Caracterização petrológica dos granitos das suítes Serrote e Santa Luzia, na região de Paraíso do Tocantins - PUGMIL

Dissertação (mestrado)—Universidade de Brasília, Instituto de Geociências, Programa de Pós-Graduação em Geologia, 2018.O Cinturão Araguaia está inserido no contexto de colisão continental da Província Tocantins, formada a partir do amalgamento dos crátons Amazônico, São Francisco- Congo e do Bloco Paranapanema durante o Neoproterozoico. Ele é constituído essencialmente por seu embasamento arqueano e paleoproterozoico, rochas supracrustais neoproterozoicas e rochas graníticas ediacaranas/cambrianas. Com relação ao tempo geológico, há dois principais grupos de granitos relacionados ao Cinturão Araguaia. O primeiro deles é paleoproterozoico, representado pela Suíte Ipueiras (2,08 Ga), Gnaisse Cantão (1,86 Ga) e Granito Serrote (1,86 Ga), que hoje são parte do embasamento; enquanto o outro é ediacarano/cambriano, representado pelo Granito Ramal do Lontra (549 Ma), Granodiorito Presidente Kennedy (539 Ma), Granito Barrolândia (538 Ma), Granito Santa Luzia (538 Ma) e Suíte Lajeado (550 Ma). Os granitos Serrote e Santa Luzia, alvos desta dissertação, afloram próximo às cidades de Pugmil, Paraíso do Tocantins e Barrolândia, na porção sul do Cinturão Araguaia. O Granito Serrote é constituído principalmente por microclínio granito, sienogranito e, em menor proporção, por monzogranito. A assembleia mineral mais comum é formada por quartzo, microclínio e plagioclásio, com biotita e muscovita subordinadas. Além disso, as fases acessórias são titanita, magnetita, allanita, zircão e apatita. A geoquímica de rocha total revela que esses magmas são metaluminosos a peraluminosos, de caráter calci-alcalino de alto-K e que provavelmente originaram-se em ambiente tectônico pós-colisional. Três amostras foram selecionadas para datação U-Pb em zircão por MC-LA-ICP-MS e somente duas forneceram idades satisfatórias de 1863,1 ± 5,2 Ma e 1846,5 ± 6,5 Ma, interpretadas como idades de cristalização. Em imagens BSE e de catodoluminescência dessas amostras, não foram identificadas bordas metamórficas. Foram obtidas idades-modelo TDM entre 2,03 e 2,17 Ga. Os valores εNd (1863 Ma) estão entre -2 e 0,6. O Granito Santa Luzia compreende granodiorito, monzogranito, pegmatitos e, em menor proporção, sienogranito. Essas rochas são formadas principalmente por quartzo, microclínio, plagioclásio, biotita e muscovita, além de monazita, zircão, magnetita, apatita, ilmenita e pirita como minerais acessórios. A química mineral de biotita e muscovita revela que elas possuem origem magmática e que não foram submetidas a reequilíbrio químico. A litogeoquímica mostra que esses magmas são essencialmente peraluminosos, magnesianos a levemente ferrosos, possuem caráter calci-alcalino e foram gerados em ambiente tectônico tardi-orogênico a pós-orogênico (ao final da orogênese Brasiliana/Pan-Africana). Foram selecionadas três amostras para datação U-Pb em zircão e monazita por MC-LA-ICP-MS, além de uma amostra de pegmatito para datação em monazita. Apesar da abundante presença de zircões herdados, algumas amostras de zircão forneceram idades entre 532-538 Ma, enquanto as amostras de monazita geraram idades entre 524-534 Ma, ambas interpretadas como idades de cristalização. Foram obtidas idades de 512,3 ± 0,81 e 501,4 ± 1,1 Ma em monazita de pegmatito, interpretada como idade dos estágios finais de magmatismo do Granito Santa Luzia. As idades-modelo TDM obtidas estão entre 1,3 e 2,87 Ga, enquanto os valores εNd (538 Ma) estão entre -6 e -12. Baseado em critérios petrográficos, geoquímicos, geocronológicos e isotópicos, deste trabalho e da literatura, sugere-se que o Granodiorito Presidente Kennedy, o Granito Barrolândia e o Granito Santa Luzia sejam agrupados em uma única suíte denominada Suíte Santa Luzia.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).The Araguaia Belt is included within the continental collision context of the Tocantins Province, formed by amalgamation of the Amazonian and São Francisco- Congo cratons and the Paranapanema Block during the Neoproterozoic. It comprises basically an Archean to Paleoproterozoic basement, Neoproterozoic supracrustal rocks and Ediacaran/Cambrian granitic rocks. Regarding the geologic time, there are two major groups of granites related to the Araguaia Belt. The first one is Paleoproterozoic, represented by the Ipueiras Suite (2.08 Ga), the Cantão Gneiss (1.86 Ga) and the Serrote Granite (1.86 Ga), which are part of the basement today; while the another one is Ediacaran/Cambrian, represented by the Ramal do Lontra Granite (549 Ma), the Presidente Kennedy Granodiorite (539 Ma), the Barrolândia Granite (538 Ma), the Santa Luzia Granite (538 Ma) and the Lajeado Suite (550 Ma). Serrote and Santa Luzia granites, aim of this work, crop out near the Pugmil, Paraíso do Tocantins and Barrolândia cities, in the southern portion of Araguaia Belt. The Serrote Granite is composed of microcline granite, syenogranite and, to a lesser extent, monzogranite. The most common mineralogy within these rocks consists of quartz, microcline and plagioclase, with subordinated biotite and muscovite. Moreover, titanite, magnetite, allanite, zircon and apatite are accessory phases. Whole-rock geochemistry demonstrates that these magmas are metaluminous to peraluminous, possess a high-K calc-alkaline character and probably originated within a post-collisional tectonic setting. Three samples were selected for U-Pb MC-LA-ICP-MS dating in zircon, but only two samples yielded satisfying ages of 1863.1 ± 5.2 Ma and 1846.5 ± 6.5 Ma, interpreted as crystallization ages. In BSE and CL images, metamorphic rims were not identified. TDM model ages are between 2.03 and 2.17 Ga. εNd (1863 Ma) values are between -2 and 0.6. The Santa Luzia Granite comprises granodiorite, monzogranite, pegmatites and, to a lesser extent, syenogranite. These rocks are composed of quartz, microcline, plagioclase, biotite and muscovite. Accessory phases are monazite, zircon, magnetite, apatite, ilmenite and pyrite. Mineral chemistry of biotite and muscovite of these samples revealed that they have a magmatic origin and that they have not undergone mineral reequilibration. Lithogeochemistry demonstrates that these magmas are essentially peraluminous, magnesian to slightly ferroan, possess a calc-alkaline character and originated in a late-orogenic to post-orogenic tectonic setting (at the end of the Brasiliano/Pan-African Orogeny). Three samples were selected for U-Pb MC-LAICP- MS zircon and monazite dating, as well as one pegmatite sample for monazite dating. Despite abundant zircon inheritance, some zircon samples yielded ages between 532-538 Ma, while monazite samples yielded ages between 524-534 Ma, both interpreted as crystallization ages. Two ages of 512.3 ± 0.81 and 501.4 ± 1.1 Ma in monazite of pegmatite are interpreted as representatives of the final stages of the Santa Luzia Granite magmatism. TDM model ages are between 1.3 and 2.87 Ga, while εNd (538 Ma) values are between -6 and -12. Based on petrographic, geochemical, geochronological, isotopic and geological context criteria, it is suggested that Presidente Kennedy Granodiorite, Barrolândia Granite and Santa Luzia Granite are grouped in a single suite named Santa Luzia Suite

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI. Supplemental material in the ancillary file

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost