Orientador: Hans Dirk Ebert / Banca: Sebastião Gomes de Carvalho / Banca: Fábio Soares Magalhães / Possui 22 gráficos anexos - MSF seção vertical / Resumo: A Jazida Fortaleza de Minas de níquel, cobre e cobalto localiza-se cerca de 6 km a sudoeste da cidade de Fortaleza de Minas (MG). Ela está inserida na Seqüência Morro do Niquel, do Greenstone Belt Morro do Ferro, na Faixa Fortaleza de Minas, ocorrendo no Cinturão de Cisalhamento Campo do Meio e apresentando os seguintes litotipos: Anfibólio Xistos, Serpentinitos, Formação Ferrífera Bandada e Talco Xistos. A mina é constituída por um corpo de sulfeto maciço explorado em uma cava de 1600 m de comprimento e 300 m de largura, atingindo a cota 940 no fundo do open pit e possuindo galerias nos subníveis 920, 919, 900, 870, 851, 833, 817, 801, 781 e 761. O corpo do minério ocorre em uma zona de cisalhamento transtensiva, sinistral (Santos 1996), onde o amendoamento dos corpos provoca uma variação na direção e no mergulho da foliação. Realizou-se uma análise dos elementos estruturais observados em superfície e subsuperfície, uma análise de strain e produziu-se um modelo tridimensional do corpo do minério. Os dados estruturais levantados em todos os subníveis, divididos em norte e sul, e excluindo-se os subníveis 900 e 761., mostraram que a foliação mantém o mesmo padrão em profundidade, isto é, elevado mergulho para SW com máximos em torno de 221/78 e padrão amendoado. Os dados de lineação mineral e de estiramento obtidos mostram que a lineação não é direcional, mas concentrada nos máximos de 137/54 e subordinadamente 326/49, isto é, com plunge respectivamente para SE e NW. A direção principal corresponde ao eixo X do elipsóide de deformação, e a segundária ao eixo Y, que também é de estiramento (Y>1), como revelado pela análise da deformação em quatro amostras de minério, que mostrou elipsóides de deformação finita oblatos, isto é, no campo do achatamento geral. Estes dados indicam uma movimentação oblíqua, sinistral, normal para a zona de cisalhamento na qual insere-se a jazida. / Abstract: The nickel, copper and cobalt Fortaleza of Mines ore deposit is located about six km southwest of Fortaleza of Mines town, Minas Gerais. The mine is constituted of a body of solid sulfites which is explored in a digging of 1600 m of length and 300 m of width along the galleries of level 920, 919, 900, 870, 851, 833, 817, 801, 781 and 761. The mine levels are physically divided in northem and the southern sector by a small gallery, which is originated in the access ramp to the underground. The structural analysis of surface and underground data, strain analysis and a three-dimensional geometric model of the ore deposit confirmed its setting along a ductile sinistral transtensive shear zone, as previously mentioned in Santos (1996). Lenticular ore bodies and anastoming pattern provokes variation in the strike and dip of the foliation around a maximum of 221/78. Stretching and mineral lineations plunge preferentially to SW (maximum around 137/54) and secondarily to NW (326/49), which indicates the strong oblique character of the sinistral shear zone. The strain analysius of four deformed ore samples revealed finite strain ellipsoids of strong oblate shape and deformation in the flattening field, where the X axes is parallel to the main direction of the stretching lineations and Y, also of stretching (Y>1), is parallel to the secondary direction of the lineations. / Mestre

Orientador: Alfonso Schrank / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociencias / Made available in DSpace on 2018-08-06T16:33:27Z (GMT). No. of bitstreams: 1 Spreafico_RicardoRamos_M.pdf: 74748494 bytes, checksum: 5ea89bb7faa599f44ce1b9c5c4dc8024 (MD5) Previous issue date: 2006 / Resumo: A área mineralizada a ouro de Morro da Glória, centro-norte do Quadrilátero Ferrífero, Minas Gerais, contém depósitos hospedados na sequência vulcano-sedimentar do Greenstone Belt Rio das Velhas. Estes depósitos são controlados por estruturas e condições químicas influenciadas pela formação ferrífera bandada (FFB), identificadas em mapeamento geológico de superficie na escala 1: 4000 e em análises petrográficas e de petrotexturas. A FFB está intercalada em meta-basaltos do Grupo Nova Lima, e ambos estão alterados hidrotermalmente. A sericitização é o mais importante processo de alteração e foi principalmente desenvolvido no contato de quartzo-sericita xisto com FFB da Serra do Vum Vum. Nas outras ocorrências de FFB no centro e sul da área, entretanto, a c1oritização é dominante. A carbonatação é sempre subordinada, como um estágio intermediário entre as porções c1oritizada e sericitizada. Estas transformações estão associadas à sulfetação e à mineralização aurífera, assim como ao comportamento estrutural dos litotipos durante os principais eventos deformacionais. Três fases deformacionais são propostas para explicar a evolução estrutural. Uma fase D1, caracterizada por dobras isoc1inais de flanco invertido, com eixos de atitude média 90/37, como parte de zona de cisalhamento dúctil vergente para NNW, no contexto geológico regional. Uma fase O2, caracterizada por dobras desarmônicas, parasíticas, cilíndricas ou suaves, que evidenciam cisalhamento puro confirmado pela orientação de eixo-c de grãos de quartzo de veios recristalizados em O2. A c1ivagem de fratura plano-axial S2 indica deformação sob regime dúctil-rúptil. A fase D3 é evidenciada por falhas inversas com vergência para NW. A entrada de fluidos mineralizantes teria ocorrido durante a fase DI, quando os condutos foram criados como estruturas geradas durante o cisalhamento, na forma de aberturas tensionais, que permitem a passagem de fluidos, os quais reagem com as rochas hospedeiras. Na paragênese do minério predomina a pirita. À medida que a deformação progrediu, os veios e os próprios corpos mineralizados foram paralelizados, estirados e acomodaram a foliação SI. A rotação do pacote de FFB, como um corpo mais rígido, envolvido por basaltos hidrotermalizados, agora transformados em assembléias de xistos, formou a dobra principal que forma a Serra do Vum Vum. Essa rotação leva ao aparecimento de nova estrutura planar, representada pela clivagem de fratura S2 e novas aberturas tensionais. Estas são ocupadas por fluidos, que ainda não deixaram de circular, mas que podem ter natureza um pouco distinta, mais ricos em Cu e Au. O minério é agora formado por abertura na pirita preenchida por calcopirita e ouro (minério de pirita-calcopirita-ouro). No final dos eventos de deformação as estruturas S3 foram formadas, em nível crustal mais superficial e seccionaram os corpos mineralizados. análise das estruturas geológicas feita na área mineralizada do Morro da Glória, em particular, de controles estrutural e químico, ou metalotectos, mostrou o quanto essencial é a FFB para a criação de permeabilidade estrutural, para reações de sulfetação e, juntamente, para precipitação de ouro. Este modelo de redobramento da FFB é muito importante para delinear, em superficie e sub-superfície, a geometria da FFB, hospedeira da mineralização, que é aplicável em prospecção aurífera nessa área e também na exploração regional. O mapeamento de corredores com foliação S: predominante pode direcionar descoberta de zonas de concentração preferencial de ouro durante a fase deformacional D2 / Abstract: The gold mineralized area of Morro da Glória, center-north of Quadrilátero Ferrífero, Minas Gerais, Brasil, contain deposits hosted by the volcano-sedimentary pile of the Rio das Velhas Greenstone BeIt. This deposits are controlled by structures and chemical conditions influenced by banded iron fonnation (FFB), identified in surface geological mapping in scale 1:4000 and studied by petrographic and petrofabric approaches. The FFB is interbeded in metabasalts from Nova Lima Group, and bOth are hydrothennal altered. A sericitization is the main alteration process and was mainly developed on the outer contact of FFB at the Serra do Vum Vum. On others FBB occurrences in central e south of the area, however, the chloritization is dominant. The carbonatization is ever subordinated, as an intermediary stage between the chloritized and the sericitized portions. Those transformations as played major rules even on sulphides and gold mineralization as on the structural behavior during the main deformational events. Three deformational phases are proposed to explain the structural evolution history. A DI phase, characterized by isoclinal folds of inverted limb, with averaged axis climbing of 90/37, as a part of an ductile shear zone verging to NNW, in the broad geological context. A D2 phase, characterized by tuneless, drag, cylindrical or gentle folds, which evidences pure shear confinned by the orientation of c-axis of quartz grains from recristalized veins in D2. The cleavage fracture axial planes S2 indicate deformation under a ductile-ruptile regime. The D3 phase is evidenced by inverse faults verging to NW. The onset of mineralized fluids would be occurred during the DI phase, when the conduits were formed as structures generated during shear, in form of tension gashes, allows the fluids to pass trough and react with host rocks. The ore paragenesys was pyrite droved. As the deformation as increased, the veins and the mineralized bodies stretched, becomes parallel, and accommodates the SI foliation.The rotation of the FF B package, as rigid bodies, enveloped by the hydrothermalized basalts, then transformed in ductile schist assemblages, developed the main fold that fonns the Serra do Vum Vum. This rotation leads to the development of new planar structures, represented by cleavage fractures 82 and new tension gashes. These are drained by fluids, that yet don't stopped to circulate, but can have a little distinct provenance, as it is richer in Cu e Au. Ore is now formed by broken pyrite filled by chalcopyrite and gold drops (pyrite-chalcopyrite-gold ore). Previous pyrite ore was rigid during the D2 ductile event. At the end of deformational events the S3 structures as formed, at most superficial crustallevels and has sectioned the mineralized bodies. The geological structures analysis done at Morro da Glória mineralized area, in particular, from structural and chemical controls, or metalotects, showed as essential is the FFB to allow the creation of structural permeability, the reactions of sulphidation and, besides, the gold precipitation. Also, this standard of refolded FBB is very important to delineate, in surface and underground, the geometry of FFB hosting gold mineralization, which is applicable to gold prospecting on this area but also on regional exploration. Mapping of corridors with dominant S2 foliation can drive to discover zones of preferential gold concentration during the D2 deformational phase / Mestrado / Metalogenese / Mestre em Geociências

The potentially hazardous nature of open pit mining requires the application of sound geotechnical engineering practice to mine design, for the purpose of permitting safe and economic mining of any commodity within any rock mass. The Lerala Diamond Project is situated in the south west of Botswana near the Martin’s Drift Border Post. A 2m-soil cover made surface mapping of geological features impossible, so a number of geotechnical holes were drilled to evaluate the characteristics of the kimberlite pipes and the Granite/gneiss host rock. The Lerala Diamond Project is a typical example of the geotechnical assessment of a kimberlite pipe in Greenstone belt granites. The explosive nature of the formation of these pipes was seen in the various types of joint and fracture pattern identified during this study that could have an influence on the stability of the open pit. Estimating the stability of rock slopes is required by the mining engineering industry for a wide variety of projects. Of importance in this regard is the preliminary evaluation of slope stability at the feasibility stage, excavation stage, and operating stage. The Lerala Diamond Project is currently undertaking a preliminary evaluation as part of a feasibility study. The aim of the geotechnical assessment was to divide the local rock into easily identifiable types that could be geotechnically evaluated. Two classification systems were used during the quantification of the rock mass types. These are the Rock Mass Rating (RMR) system of Bieniawski (1976) and the Mining Rock Mass Rating (MRMR) system of Laubscher (1990). Observations and recordings of the drill core were carried out and these, in conjunction with laboratory results, enabled the determining of the characteristics of the rock mass that will be exposed in the slopes. Computer modelling programmes such as ROCKPAK III were used to test the designs against potential failures. The various potential failures were identified for the different highwalls. Recommendations including the continuous logging of geotechnical features were proposed for the purpose of developing a sound geotechnical model for identifying potential unstable areas within the pit. / Dissertation (MSc)--University of Pretoria, 2008. / Mining Engineering / unrestricted

<p> A rapid and simple radiochemical neutron activation technique involving tellurium coprecipitation of Au, lr, Pd and Pt was evaluated using the U.S.G.S. standards PCC-1 (peridotite) and DTS-1 (dunite) as well as a house standard, JHC-6 (spinifex zone of a komati itic peridotite). It was then applied to the analysis of samples of Archean greenstone from the Red Lake area.</p> <p> The technique gives detection limits of 0.01-0.02, 0.02, 0.1-0.4 and 1-2 ppb for Au, Ir, Pd and Pt respectively and precisions of <25-35%. The method can be successfully applied to the analysis of PGE levels in sulphur-poor rocks, and large numbers of samples can be processed in a short period of time.</p> <p> A comparison of PGE content between several types of mafic rocks was made as well as an investigation of possible secular trends (Archean vs. Phanerozoic) in PGE concentration.</p> / Thesis / Master of Science (MSc)

Orientador: Luiz Sérgio Amarante Simões / Resumo: 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

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH 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.

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Agradecemos a compreensão. on 2016-05-09T14:15:22Z (GMT) / Submitted by José Antonio Cirillo de Assis null (jcirillo.assis@gmail.com) on 2016-05-10T11:56:37Z No. of bitstreams: 1 DissertaçãodeMestrado_JoséAntonioCirilloAssis.pdf: 5492695 bytes, checksum: 098f2796a7e2e2a2b876f0e44a85c57b (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-05-13T11:44:14Z (GMT) No. of bitstreams: 1 assis_jac_me_rcla.pdf: 5492695 bytes, checksum: 098f2796a7e2e2a2b876f0e44a85c57b (MD5) / Made available in DSpace on 2016-05-13T11:44:14Z (GMT). No. of bitstreams: 1 assis_jac_me_rcla.pdf: 5492695 bytes, checksum: 098f2796a7e2e2a2b876f0e44a85c57b (MD5) Previous issue date: 2016-03-28 / A análise e identificação do controle estrutural de um depósito de ouro é de grande importância para o estudo e pesquisa da mineralização aurífera, permitindo guiar e otimizar a prospecção e exploração de determinada ocorrência. O objetivo do presente trabalho é definir o empilhamento tectonoestratigráfico e a estruturação do depósito de ouro de C1-Santaluz, bem como seu controle estrutural. Como faz parte de um Greenstone Belt, em uma área de significativa atividade tectônica, esta ocorrência apresenta complexo arcabouço estrutural, havendo a necessidade de compreender melhor as estruturas que influenciam na geometria dos corpos mineralizados. As rochas da área de estudo foram mapeadas na escala 1:750 e foram estudadas através de descrições macroscópicas, microscópicas além de análises em microscópio eletrônico de varredura e análises de difração de raios-x. As unidades encontradas foram subdivididas em dois grandes domínios, sendo da base ao topo, Sequência Vulcânica e Sequência Metassedimentar, compostas por metadacitos e metadacitos brechados, e clorita sericita quartzo xisto, metassedimento carbonoso, brecha carbonosa, respectivamente. Também foi mapeado um corpo de metadiorito que corresponde à unidade Rochas Intrusivas Subvulcânicas Intermediárias. As fases minerais relacionadas com a mineralização aurífera são representadas por sulfetos, tais como, pirita, arsenopirita, esfalerita, calcopirita e stibinita, sendo que a arsenopirita mostrou relação direta com a presença de ouro, este ocorrendo associado ao sulfeto. Ao todo foram identificadas 3 fases deformacionais: Dn-1, Dn, Dn+1. Dentre essas fases, observa-se que a presença da mineralização na área de estudo possui direta relação com as fases Dn-1 ou Dn, visto que os veios de quartzo mineralizados se encontram encaixados na foliação Sn. A interação entre o bandamento composicional S0//Sn-1 e a foliação Sn gera lineação de intersecção paralela aos eixos de dobra Dn, com caimento para NW. A orientação dessa lineação é favorável para o posicionamento do corpo de minério, podendo apresentar inclusive espessuras maiores nessa orientação. As rochas que compõem as unidades mapeadas apresentaram metamorfismo regional progressivo na fácies xisto verde baixo, zona da biotita. / Structural control plays a major role in gold deposits. Thus, understanding the different structures present in the area, as well as the relationship between these structures, is a key issue. This work aims to identify the structural control of the gold deposit of C1-Santaluz. It also presents the tectono-stratigraphic stacking of the rocks and the main deformation phases that occur in the area. The C1-Santaluz deposit is located in a Greenstone Belt and has a complex structural setting. Therefore, there is a need to better understand the structures that can influence the geometry of the mineralized bodies. The rocks of the study area were mapped in 1:750 scale. The study was carried out through macroscopic and microscopic description of rocks, as well as scanning electron microscope and of x-ray diffraction analyses. The rock units that occur in the area were divided in two main domains, base to top, Sequência Vulcânica and Sequência Metassedimentar. The mineral paragenesis related to the auriferous mineralization is represented by sulphides, pyrite, arsenopyrite, sphalerite, chalcopyrite and stibnite. Arsenopyrite showed direct relation with the presence of gold, detected by scanning electron microscope analysis. A total of 3 deformational phases were identified: Dn-1, Dn, Dn+1. Phase Dn-1 and Dn have direct relation with the mineralization since mineralized quartz veins occur parallel to the Sn foliation (S0//Sn-1//Sn). The intersection between the bedding S0//Sn-1 and Sn foliation generates an intersection lineation that is parallel to the Dn fold axis, plunging to NW. These structures are favorable for the increase of the volume of the mineralized bodies, plunging to NW. The rocks were metamorphosed under lower greenschist facies conditions (biotite zone).

A Thesis submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirement for the degree of Doctor of Philosophy. Johannesburg March 2016 / This study aims to provide a comprehensive description of the Flora, biogeography and diversity of the serpentine outcrops of Barberton Greenstone Belt in Mpumalanga, South Africa in order to set conservation priorities for these areas. About 30 large and many smaller serpentine outcrops form part of the Barberton Greenstone Belt and consist of various combinations of serpentinized minerals. Seven outcrops were selected to be studied in detail. A floristic analysis recorded 744 species and subspecies, 319 genera and 94 families. The flora includes 33 taxa endemic to serpentine soils and six taxa, which are hyperaccumulators of nickel. The endemic taxa make up 41 % of the endemics of the Barberton Centre of Endemism. The serpentine flora was found to be different to the surrounding non-serpentine vegetation in terms of numbers of species per family, the ratios of dicotyledons to monocotyledons and familial composition. The Asteraceae and the Anacardiaceae support a higher number of endemics than expected, which suggests genetic pre-adaptation within these families and specifically within the genera Berkheya, Helichrysum and Ozoroa. Most of the endemic taxa exhibit long-range dispersal suggesting gene flow between populations on different outcrops. The endemics represent a mix of neo-endemics and paleoendemics. Non-parametric species richness estimators used to predict the species richness of each site, indicated that five serpentine outcrops have higher species richness than the surrounding non-serpentine areas. Indices of diversity calculated showed similar patterns to those of the species richness estimates. The Barberton Greenstone Belt serpentine outcrops show relatively high plant diversity when compared to some other serpentine outcrops around the world. Beta diversity calculated for each site was not correlated with altitude and weakly correlated with the size of outcrops. Species turnover between outcrops is high and is positively correlated with the geographical distance between outcrops. Diversity at higher taxonomic levels were calculated, and results suggest that genera have some potential for facilitating the ranking of outcrops in terms of biological richness to select sites for conservation planning. Less than 30% of serpentine outcrops are adequately conserved. Species and genus richness and endemism were used to select five outcrops that have high conservation priority / MT2016

O significado da idade do magmatismo, reconhecimento das séries magmáticas e ambientes tectônicos que controlaram a origem das rochas metavulcânicas do Greenstone Belt da Vila Nova (GBVN), é uma importante ferramenta para entender a evolução do Escudo das Guianas durante o Paleoproterozóico. Este trabalho apresenta novos dados geoquímicos de rochas metavulcânicas e de U/Pb em zircão (LA-MC-ICPMS), que foram suplementados por petrografia, dados estratigráficos e estruturais obtidos através de mapeamento geológico e descrição de furos de sondagem. Na região de Vila Nova, as unidades do GBVN repousam sobre o embasamento Arqueano composto por ortognaisses, metagranitos e anfibolitos do Complexo Tumucumaque. A base do GBVN é composta por metabasaltos e metabasaltos andesíticos, sotoposto por um domínio superior metassedimentar com rochas químico exalativas e metavulcânicas subordinadas. As rochas metavulcânicas incluem anfibolitos e anfibólio xistos, cujos corpos estão alongados segundo a xistosidade regional de direção NW-SE. A geocronologia pelo método U-Pb em zircão mostra uma idade de 2.154 ± 6 Ma para um meta-andesito da porção inferior do GBVN. O evento de metamorfismo orogênico esteve associado a três eventos deformacionais. Os eventos D1 e D2 formaram a xistosidade (S1), preservada como dobras intrafoliais (F2) e a clivagem de crenulação (S2), originadas a partir de movimentos de cavalgamento. O pico metamórfico (M1) está marcado pela assembleia plagioclásio+hornblenda+granada e, plagioclásio+hornblenda+diopsídio, indicando temperaturas entre 450 e 650 °C e pressão entre 4 e 6 kbares. Os metabasitos compreendem Fe-toleítos e Mg-toleítos com afinidade komatitica, composições geoquímicas enriquecidas em LILE e ETR e empobrecidas em HFSE (com anomalias negativas de Nb, Ti e P) e padrões de ETR semelhantes ao MORB. As características observadas indicam um magmatismo toleítico relacionado à bacias de retro-arco e arco de ilhas de 2.15 Ga no Escudo das Guianas. / The significance of the age of magmatism, magma series and tectonic settings that controls the origin of metavolcanic rocks of Vila Nova Greenstone Belt (VNGB) is an important issue in order to understand the evolution of Guiana Shield in Paleoproterozoic times. This work presents new U-Pb LA-ICP-MS geochronological and geochemical analyzes carried out on zircon grains and metavolcanic rocks of the Vila Nova greenstone belt (VNGB) which were supplemented by petrography, and stratigraphic and structural data acquired through description of boreholes and field work. In the Vila Nova region, the VNGB units rest on the Archaean basement composed of orthogneisses of the Tumucumaque Complex. The lower portion of the VNGB is composed of metabasalts and andesitic metabasalts, supported by an upper metasedimentary domain with exhalative chemical rocks and subordinate metavolcanic rocks. The metavolcanic rocks include amphibolites and amphibole schists, whose bodies are elongated according to the regional NW-SE schistosity. U-Pb zircon geochronology data showed an age of 2154 ±6 Ma for a meta-andesite of the lower portion of VNGB. Orogenic metamorphism event followed by three deformation events were recognized. The D1 and D2 events formed the schistosity (S1), preserved as intrafolial folds (F2) and the crenulation cleavage (S2), derived from thrust movements. The assemblages plagioclase + hornblende + garnet and plagioclase + hornblende + diopside define the metamorphic peak (M1-M2) with temperatures from 450-650 °C and lithostatic pressure between 4 and 6 kbars. The metabasites comprise Fe-tholeiites and Mg-tholeiites with komatiitic affinity, geochemical compositions enriched in LILE and REE and depleted in HFSE (with negative Nb, Ti and P anomalies) and MORB-like REE patterns. The observed features indicate an expressive magmatism related to back-arc basins and island arcs at 2.15 Ga in Guiana Shield.

Orientador: Luiz Sérgio Amarante Simões / Banca: 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