zone greenschist facies to sillimanite zone amphibolite facies. Three main aspects, which supplement earlier research, are addressed in this study: 1) Investigation of the sulfide paragenesis at Loch Lomond and Stonehaven was carried out to map the evolution of sulfides with metamorphic grade and the possible relations to the distribution of gold. Using SEM scanning to quantify the abundance of different sulfide minerals together with previous data on the Glen Esk region, a complex sulfide evolution pattern for the Dalradian Supergroup is identified. The sulfide evolution describes the same changes in texture and chemistry as observed in the Otago Schists but is made complex by the difference in geological evolution for the different regions. 2) Reinvestigation of the higher grade zones of Glen Esk (staurolite to sillimanite) was carried out as samples from the previous study were very weathered. Results from ultralow detection limit methods (HG-AFS and a gold detection method developed by Pitcairn et al. 2006) showed significant systematic depletion of Au and As with metamorphic grade. From chlorite to sillimanite zone average values of Au and As were showed to decrease by 65% and 88% respectively. Furthermore, a suite of 10 major and 12 trace elements were analyzed using ICP methods showing no trends of systematic depletion with increased metamorphic grade.  3) Investigation of Pb-Ag Veining and vein samples from each of the metamorphic index mineral zones in the Glen Esk area was carried out to identify fluid composition and ore mineralogy. Using microthermometry and Raman laser spectroscopy two distinct fluids were identified. The first type is a H2O-CO2-N2-salt fluid of low salinity (0-15 weight percent NaCl equivalent) and medium temperature (150 to 250 °C) locally containing minor amounts of CH4. It is found in the veins from the mineral index zones of Glen Esk and was formed in the ductile regime most likely related to late stage metamorphic devolatilization released during Caledonian uplift of the Dalradian. Pb-Ag veins from the locality of Hardhill host the second fluid type which was formed in the brittle regime  accompanied by brecciation as a high salinity (15 to 20 weight percent NaCl equivalent) low temperature (70-140°C) H2O-salt fluid with calcic composition was precipitated. This fluid bears much resemblance to Carboniferous calcic brines responsible for economic base-metal precipitation with widespread occurrence in southwest Scotland and Northern Ireland. Results of this thesis show many similarities with the Otago study, with a connection between metal mobility and metamorphic grade, providing support for the dehydration model as a viable mechanism for the generation of orogenic gold deposits.

This thesis aims to provide a better understanding of the role of mountain building in the carbon cycle. The amount of CO2 released into the atmosphere due to metamorphic processes is largely unknown. To constrain the quantity of CO2 released, fluid-driven reactions in metamorphic rocks can be studied by tracking fluid-rock interactions along ancient fluid flow pathways. The thesis is divided into two parts: 1) modeling of fluid flow rates and durations within shear zones and fractures during greenschist- and blueschist-facies metamorphism and 2) the assessment of possible mechanisms of fluid infiltration into rocks during greenschist- to epidote-amphibolite-facies metamorphism and controlling chemical and mineralogical factors of reaction front propagation. On the island Syros, Greece, fluid-rock interaction was examined along a shear zone and within brittle fractures to calculate fluid flux rates, flow velocities and durations. Petrological, geochemical and thermodynamic evidence show that the flux of CO2-bearing fluids along the shear zone was 100-2000 times larger than the fluid flux in the surrounding rocks. The time-averaged fluid flow velocity and flow duration along brittle fractures was calculated by using a governing equation for one-dimensional transport (advection and diffusion) and field-based parameterization. This study shows that fluid flow along fractures on Syros was rapid and short lived. Mechanisms and controlling factors of fluid infiltration were studied in greenschist- to epidote-amphibolite-facies metabasalts in SW Scotland. Fluid infiltration into metabasaltic sills was unassisted by deformation and occurred along grain boundaries of hydrous minerals (e.g. amphibole) while other minerals (e.g. quartz) prevent fluid infiltration. Petrological, mineralogical and chemical studies of the sills show that the availability of reactant minerals and mechanical factors, e.g. volume change in epidote, are primary controls of reaction front propagation. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.</p><p> </p>

A variety of benefits motivate the development of epitaxial metals, among which include the ability to design fully integrated layer structures where metallic films and nanostructures can be embedded into the cores of optoelectronic devices. Applications include high-performance tunnel-junctions, epitaxial transparent Ohmic contacts, photomixer material, and thermoelectrics. Additionally, the integration of metallic nanostructures and films into optoelectronic devices has shown potential for improving device performance and functionality through sub-wavelength confinement of plasmonic modes and enhancement of light/matter interactions. The rare-earth monopnictide (RE-V) material system can be integrated epitaxially with conventional zincblende III-V substrates under normal growth conditions, resulting in high-quality, thermodynamically stable interfaces. The RE-V semimetals span a range of optical, electrical, and structural properties, making them ideal for integration into III-V-based optoelectronic devices and applications. In this dissertation, high-quality epitaxial LuAs, LaAs and La(x)Lu(1-x)As films and nanostructures were grown and characterized for their structural, electrical, optical, and plasmonic properties. Through a sweep of alloy film compositions of the RE-V alloy material La(x)Lu(1-x)As, the ability to produce tunable epitaxial metals was demonstrated, with a range of peak transmission spectra from near- to mid-infrared wavelengths, plasmonic response in the mid-infrared, moderate resistivity, and lattice-matching potential to many relevant III-V substrates. Additionally, there is a great deal of interest in developing techniques to produce optoelectronic devices that are not restricted by substrate lattice constant. Many epitaxial approaches have been tried, with moderate success; however, growing low defect-density heteroepitaxial materials with differing crystal structures and highly-mismatched lattice parameters is extremely challenging, and such structures suffer from poor thermal properties and reliability issues. A general approach is needed for thin metamorphic buffer layers with minimal threading dislocations that simultaneously have low thermal resistance for effective heat-sinking and device reliability. An investigation was conducted into the use of RE-V nanostructure superlattices towards the reduction of dislocation density in highly-mismatched III-V systems. / text

The formation and evolution of metamorphic core complexes has been widely studied using low temperature thermochronometry methods. Interpretation of these data has historically occurred through the lens of the traditional slip rate method which provides a singular rate that unroofing occurs at temporally as well as spatially, and assumes unroofing is dominated by motion on a single master detachment fault. Recently, several new studies have utilized (U-Th)/He ages with a higher spatial density and greater nominal precision to suggest a late-stage rapid increase in the rate of unroofing. This analysis is based on the traditional slip rate method interpretation of broad regions of core complexes that display little to no change in age along the slip direction. An alternative interpretation is presented that instead of a change in slip rate, there may have been a change in the style of unroofing, specifically caused by the transfer of displacement from low-angle detachment faulting to high-angle normal faults. Apatite fission-track (AFT), and apatite and zircon (U-Th)/He (AHe and ZHe) analyses were applied to samples from the Santa Catalina-Rincon (n=8 AHe, and n=9 ZHe) and Harcuvar (n=12 AFT, n=16 AHe, and n=17 ZHe) metamorphic core complexes in an attempt to resolve the possible thermal effects of high-angle normal faulting on core complex formation. Samples from the Harcuvars were taken along a transect parallel to slip direction with some samples specifically targeting high-angle normal fault locations. The AFT data collected here has the advantage of improved analysis and modeling techniques. Also, more than an order of magnitude more data were collected and analyzed than any previous studies within the Harcuvars. The AFT ages include a trend from ~22 Ma in the southwest to ~14 Ma in the northeast and provide a traditional slip rate of 7.1 mm/yr, similar to previous work. However, two major high-angle, detachment-parallel normal faults were identified, and hanging-wall samples are ~3 m.y. older than the footwalls, indicating high-angle normal faults rearranged the surface expression of the distribution of thermochronometer ages to some extent. AHe ages range from 8.1 Ma to 18.4 Ma but in general decrease with increasing distance in the slip direction. ZHe ages generally range between 13.6 Ma and 17.4 Ma. A series of unexpectedly young AFT ages (10-11 Ma), given by three complete samples and distinct population modes in others, suggest that some parts of the range underwent a later-stage unroofing event possibly caused by high-angle faulting. Confined fission-track length distributions were measured for Harcuvar samples and modeled using the modeling software HeFTy to infer thermal histories and calculate local cooling rates. These imply a component of steady cooling in some parts of the range, evidence of a different departure from a single-detachment dominated model. / text

Thèse (M.A.Sc.)--Université du Québec à Chicoutimi, 1984. / Une carte géologique dans une pochette. "Mémoire présenté en vue de l'obtention de la maîtrise en sciences appliquées (géologie)" CaQCU CaQCU Document électronique également accessible en format PDF. CaQCU

Thèse (D.R.Min.) -- Université du Québec à Chicoutimi, 1992. / These présentée en collaboration de l'Université du Québec à Chicoutimi et Institute of geochemistry, Academia Sinica. CaQCU Document électronique également accessible en format PDF. CaQCU