Dissertations / Theses on the topic 'Greenstone'
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Bennett, Erin Kay. "Re-designing Greenstone for Seniors." The University of Waikato, 2008. http://hdl.handle.net/10289/2278.
Full textSilva, Katherine E. "Komatiites from the Belingwe Greenstone Belt, Zimbabwe : constraints on the development of Archaean Greenstone Belts." Thesis, Royal Holloway, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263522.
Full textBurke, Shyne Duncan Caleb Padraig. "On carbonate alteration zones in a greenstone keel of the East Pilbara Terrane (Doolena Gap Greenstone Belt)." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/107570/1/Duncan_Burke%20-%20Shyne_Thesis.pdf.
Full textBrake, Chris. "Tholeiitic magmatism in the Belingwe greenstone belt, Zimbabwe." Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/12669.
Full textSOUZA, Zorano Sérgio de Souza. "Geologia e petrogênese do “Greenstone Belt” identidade: implicações sobre a evolução geodinâmica do terreno granito - “Greenstone” de Rio Maria, SE do Pará." Universidade Federal do Pará, 1994. http://repositorio.ufpa.br/jspui/handle/2011/7665.
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Este trabalho trata da geologia e petrogênese do "greenstone belt" Identidade, situado entre as cidades de Xinguara e Rio Maria, SE do Estado do Pará. Os dados obtidos permitiram discutir a evolução geodinâmica do terreno granito - "greenstone" da região de Rio Maria, inserindo-a no contexto da Província Mineral de Carajás (PMC), SE do cráton Amazônico. O "greenstone" em lide compõe um cinturão "sinformal" direcionado WNW-ESE, correspondendo a um pacote metavulcãnico, com xistos ultramáficos (UM), basaltos (BAS) e gabros (GB) na base, e, no topo, rochas hipabissais dacíticas (DAC - ca. 2,94 Ga, Pb/Pb). O conjunto foi intrudido por metaplutônicas Mesoarqueanas, os tipos mais precoces sendo quartzo dioríticos, seguidos sucessivamente por granodioritos (com enclaves máficos), trondhjemitos / tonalitos e leucogranitos. O embasamento gnáissico (GN - aflorante a norte e reconhecido por conter uma fábrica mais antiga Sn-1/D1), o "greenstone" e os metagranitóides foram intrudidos no final do Paleoproterozôico por enxames de diques riolíticos (ca. 1,60 Ga, Rb/Sr) e diabásicos. O "greenstone" apresenta estruturas e texturas ígneas reconhecíveis, porém obliteradas em regiões de contato com metagranitóides e em zonas de cisalhamento. As ultramáficas ocorrem como tremolititos, tremolita - talco xistos e talco xistos; o anfibólio é bastante alongado e fino, comumente em arranjos paralelos, interpretados como fantasmas de texturas "spinifex". Os basaltos são maciços ou almofadados, freqüentemente variolíticos. Mostram diferentes graus de recristalização, sendo identificados restos de texturas hialofiticas, pilotaxíticas e traquitóides. Clinoanfibólio (hornblenda actinolítica), epídotos e plagioclásio (albita - andesina) são os minerais mais abundantes. Os gabros são maciços a porfiriticos, distinguindo-se relíquias de texturas subofiticas e granofiricas. Os dacitos são porfiríticos, com fenocristais de quartzo e plagioclásio (oligoclásio), além de hornblenda e nódulos máficos (biotita, clorita, opacos, epidotos, titanita, apatita) nas variedades menos evoluídas. Dentre os metagranitóides, os leucogranitos e trondhjemitos contêm biotita cloritizada, enquanto granodioritos e parte dos tonalitos portam biotita ou biotita + hornblenda (também em quartzo dioritos). O "greenstone" e os metagranitóides foram afetados por uma deformação dúctil, heterogênea, que evoluiu para zonas miloníticas. A estruturação da área é marcada por uma fábrica planar (Sn//Sm/D2) direcionada WNW-ESE a E-W, de mergulhos divergentes. Lineações de estiramento E-W, WNW-ESE ou NW-SE, meso e microestruturas assimétricas S-C, peixes de micas e de clinoanfibólios, e rotações de porfiroclastos a e 15 indicaram uma megaestrutura resultante de um binário com encurtamento NW-SE. A geometria atual do "greenstone" seria derivada de transpressão dextrógira, com o "greenstone" compondo uma estrutura em flor positiva. O regime transpressivo favoreceu a criação de regiões transtrativas, onde se alojaram plútons graníticos no NW, além de clivagens de crenulação extensional (Sn+i/D2) no SW. A quantificação da deformação revelou encurtamento da ordem de 60%, extensão subhorizontal, paralela ao "trend" do "greenstone", de 68 a 500%, e extensão vertical de 101 a 280%. O elipsóide de deformação variou de oblato a prolato, com mudanças de densidade e rotação do eixo de estiramento máximo (X) nas zonas miloníticas. A inversão da deformação permitiu reconstruir a forma original do "greenstone", que seria também alongada WNW-ESE, embora de excentricidade menor que a atual. Estes dados, juntamente com a petrofábrica do eixo c do quartzo, sugeriram que a deformação progressiva envolveu mecanismos de cisalhamento puro e simples, sendo o arcabouço final resultante deste último. Falhas e fraturas rúpteis diversas, afetando também diques riolíticos e diabásicos, marcaram o último evento (D3). As paragêneses minerais do metamorfismo principal (Mn/M2) originaram-se de recristalização estática, pré-tectônica, que modificou parte das texturas e quase totalmente a mineralogia das rochas do "greenstone". Formaram-se anfibólio verde azulado (hornblenda actinolítica), epídotos (pistacita predominante), titanita e quartzo em BAS e GB; tremolita, talco e clorita em UM. Saussuritização e sericitização de plagioclásio, biotitização de anfibólio, cloritização de biotita e transformação de hornblenda em titanita verificaram-se nos metagranitóides. A coexistência de hornblenda + plagioclásio (An> 17) e/ou hornblenda actinolítica + epidotos + clorita em rochas metabásicas mostrou que o evento supra foi de pressão baixa e temperaturas transicionais entre as fácies xisto verde e anfibolito. Este episódio essencialmente térmico refletiu o aquecimento crustal produzido pelo plutonismo do final do Mesoarqueano, tendo obliterado as associações prévias do metamorfismo de fundo oceânico. Ligeiramente concomitante a francamente subseqüente, houve um evento de recristalização dinâmica extensiva (Mm/M2) na fácies xisto verde, particularmente em zonas de cisalhamento e contatos litológicos. Em tais locais, existem evidências de aporte de fluidos (blastomilonitos xistosos e abundantes veios de quartzo) e remobilização da maioria dos elementos químicos (Al, Fe, Ca, K, Na, Rb, Sr, Zr). Em condições PT ainda menores, deu-se finalmente a ação de um evento discreto, relacionado com crenulações e formando clorita, epídotos e quartzo (Mn+1/M2). O evento M2, bem como aquele detectado somente em GN (M1 em fácies anfibolito), foram de natureza dúctil, o que os distinguiu nitidamente do último episódio (D3/M3). Este foi posicionado no final do Paleoproterozóico, tendo caráter hidrotermal e associado á feições rúpteis de alto nível crustal. A evolução progressiva do metamorfismo M2, com pico térmico precoce ao pico da deformação, sugeriu uma trajetória P-T-t anti-horária, correspondente á evolução metamórfica de bacias marginais fanerozóicas. Algumas análises químicas de rochas metavulcânicas permitiram a definição de séries magmáticas e discussão de modelos petrogenéticos. Reconheceram-se três séries geoquímicas, a saber, da mais antiga para a mais nova, komatiítica (UM), toleitica (BAS e GB) e cálcio-alcalina (DAC). A primeira corresponde a komatiitos peridotíticos, com MgO>18% em peso (base anidra), com um "trend" de enriquecimento em Al, tal como em Geluk e Munro, e menos cálcico do que Barberton. Os padrões de terras raras leves são irregulares, com razões (La/Sm)N entre 0,42 e 4,2 e anomalias negativas de Eu. Os terras raras pesadas pareceram menos afetados por processos pós-eruptivos, sendo planos ou ligeiramente fracionados (1,0<(Gd1Yb)N<2,3). Modelos quantitativos foram de dificil execução em virtude da remobilização de vários elementos, porém, em termos qualitativos, foi possível estimar cumulados ricos em olivina e ortopiroxênio. Dentre os toleítos, BAS e GB apresentaram padrões geoquímicos muito similares entre si. Ambos são toleítos de baixo potássio, comparáveis a toleítos arqueanos empobrecidos. Os elementos terras raras são quase planos, com valores 10X o condrito, e anomalias fracas ou inexistentes de Eu. Modelos preliminares sugeriram cumulados semelhantes para BAS e GB, compostos essencialmente de clinopiroxênio e plagioclásio. De acordo com alguns cálculos geoquímicos, a fonte dos magmas que originaram os komatiitos e toleítos seria o lherzolito a granada. Os DAC apresentaram características geoquímicas afins à metavulcânicas e metaplutônicas cálcio-alcalinas tanto modernas quanto arqueanas, seguindo o "trend" trondhjemítico. A diferenciação magmática teria decorrido por fracionamento de plagioclásio>quartzo>hornblenda>K-feldspato, com quantidades accessórias de biotita, magnetita, titanita, alanita e zircão. A fonte do magma dacítico seria crustal do tipo toleíto metamorfisado em fácies granada anfibolito e ligeiramente enriquecido em terras raras leves. No modelo geodinâmico proposto, já existia um embasamento gnáissico antes de 2,96 Ga. Entre 2,96 e 2,90 Ga, a conjugação de alto gradiente geotérmico com extensão litosférica provocou o rifteamento continental, formando bacias marginais, onde se daria a extrusão de komatiitos e toleítos. Em torno de 2,94(?)-2,90 Ga, geraram-se os DAC através de fusão de crosta oceânica em zonas de subducção, evoluindo por fracionamento a baixas pressões. Os mesmos mecanismos geradores dos DAC também seriam responsáveis pelo plutonismo cálcio-alcalino, culminando com a inversão estrutural do "greenstone", espessamento crustal e forma final do terreno granito - "greenstone" (transpressão dextrógira ca. 2,88-2,86 Ga). A região sofreu ainda um episódio de (rea)quecimento, detectado a nível de minerais, sem deformação e metamorfismo correlatos, ao final do Eoarqueano (2,69-2,50 Ga), e intrusão de enxames de diques riolíticos (1,60 Ga, Rb/Sr) e diabásicos ao final do Paleoproterozóico. A correlação com o conhecimento atual da PMC permitiu admitir que o terreno granito - "greenstone" de Rio Maria já estava configurado quando da implantação do Supergrupo Itacaiúnas (ca. 2,76 Ga) e da granitogênse alcalina na Serra dos Carajás. Assim, a transpressão sinistrógira que inverteu aquele supergrupo corresponderia a um evento posterior e bem distinto da transpressão dextrógira da região de Rio Maria.
This thesis deals to the geology and petrogenesis of the Identidade greenstone belt, located between Xinguara and Rio Maria towns, SE of Pará state. The data of this area permitted the discussion of the tectonic evolution of the gravite greenstone terrain of the Rio Maria region in the context of the Província Mineral de Carajás, SE of the Amazonian craton. The greenstone studied compose a synformal belt in the WNW-ESE direction, corresponding to one metavolcanic pile, formed predominantly by ultramafic schists (UM), basalts (BAS) and gabbros (GB) at the base, and hypabyssal dacitic rocks (DAC - ca. 2.94 Ga, Pb/Pb) at the top. The whole was intruded by metaplutonic rocks of Mesoarchean ages, the older one being quartz diorites, followed successively by granodiorites, trondhjemites / tonalites and leucogranites. The gneissic basement (GN - outcroping toward north and recognized for having an older fabric Sn-1/D1), the greenstone and the metagranitoids were intruded by hypabyssal rhyolitic (ca. 1.60 Ga, Rb/Sr) and basic dykes at the end of the Paleoproterozoic. The greenstone presents igneous structures and textures still recognized, although obliterated near the contacts with the metagranitoids and shear zones. The ultramafics occur as tremolitites, tremolite - talc schists and talc schists; the amphibole is very elongated and thin, commonly in parallel arrays, interpreted as ghosts of spinifex textures. The basalts are massive or pillowed and frequently variolitic. They show different degrees of recrystallization, with some relicts of hyalophitic, pilotaxitic and traquitoid textures. Clinoamphibole (actinolitic hornblende), epidotes and plagioclase (albite - andesine) are the most abundant minerais. The gabbros may be massives to porphyritics (plagioclase phenocrysts), still with some relicts of subophitic and granophyric textures. The dacites are porphyritic, with phenocrysts of quartz and plagioclase (oligoclase), besides hornblende and mafic clots (biotite, chlorite, opaque minerais, epidotes, sphene, apatite) in the less evolved samples. Concerning the metagranitoids, the leucogranites and trondhjemites have chloritized biotite, whereas the granodiorites and some tonalites comprise biotite or biotite + hornblende (also in quartz diorites). The greenstone and the metagranitoids were affected by one event of heterogeneous, ductile deformation, that evolved to mylonitic zones. The structural framework of the area is marked by a planar fabric (Sn//Sm/D2) in the WNW-ESE to E-W direction, with moderate to strong dips in a divergent fan. E-W, WNW-ESE or NW-SE stretching lineations, meso and asymmetric S-C microstructures, mica and clinoamphibole fishes, and rotation of o and i porphyroclasts indicated one megastructure resulting from a binary system with NW-SE shortening direction. The actual geometry of the greenstone would be derived from a dextral transpression, with the greenstone forming a positive flower structure. The transpressional regime favored the grow of transtensional cites and subsequent emplacement of granitic plutons on the NW contact, and extensional crenulation cleavage (Sn+1/D2) on the SW of the greenstone. Strain measurements displayed a ca. 60% shortening, subhorizontal extension of ca. 60 to 500% parallel to the greenstone trend, and vertical extension of ca. 101 to 280%. The strain ellipsoid may be oblate to prolate, with changes in density and rotation of the axis of maximum stretching (X) toward the mylonitic zones. The inversion of the deformation permitted the reconstruction of the original shape of the greenstone, that would be also elongated WNW-ESE, but with lesser eccentricity than today. These data, together with the quartz petrofabric, suggested that the deformation has been accommodated by pure and simple shear mechanisms, the final framework resulting essentially from the later. The last event (D3) are represented by faults and fractures which also affected the felsic and basic dykes. The paragenesis of the main metamorphic event (Mn/M2) is represented by static recrystallization, which modified some textures and almost ali minerais within the greenstone. The minerais formed phases were bluish green amphibole (actinolitic hornblende), epidotes, sphene and quartz in BAS and GB; tremolite, talc and chlorite in UM. The metagranitoids show transformations of plagioclase (saussurite, fine white mica), amphibole (to biotite and/or sphene) and biotite (to chlorite). The coexistence of hornblende + plagioclase (An>17) and/or actinolitic hornblende + chlorite in metabasic rocks shows that this event was of low pressures and temperatures in the transitional field of the greenschist and amphibolite facies. This episode should reflect a regional crustal heating produced by the plutonism at the end of the Mesoarchean, that obliterated the previous associations of ocean floor metamorphism. Slightly coeval to subsequently, it occurred one event of extensive dynamic recrystallization (Mm/M2) in the greenschist facies, specially within shear zones and lithological contacts. In these places, there are evidences of fluid incoming (schistose blastomylonites and abundant quartz veins) and remobilization of chemical elements (Al, Fe, Ca, K, Na, Rb, Sr, Zr). Finally, under lower PT conditions, it occurred a less expressive event related to crenulation cleavages and forming chlorite, epidotes and quartz (Mn+1/M2). The M2 event, as well as the one detected only in GN (M1 under amphibolite facies), was of ductile nature and cleary distinguished from the last one (D3/M3). The later was placed at the end of the Paleoproterozoic, being of hydrothermal character and associated to high crustal structures. The progressive evolution of the M2 metamorphism with its thermal peak predating the deformation suggested a counterclockwise P-T-t path, corresponding to the metamorphic evolution of Phanerozoic marginal basins. Some chemical analysis of the metavolcanic rocks permitted the definition of magmatic series and a discussion of petrogenetical modeling. It was possible to recognize three geochemical series, that is, from the older to the younger, komatiitic (UM), tholeiitic (BAS and GB) and calc-alkaline (DAC). The first one corresponds to peridotitic komatiites with MgO>18 weight % (volatile-free basis), with an enrichment trend in Al, such as in Geluk and Munro, and less calcic than the Barberton one. The light rare earth element patterns are irregular with (La/Sm)N ratios between 0.42 and 4.2 and negative Eu anomalies. The heavy rare earth elements seem less affected by post-eruptive processes, being plate or slightly fractionated (1.0<(Gd/Yb)N<2.3). The quantitative models were of hard execution due to the remobilization of several elements. It was possible estimate cumulates rich in olivine and orthopyroxene. With regarding to tholeiites, the BAS and GB showed very similar geochemical signatures, both being low potassium tholeiites comparable to depleted Archean tholeiites. The rare earth elements are almost plate, with values 10X the chondrite, and slight or no Eu anomaly. Preliminary modeling suggested similar cumulates for BAS and GB, composed essentially by clinopyroxene and plagioclase. The magma sources that originated the komatiites and tholeiites would be a garnet lherzolite. The DAC presented geochemical characteristics of modern and Archean metavolcanics and metaplutonics of trondhjemitic nature. The magmatic differentiation would be achieved by fractionation of plagioclase>quartz>hornblende>K-feldspar, with subordinated amount of biotite, magnetite, sphene, allanite and zircon. The source of the dacitic magma would be a tholeiite metamorphosed to the garnet amphibolite facies and somewhat enriched in light rare earth elements. The geodynamical model proposed admit the existence of a gneissic basement prior to 2.96 Ga. Between 2.96 and 2.90 Ga, the interplay of high geothermal gradients and lithospheric extension was responsible for extensive rifting, forming marginal basin systems, where extruded the komatiitic and tholeiitic rocks. At 2.94(?)-2.90 Ga, the DAC were generated from partia' melting of oceanic crust in subduction zone settings, and evolved by low pressure fractional crystallization. The same mechanisms that generated the DAC are extended also to the calc-alkaline plutonism, this one being responsible for the structural inversion of the greenstone, crustal thickening and final shape of the granite - greenstone terrain (dextral transpression ca. 2.88-2.86 Ga). The region still suffered a late episode (end of Eoarchean, 2.69-2.50 Ga) of (re)heating, registered only in sorne mineral, without any evidente of deformation and/or metamorphism. Finally, it occurred the intrusion of felsic (1.60 Ga, Rb/r) and basic dykes at the end of the Paleoproterozoic. The correlation with the actual understanding of the Província Mineral de Carajás permitted envisage that the Rio Maria granite - greenstone terrain was then configured at the moment of implantation of the Itacaiúnas Supergroup (ca. 2.76 Ga) and alkaline granitic plutonism at the Serra dos Carajás. So the sinistrai transpression that inverted that supergroup would correspond to a newer event, very distinct as regards as the dextral transpression of the Rio Maria region.
Hunter, Morag. "The tectonic setting of the Belingwe Greenstone Belt, Zimbabwe." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245104.
Full textDiergaardt, Byron Nico. "Rhyolitic volcanism in the Onverwacht Group, Barberton Greenstone Belt." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80255.
Full textENGLISH ABSTRACT: The source of the K2O in the K2O-rich ~3.45 Ga felsic intrusive rocks of the H6 unit in the Hooggenoeg Formation of the Onverwacht Group in the Barberton Granite Greenstone Terrain (BGGT) is examined in this study. This is of particular research interest because the Paleoarchaean rock record is considered to lack K2O-rich magmatic rocks. Previous studies on the felsic igneous rocks of the H6 unit have proposed that these rhyolites are K-metasomatised eruptive equivalents of the sodium-rich ~3.45 Ga TTGs of the BGGT and that the K-feldspar crystals in the rocks formed as a consequence of subsolidus replacement of plagioclase by K-feldspar. Furthermore, the timing of K-metasomatism has previously been related to the formation of the Buck Ridge Chert (BRC), which overlies the H6 unit. However, it has recently been demonstrated from granitic clasts in the conglomerate layer at the base of the Moodies sucession that K2O-rich magmatic rocks formed concurrently with TTG magmas during each of three episodes of TTG magmatism observed in the BGGT. Consequently, the hypothesis of a metasomatic origin for the K2O-rich character of the felsic rocks of the H6 unit requires further examination. Previous studies of the chemistsry of felsic volcanic rocks within the H6 unit were based on relatively low numbers of samples. This study has examined a substantial set of the freshest material available. Two varieties of felsic volcanic rocks were identified; K2O-rich, CaO-poor, Na2O-poor rhyolites and Na2O-rich, CaO-poor, K2O-poor Na-rhyolites. The K2O- rich rhyolite variety is dominant. Consequently, it is possible that the K2O-rich character of these rocks represents a primary magmatic signature. However, this judgment is complicated by the presence of a greenschist-facies metamorphic overprint at 3.2 Ga, which has resulted in complete replacement of micrystalline groundmass and partial replacement of the phenocryst assemblages by greenschist- and sub-greenschist-facies mineral assemblages, which undoubtedly allowed possible shifts in chemical compositions In this thesis, I test the source of K2O in these rocks by using the porphyritic textures of the rocks as an indication of the primary composition of the magmas they were formed from. These textures are typically defined by K-feldspar or albite and quartz phenocrysts within a microcrystalline groundmass. The rocks containing albite are Na-rich (Na-rhyolites) whereas the rocks defined by K-feldspar phenocrysts are rhyolites. XRD study of the structural state of the K-feldspar phenocrysts in the rhyolites indicates that these crystals are orthoclase and intermediate microcline, i.e. medium temperature K-feldspar polymorphs. The modal proportions of K-feldspar, quartz and microcrystalline groundmass in the rhyolites were calculated by using image analysis software. The compositions of the feldspar minerals were determined by electron beam analysis. Minimum bulk rock K2O content of the rhyolites were calculated from the proportions of K-feldspar crystals and their compositions. Even where the proportion of K-feldspar phenocrysts is relatively low (~ 30%), the calculated minimum bulk-rock K2O content is still above 5 wt%. The HREE slope (GdN/LuN) of the felsic porphyritic rocks of the H6 rhyolites is similar to that of ~3.45 Ga TTG plutons and steeper than that of granitic clasts of identical age contained in the basal conglomerate of the Moodies Group. Hence this study has illustrated that the rhyolites of the H6 unit were primary K-feldspar-rich, K2O-rich magmas that formed contemporarily with the ~3.45 Ga TTGs. This implicitly means that rhyolitic volcanism was more wide spread than previously thought in the Paleoarchaean and that it occurred together with the intrusion of the ~3.45 Ga TTGs in the BGGT.
AFRIKAANSE OPSOMMING: Die bron van die K2O in die K2O-ryk ~ 3,45 Ga felsiese vulkaniese rotse van die H6-eenheid in die Hooggenoeg formasie van die Onverwacht Groep in die Barberton Graniet Groensteen Terrein (BGGT) is in hierdie studie ondersoek. Dit is van besondere navorsingsbelang omdat die Paleoargeïse gesteenterekord beskou word as vry van magmatiese K2O ryke gesteentes. Vorige studies oor die felsiese vulkaniese rotse van die H6 eenheid het voorgestel dat hierdie rioliete K-gemetasomatiese eruptiewe ekwivalente van die natrium-ryke ~ 3,45 Ga TTGs van die BGGT is en dat die K-veldspaat kristalle in die gesteentes gevorm is as gevolg van subsolidus vervanging van plagioklaas deur K-veldspaat. Verder is die tydsberekening van K-metasomatisme voorheen gekoppel aan die vorming van die Buck Ridge Chert (BRC) wat die felsiese H6 eenheid bedek. Dit is egter onlangs aangetoon dat K2O-ryke magmatiese rotse gelyktydig met TTG magmas gevorm is tydens elk van drie episodes van TTG magmatisme waargeneem in die BGGT. Gevolglik vereis die hipotese van 'n metasomatiese oorsprong vir die K2O-ryke karakter van die felsiese gesteentes van die H6 eenheid verdere ondersoek. Vorige studies van die felsiese vulkaniese gesteentechemie in die H6 eenheid is gebaseer op 'n relatief klein getal monsters. Hierdie studie het 'n aansienlike stel van die varsste materiaal beskikbaar vir analise ondersoek. Twee variëteite van peralumineuse felsiese vulkaniese gesteentes naamlik 'n K2O-ryk, CaO-arm, Na2O-arm rioliet en Na2O-ryk, CaO-arm, K2O-arm Na-rioliet. Die K2O-ryke rioliet variëteit is meer oorheersend as die Na-rioliete. Dit is dus moontlik dat die K2O-ryk karakter van hierdie rotse 'n primêre magmatiese kenmerke verteenwoordig. Hierdie uitspraak is egter bemoeilik deur die teenwoordigheid van 'n groenskisfasies metamorfe oorprint op 3,2 Ga, wat gelei het tot die volledige vervanging van mikrokrisstalyne grondmassa en gedeeltelike vervanging van fenokrist samestellings deur groenskis en sub-groenskisfasies minerale samestellings en wat ongetwyfeld toegelaat het vir 'n moontlike verskuiwing in chemiese samestelling. In hierdie tesis toets ek die bron van K2O in hierdie gesteentes deur gebruik te maak van die vulkaniese teksture van die gesteentes as 'n aanduiding van die primêre samestelling van die magmas waaruit hulle gevorm het. Hierdie teksture word gewoonlik gedefinieer deur K-veldspaat of albiet en kwarts fenokriste binne 'n grondmassa van wat vroeërglasoorblyfsels was. Die rotse wat albiet bevat is Na-ryk (Na-rioliete) terwyl die rotse gedefinieer deur K-veldspaat fenokriste rioliete is. XRD studie van die strukturele toestand van die K-veldspaat fenokriste in die rioliete dui aan dat hierdie kristalle ortoklaas en intermediêre mikroklien is, dit wil sê die hoër temperatuur K-veldspaat polimorfe. Die modale proporsies van K-veldspaat, kwarts en glasoorblyfsels in die rioliete is akkuraat bereken deur gebruik te maak van beeld analise sagteware. Verder is die samestellings van die veldspaat minerale bepaal deur die elektronstraal analise. Minimum grootmaat rots K2O inhoud van die rioliet is berekén vanaf die fase verhouding van K-veldspaat en hul komposisies. Resultate dui daarop dat selfs waar die verhouding van K-veldspaat phenocrysts is relatief laag (~ 30%), die berekende minimum K2O grootmaat rots samestelling is nog steeds bo 5 wt%. Die REE-helling (GDN / Lun) van felsiese porphyritic rotse van die H6 is soortgelyke relatief tot die REE helling van ~ 3,45 Ga TTGs en steiler REE helling relatief tot granitiese klaste vervat in die basale konglomeraat van die Moodies-groep. Dus het hierdie studie getoon dat die rioliete van die H6-eenheid primêre K-veldspaat-ryke, K2O-ryke en peralumineuse magmas was wat gevorm is terselfdertyd met die ~3,45 Ga TTGs. Dit beteken implisiet dat riolitiese vulkanisme meer wyd verspreid was as wat voorheen gedink is in die Paleoargeïkum en dat dit tesame met die indringing van die ~ 3,45 Ga TTGs in die BGGT plaasgevind het.
Dai, Tianhuan. "Kinematics and deformation history of the Cross Lake Greenstone Belt." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/2162.
Full textThesis research directed by: Dept. of Geology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
Lafleur, Pierre Jean. "The Archean Round Lake Batholith, Abitibi Greenstone Belt a synthesis." Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/5049.
Full textJurkowski, Jacek. "U-Pb geochronology study of Lynn Lake greenstone belt, Manitoba." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0011/MQ52583.pdf.
Full textBammeke, B. O. "Geochemical prospecting in a greenstone-granite complex, South West Nigeria." Thesis, Swansea University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636029.
Full textChiarini, Alexandre Patricio. "Geologia da porção basal do \"Greenstone Belt\" de Piumhi-MG." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/44/44135/tde-16072015-101156/.
Full textThe metavulcano-sedimentary sequence (VSS) portion of Piumhi, focused in this work, represents the basal part of an Archean to Paleoproterozoic greenstone belt, and has been studied in its structural, petrographical, geochemical and metalogenetic aspects. The structural analysis provided a better understanding of the geometric/stratigraphic tectonic evolution and internal kinetics of the VSS, and of its relationship with the other juxtaposed precambrian units in direct contact. The VSS occurs thrusting a TTG granitic body to the north, in shear zones with strong milonitization near the contact. This set corresponds to the basement of the Bambuí Group, that covers it with sedimentary contacts, presenting only some tectonic local disturbances, represented by some small reverse and transcurrent ruptile faults. In the last important regional tectonic event, this autoctonous TTG-greenstone belt set, and its plataformal cover (Bambuí Group), were covered by the quartzitic aloctonous sequences of the Canastra Group nappe. The petrographical and geochemical studies showed the necessity of a redefinition on the classification and nomenclature used in the literature for the VSS. They also lead to the revision on the magmatic evolution of the VSS, and to the characterization of the hydrothermal alteration that modified the original litologic association. Still, the relation among these processes with the metalogenetic aspects has been studied, in the generation of hydrothermalites and exalative sedimentary rocks, containing traces of gold and base metals mineralizations. The mapped basal unit is constituted by volcanic rocks of acid to intermediate composition (basaltic andesites, dacites and rhyolites), of toleiitic to transitional calcalkaline feature. Litogeochemical calculations and modeling support the cogenetic evolution of these litotypes through differentiation by magmatic fractionating. Most of these rocks were altered hydrothermally by espilitization, epidotization, keratophyrization and silicification processes. The uppermost unit is composed by magnesian basaltic volcanic rocks, with well developed spinifex textures, although they are always in pseudomorphs replaced by metamorphic secondary paragenesis of medium to high greenschist facies. In literature, these rocks are referred notoriously as komatiites, however, their mineralogical and geochemical aspects indicate that they are not these litotypes. They present acicular spinifex textures, as clinopyroxene shapes, and rarely blade spinifex, as olivine shaped crystals. Besides, their silica rates are high, reaching intermediate rock values. Through fractionating, that occurs in differentiated basaltic flows, these magnesian basalts originated basaltic andesites. It is assumed here, based on geochemical data, that these basaltic rocks may represent extrusive equivalents of the most primitive magmas, which originated the intermediate volcanic rocks of the basal unit, differentiated in depth. The magnesian basalts, less altered, show toleiitic characteristics, evolving in a back-arc environment, in a thin continental crust. Intercalated in this unit is the majority of the banded iron formations (BIF) in the VSS, which constitutes important metalogenetic targets. The chemical composition of the iron formations was compared to the mobilized elements of the volcanic rocks in the alteration processes, identified and quantified through mass balance calculations. The chemical characteristics of the BIF showed strong correlation mainly with the leached elements in the espilitization processes suffered by the basaltic andesites. Therefore, with the application of numerical models to the natural occurrences in Piumhi, is suggested the possible link of these processes of deep-sea hydrothermal alterations, with the exalative fluids that originated and eventually mineralized the iron formations. Gold occurs in these iron formations, as verified in geochemical analysis made by ICP-AES in selective extractions, sometimes, with strong anomalies (nugget effects). Calculations indicated positive correlation of Au, with Co, As, Zn, Ni and Sb, confirming them as tracer elements in prospection.
Hamman, Jurgens Petrus Eden. "Geotechnical assessment of a kimberlite pipe in Greenstone belt granites." Diss., University of Pretoria, 2008. http://hdl.handle.net/2263/24842.
Full textDissertation (MSc)--University of Pretoria, 2008.
Mining Engineering
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Donatti, Filho Jose Paulo 1981. "Reavaliação do contexto tectonico dos basaltos do greenstone belt do Rio Itapicuru (Bahia), com base na geoquimica de elementos-traço." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/287302.
Full textDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociencias
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Resumo: O Greenstone Belt Paleoproterozóico do Rio Itapicuru, nordeste do Cráton do São Francisco, está inserido integralmente no Bloco Serrinha e possui um domínio vulcânico máfico com um contexto geodinâmico de formação em debate, se arco, bacia de retro-arco ou rifte intracontinental. Dados geoquímicos dos basaltos deste domínio foram obtidos com o intuito de reavaliar a geoquímica e o contexto tectônico de formação dessas rochas com base principalmente na geoquímica de elementos-traço de elevado poder interpretativo (e.g. Low Field Strenght Element (LFSE), High Field Strenght Element (HFSE), e Rare Earth Element (REE)). Este domínio é composto de lavas almofadadas, basaltos variolíticos, basaltos maciços e porfiríticos, bem expostos no curso médio do Rio Itapicuru. A paragênese metamórfica indica condições variando de fácies xisto verde a fácies anfibolito. O domínio é composto basicamente por basaltos Fe-toleíticos subalcalinos, que são divididos geoquimicamente em dois grupos: ThI ¿ enriquecidos em Ti-P e elementos-traço incompatíveis, e outro, representado pelos toleiítos tipo II (ThII) que exibem baixas concentrações nesses elementos. Os ThII são mais primitivos geoquimicamente, exibindo valores relativamente mais elevados em Mg, Ni e Cr. Espacialmente os dois grupos distribuem-se em dois domínio distintos, um a leste (ThI), e outro a oeste (ThII). O enriquecimento seletivo e a alta mobilidade de alguns elementos litófilos (e.g. Rb, Ba, Na, Cs) indicam que os basaltos passaram por processos de metassomatismo em ambiente oceânico. A lacuna composicional entre elementos incompatíveis dos dois grupos (e.g. P, Ti, Zr, Th, Nb) indica que a petrogênese não pode ser explicada por cristalização fracionada isoladamente. Provavelmente, diferentes estágios de fusão parcial seguido de cristalização fracionada foram suficientes para gerar líquidos basálticos distintos. A modelagem geoquímica sugere taxas de fusão variando entre 10-25% de uma mesma fonte sublitosférica (LaN/NbN =1) sem a presença de granada (LaN/LuN ~1). A composição sugerida da fonte mantélica dos basaltos foi um lherzolito ou plagioclásio lherzolito, que passou por um primeiro estágio de fusão (10-15%) dando origem aos ThI, e sucessivamente um segundo estágio de fusão (15-25%) que gerou os ThII. A presença de uma nítida anomalia negativa de Nb e a semelhança geoquímica com basaltos continentais (e.g. Paraná e Deccan), indicam uma significante assinatura crustal. Os resultados geoquímicos de elementos-traço sugerem para os basaltos do Greenstone Belt do Rio Itapicuru uma semelhança petrotectônica com basaltos transicionais (T-MORB) de ambiente continental a oceânico, similar nos dias de hoje com a margem continental Atlântica
Abstract: The Paleoproterozoic Rio Itapicuru Greenstone Belt, situated in the Serrinha Block - northeast São Francisco Craton, has a sequence of basaltic rocks whose tectonic setting is under discussion, i.e whether a back arc setting or intracontinental rift. The basalt geochemistry was revisited on the basis of incompatible trace elements data, such as high field strength elements (HFSE), low field strength element (LFSE) and the rare earth elements (REE). The basalts are well exposed along the Itapicuru River where the study is concentrated. They are composed of massive and pillowed flows with occasional variolitic to porphyritic structures; they show metamorphic paragenesis indicative of greenschist to amphibolite facies. The basalts are essentially Fe-rich tholeiites that can be separated into two groups: ThI ¿ with high abundances of Ti-P and other trace elements, and ThII ¿ with low abundances of Ti-P and other trace elements. The ThII group is geochemically more primitive than ThI and is relatively enriched in compatible elements (e.g. Mg, Ni e Cr) and show higher mg-number. The two basalt groups crop out in geographically distinct areas: ThI dominates in the eastern part of the basalts exposure area, whereas ThII is restricted to the western part of it. Selective enrichment in some large ion lithophile elements (LILE), such as Rb, Ba, Na and Cs indicates that the basalts were affected significantly by postmagmatic processes (low-grade metamorphism and ocean water interaction). The large variation of some trace element ratios (e.g. Ti, P, Zr, Nb, Th), indicate that the two basalt groups cannot be linked by fractional crystallization of a single parental magma. Instead, the two groups are likely to have derived from liquids resulting from different degrees of partial melting from a similar mantle source, followed by shallow level fractional crystallization. Geochemical modelling suggests melt rates around 10-25% of the same lithospheric mantle source (LaN/NbN = 1), with no garnet in the residue (LaN/LuN ~ 1). The suggested source is a lherzolite or plagioclase lherzolite that experienced a first stage of partial melting (10-15%) to give the ThI, and later the ThII group by higher partial melting rates (15-25%). The negative Nb anomaly on mantle-normalised multi-element diagrams and the geochemical similarities with continental flood basalts (e.g. Paraná and Deccan) indicate a significant crustal signature. The combined mode of field occurrence and the trace-element data indicate petrotectonic similarities with transitional-type basalts, thus rendering support to a tectonic setting transitional between continent and ocean, probably similar to the present-day Atlantic continental margin
Mestrado
Geologia e Recursos Naturais
Mestre em Geociências
Silva, Alex Joaquim Choupina Andrade [UNESP]. "Caracterização estrutural da porção sul do greenstone belt de Guarinos, GO." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/92877.
Full textConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Na porção norte do Maciço de Goiás são reconhecidas três faixas greenstone belt de idades arqueano/paleoproterozóicas denominadas de Crixás, Guarinos e Pilar de Goiás. A área em estudo está inserida na porção sul do Greenstone belt de Guarinos, sendo limitada a oeste e leste, através de contatos tectônicos, pelos gnaisses dos Complexos Caiamar e Moquém, respectivamente. O mapeamento geológico possibilitou uma individualização das unidades litológicas com nova interpretação do empilhamento estratigráfico bem como a caracterização de feições estruturais da área. O empilhamento das unidades foi dividido da base para topo nas formações Serra do Cotovelo (metaultramáfica); Serra Azul (metamáfica); Unidade A (associação de rochas metaultramáficas, metamáficas e psamo-pelíticas); Cabaçal (xistos carbonosos com formações ferríferas e gonditos) subdividida em Ca-1, Ca-2, Ca-3 e Ca-4; Aimbé, com uma subunidade inferior (formações ferríferas bandadas ricas em muscovita) e outra superior (metapelitos associados esporadicamente a formações ferríferas fácies óxidos); e São Patricinho (metapelitos, subordinadamente gonditos). Embora diversos trabalhos da literatura descrevam este empilhamento do greenstone de Guarinos como invertido, neste trabalho considera-se a sequência apresentada como normal devido, à ausência de estruturas geopetálicas, que pudessem mostrar a polaridade estratigráfica do pacote, e de estruturas tectônicas que indicassem situação de flanco invertido. Um pacote de metassedimentos psamopelíticos atribuídos na literatura ao “Grupo Araxá” está sobreposto à sequência vulcanossedimentar através de uma descontinuidade, interpretada neste trabalho como uma discordância estratigráfica e não como falha de empurrão de baixo ângulo, como descrito na literatura...
In the North portion of the Maciço de Goiás three greenstone belt of Archaean/Paleoproterozoic age are recognized, namely: Crixás, Guarinos and Pilar de Goiás. The study area is located on the southern portion of the Guarinos Greenstone Belt, and is delimited by faults to the west an east with the gneiss of the Caiamar Complex and Moquém Complex, respectively. The geological mapping allowed the individualization of lithological units, new interpretation of the stratigraphic stacking and the description of structural features found in the area. Previous studies describe the stratigraphic stacking of the Guarinos Greenstone Belt as inverteded. However, in this work, the stacking is interpreted as normal, due to the lacking of geopetalic and tectonic structures that could indicate top and basis of the sequence. The stratigraphic stacking was divided, from basis to top in Serra do Cotovelo Formation (metaultramafic); Serra Azul Formation (metamafic); Unit A (metaultramafic, metamafic and psammo pelitic association); Cabaçal Formation (carbonous schists with iron formations and gondites), which was subdivided in Ca-1, Ca-2, Ca-3 and Ca-4; Aimbé Formations, which contains a basal (banded iron formations, rich in muscovite) and a top subunit (metapelites, associated with rare iron formations, oxide facies); and São Patricinho Formation (metapelites, with subordinated gondites). Although several studies in the literature describe this stacking of the greenstone Guarinos as inverted, this paper considers the sequence presented as normal due to the lack of geopetálicas, which could show the polarity of the stratigraphic package, and tectonic structures to indicate status limb inverted. A package of metasediments in the literature psammo pelitic assigned to the Group Araxá volcanic sedimentary is superimposed on the sequence... (Complete abstract click electronic access below)
Cessford, Gordon R. "Recreation in the Greenstone and Caples Valleys: for whom and how?" Lincoln College, University of Canterbury, 1987. http://hdl.handle.net/10182/1365.
Full textLiu, Mian. "Migmatization and volcanic petrogenesis in the La Grande greenstone belt, Quebec." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63353.
Full textHorstwood, Matthew Simon Anthony. "Stratigraphy, geochemistry and zircon geochronology of the Midlands Greenstone Belt, Zimbabwe." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246222.
Full textGrisolia, Maria Fernanda Pereira. "Proveniência de rochas metassedimentares do Greenstone Belt do Rio Itapicuru, Bahia." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/287262.
Full textDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências
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Resumo: A área em estudo localiza-se entre o embasamento mesoarqueano do Núcleo Serrinha e o Greenstone Belt do Rio Itapicuru (BA). O Núcleo Serrinha é constituído pelo Complexo Santa Luz, caracterizado por rochas metamórficas gnáissico-migmatíticas (Mascarenhas 1979), cobertas pelas vulcânicas do Grupo Capim (Winge 1984, apud. Cruz Filho et al. 2003) e pelas seqüências vulcano-sedimentares do Greenstone Belt do Rio Itapicuru (Brito Neves et al. 1980), intrudidas por granitóides diversos e recobertas por unidades fanerozóicas. Embora vários estudos tenham sido feitos, ou estão em desenvolvimento no GBRI, pouco se conhece sobre as rochas sedimentares do mesmo e quase nada sobre as relações de contato do GBRI e o embasamento. Por este motivo, foi planejado um projeto de cartografia geológica da transição embasamento-greenstone que resultou em um mapa geológico de uma área com cerca de 700 km2 entre as cidades de Nordestina, Queimadas e Santa Luz, a oeste da exposição principal do greenstone belt do Rio Itapicuru. Nesta região foi mapeada uma sequência de rochas sedimentares clásticas metamorfisadas denominada Sequência Metassedimentar Monteiro por Grisolia (2007) e Moreto (2007) em seus trabalhos de conclusão de curso de Geologia. Estudos de proveniência de sedimentos, erosão e possíveis ambientes tectônicos foram feitas pela primeira vez em metassedimentos do greenstone belt Rio Itapicuru, Bloco Serrinha, Bahia, utilizando geocronologia U-Pb, LA-ICP-MS em zircões detríticos, geoquímica e isótopos Sm- Nd. O protólito das rochas metassedimentares foram classificados como arcósia, xistos, grauvacas e arenitos. O índice químico de alteração (CIA) varia 39-70 indicando intemperismo químico moderado nas áreas fonte. Rochas félsicas a intermediárias (granito, granodiorito, andesito e riolito) são as principais rochas fonte, e, secundariamente, rochas máficas (basalto e gabro). A maioria das amostras mostram ?Nd negativo (0) valores variando de -6,83 a -34,29 e apenas uma amostra resultou ?Nd (0) = +2,38. Idades modelo de Nd (TDM) apresentam idades entre 2,0-2,2 Ga, com alguns outliers em 2,67 Ga. Os dados U-Pb em zircões detríticos de quatro amostras resultaram em populações com idades 207Pb/206Pb de 2,16, 2,14, 2,15, 2,17, 2,18, 2,20, 2,21 e 2,23 Ga, com alguns grãos mais velhos sendo alguns arqueanos. Os resultados isotópicos indicam que o metassedimentos do greenstone belt Rio Itapicuru possuem áreas fonte principalmente em terrenos Palaeoproterozoicos como os Greenstone Belts Rio Itapicuru e Rio Capim, e muito raramente rochas arqueanas. No entanto, as populações de zircão entre 2,17 Ga e 2,24 Ga não são encontradas no bloco Serrinha, exigindo, portanto, fontes ainda não encontradas. Diagramas de configuração tectônica sugerem que os sedimentos podem ter sido depositados principalmente em margens continentais ativas. Nossos dados confirmam um modelo em que os basaltos e granitos de arco do greenstone belt Rio Itapicuru acrescionaram para uma margem continental ativa desconhecida que colodidiu com outras estruturas pré-existentes, sendo posteriormente empurradas contra um microcontinente Arqueano.
Abstract: The area is located between the basement of the mesoarchean Serrinha Block and the Rio Itapicuru Greenstone Belt (BA). The Serrinha Block consists in the SantaLuz Complex, characterized by gneissic-migmatitic rocks (Mascarenhas 1979), covered by (Winge 1984, apud. Cruz Filho et al. 2003) volcano-sedimentary sequences of the Rio Itapicuru and Rio Capim greenstone belts (Brito Neves et al. 1980), intruded by granitoids and covered by several Phanerozoic units. Although several studies have been conducted or are under development in RIGB, little is known about the sedimentary rocks and almost nothing about the geological relations between RIGB and basement. For this reason, a project was planned with geological mapping of the transition-greenstone basement, which resulted in a geological map of an area of approximately 700 km2 between the towns of Nordestina, Queimadas and Sant Luz, west of the main display of the RIGB. A sequence of metamorphosed clastic sedimentary rocks was mapped known as Monteiro metamorphic sequence by Grisolia (2007) and Moreto (2007) in their final graduation work of Geology. Studies of sediment provenance, weathering and possible tectonic environments have been made for the first time in metasedimentary rocks of the Rio Itapicuru greenstone belt, Serrinha Block, Bahia, using LA-ICP-MS U-Pb geochronology in detrital zircons and whole-rock geochemistry and Sm-Nd isotope data. The protolith of the metasedimentary rocks were classified as arkose, shale, greywacke and sandstone. The chemical index of alteration (CIA) ranges from 39-70 indicating moderate chemical weathering in source areas. Intermediate and felsic rocks (granite, granodiorite, rhyolite and andesite) are the likely main source rocks, and secondarily mafic rocks (basalt and gabbro). Most samples show negative ?Nd(0) values ranging from -6.83 to -34.29 and only one sample yielded ?Nd(0) = +2.38. Depleted mantle Nd model ages (TDM) fall most in the range 2.0 to 2.2 Ga, with a few outliers at 2.67 Ga. The U-Pb data on detrital zircons of four samples yielded 207Pb/206Pb age populations of 2.16 to 2.23 Ga, with a few grains older and only on Archaean grain. The isotope results indicate that the metasedimentary rocks the Rio Itapicuru greenstone belt have source areas mostly in Palaeoproteroic terranes such as the Rio Itapicuru and Rio Capim greenstone belts, and very much rarely in Archaean rocks. However, zircon populations between 2.17 Ga and 2.24 Ga are not found in the Serrinha block, thus requiring sources not yet found. Diagrams of tectonic setting suggest that the sediments may have been deposited mostly on active continental margins. Our data support a model in which basalts and arc granites of Rio Itapicuru greenstone belt accretted onto an unknown active continental margin and the entire pile collided with, and was thrusted onto Archaean microcontinents.
Mestrado
Geologia e Recursos Naturais
Mestre em Geociências
Silva, Alex Joaquim Choupina Andrade. "Caracterização estrutural da porção sul do greenstone belt de Guarinos, GO /." Rio Claro, 2011. http://hdl.handle.net/11449/92877.
Full textBanca: Hardy Jost
Banca: Marcelo Juliano de Carvalho
Resumo: Na porção norte do Maciço de Goiás são reconhecidas três faixas greenstone belt de idades arqueano/paleoproterozóicas denominadas de Crixás, Guarinos e Pilar de Goiás. A área em estudo está inserida na porção sul do Greenstone belt de Guarinos, sendo limitada a oeste e leste, através de contatos tectônicos, pelos gnaisses dos Complexos Caiamar e Moquém, respectivamente. O mapeamento geológico possibilitou uma individualização das unidades litológicas com nova interpretação do empilhamento estratigráfico bem como a caracterização de feições estruturais da área. O empilhamento das unidades foi dividido da base para topo nas formações Serra do Cotovelo (metaultramáfica); Serra Azul (metamáfica); Unidade A (associação de rochas metaultramáficas, metamáficas e psamo-pelíticas); Cabaçal (xistos carbonosos com formações ferríferas e gonditos) subdividida em Ca-1, Ca-2, Ca-3 e Ca-4; Aimbé, com uma subunidade inferior (formações ferríferas bandadas ricas em muscovita) e outra superior (metapelitos associados esporadicamente a formações ferríferas fácies óxidos); e São Patricinho (metapelitos, subordinadamente gonditos). Embora diversos trabalhos da literatura descrevam este empilhamento do greenstone de Guarinos como invertido, neste trabalho considera-se a sequência apresentada como normal devido, à ausência de estruturas geopetálicas, que pudessem mostrar a polaridade estratigráfica do pacote, e de estruturas tectônicas que indicassem situação de flanco invertido. Um pacote de metassedimentos psamopelíticos atribuídos na literatura ao "Grupo Araxá" está sobreposto à sequência vulcanossedimentar através de uma descontinuidade, interpretada neste trabalho como uma discordância estratigráfica e não como falha de empurrão de baixo ângulo, como descrito na literatura... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In the North portion of the Maciço de Goiás three greenstone belt of Archaean/Paleoproterozoic age are recognized, namely: Crixás, Guarinos and Pilar de Goiás. The study area is located on the southern portion of the Guarinos Greenstone Belt, and is delimited by faults to the west an east with the gneiss of the Caiamar Complex and Moquém Complex, respectively. The geological mapping allowed the individualization of lithological units, new interpretation of the stratigraphic stacking and the description of structural features found in the area. Previous studies describe the stratigraphic stacking of the Guarinos Greenstone Belt as inverteded. However, in this work, the stacking is interpreted as normal, due to the lacking of geopetalic and tectonic structures that could indicate top and basis of the sequence. The stratigraphic stacking was divided, from basis to top in Serra do Cotovelo Formation (metaultramafic); Serra Azul Formation (metamafic); Unit A (metaultramafic, metamafic and psammo pelitic association); Cabaçal Formation (carbonous schists with iron formations and gondites), which was subdivided in Ca-1, Ca-2, Ca-3 and Ca-4; Aimbé Formations, which contains a basal (banded iron formations, rich in muscovite) and a top subunit (metapelites, associated with rare iron formations, oxide facies); and São Patricinho Formation (metapelites, with subordinated gondites). Although several studies in the literature describe this stacking of the greenstone Guarinos as inverted, this paper considers the sequence presented as normal due to the lack of geopetálicas, which could show the polarity of the stratigraphic package, and tectonic structures to indicate status limb inverted. A package of metasediments in the literature psammo pelitic assigned to the Group Araxá volcanic sedimentary is superimposed on the sequence... (Complete abstract click electronic access below)
Mestre
Sousa, Victor Hugo Vasco de. "Estratigrafia isotópica do greenstone belt de pilar de goiás e correlações." reponame:Repositório Institucional da UnB, 2011. http://repositorio.unb.br/handle/10482/9653.
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O Maciço de Goiás tem despertado interesse crescente em função da presença de seqüências do tipo greentone belt que alojam importantes ocorrências e depósitos de ouro. Apresentamos neste trabalho dados de geoquímica de Elementos Terras Raras e Isótopos de Carbono, Oxigênio e Enxofre ao longo de cerca de 800 m de sondagem, que recortam as rochas superiores dominantemente metassedimentares pertencentes a Formação Serra do Moinho do Greenstone Belt de Pilar de Goiás. Análises de ETRs em conjunto com petrografia revelaram metassedimentos com assinaturas típicas de sedimentos pós-arqueanos. Carbonatos estão presentes em quase toda a extensão do testemunho, tanto como macroestrutura maciça quanto disseminada. A exceção de carbonatos maciços presentes na porção superior do testemunho, a composição isotópica do carbono dos carbonatos varia de - 14 a -2 por mil, sendo que os valores mais negativos podem estar associados a trocas isotópicas com xistos carbonosos também presentes na sessão. Os carbonatos maciços da porção superior possuem δ13C variando entre +6 e +9 por mil, o que representa importante anomalia isotópica positiva coeva ao Grande Evento Oxidante (GOE) de 2.1 Ga. Consideramos que os carbonatos com alto δ13C encontrados em Pilar são correlacionáveis a rochas similares encontrados nos Greentone Belts de Crixás, Faina e Serra de Santa Rita, também pertencentes ao Bloco Arqueano Crixás-Goiás. Esta excursão positiva de carbono constitui um importante marco estratigráfico entre as seqüências superiores desses greentones. ______________________________________________________________________________ ABSTRACT
The Goiás Massif has attracted increasing interest due to the presence of greenstone belts´ sequences that host major gold deposits and occurrences. In this study we present Rare Earth Elements geochemistry and Carbon, Oxigen and Sulphur isotope data of an 800m drill core that cuts the upper metasedimentary rocks of the Serra do Moinho Formation of Greenstone Belt of Pilar de Goiás. RRE analyses and with the petrographyc studies revealed metassediments with typical of post arquean sediments signature. Carbonates are present in almost the entire length of the testimony, as a macrostructure that is both disseminated and massive. With the exception of massive carbonates in the testimonies upper portion, the carbonate´s carbon´s isotopic composition varies from -14.2 to -2.7 per mil. The most negative values are associated with isotope exchange with carbonaceous schist also present in the section. The upper massive carbonate layer show δ13C values between +6 and +9 per mil, that represents an important positive isotopic anomaly that is coeval to the 2.1 Ga Great Oxidant Event (GOE). We believe that the high positive carbonates from Pilar are correlated to similar rocks from the Greentone Belts of Crixás, Faina and Serra de Santa Rita, with also belong to the Goiás-Crixas Arquean Block. This positive carbon excursion constitutes an important stratigraphic mark among the greenstone´s upper sequences.
Müller, M. (Matthias). "The Mustajärvi orogenic gold occurrence, Central Lapland Greenstone Belt, northern Finland." Master's thesis, University of Oulu, 2019. http://jultika.oulu.fi/Record/nbnfioulu-201905141779.
Full textDurkin, Kenneth Michael. "Post-orogenic development of a Cornubian metabasite (tectonic evolution, metasomatic change, and epigenetic mineralisation)." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294240.
Full textMcKeagney, Catherine Judith. "Structural and alteration characteristics of the Indarama lode gold deposit, Zimbabwe : implications for craton-wide tectonism and mineralization." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264744.
Full textGreen, Michael Godfrey. "Early archaean crustal evolution evidence from 3̃.5 billion year old greenstone successions in the Pilgangoora Belt, Pilbara Craton, Australia /." Connect to full text, 2001. http://hdl.handle.net/2123/505.
Full textTitle from title screen (viewed Apr. 23, 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Geosciences, Division of Geology and Geophysics. Degree awarded 2002; thesis submitted 2001. Includes bibliography. Also available in print form.
Xie, Qianli. "Trace element systematics of mafic-ultramafic volcanic rocks from the Archean Abitibi greenstone belt, Canada, implications for chemical evolution of the mantle and archean greenstone belt development." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq24020.pdf.
Full textMedeiros, Isabella Da Gama de. "Caracterização estrutural da região do depósito aurífero Sertão, greenstone belt de Faina - GO /." Rio Claro, 2019. http://hdl.handle.net/11449/182257.
Full textResumo: O Terreno Arqueano Paleoproterozoico de Goiás é um fragmento de crosta que contém complexos TTG arqueanos e sequências greenstone belt. A área de estudo está inserida na região sul desse terreno e abrange a porção sudeste do Greenstone belt de Faina (GBF), onde ocorre o depósito aurífero Sertão, a porção norte do Greenstone belt Serra de Santa Rita (GBSSR), e parte dos complexos TTG Uvá e Caiçara. Esses dois greenstone belts são separados pela Falha direcional de Faina com direção N50E e movimentação destral. No GBF, foram identificadas rochas de duas sequências metassedimentares, uma denominada de Inferior e outra de Superior, que apresentam contato tectônico. A Sequência Inferior é constituída de camadas de quartzito, xisto, formação ferrífera bandada e mármore. A Sequência Superior apresenta espesso pacote de clorita-muscovita-quartzo xisto com algumas intercalações de formação ferrífera e quartzito que para o topo grada para uma sequência química com mármore e mármore impuro sobreposta por quartzito. No GBSSR, identificou-se uma Sequência Metavulcânica Ultramáfica sotoposta a uma Sequência Metassedimentar, esta última constituída por xistos muscovíticos e carbonosos, quartzitos, formação ferrífera e metachert. O mapeamento geológico permitiu avanços na definição da estratigrafia da área, como a identificação de rochas da Sequência Metassedimentar Inferior nas porções sudeste e sudoeste do GBF, caracterizando-se que é esta a unidade que hospeda o depósito aurífero Sertão, ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The Archean-Paleoproterozoic Terrane of Goiás is a crust block consisting of Archean TTG Complexes and greenstone belt sequences. The study area is in the southern region of this terrane comprising the southeastern portion of the Faina Greenstone Belt (FGB), where Sertão gold deposit is located, the northern portion of the Serra de Santa Rita Greenstone Belt (SSRGB), and small portions of Caiçara and Uvá TTG complexes. These two greenstone belts are separated by a strike-slip fault, known as Faina Fault, that strikes N50E showing dextral movement. Rocks of two distinct sedimentary cycles separated by a tectonic contact were identified in the FGB, denominated Lower and Upper Metasedimentary Sequences. The Lower Sequence shows quartzite, schist, banded iron formation and marble. The Upper Sequence shows, at the base, a thick package of chlorite-muscovite-quartz schist, with quartzite and BIF intercalations that grades to a sequence of marble and impure marble overlaid by quartzite. In the SSRGB, a Meta-ultramafic Volcanic sequence and a Metasedimentary Sequence were mapped. The last one comprises muscovitic and carbonaceous schists, quartzite, banded iron formation and metachert. The geological mapping provided advances in the definition of the stratigraphy of the area, such as the identification of rocks belonging to the Lower Metasedimentary Sequence in the southeastern and southwestern portion of the FGB, revealing that the Sertão gold deposit is hosted by this unit, and the... (Complete abstract click electronic access below)
Mestre
Jones, Michael G. "The geology of the Mt. Mare area, Pietersburg Greenstone Belt, South Africa." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/7329.
Full textChamberlain, Claire Mary. "Geology and genesis of the Bulyanhulu gold deposit, Sukumaland Greenstone Belt, Tanzania." Thesis, Imperial College London, 2003. http://hdl.handle.net/10044/1/7162.
Full textOpiyo-Akech, Norbert. "Geology and geochemistry of the late Archaean greenstone associations, Maseno area, Kenya." Thesis, University of Leicester, 1988. http://hdl.handle.net/2381/35080.
Full textPolat, Ali. "Geodynamics of the late Archean Wawa Subprovince Greenstone Belts, Superior Province, Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0014/NQ32797.pdf.
Full textBiandja, Jean. "Approche métallogénique du "Greenstone Belt" de Bogoin (RCA). Sa minéralisation en or." Phd thesis, Université Pierre et Marie Curie - Paris VI, 1988. http://tel.archives-ouvertes.fr/tel-01053229.
Full textHeather, Kevin B. "The geological evolution of the Archean Swayze Greenstone Belt, Superior Province, Canada." Thesis, Keele University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341304.
Full textBiandja, Jean. "Approche métallogénique du "Greenstone Belt" de Bogoin (R.C.A.) sa minéralisation en or /." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376119291.
Full textMarkham, Michael. "Provenance studies of British prehistoric greenstone implements using non-destructive analytical methods." Thesis, n.p, 2000. http://ethos.bl.uk/.
Full textFedo, Christopher M. "Geologic evolution of the Archean Buhwa Greenstone Belt and surrounding granite-gneiss terrane, southcentral Zimbabwe." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-164845/.
Full textMader, Marianne M. "From genesis to juxtaposition : the evolution of the Ivisârtoq greenstone belt, southwest Greenland /." Internet access available to MUN users only, 2005. http://collections.mun.ca/u?/theses,64637.
Full textTarnocai, Charles A. "Gold mineralization at the Campbell Mine, Red Lake greenstone belt, Uchi subprovince, Ontario." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/6216.
Full textJones, Murray Ira. "Variolitic basalts: Relations to Archean epigenetic gold deposits in the Abitibi Greenstone Belt." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/10762.
Full textKitayama, Yumi. "Iron-rich alkaline magmatism in the Archean Schreiber-Hemlo greenstone belt, Ontario, Canada." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110523.
Full textLa découverte de basaltes picritiques riches en fer à la surface de Mars (notamment dans le cratère Gusev) a ravivé l'interêt des chercheurs pour les magmas terrestres de même type, bien plus faciles d'accès. En effet, de nombreuses ferropicrites ont été identifiées dans les terrains Archéens, et une étude détaillée de leur minéralogie et de leur contexte géologique pourrait, par analogie avec la Terre primitive, nous renseigner sur la pétrogenèse des ferropicrites martiennes. L'un des meilleurs affleurements de ferropicrites terrestres se situe dans la séquence volcanique de Pulpwood Harbour à Heron Bay (~2.6-2.7Ga), au sein de la ceinture de roches vertes de Schreiber-Hemlo, dans la Province géologique du Supérieur au Canada. Les affleurements de ferropicrites sont constitués de cumulats à leur base, et d'une partie supérieure de laves riches en fer. L'évolution des compositions de ces ferropicrites peut être expliquée par l'accumulation progressive de cristaux d'olivine (~Fo76), puis de clinopyroxenes et d'oxides de Fe et Ti, dans un système relativement clos, avec de plus en plus de liquide interstitiel contenu dans les cumulats. Les laves riches en fer situées au-dessus des cumulats représentent des liquides très riches en fer, avec jusqu'à 17 pds.% FeO*, et sont co-magmatiques avec les cumulats. Bien que la composition chimique des bordures figées des horizons lithologiques ressemble à celle de laves martiennes provenant du cratère Gusev, les liquides ferropicritiques de Pulpwood Harbour sont légèrement sous-saturées en Silice, contrairement aux compositions fortement normatives en orthopyroxenes des ferropicrites martiennes. Ils sont aussi enrichis en éléments incompatibles à la manière des basaltes alcalins modernes de type îles océaniques. Des incohérences entre nos modélisations des éléments traces et celles des éléments majeurs suggèrent cependant que le magma parent des ferropicrites contenait une quantité importante de carbonates. Ces carbonates se seraient échappés des roches volcaniques lors de leur éruption, mais auraient été partiellement retenus dans les cumulats ferropicritiques de Pulpwood Harbour.
Tomlinson, Kirsty Y. "The geochemistry and tectonic setting of early Precambrian greenstone belts, Northern Ontario, Canada." Thesis, University of Portsmouth, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388557.
Full textScholey, Stephen Philip. "The geology and geochemistry of the Ngezi group volcanics, Belingwe Greenstone Belt, Zimbabwe." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334443.
Full textPires, Paulo Fernando Ravacci. "Caracterização tectono-metamorfica do deposito aurifero Ambrosio, Greenstone Belt do Rio Itapicuru - Bahia." [s.n.], 1996. http://repositorio.unicamp.br/jspui/handle/REPOSIP/286814.
Full textDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociencias
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Resumo: O depósito aurífero Ambrósio situa-se no setor norte do Greenstone Be/t do Rio Itapicuru, de idade Proterozóica inferior (2.200 a 2.000 Ma), associado a uma estreita faixa de rochas supracrustais, intensamente deformada, entre dois domos sin-tectônicos (dom os Ambrósio e Pedra Alta). A mineralização encontra-se no contato entre metassedimentos clásticos e químicos / anfibolitos, que fazem parte do Domínio Vulcânico Máfico, porção basal da seqüência litoestratigráfica deste greenstone. Os metassedimentos e anfibolitos são a lapa e a capa da mineralização, respectivamente, sendo os primeiros representados por andaluzita-granada-biotita xistos e os últimos formados essencialmente por homblenda e plagioclásio. Estes litotipos apresentam aspecto milonitico desenvolvido em fácies anfibolito. O controle estrutural do depósito está intimamente associado a estruturas geradas em função do desenvolvimento de um sistema de dup/exes direcionais dúcteis, na região de recobrimento entre duas zonas de cisalhamento principais, situadas nas bordas dos domos granito-gnáissicos. O ouro é encontrado em veios quartzo-sulfetados (arsenopirita, pirrotita e pirita), com biotita, plagioclásio e muscovita em menor quantidade. Os veios foram submetidos a intenso processo de recristalização, sendo controlados por: I) zona transcorrente (NNE) e 2) dobras de arrasto com eixos subhorizontais na direção NNE. Estas estruturas mineralizadas estão relacionadas aos estágios iniciais da evolução deste sistema de dup/exes, concomitantes ao metamorfismo regional. Estudos de inclusões fluidas, nos veios mineralizados, revelam o predomínio de inclusões monofásicas ricas em CO2 (a temperatura ambiente). Estas inclusões ricas em CO2 aparecem restritas às trilhas intergranulares ou ao longo dos limites dos sub-grãos. Dados de microtennometria e microssonda Raman demonstram que os fluidos carbônicos são compostos por CO2 puro. A caracterização do fluido e a petrografia no veio mineralizado sugerem que o ouro foi transportado por tiocomplexos, em um fluido original aquo-carbônico que, durante a formação do veio e posteriormente com a deformação, foi enriquecido em CO2 pela perda de H20
Abstract: The Ambrósio lode gold deposit, located in the northem sector ofthe lower Proterozoic (2.200 to 2.000 Ma) Rio Itapicuru greenstone belt, northeast Brazil, is enclosed within a narrow belt ofhighly deformed supracrustals, tightly squeezed between two syn-tectonic granitic batholiths (pedra Alta and Ambrósio domes). The deposit is hosted at the contact of amphibolites and clastic-chemical metasediments, which represent part ofthe mafic volcanic domain at the basal portion ofthe greenstone belt sequence. The metasediments and amphibolites comprise the footwall and hangingwall ofmineralization, respectively. The former are represented by andalusite-gamet-biotite schist and the latter consits mainly ofhomblende and plagioclase; these lithotypes show mylonite texture devoloped in amphibolites facies. The deposit is closely associated with structures developed in a ductile strike-slip duplexes system, in the offset region between two main shear zones at the boundary of the granite-gneiss domes. The gold mineralization occurs in centimetre-wide quartz veins containing disseminations of iron sulphides (arsenopyrite, pyrrhotite and pyrite), and subordinate amounts ofbiotite, plagioclase and muscovite. The veins were submitted to intense recrystallization processes and are controUed by: 1) transcurrent shear zone (NNE) and 2) drag folds with subhorizontal axis in the NNE direction. These minera1ized structures are related to early stages of evolution ofthe duplexes system, and are broadly synchronous with regional metamorphism and granite intrusions. CO2 - rich inclusions, mostly monophase at room temperature, are the dominant or virtually the only fluid inclusion type, in the quartz veios of the Ambrósio deposito The CO2 - rich inclusions appear restricted to intergranular trails, or along subgrain boundaries. Microthermometry and laser Raman microphobe data demonstrate that the carbonic fluids are composed of pure CO2. Fluid inclusions and petrographic studies suggest that gold was transported by tiocomplex in an original H20-C02 fluid, which was enriched in C02 by loss ofH20 during the vein formation and later deformation
Mestrado
Metalogenese
Mestre em Geociências
Sumburane, Estevão Inácio. "Evolução crustal dos terrenos granito-greenstone de Manica, região centro-oeste de Moçambique." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-11112015-145408/.
Full textThe main prupose of this work is to identify and to characterize the main geological events related to the Manica granite-greenstone terrains, as well as to define the age and stratigraphy of the rock units of the Manica Greenstone Belt. The Manica district is located at the central-west of Mozambique between the parallels 18°50\'S - 19°00\'S and meridians 32°45\'E-32°55\'E. It is constituted mainly of Achean granite-greenstones and represents the eastern extension of the Zimbabwe craton. This greenstone assemblage is comprised of mafic and ultramafic metavolcanic rocks (the Macequece Formation) in lithological discordance with a succession of clastic metasediments (Vengo Formation). TTG-type granitoids, felsic and mafic/ultramafic volcanic and sedimentary rocks were sampled and analyzed for U-Pb (zircon) by TIMS and LA-HR-ICP-MS, and for Rb-Sr, Sm-Nd, and K-Ar. The Pb isotopic compositions of two mineral deposits (Monarch and Mundonguara) associated to these trerrains were studied. The ages of granitoids from the TTG suites were analyzed by U-Pb zircon method. The ages are as follows: a) an age of 2,9 Ga for the TTG suites at the far south of the belt, b) an age of 2,7 Ga for the internal granitoids, c) an age of 2,8 Ga for the northern granitoid and d) and age of 2,6 Ga for samples of Messica. Ages of 2,7 Ga and 2,8 Ga (Rb-Sr) and \'ANTPOT. 87 Sr\'/\'ANTPOT. 86 Sr\' = 0,7015 and 0,7021 were also obtained for the samples of Mundongura and Vumba. The maximum age for the deposition of the sedimentary rocks of the Vengo Formation is about 2,65 Ga. An age of 2,9 Ga (U-Pb, zircon) was obtained for the felsic volcanic rocks and an Sm-Nd isochron age of ~3,2 Ga for the ultramafic rocks. An isochron age of 2,0 Ga for the metabasalts, 2,0 Ga and 0,8 for the dolerites were also obtained by Sm-Nd. Sm-Nd mantle-depleted model ages range from 3,1 to 2,8 Ga as the most important period for continental crustal accretion in the Manica area. The calculated \'épsilon\' Nd values for 2,9 Ga and 2,7 Ga of -5,15 to 0,79, for the TTG suites, depict and origin by partial melting of crustal rocks with a subordinate involvement of mantle-derived magmas. Some mafic and ultramafic rocks have a positive \'épsilon\' Nd (T), suggesting that their mantle-derived parental magmas did not suffer importante continental crustal contamination. The fractionated rocks might have suffered metasomatism in the upper mantle through the addition of crustal material, which could justify the negative contamination. The \'épsilon\' Nd (T) values. The K-Ar ages (522 - 519 Ma) obtained in biotites indicate an event of Pan-African tectonic reactivation in the Manica area, as a reflex of the Mozambique Belt evolution. The Pb isotopic compositions show that the two main deposits of the Manica district have distinct isotopic compositions, the Mundonguara deposit being more radiogenic than that of Monarch. Both have significant Pb derived from the upper continental crust, indicating that the present mineralizations are epigenetic. The Cu and Au were incorporated in the crust at 3,0 Ga were remobilized later by events of magmatic intrusions and reactivation of shear zones around 2,6 Ga. Based on the data obtained in this work, the Archean terrains of Manica evolved from a continental crust at 3,2 Ga that suffered rifting and hence, crustal thinning, asthenospheric upwelling and bimodal volcanism of acid, mafic/ ultramafic rocks between 2,9 Ga and 3,1 Ga. These rocks with the associated sediments were metamorphosed during the closing of the basin to produce the greenstone belt. Later on, there were granitic intrusions, with the last event ~2,6 Ga. The intracontinental rifting model is that which best fits with the evolution of the Manica terrains.
Lodge, Robert Wilfred David. "REGIONAL VOLCANOGENIC MASSIVE SULPHIDE METALLOGENY OF THE NEOARCHEAN GREENSTONE BELT ASSEMBLAGES ON THE NORTHWEST MARGIN OF THE WAWA SUBPROVINCE, SUPERIOR PROVINCE." Thesis, Laurentian University of Sudbury, 2013. https://zone.biblio.laurentian.ca/dspace/handle/10219/2081.
Full textLegault, Marc Ian. "Petrology and geochemistry of Timiskaming Group sedimentary rocks, Kirkland Lake area, Abitibi greenstone belt." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6510.
Full textMiles, Warner Frederick. "An interpretation of high resolution aeromagnetic data over the Manitouwadge greenstone belt, Ontario, Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0005/MQ36726.pdf.
Full textShannon, Andrew J. "Volcanic framework and geochemical evolution of the Archean Hope Bay Greenstone Belt, Nunavut, Canada." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/741.
Full textO'Neil, Jonathan. "The geology of Nuvvuagittuq greenstone belt and its implications for the early earth's evolution." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66884.
Full textLa ceinture de roches vertes de Nuvvuagittuq est une succession Éoarchéenne/Hadéenne préservée le long the la côte Est de la Baie d'Hudson dans la Province du Supérieur, Québec, Canada. Elle est essentiellement composée de trois unités lithologique majeures : 1) une amphibolite à cummingtonite appelée « faux-amphibolite » étant la lithologie dominante de la ceinture, 2) des filons-couches mafiques et ultramafiques en intrusion dans la faux-amphibolite, et 3) des roches sédimentaires chimiques comprenant une formation de fer rubanée (BIF) and une formation de silice. La faux-amphibolite est basaltique à andésitique en composition. Elle est constituée de différentes proportions de cummingtonite + biotite + quartz, ± plagioclase ± grenat ± anthophyllite ± cordiérite variant d'amphibolite à cummingtonite à schiste à biotite-grenat. Certaines roches de la ceinture de roches vertes de Nuvvuagittuq présentes des rapports 142Nd/144Nd inférieurs aux standards terrestres (epsilon142Nd = -0.07 to -0.15). Les rapports 142Nd/144Nd de la faux-amphibolite corrèle positivement avec leurs rapports Sm/Nd produisant une isochrone 146Sm-142Nd avec un âge de 4280 +53 –81 millions d'années. Des filons-couches de gabbro hautement déformés en intrusion dans la faux-amphibolite âgée de 4.28 Ga, produisent une isochrone 147Sm-143Nd avec une pente correspondant à un âge de 4023 ± 110 Ma. La ceinture de roches vertes de Nuvvuagittuq compte également des bandes felsiques de 3.8 Ga et est entourée par une tonalite datée à 3.66 Ga interprétée comme étant produite par la fusion des amphibolites mafiques plus âgées. La ceinture de roches vertes de Nuvvuagittuq représente donc une section crustal Éoarchéenne/Hadéenne comprenant les roches les plus vieilles préservées sur la Terre. La faux-amphibolite est divisée en un groupe riche en Ti et un groupe pauvre en Ti avec des filons-c
Kerr, Charles Henry. "An integrated remote sensing and geophysical investigation of the Gwanda greenstone belt, southern Zimbabwe." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243191.
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