O depósito de Au-Cu-Mo Paraíba (MT) : integração de técnicas espectrais e convencionais para a exploração mineral

Orientador: Diego Fernando DucartDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de GeociênciasResumo: O Paraíba é um depósito de Au-Cu-Mo localizado na porção sul do cráton Amazônico, na Província Mineral de Alta Floresta, Mato Grosso, Brasil. É formado por veios de quartzo com ouro e por brechas hidrotermais ricas em Cu-Mo, ambos associados a diversas zonas de alteração hidrotermal. Foi aplicado um novo método de estudo, envolvendo uma integração entre técnicas espectrais (espectroscopia pontual e de imageamento) e convencionais (petrografia, geoquímica, microssonda e MEV), com o objetivo de compreender a geometria e evolução do depósito, e utilizar essa informação no desenvolvimento de vetores de exploração para zonas mineralizadas. Mais de 1400 espectros de mica branca, clorita, biotita e epídoto, foram coletados de amostras de testemunhos de sondagem através de um espectrômetro. Adicionalmente, foram geradas imagens hiperespectrais com resolução espacial de 156 e 30 ?m em porções representativas das amostras de testemunhos. A integração desses dados com estudos petrográficos permitiu um mapeamento detalhado da alteração mineral, bem como o reconhecimento das relações temporais e espaciais entre as zonas de alteração. Foram geradas seções litológicas e de alteração, juntamente com uma tabela da sequência paragenética e evolução hidrotermal. Análises por microssonda eletrônica revelaram informações sobre a composição e temperatura de cristalização do minério. A integração deste conjunto de dados de múltiplas fontes mostra que a gênese do depósito Paraíba está associada a dois grandes estágios de mineralização: (i) um metamórfico-hidrotermal (Estágio 1), relacionado aos veios de quartzo ricos em Au, em um Sistema dúctil-rúptil; e (ii) um magmático-hidrotermal (Estágio 2), associado com intrusão de sienogranito porfirítico e mineralização de Cu-Mo. Cada estágio foi dividido em três principais sub-estágios: pré-mineralização, mineralização e pós-mineralização. Estágio 1 compreende zonas de alteração marcadas pela desestabilização do plagioclásio, biotitização, silicificação e alteração da biotita do filonito. O Estágio 2 abrange zonas de alteração cálcica, potássica, sericítica e propilítica, com extensiva epidotização, cloritização e vênulas tardias estéreis. Foram discriminados cinco grupos espectral e quimicamente distintos de mica branca, e três de clorita. O uso combinados da composição, abundância e cristalinidade, extraídos de métricas espectrais para mica branca, representam um forte farejador para zonas mineralizadas. A mineralização de Au-Cu-Mo está associada à abundância de mica branca altamente cristalina, pobre em Al e rica em Mg, predominantemente com composição tendendo a fengita a fengítica. Nesse sentido, a Mica Branca 2 e Mica Branca 4 estão diretamente relacionadas a mineralizações de Au e Cu-Mo, respectivamente, enquanto que a Mica Branca 1,3 e 5, rica em Al e Fe, não apresenta relação com zonas mineralizadas. Grupos da Clorita 1 e 3, com composição rica em Mg, estão relacionados a cloritização de filonitos. Foi estabelecida uma relação espacial entre zonas epidotizadas e altos teores de Cu. A aplicação de técnicas espectrais auxiliou na caracterização mineralógica de diferentes zonas de alteração e na definição de minerais vetores para exploração no depósito Paraíba. Este trabalho demonstra a importância de combinar técnicas espectrais e convencionais para o estudo de sistemas hidrotermais complexosAbstract: The Paraíba is an Au-Cu-Mo deposit located in the southern part of the Amazon Craton, in Alta Floresta Mineral Province, Mato Grosso, Brazil. It is composed by gold-rich quartz veins and Cu-Mo-rich hydrothermal breccias, both associated to several hydrothermal alteration zones. A novel method was applied here, involving the full integration of spectral (pontual and imaging spectroscopy) and conventional techniques (petrography, geochemistry, electron microprobe and SEM), with the aim to understand the geometry and evolution of the deposit and use this information to develop exploration vectors to mineralized zones. More than 1,400 spectra of white mica, chlorite, biotite and epidote-bearing drill core samples were collected along transversal sections in the deposit by a spectrometer. In addition, hyperspectral images, with spatial resolutions of 156 and 30 ?m, were acquired on representative drill core samples. These data, integrated with petrographic studies and core logging, allowed a detailed alteration mineral mapping, as well as the recognition of temporal and spatial relationships among the alterations zones. Lithological and alteration sections, together with a mineral paragenetic sequence table and hydrothermal system evolution, were generated. Electron micro probe analysis revealed further information on the composition and crystallization temperature of the ore. The integration of this multi-source dataset shows that the genesis of the Paraíba deposit is associated with two major mineralizing stages : (i) a first metamorphic-hydrothermal stage (Stage 1), related to Au-rich quartz veins in a ductile shear system; and (ii) a second magmatic-hydrothermal stage (Stage 2), associated with a syenogranite porphyry intrusion and Cu-Mo mineralization. Each stage has been divided into three principal sub-stages of mineralization: pre-ore, ore emplacement and post ore. Stage 1 comprises alteration zones marked by plagioclase destabilization, biotitization, silicification and phyllonite biotite's breakdown. Stage 2 comprises calcic, potassic, sericitic, propylitic alteration zones, with extensive epidotization, chloritization and late barren venules. Five chemically and spectrally different white mica groups, plus three chlorite groups, were discriminated. The combined use of composition, abundance and crystallinity extracted from spectral metrics for white mica represent a strong proxy to mineralized zones. The Au-Cu-Mo mineralization proved to be associated with higher abundance of well-ordered, highly crystalline, Al-poor and Mg-rich white micas, dominantly with tending-to-phengite to phengite composition. In this sense, the White Mica 2 and White Mica 4 are directly related to Au and Cu-Mo mineralization respectively, whereas the Al- and Fe-rich White Mica 1, 3 and 5 do not present relationship with ore zones. Chlorite groups 1 and 3, with a Mg-rich composition, are related to chloritization of phyllonites. A spatial relationship between epidotized zones and higher Cu contents was established. The application of spectral techniques helped in the mineralogical characterization of different alteration zones and definition of mineral vectoring tools for exploration at the Paraíba deposit. This work demonstrates the importance of combining spectral and conventional techniques for the study of hydrothermal systems within complex mineral depositsMestradoGeologia e Recursos NaturaisMestre em Geociências2016/04370-5CAPESFAPES

Radiometric Correction and 3D Integration of Long-Range Ground-Based Hyperspectral Imagery for Mineral Exploration of Vertical Outcrops

Recently, ground-based hyperspectral imaging has come to the fore, supporting the arduous task of mapping near-vertical, difficult-to-access geological outcrops. The application of outcrop sensing within a range of one to several hundred metres, including geometric corrections and integration with accurate terrestrial laser scanning models, is already developing rapidly. However, there are few studies dealing with ground-based imaging of distant targets (i.e., in the range of several kilometres) such as mountain ridges, cliffs, and pit walls. In particular, the extreme influence of atmospheric effects and topography-induced illumination differences have remained an unmet challenge on the spectral data. These effects cannot be corrected by means of common correction tools for nadir satellite or airborne data. Thus, this article presents an adapted workflow to overcome the challenges of long-range outcrop sensing, including straightforward atmospheric and topographic corrections. Using two datasets with different characteristics, we demonstrate the application of the workflow and highlight the importance of the presented corrections for a reliable geological interpretation. The achieved spectral mapping products are integrated with 3D photogrammetric data to create large-scale now-called “hyperclouds”, i.e., geometrically correct representations of the hyperspectral datacube. The presented workflow opens up a new range of application possibilities of hyperspectral imagery by significantly enlarging the scale of ground-based measurements

Hydrothermal alteration of medium-grade metamorphic rocks of Metsämonttu VMS deposit, southern Finland : A comparative portable XRD and near-infrared spectroscopy analysis

Hydrothermal alteration processes are connected to the formation of many economically important ore deposits. This study represents a comparative portable XRD (pXRD) and near-infrared (NIR) spectroscopy analysis of four drill cores of Metsämonttu volcanogenic massive sulphide (VMS) deposit, southwestern Finland. The drill cores represent hydrothermally altered low-grade metamorphic lithologies of lower amphibolite facies. The NIR spectroscopy focuses on short-wave infrared (SWIR; 1.0-2.5 μm) analysis with some supplementing visible, near-infrared (VNIR; 0.4-1.0 μm) data. The SWIR and VNIR data were gathered with ASD Terraspec 4 Portable NIR Spectrometer as point measurements and were interpreted with The Spectral Geologist software. The pXRD data were measured using Olympus Portable Onsite XRD Terra-542 device and were interpreted with XPowder software. In this study, the mineral assemblages identified with the pXRD, and the SWIR spectroscopy are compared to the petrophysical and geochemical data measured with portable X-ray fluorescence (pXRF). The SWIR data are connected to the lithological data by using the wavelength positions of AlOH, FeOH, and MgOH absorption features and identifying the mineralogical alterations pointed by them. The pXRD measurements used in this study show to have quality issues like rising of the diffractogram background with the samples including sulphidic minerals, especially galena. Another quality issue is observed with the samples including minerals with preferred orientations, particularly muscovite. High amount of amorphous, or nanocrystalline material of extremely fine grain size in the sample is one uncertainty factor that is shown to produce quality problems to the diffractograms. Due to previously mentioned and several other quality issues such as short measurement time and low resolution, the method is shown not to be reliable enough to be used in identification of minor mineral phases (<5 wt%) or accessory minerals. Furthermore, it is shown that the point measurements done with the spectrometer, using the SWIR and VNIR wavelengths, have their limitations regarding the number of minerals that could have been identified. In addition, the representativeness of the point measurements is shown to be limited. However, both the pXRD and the SWIR spectroscopy describe the mineral variation in a different manner. The pXRD data are used to identify most of the major mineral phases in the sample, while the SWIR data are used to observe chemical alterations of white mica and chlorite group phases. The study identifies the alterations of the altered rocks of the Metsämonttu deposit by combining the pXRD and the SWIR data with the pXRF and the petrophysical data, and specifies the information related to the previously logged lithological units. This approach is a suggested way to overcome the limitations of each method.Hydrotermiset muuttumisprosessit ovat yhteydessä monien taloudellisesti merkittävien malmivarantojen syntyyn. Tässä työssä esitetään vertaileva kannettavalla röntgendiffraktioanalysaattorilla (pXRD) ja lähi-infrapunaspektroskopialla (NIR) tehty analyysi neljästä kairasydämestä, jotka on kairattu Metsämontun vulkanogeenisesta massivisesta sulfidiesiintymästä (VMS). Kairasydämet edustavat matalan metamorfoosiasteen alemman amfiboliittifasieksen litologioita. NIR-spektroskopia keskittyi lyhytaaltoisen infrapuna-alueen (short-wave infrared, SWIR; 1.0-2.5 μm) mittauksiin, joita täydennettiin näkyvän valon lyhytaaltoisen infrapuna-alueen (visible, near-infrared, VNIR; 0.4-1.0 μm) mittausaineistolla. SWIR- ja VNIR-aineisto kerättiin ASD Terraspec 4 Portable NIR -spektrometrillä pistemittauksina ja tulkittiin The Spectral Geologist -ohjelmistolla. pXRD-aineisto kerättiin käyttäen Olympus Portable Onsite XRD Terra-542 -laitteistoa ja tulkittiin XPowder-ohjelmistolla. pXRD:llä ja SWIR-spektroskopialla havaittuja mineraalikokoonpanoja vertailtiin petrofysikaaliseen ja kannettavalla röntgenfluoresenssilaitteistolla (pXRF) mitattuun geokemialliseen aineistoon. SWIR-aineisto yhdistettiin litologiseen aineistoon käyttämällä Al-, Fe- ja Mg-hydroksidien absorptiokäyrien sijaintien vaihtelua ja havainnoimalla mineralogista muuttumista niiden kautta. pXRD-mittauksien laatuongelmia, kuten diffraktogrammien taustojen nousua, ilmeni sulfideja, etenkin lyijyhohdetta, sisältävissä näytteissä. Toinen laatuseikka liittyi näytteisiin, jotka sisälsivät preferoitua orientaatiota suosivia mineraaleja, kuten muskoviittia. Paljon amorfista tai nanokiteistä, erittäin hienojakoista materiaalia sisältävät näytteet ovat epävarmuustekijöitä, jotka aiheuttivat laatuongelmia diffraktogrammeihin. Edellämainituista sekä useista muista virhelähteistä, kuten lyhyestä mittausajasta ja alhaisesta resoluutiosta johtuen metodia ei voida todeta luotettavaksi pieninä pitoisuuksina (<5 wt%) esiintyvien mineraalien ja aksessoristen mineraalien tunnistamisessa. SWIR- ja VNIR-spektroskopialla tehdyillä pistemittauksilla havaittiin olevan omat rajoitteensa siinä, kuinka paljon eri mineraalifaaseja niillä voidaan tunnistaa. Pistemittausten edustavuus on myös rajallinen. pXRD ja SWIR-spektroskopia kuvaavat mineraalien vaihtelua eri tavoin. pXRD-aineistoa käytetään yleisimpien päämineraalien tunnistuksessa, kun taas SWIR-aineistoa käytetään vaaleiden kiilteiden ja kloriitti-ryhmän mineraalien kemiallisen vaihtelun havaitsemiseen. Yhdistämällä pXRD- ja SWIR-aineistoista saatua tietoa petrofysikaaliseen ja pXRF-aineistoon on voitu tunnistaa eri muuntumistyyppejä Metsämontun esiintymän muuntuneissa kivissä, ja jo olemassa olevia tietoja litologisista yksiköistä on voitu tarkentaa.. Tämä lähestymistapa on suositeltava ja sillä voidaan kompensoida eri menetelmien puutteita

The Need for Accurate Pre-processing and Data Integration for the Application of Hyperspectral Imaging in Mineral Exploration

Die hyperspektrale Bildgebung stellt eine Schlüsseltechnologie in der nicht-invasiven Mineralanalyse dar, sei es im Labormaßstab oder als fernerkundliche Methode. Rasante Entwicklungen im Sensordesign und in der Computertechnik hinsichtlich Miniaturisierung, Bildauflösung und Datenqualität ermöglichen neue Einsatzgebiete in der Erkundung mineralischer Rohstoffe, wie die drohnen-gestützte Datenaufnahme oder digitale Aufschluss- und Bohrkernkartierung. Allgemeingültige Datenverarbeitungsroutinen fehlen jedoch meist und erschweren die Etablierung dieser vielversprechenden Ansätze. Besondere Herausforderungen bestehen hinsichtlich notwendiger radiometrischer und geometrischer Datenkorrekturen, der räumlichen Georeferenzierung sowie der Integration mit anderen Datenquellen. Die vorliegende Arbeit beschreibt innovative Arbeitsabläufe zur Lösung dieser Problemstellungen und demonstriert die Wichtigkeit der einzelnen Schritte. Sie zeigt das Potenzial entsprechend prozessierter spektraler Bilddaten für komplexe Aufgaben in Mineralexploration und Geowissenschaften.Hyperspectral imaging (HSI) is one of the key technologies in current non-invasive material analysis. Recent developments in sensor design and computer technology allow the acquisition and processing of high spectral and spatial resolution datasets. In contrast to active spectroscopic approaches such as X-ray fluorescence or laser-induced breakdown spectroscopy, passive hyperspectral reflectance measurements in the visible and infrared parts of the electromagnetic spectrum are considered rapid, non-destructive, and safe. Compared to true color or multi-spectral imagery, a much larger range and even small compositional changes of substances can be differentiated and analyzed. Applications of hyperspectral reflectance imaging can be found in a wide range of scientific and industrial fields, especially when physically inaccessible or sensitive samples and processes need to be analyzed. In geosciences, this method offers a possibility to obtain spatially continuous compositional information of samples, outcrops, or regions that might be otherwise inaccessible or too large, dangerous, or environmentally valuable for a traditional exploration at reasonable expenditure. Depending on the spectral range and resolution of the deployed sensor, HSI can provide information about the distribution of rock-forming and alteration minerals, specific chemical compounds and ions. Traditional operational applications comprise space-, airborne, and lab-scale measurements with a usually (near-)nadir viewing angle. The diversity of available sensors, in particular the ongoing miniaturization, enables their usage from a wide range of distances and viewing angles on a large variety of platforms. Many recent approaches focus on the application of hyperspectral sensors in an intermediate to close sensor-target distance (one to several hundred meters) between airborne and lab-scale, usually implying exceptional acquisition parameters. These comprise unusual viewing angles as for the imaging of vertical targets, specific geometric and radiometric distortions associated with the deployment of small moving platforms such as unmanned aerial systems (UAS), or extreme size and complexity of data created by large imaging campaigns. Accurate geometric and radiometric data corrections using established methods is often not possible. Another important challenge results from the overall variety of spatial scales, sensors, and viewing angles, which often impedes a combined interpretation of datasets, such as in a 2D geographic information system (GIS). Recent studies mostly referred to work with at least partly uncorrected data that is not able to set the results in a meaningful spatial context. These major unsolved challenges of hyperspectral imaging in mineral exploration initiated the motivation for this work. The core aim is the development of tools that bridge data acquisition and interpretation, by providing full image processing workflows from the acquisition of raw data in the field or lab, to fully corrected, validated and spatially registered at-target reflectance datasets, which are valuable for subsequent spectral analysis, image classification, or fusion in different operational environments at multiple scales. I focus on promising emerging HSI approaches, i.e.: (1) the use of lightweight UAS platforms, (2) mapping of inaccessible vertical outcrops, sometimes at up to several kilometers distance, (3) multi-sensor integration for versatile sample analysis in the near-field or lab-scale, and (4) the combination of reflectance HSI with other spectroscopic methods such as photoluminescence (PL) spectroscopy for the characterization of valuable elements in low-grade ores. In each topic, the state of the art is analyzed, tailored workflows are developed to meet key challenges and the potential of the resulting dataset is showcased on prominent mineral exploration related examples. Combined in a Python toolbox, the developed workflows aim to be versatile in regard to utilized sensors and desired applications

Hyperspectral drill-core scanning in geometallurgy

Driven by the need to use mineral resources more sustainably, and the increasing complexity of ore deposits still available for commercial exploitation, the acquisition of quantitative data on mineralogy and microfabric has become an important need in the execution of exploration and geometallurgical test programmes. Hyperspectral drill-core scanning has the potential to be an excellent tool for providing such data in a fast, non- destructive and reproducible manner. However, there is a distinct lack of integrated methodologies to make use of these data through-out the exploration and mining chain. This thesis presents a first framework for the use of hyperspectral drill-core scanning as a pillar in exploration and geometallurgical programmes. This is achieved through the development of methods for (1) the automated mapping of alteration minerals and assemblages, (2) the extraction of quantitative mineralogical data with high resolution over the drill-cores, (3) the evaluation of the suitability of hyperspectral sensors for the pre-concentration of ores and (4) the use of hyperspectral drill- core imaging as a basis for geometallurgical domain definition and the population of these domains with mineralogical and microfabric information.:Introduction Materials and methods Assessment of alteration mineralogy and vein types using hyperspectral data Hyperspectral imaging for quasi-quantitative mineralogical studies Hyperspectral sensors for ore beneficiation 3D integration of hyperspectral data for deposit modelling Concluding remarks Reference

Literature review of the remote sensing of natural resources

Abstracts of 596 documents related to remote sensors or the remote sensing of natural resources by satellite, aircraft, or ground-based stations are presented. Topics covered include general theory, geology and hydrology, agriculture and forestry, marine sciences, urban land use, and instrumentation. Recent documents not yet cited in any of the seven information sources used for the compilation are summarized. An author/key word index is provided

Remote Sensing-Based Exploration of Structurally-Related Mineralizations around Mount Isa, Queensland, Australia

Hyperspectral imaging is a powerful tool for mineral mapping and increasingly used in poorly-accessible areas. It only requires a limited amount of validation sample points, but can fail to discriminate spectrally-similar features. In this manuscript, we show that we improve the identification of interesting targets by including geomorphological data in the spectral mapping scheme. We jointly use geomorphic and spectral features to locate gossanous ironstone ridges as an indicator for possible Pb-Zn-Ag-mineralization and provide an application around Mount Isa and George Fisher/Hilton mine, Queensland, Australia. We combine hyperspectral HyMap data using mixture tuned matched filtering with topographical indices, such as maximum curvature and the topographical position index. As it is often the case with structurally-controlled mineralization, the amount of training sites is limited, and supervised classification methods cannot be implemented. Therefore, we implement expert knowledge in a decision tree to take advantage of the relationship between mineralization, alteration and structure. Optimized rock sampling and spectral measurements provided data for validation. We are able to map sets of gossanous ridges with a minimum of validation points, not only within the Mount Isa mining area itself, but also outside the commonly-accepted host rocks. The ridges are parallel to north-south trending geomorphological features and probably associated with the Paroo fault zone. Similarities between the ridges were confirmed by field observations, spectral measurements and a qualitative rock sample analysis. We identified new mineralized ridges that we could subsequently attribute to a poorly-known and sub-economic deposit known as the Mount Novit Pb-Zn-deposit

Fractals and implications for mineral favorability maps: the example of iron oxide-copper-gold deposits from Carajás (PA)

Orientadores: Carlos Roberto de Souza Filho, Emmanuel John Muico CarranzaDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de GeociênciasResumo: Desde a definição do conceito da geometria fractal na segunda metade do século XX, a importância dos fractais para a descrição e entendimento de feições geológicas gradualmente ganhou importância. Mais recentemente, diversos trabalhos têm sugerido que a distribuição espacial de depósitos minerais apresenta geometria fractal, a qual representaria a complexa interação de processos geológicos necessários para a gênese de uma mineralização. A manifestação da geometria fractal se dá através da invariância escalar, ou seja, a propriedade de uma feição conservar suas características geométricas independente da escala espacial. Esta característica é promissora para o estudo de depósitos minerais, pois sugere a possibilidade de que informações sobre a geometria da mineralização em uma escala possa ser usada para inferir aspectos da geometria em outras escalas. Uma vez que a geometria das mineralizações é consequência dos controles que atuaram durante e após sua formação, a possibilidade de estudos com uma abordagem fractal tem aplicações teóricas e práticas. Considerando o exposto, a presente pesquisa dedicou-se a investigar se de fato a geometria de depósitos minerais apresenta invariância escalar, e em caso positivo, que informações ela permite inferir sobre os controles de mineralização. Para esta investigação foi escolhida como área de estudo a região do depósito Iron Oxide-Copper-Gold (IOCG) de Sossego, na Província Mineral de Carajás (PA). Depósitos IOCG apresentam forte controle estrutural, que somados a farta disponibilidade de dados nas escalas regional, local e microscópica tornam a área da mina de Sossego ideal para a pesquisa proposta. Assim, os dados já disponíveis na literatura foram integrados com novas medidas estruturais e novas lâminas orientadas de amostras coletadas nas cavas da mina. A geometria da mineralização foi avaliada em três diferentes escalas: na escala regional examinou-se a distribuição espacial dos depósitos IOCG conhecidos; na escala local examinou-se a geometria das estruturas e corpos mineralizados no depósito de Sossego; na escala microscópica foi avaliada a geometria da distribuição espacial e da forma dos grãos de minerais de minério. O conjunto de resultados indica que os depósitos IOCG da região de Carajás, e em particular o depósito de Sossego, apresentam geometria fractal, conservando a orientação e anisotropia nas diferentes escalas. A orientação e anisotropia das mineralizações são aspectos geométricos que resultam diretamente do controle exercido pela trama estrutural subjacente. Desta forma, os resultados indicam que o controle estrutural gera a invariância escalar devido à influência que exerce sobre a permeabilidade das rochas, um fator essencial para a geração de depósitos hidrotermais. A permeabilidade é definida em escala microscópica através de planos de foliação, microfraturas e vênulas, as quais se relacionam diretamente com estruturas de escalas maiores, tais como zonas de cisalhamento, falhas e veios, criando uma rede permeável consistente através das escalas. No caso de Carajás, a geometria destas áreas permeáveis reflete a interação entre uma trama dúctil anterior, de permeabilidade difusa, e uma trama rúptil posterior, com permeabilidade focada. Os resultados deste trabalho sugerem que a abordagem fractal para o estudo da gênese de depósitos minerais tem potencial concreto para gerar resultados relevantes, inclusive para a avaliação da favorabilidade mineral de áreas em exploraçãoAbstract: Since the concept of fractal geometry was defined in the second half of the twentieth century, the importance of fractals for the description and understanding of geological features has gradually gained importance. More recent work has suggested that the spatial distribution of mineral deposits presents fractal geometry, which represents the complex interaction of geological processes necessary for the genesis of a mineralization. The manifestation of fractal geometry occurs through scale invariance, i.e. the property of a feature that conserves its geometrical characteristics independent of the spatial scale. This property is promising for the study of mineral deposits because it suggests the possibility that information about the geometry of a mineralization at one scale can be used to infer aspects of its geometry at other scales. Since mineralization geometry is a consequence of controls that acted during and after its formation, studies with a fractal approach have theoretical and practical applications. Considering the above, the present research investigated if the geometry of mineral deposits presents scale invariance, and if so, what information it permits to infer about the mineralization controls. For this investigation the study area chosen was the iron oxide-copper-gold (IOCG) Sossego deposit, in the Carajás Mineral Province (PA). IOCG deposits present strong structural control, which taken in conjunction with data availability at the regional, local and microscopic scales make the Sossego deposit area ideal for the proposed research. Thus, data already available in the literature were integrated with new structural measurements and new oriented thin sections of samples collected in the mine pits. Mineralization geometry was evaluated at three different scales: in the regional scale the spatial distribution of the known IOCG deposits was examined; in the local scale the geometry of the mineralized structures and orebodies at the Sossego deposit was examined; in the microscale the geometry of the spatial distribution and the shape of ore mineral grains were evaluated. The bulk of results indicate that the IOCG deposits of Carajás province, and in particular the Sossego deposit, present fractal geometry, conserving the orientation and anisotropy at the different scales. The orientation and anisotropy of the mineralization are geometric aspects that result directly from the control exerted by the underlying structural framework. As a consequence, the results indicate that the structural control generates the scale invariance due to its influence on rock permeability, an essential factor for the genesis of hydrothermal deposits. Permeability is defined at the microscale through foliation planes, microfractures and veinlets, which are directly related to structures of larger scales, such as shear zones, faults and veins, creating a consistent permeable network throughout the scales. In the case of Carajás, the geometry of these permeable areas reflects the interaction between an older ductile framework with diffuse permeability, and a posterior brittle network with focused permeability. The results of this work suggest that the fractal approach to the study of the genesis of mineral deposits has concrete potential to generate relevant results, including for the evaluation of the mineral favorability on exploration areasMestradoGeologia e Recursos NaturaisMestre em Geociências2015/11186-3401316/2014-9CAPESFAPESPCNP

Multielement geochemical reconnaissance for uranium in the Palmyrides region, central Syria

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