Quantificação das estruturas de fluxo sin-magmáticas do Plutão de Vila Pouca de Aguiar: uma ferramenta para a quantificação estrutural e da qualidade da rocha

Mineral distribution pattern of Variscan post-tectonic granites from Vila Pouca de Aguiar Pluton (NE Portugal) were analyzed with methods partially based on fractal geometry and, with respect to rock inhomogeneity and anisotropy. The result of the analysis provides information about magmatic flux and mineral equilibrium processes in a crystallizing magma chamber. In addition, the used methods may also provide important information for the ornamental rock industry, because they allow fast and automatic evaluation of economic rock parameters.Os padrões de distribuição mineral dos granitos póstectónicos do plutão de Vila Pouca de Aguiar foram analisados com métodos parcialmente baseados na geometria fractal, atendendo à homogeneidade e anisotropia da rocha. O resultado desta análise forneceu informação acerca do fluxo magmático e dos processos de equilíbrio mineral na cristalização no interior de uma câmara magmática. Adicionalmente, os métodos utilizados ainda disponibilizaram informação importante para a indústria de pedra ornamental, pois permitem uma avaliação rápida e automática dos parâmetros que valorizam economicamente a rocha.(undefined

Grain boundary networks and shape preferred orientation : A fresh angle on pattern quantification with GBPaQ

A quantitative understanding of grain shape preferred orientation (SPO) and grain boundary networks as fundamental characteristics of rocks and other crystalline solids is of major interest in geology and material science. Grain boundary networks contain useful information on the deformation history of polycrystalline aggregates, and their diagenetic and metamorphic histories. SPO can have a major impact on material characteristics such as permeability, acoustic velocity and mechanical strength, and on reaction surfaces. The objective of this study is to present a semi-automated toolbox of MATLAB™ scripts, named Grain Boundary Pattern Quantification (GBPaQ), that incorporate different methods for grain boundary pattern quantification for their application to, for example, seismic wave attenuation estimation. GBPaQ uses grain boundary statistics and calculates radial scan line intercepts. In this paper, GBPaQ is tested on two example grain boundary patterns, a granular texture and a foam texture with equant grains, which have been digitally stretched (deformed) to analyse their SPO evolution. The results show that a combination of grain ellipse, grain boundary segment orientation, and grain boundary segment intercept density rose diagrams provide a complete, detailed quantification of grain boundary pattern anisotropy. Grain boundary segment intercept (GBSI) analysis using GBPaQ yields a new grain boundary network parameter – the minimum intensity of grain boundary intercepts (Imin) – which follows a power law relationship with the average axial ratio of grain-fitted ellipses (r) during SPO development. We propose that Imin can be used for the quantitative analysis of SPO strength as a useful tool to assess the deformation history of polycrystalline aggregates. Further studies involving a broader range of different patterns and strain histories are necessary to fully investigate the potential of Imin versus r diagrams

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

Handbook of Mathematical Geosciences

This Open Access handbook published at the IAMG's 50th anniversary, presents a compilation of invited path-breaking research contributions by award-winning geoscientists who have been instrumental in shaping the IAMG. It contains 45 chapters that are categorized broadly into five parts (i) theory, (ii) general applications, (iii) exploration and resource estimation, (iv) reviews, and (v) reminiscences covering related topics like mathematical geosciences, mathematical morphology, geostatistics, fractals and multifractals, spatial statistics, multipoint geostatistics, compositional data analysis, informatics, geocomputation, numerical methods, and chaos theory in the geosciences

Tracing back the source of contamination

From the time a contaminant is detected in an observation well, the question of where and when the contaminant was introduced in the aquifer needs an answer. Many techniques have been proposed to answer this question, but virtually all of them assume that the aquifer and its dynamics are perfectly known. This work discusses a new approach for the simultaneous identification of the contaminant source location and the spatial variability of hydraulic conductivity in an aquifer which has been validated on synthetic and laboratory experiments and which is in the process of being validated on a real aquifer

EVOLUTION OF THE SUBCONTINENTAL LITHOSPHERE DURING MESOZOIC TETHYAN RIFTING: CONSTRAINTS FROM THE EXTERNAL LIGURIAN MANTLE SECTION (NORTHERN APENNINE, ITALY)

Our study is focussed on mantle bodies from the External Ligurian ophiolites, within the Monte Gavi and Monte Sant'Agostino areas. Here, two distinct pyroxenite-bearing mantle sections were recognized, mainly based on their plagioclase-facies evolution. The Monte Gavi mantle section is nearly undeformed and records reactive melt infiltration under plagioclase-facies conditions. This process involved both peridotites (clinopyroxene-poor lherzolites) and enclosed spinel pyroxenite layers, and occurred at 0.7–0.8 GPa. In the Monte Gavi peridotites and pyroxenites, the spinel-facies clinopyroxene was replaced by Ca-rich plagioclase and new orthopyroxene, typically associated with secondary clinopyroxene. The reactive melt migration caused increase of TiO2 contents in relict clinopyroxene and spinel, with the latter also recording a Cr2O3 increase. In the Monte Gavi peridotites and pyroxenites, geothermometers based on slowly diffusing elements (REE and Y) record high temperature conditions (1200-1250 °C) related to the melt infiltration event, followed by subsolidus cooling until ca. 900°C. The Monte Sant'Agostino mantle section is characterized by widespread ductile shearing with no evidence of melt infiltration. The deformation recorded by the Monte Sant'Agostino peridotites (clinopyroxene-rich lherzolites) occurred at 750–800 °C and 0.3–0.6 GPa, leading to protomylonitic to ultramylonitic textures with extreme grain size reduction (10–50 μm). Compared to the peridotites, the enclosed pyroxenite layers gave higher temperature-pressure estimates for the plagioclase-facies re-equilibration (870–930 °C and 0.8–0.9 GPa). We propose that the earlier plagioclase crystallization in the pyroxenites enhanced strain localization and formation of mylonite shear zones in the entire mantle section. We subdivide the subcontinental mantle section from the External Ligurian ophiolites into three distinct domains, developed in response to the rifting evolution that ultimately formed a Middle Jurassic ocean-continent transition: (1) a spinel tectonite domain, characterized by subsolidus static formation of plagioclase, i.e. the Suvero mantle section (Hidas et al., 2020), (2) a plagioclase mylonite domain experiencing melt-absent deformation and (3) a nearly undeformed domain that underwent reactive melt infiltration under plagioclase-facies conditions, exemplified by the the Monte Sant'Agostino and the Monte Gavi mantle sections, respectively. We relate mantle domains (1) and (2) to a rifting-driven uplift in the late Triassic accommodated by large-scale shear zones consisting of anhydrous plagioclase mylonites. Hidas K., Borghini G., Tommasi A., Zanetti A. & Rampone E. 2021. Interplay between melt infiltration and deformation in the deep lithospheric mantle (External Liguride ophiolite, North Italy). Lithos 380-381, 105855

Impact of Etna’s volcanic emission on major ions and trace elements composition of the atmospheric deposition

Mt. Etna, on the eastern coast of Sicily (Italy), is one of the most active volcanoes on the planet and it is widely recognized as a big source of volcanic gases (e.g., CO2 and SO2), halogens, and a lot of trace elements, to the atmosphere in the Mediterranean region. Especially during eruptive periods, Etna’s emissions can be dispersed over long distances and cover wide areas. A group of trace elements has been recently brought to attention for their possible environmental and human health impacts, the Technology-critical elements. The current knowledge about their geochemical cycles is still scarce, nevertheless, recent studies (Brugnone et al., 2020) evidenced a contribution from the volcanic activity for some of them (Te, Tl, and REE). In 2021, in the framework of the research project “Pianeta Dinamico”, by INGV, a network of 10 bulk collectors was implemented to collect, monthly, atmospheric deposition samples. Four of these collectors are located on the flanks of Mt. Etna, other two are in the urban area of Catania and three are in the industrial area of Priolo, all most of the time downwind of the main craters. The last one, close to Cesarò (Nebrodi Regional Park), represents the regional background. The research aims to produce a database on major ions and trace element compositions of the bulk deposition and here we report the values of the main physical-chemical parameters and the deposition fluxes of major ions and trace elements from the first year of research. The pH ranged from 3.1 to 7.7, with a mean value of 5.6, in samples from the Etna area, while it ranged between 5.2 and 7.6, with a mean value of 6.4, in samples from the other study areas. The EC showed values ranging from 5 to 1032 μS cm-1, with a mean value of 65 μS cm-1. The most abundant ions were Cl- and SO42- for anions, Na+ and Ca+ for cations, whose mean deposition fluxes, considering all sampling sites, were 16.6, 6.8, 8.4, and 6.0 mg m-2 d, respectively. The highest deposition fluxes of volcanic refractory elements, such as Al, Fe, and Ti, were measured in the Etna’s sites, with mean values of 948, 464, and 34.3 μg m-2 d-1, respectively, higher than those detected in the other sampling sites, further away from the volcanic source (26.2, 12.4, 0.5 μg m-2 d-1, respectively). The same trend was also observed for volatile elements of prevailing volcanic origin, such as Tl (0.49 μg m-2 d-1), Te (0.07 μg m-2 d-1), As (0.95 μg m-2 d-1), Se (1.92 μg m-2 d-1), and Cd (0.39 μg m-2 d-1). Our preliminary results show that, close to a volcanic area, volcanic emissions must be considered among the major contributors of ions and trace elements to the atmosphere. Their deposition may significantly impact the pedosphere, hydrosphere, and biosphere and directly or indirectly human health

Impact of geogenic degassing on C-isotopic composition of dissolved carbon in karst systems of Greece

The Earth C-cycle is complex, where endogenic and exogenic sources are interconnected, operating in a multiple spatial and temporal scale (Lee et al., 2019). Non-volcanic CO2 degassing from active tectonic structures is one of the less defined components of this cycle (Frondini et al., 2019). Carbon mass-balance (Chiodini et al., 2000) is a useful tool to quantify the geogenic carbon output from regional karst hydrosystems. This approach has been demonstrated for central Italy and may be valid also for Greece, due to the similar geodynamic settings. Deep degassing in Greece has been ascertained mainly at hydrothermal and volcanic areas, but the impact of geogenic CO2 released by active tectonic areas has not yet been quantified. The main aim of this research is to investigate the possible deep degassing through the big karst aquifers of Greece. Since 2016, 156 karst springs were sampled along most of the Greek territory. To discriminate the sources of carbon, the analysis of the isotopic composition of carbon was carried out. δ13CTDIC values vary from -16.61 to -0.91‰ and can be subdivided into two groups characterized by (a) low δ13CTDIC, and (b) intermediate to high δ13CTDIC with a threshold value of -6.55‰. The composition of the first group can be related to the mixing of organic-derived CO2 and the dissolution of marine carbonates. Springs of the second group, mostly located close to Quaternary volcanic areas, are linked to possible carbon input from deep sources