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Made available in DSpace on 2020-12-11T09:37:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-03-15 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Australian Research Council - ARC The Jacobina Basin has a well-preserved sedimentary record, including continental and marine deposits, and hosts Au-(U)Py mineralization in metaconglomerate beds similar to the Witwatersrand gold province. Based on petrographic observations, in situ trace-elements, and multiple sulfur isotope analyses (S-32, S-33, S-34, and S-36) on pyrite from alluvial and marine facies, several types of pyrite were recognized. The pyrite grains identified in the alluvial metaconglomerates resemble those found in several pre-GOE gold-bearing metaconglomerates, including detrital and epigenetic varieties. Detrital inclusion-bearing pyrite is enriched in several redox-sensitive trace-metals as well as Au, which indicate an association with carbonaceous shales. On the other hand, the sources of detrital massive pyrite are more variable and include igneous, metamorphic, and hydrothermal sources from the Paleoarchean hinterland of Jacobina Basin. Epigenetic pyrite in metaconglomerates formed during metamorphism by the recrystallization of detrital pyrite with negligible contributions from external hydrothermal fluids to the basin. Diagenetic and epigenetic pyrite are found in marine lithologies. In a metapelite sample, the pyrite grains formed near the sediment-water column interface, with S sourced from the photolytic sulfate (SO42-, D Delta S-33 < 0) dissolved in the water column. A quartzite sample, in turn, has detrital pyrite grains that were likely reworked from continental deposits, as well as pyrite formed by the assimilation of elemental sulfur (S-8, Delta S-33 > 0) that accumulated in sediment pore water during diagenesis. Significantly, the pyrite associated with terrestrial metasediments shows a wide range in delta S-34 values but quite restricted ranges in Delta S-33 and Delta S-36 values, whereas pyrite associated with the marine metasedimentary rocks exhibits limited delta S-34 values but has a wide range in Delta S-33 values and correlated Delta S-36 values close to the Archean array. These data suggest distinct preservation routes for MIF-S from atmospheric SO42- and S-8 in terrestrial and marine environments. Conditions on the terrestrial surface resulted in re-equilibration of distinct S sources, diminishing the amplitude of the Archean atmospheric signal. In contrast, SO42- dissolved in shallow marine settings while S-8 settled to the floor, favoring the preservation of MIF-S isotopic signatures. Such processes may also explain the apparent differences in interpretations of atmospheric conditions derived from uncharacterized pyrites from Archean sources. Our data suggest that the Earth's atmosphere remained anoxic, and terrestrial conditions were such as to allow the syngenetic accumulation of gold, as recently proposed for the Witwatersrand gold deposits. (C) 2020 Elsevier Ltd. All rights reserved. Univ Fed Campina Grande, Unidade Acad Mineracao & Geol, Campina Grande, Paraiba, Brazil Univ Brasilia, Programa Posgrad Geol, Brasilia, DF, Brazil Univ Vale Rio dos Sinos, Programa Posgrad Geol, Sao Leopoldo, Brazil Australian Natl Univ, Res Sch Earth Sci, Canberra, ACT 2601, Australia Univ Fed Sao Carlos, Dept Fis Quim & Matemat, Sorocaba, Brazil Univ Estadual Paulista, Dept Fis, Presidente Prudente, Brazil Univ Estadual Paulista, Dept Fis, Presidente Prudente, Brazil CNPq: 163459/2013-4 CNPq: 202267/2014-8 Australian Research Council - ARC: DP140103393

Made available in DSpace on 2021-06-25T15:01:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-04-01 Universidade Federal de Santa Catarina Micropaleontology is crucial branch of Earth Sciences, with a pivotal role in the success of the oil and gas industry over the decades. This sector of paleontology is based on the taxonomical description of microfossils, which encompass fossils with size variation from 0.001 mm to 1 m. Normally these microorganisms have a high rate on preservation, thus they are widely accepted as reliable evidence to infer about paleodepositional settings and paleoclimate change. Furthermore, microfossils are critical to understanding the evolution through time, being many of them recognized as index fossil and providing useful biozones to correlation. Since 1950, microfossils have been taxonomically described mainly by stereomicroscopes. However, as the technology progress, traditional ways to study these organisms are challenged and improved by nondestructive three-dimensional imaging techniques, as X-ray tomographic microscopy (SRXTM), three-dimensional X-ray microscopy (3DXRM), the X-ray computed microtomography (microCT) and X-ray computed nanotomography (nanoCT). Recently, one of the most compelling research areas in micropaleontology is the desire to automatize and enhance the details of systematic classification. Thereby, an increasing number of researches have applied the high-resolution X-ray analysis aiming to improve the morphological, taxonomic and taphonomic examination. Most of them have detailed the enhancement provided by the technique when compared with the standard microscopes, and raised questions about the traditional characters used on the microfossil systematic taxonomy. Nevertheless, even with the surpassing detail on microfossil characterization, the application of microCT has been hampered by the costs and sometimes by the needs of specific computer skill. Thus, this research has evaluated the use of microCT as the technique to classify a random bulk of microfossil (comprising foraminifers, ostracods, radiolarians, gastropods and echinoderms) with no further software treatment. No standard microscope analysis was performed. Despite chemical composition of microfossils, most of the specimens morphology, especially internal structures, have been easily acquired and analyzed. 96% of the microfossils of the dataset were identified at least on genus level. Irrespective of the deepness of detail, when considering the overall taxonomic identification, the microCT seems to be effective as the standard microscope. Nonetheless, when problematic specimens are evaluated, the microCT seems to be a more reliable and practical tool than other methods as Scanning Electron Microscopy. Thus, the technique can be used solo or as a complementary method to the stereomicroscope. Additionally, the high-resolution has the potential to lead to the expected automatized & nbsp;micropaleontology, since they can provide numerous images in several planes. This may create a strong database necessary to machine learning and computer identification. Univ Fed Santa Catarina, Dept Mech Engn, Lab Meios Porosos & Propriedades Termofis LMPT, BR-88040535 Florianopolis, SC, Brazil Univ Fed Pernambuco, Dept Geol, Lab Micropaleontol Aplicada LMA, BR-50740540 Recife, PE, Brazil Univ Vale Rio dos Sinos, Inst Tecnol Micropaleontol, Itt Fossil, Sao Leopoldo, RS, Brazil Univ Vale Rio dos Sinos, Geol Grad Program, BR-93022750 Sao Leopoldo, RS, Brazil Univ Estadual Paulista, Fac Ciencias Bauru, Dept Ciencias Biol, Ave Engenheiro Luiz Edmundo Carrijo Coube, BR-17033360 Bauru, SP, Brazil Univ Fed Santa Catarina, Dept Geol, Lab Geoquim LABGEOQ, Rua Engn Agron Andrei Cristian Ferreira S-N, BR-88040535 Florianopolis, SC, Brazil Univ Estadual Paulista, Fac Ciencias Bauru, Dept Ciencias Biol, Ave Engenheiro Luiz Edmundo Carrijo Coube, BR-17033360 Bauru, SP, Brazil

Made available in DSpace on 2020-12-11T22:20:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01. Added 1 bitstream(s) on 2021-07-15T15:25:17Z : No. of bitstreams: 1 S2317-48892020000300303.pdf: 24097805 bytes, checksum: aea1d3b856436b53998a96b5c7571dc7 (MD5) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fracturing analysis of low-permeability rocks as reservoir analogs have increased in recent years. The main mechanism involved in the development of secondary porosity in low-permeability, fine-grained limestones of the Irati Formation is fracturing. In these rocks, oil accumulates along fracture planes, vuggy porosity, microfractures, breccias, as well as bedding discontinuities. Joints represent the central element for oil migration and the connection between accumulation sites. Joints are unevenly distributed across the succession of rock types, where carbonate rocks have a much denser array of joints than shales and siltstones. From a mechanical stratigraphy point of view, limestones have a brittle behavior and constitute mechanical units. Ductile shale and siltstone are mechanical interfaces capable of blocking joint propagation. Joints running NW-SE are more effective in trespassing the mechanical interface and are, therefore, more persistent. Joints running NE-SW are less persistent because the ductile behavior of the first two shale beds above the limestone blocks their propagation. The spatial arrangement of regional NW-SE and NE-SW joints promoted reservoir connection, allowing oil migration and accumulation. The joints and oil migration (at least three phases) developed as a consequence of the Gondwana Breakup and are also associated with local pressure gradients. Univ Estadual Paulista, Rio Claro, SP, Brazil Univ Vale Rio dos Sinos, Sao Leopoldo, RS, Brazil Univ Estadual Paulista, Rio Claro, SP, Brazil FAPESP: 2013/19878-6 CNPq: 311204/2017-1