To divulge geoscientific research by means of the publication of carefully analysed, original papers concerning academic and applied themes in the various Geology areas.
Universidade de São Paulo. Instituto de Geociências
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Geologia USP. Série Científica - Revista do Instituto de Geociências, USP.
Copyright (c) 2025 Daniel Machado https://creativecommons.org/licenses/by-nc-sa/4.0
Magmatic-hydrothermal signature based on sulfur isotopes, from the Paraíba vein deposit and the disseminated Target X1, Alta Floresta Mineral Province (MT)
The Paraíba structurally-controlled gold deposit and the X1 disseminated granite-hosted gold occurrence are located at eastern segment of the Alta Floresta Mineral Province, southernmost portion of the Amazon Craton. Both are hosted by Paleoproterozoic oxidized calc-alkaline granites and porphyries, often crosscut by mafic to intermediate volcanic dykes. Such deposits exhibit wide hydrothermal alteration halo with complex pervasive and vein-type paragenetic evolution. The orebodies are dominated by pyrite with variable amounts of chalcopyrite, so far at Paraíba deposit is related to quartz + calcite rich-veins, whereas at X1 occurrence, it is disseminated in the pervasive radial muscovite + quartz alteration. The gold occurs as small inclusions into pyrite. Although the X1 occurrence and Paraíba deposit exhibit distinct ore-style, the gold-rich porphyry model has been attributed to the former, whereas ambiguities related to few geological attributes of the Paraíba have allowed debate regarding its ore-forming processes. The dentification of sulfur isotopic signature of pyrite from mineralized zones allowed us to characterize the source of sulfur and better understand genetic processes in both cases. Ergo, δ34Spirita (V-CDT) values for Paraíba deposit vary from -2.17 to +0.72‰ (n = 12), whereas for the X1 occurrence such results are in the range of -4.03 to -2.43‰ (n = 7). The results are homogeneous and similar among the deposits, indicating a single mineralizing fluid would be responsible for gold precipitation. Furthermore, the sulfur isotopic signatures are strongly correlated to the magmatic source, suggesting the development of a magmatic-hydrothermal system concerning the
Copyright (c) 2025 Lorenzzo Cassaro, Rafael Rodrigues de Assis https://creativecommons.org/licenses/by-nc-sa/4.0
Supervised learning for categorization of geological domain
The geological model needs to be updated when new drill holes are added. This requires time and knowledge of the mineral deposit, as the new samples need to be categorized according to the relevant geological properties. This study employed six supervised machine learning algorithms (naive Bayes, k-Nearest Neighbors (kNN), Support Vector Machines (SVM), decision trees, random forest, and neural networks) to perform geological interpretation of a gold deposit of the metasedimentary type, located in the east-central region of the state of Bahia, with the objective of evaluating the ability of these algorithms to accurately classify the geological domains of new samples in a database. The results indicated that the random forest and neural networks algorithms successfully reproduced the geological interpretation of the mineral deposit, as the models generated were similar to those manually created by a geologist. This great performance is supported by the accuracies and precision obtained, which were 0.87 and 0.89, respectively. Therefore, it is recommended to use these algorithms for optimizing the geological model update process. However, the naive Bayes, kNN, SVM, and decision tree algorithms failed to categorize the geological domains of the samples correctly. As a result, some regions in the models exhibited distorted geological layers and a lack of statigraphic order due to interpretation erros. This is evidenced by the low accuracies and precision obtained-0.48, 0.73, and 0.75. Therefore, these algorithms are unsuitable for this task.
Copyright (c) 2025 Marcela Martins, Marcelo Monteiro da Rocha, Camila Duelis Viana https://creativecommons.org/licenses/by-nc-sa/4.0
Rediscovering Lucky Hill: SEM-EDS insights into the composition and weathering of a Jamaican meteorite
The Lucky Hill meteorite, discovered in 1885 in Jamaica, remains one of the lesser-studied Caribbean specimens. In this study, we introduce for the first time the use of scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) to characterize a representative fragment (USNM 2889) from the Smithsonian National Museum of Natural History. Our SEM-EDS investigation reveals extensive terrestrial weathering — manifested as iron oxide/oxyhydroxide conversion, including the formation of akaganeite — and confirms the presence of key meteoritic phases such as kamacite (with 7.88 wt.% Ni) and schreibersite. These findings support its extraterrestrial origin and suggest that significant alteration has obscured primary crystalline features. The results contribute to a more detailed mineral-specific understanding of Lucky Hill’s composition and provide a basis for further investigations (e.g., via LA-ICP-MS) into the effects of environmental weathering on Caribbean meteorites.
Copyright (c) 2025 Yasmani Ceballos-Izquierdo, Gabriel Gonçalves Silva, Johanset Orihuela https://creativecommons.org/licenses/by-nc-sa/4.0
Reduction of risk in short-term resource estimation with increased noise samples
This study addresses the use of secondary samples in short-term mineral resource estimation, due to the costs associated with diamond drilling (DDH). The research investigates methods for combining data from different sampling types, which often result in distinct sample supports and reliability levels, highlighting "primary" data (diamond drill hole samples) as more reliable and "secondary" data (channel samples or drill cuttings) as less reliable. The analysis includes estimations by ordinary kriging, correcting the bias of the secondary variable, and by cokriging, comparing the results with a reference model estimated only with primary samples. The findings suggest that correcting the bias of secondary data may be an effective practice for short-term mineral resource estimates by ordinary kriging.
Copyright (c) 2025 Danilo Ribeiro dos Santos, Marcelo Monteiro da Rocha https://creativecommons.org/licenses/by-nc-sa/4.0
Interaction of magmatic and meteoric water during barite crystallization in the Seival area (Cu), epithermal deposit from the Camaquã Basin, Neoproterozoic Dom Feliciano Belt of southern Brazil
Barite is a common gangue mineral of the low-temperature in hydrothermal systems. In the Seival area, the relative chronology of minerals indicates that barite, calcite, and minor hematite are associated with the low-temperature hydrothermal stages (< 157 °C) of an epithermal mineralization from the Camaquã Basin, Neoproterozoic Dom Feliciano Belt. Previous interpretations of geochemical data have suggested that the Cu enrichment in sulfides was related to albitization and chloritization, but not determined the origins or crystallization conditions of barite. The Ba and S content and their precipitation conditions were examined, and a lower Ba content was observed in the altered plagioclase with an albite composition than in the less altered portion with an andesine-labradorite composition. In addition, and rare earth elements (REEs) analysis of barite and plagioclase suggest that elementary composition of barite in Seival area came from volcanic material (magmatic) with influence of meteoric water rather than seawater. The different REEs patterns of barite show two groups related to two magmatic sources of REEs. These different sources of S, Ba, and REEs have been interpreted as dominant alteration of local volcanogenic rocks as the pyroclastic rock and andesite lava flows or less probably lamprophyric dike.
Copyright (c) 2025 Rodrigo Winck Lopes, André Sampaio Mexias, Christophe Renac, Márcia Elisa Boscato Gomes, Eduardo Fontana, Aurélie Barats https://creativecommons.org/licenses/by-nc-sa/4.0
Radiometric signatures of plutons from ediacaran magmatism in the Rio Piranhas-Seridó Domain, Borborema Province, NE Brazil
Radiometry is a geophysical method that studies the distribution of Earth's materials based on the natural radioactivity of rocks. The interpretation of radiometric data from the Rio Piranhas-Seridó Domain, Borborema Province, in northeastern Brazil, allowed for the characterization of signatures from the Shoshonitic, High-potassium Porphyritic Calc-alkaline, High-potassium Equigranular Calc-alkaline and Calc-alkaline suites. Four plutons were analyzed: Acari, Totoró, São Rafael, and Serra da Garganta. Using data on potassium (K), equivalent thorium (eTh), and equivalent uranium (eU), coupled to ternary radiometric composition, radiometric domains were delineated within a GIS environment and subsequently classified as low, medium, and high. Interpretation maps were generated with 27 color combinations in the R-red/G-green/B-blue standard. The mineralogy of the granites influences the signatures: the presence of feldspars, and micas contributes to high K and eTh values in suites such as High-potassium Porphyritic Calc-alkaline, High-potassium Equigranular Calc-alkaline and Calc-alkaline suites. The texture of the rocks also affects the distribution of the elements.
Copyright (c) 2025 Marília Cristina Santos Souza Dias, Marcos Antonio Leite do Nascimento, Nitzschia Regina Rodrigues Domingos, Rogério Cavalcante https://creativecommons.org/licenses/by-nc-sa/4.0
Data on the production and occurrence of large diamonds of the Southern Espinhaço Range diamond province, Minas Gerais, Brazil: historical record and oral memory and its geological significance
Proclaimed as the oldest in the history of the Earth, the Diamond Province of Southern Espinhaço Range was the largest producer of diamonds on the planet for more than 100 years, since production began in 1730. The history of the discovery and record of iamond production are dispersed and discontinuous, often as a single copy in the collection of museums and libraries in Brazil and Portugal, or in technical reports held by private personal. This unprecedented recovery of the documentary record and oral memory of diamond production and the extraction of large gems within the province brought relevant data about the history of mining and diamond mining activity in time and geographic space, also contributing knowledge to the geology of the Espinhaço Range. Although the Portuguese Crown took over the production and export of diamonds from 1730 until Brazil's independence in 1822, at least 2/3 of total production was undertaken by individuals or companies subordinated to the country's colonial and republican legislation. In the measured assessment of overcoming the lack of data on smuggling and clandestinity, a gap of at least 80% of diamond production was estimated, which refers to a total production in the province of at least 24 million ct in the period from 1730 to 2024. The production of large gemstones was also significant, with a few exceeding 100 ct. The concentration of larger gemstones in Extração and São João da Chapada-Campo Sampaio districts are indicative of proximal and autochthonous sources, respectively and, in the case of the breccias in the latter district, even considering their petrography, reinforces their character as volcanic breccias of maar craters.
Southern Espinhaço Range Diamond Province
Copyright (c) 2025 Friedrich Ewald Renger, Pedro Angelo Almeida-Abreu, Soraya de Carvalho Neves, Lúcio Mauro Soares Fraga https://creativecommons.org/licenses/by-nc-sa/4.0
Proposition of a Method for Estimation of Geomorphological Ratios for Watersheds: Reduction of Uncertainties by the Method of Dispersion of Morphometric Parameters
The hydrological modeling of small and medium-sized watersheds often depends on the estimation of geomorphological ratios, which are fundamental for parameterizations of models such as the Geomorphological Instantaneous Unit Hydrograph (HUIG). However, traditional estimation methods are based on aggregate means, disregarding the natural dispersion of morphometric data, which can induce significant uncertainties. This study proposes a new method to estimate geomorphological ratios, incorporating data dispersion to regression adjustment, which provides greater physical and statistical representativeness. Fourteen river basins with different physiographic characteristics were analyzed, comparing three estimation methods: simple arithmetic mean (Method 1), regression on means aggregated by order (Method 2) and regression on dispersed data (Method 3). The results demonstrate that Method 3 reduces the uncertainty in the estimates of RL and RA, maintaining statistical robustness, especially in basins with high morphometric variability. It is concluded that the proposed method is more suitable to represent the complexity of the basins and can significantly improve the performance of hydrological models that use geomorphological ratios as input.
Copyright (c) 2025 Robison Negri, Heinz Dieter Oskar August Fill https://creativecommons.org/licenses/by-nc-sa/4.0
Geologia USP. Série Científica - Journal of the Instituto de Geociências, USP.
Apatite as petrogenetic indicator in magmatic rocks: evidence from cathodoluminescence and chemical microanalysis
Cathodoluminescence (CL) and semi-quantitative spot chemical analysis (SEM-EDS) of magmatic apatite show distinct patterns according to their tectonic provenance. In this study, apatite crystals from calc-alkaline granitoids of I-type (Cunhaporanga Granitic Complex - PR and Valsungana Suite - SC) and S-type (G2 Supersuite - MG), as well as alkaline A-type granite (Serra Branca Granite - GO) and alkaline rocks (Tunas Syenite, José Fernandes Gabbro and Jacupiranga Carbonatite, in São Paulo), are examined. Under optical-CL, the crystals show a high-intensity yellowish-green luminescence, whose activator centers are Mn2+ and Ce3+, with emission peaks at 570 nm and 360 nm, respectively. Lower luminescence contributions from other REEs are observed in the CL spectra, along with distinct CL emissions from the core to the rim of the crystals, as a result of variations in their internal composition. When comparing CL emissions across all samples, the activation by Ce3+ is more intense in alkaline rocks compared to granitic ones, possibly due to its higher activity in alkaline magma. The chemical analysis (SEM-EDS) of apatite crystals from the alkaline granite and syenite shows the lowest CaO content, which increases in I-type granite and in the gabbro, and reach the highest values in S-type granite and in the carbonatite. Analysis of variance of the data allows the classification into similar groups, in terms of CaO content, the following clusters are related: i) calc-alkaline granites (I and S-types) and gabbro; ii) syenite and alkaline granite (A-type); and the carbonatite. As for Na2O content, the clustering pattern is: i) I-type granite (Cunhaporanga) and S-type granite; ii) I-type granite (Valsungana), A-type granite, and carbonatite; iii) syenite and gabbro.
Copyright (c) 2025 Alberto Caixeta Botelho, Cristina Valle Pinto-Coelho https://creativecommons.org/licenses/by-nc-sa/4.0
Evaluation of the potential of contamination of groundwater by pesticides on the Ibiapaba Plateau – CE
Industrial agriculture has contributed large loads of pollutants to the water, including pesticides, being one of its main sources of pollution. In the world, most of the water used (60% to 70%) is underground and it has also been suffering from the impacts of pollutants such as pesticides. The degradation of water quality has impacts on biodiversity, people and their health. Brazil is the largest consumer of pesticides in the world. Thus, one way to estimate risks are pesticide leaching prediction models, as they can provide an understanding of problems, identifying relationships (cause and effect), predictions and giving future suggestions. The general objective of this research is to estimate the potential risk of pollution of groundwater in the Ibiapaba Plateau caused by the active ingredients (a.i.) of pesticides most used in the city of São Benedito, using the Groundwater Ubiquity Score (GUS) and LEACH models. The results obtained indicated that five active ingredients (iprodione, methomyl, boscalid, azoxystrobin, dimethoate) are in the risk transition zone while three others (thiophanate-methyl, thiamethoxam and chlorantraniliprole) can be considered within the leaching zone. It was also concluded that there may be risk vulnerability to contamination by pesticides in the Ibiapaba region, especially in regions that have Dystrophic Red Yellow Oxisols and Quartzarene Neosols. As water is part of sustainable development concerns, there needs to be a ban or progressive reduction in the use of pesticides in the region, as well as measurement or verification of water quality and quantity parameters in Ibiapaba, on a continuous or periodic basis.
Copyright (c) 2025 Vanessa Gomes Pedroza, Rivelino Martins Cavalcante, Michael Barbosa Viana https://creativecommons.org/licenses/by-nc-sa/4.0
Influence of the barra fault system on the occurrence of mass movements in the metropolitan region of Salvador, Bahia
Mass movements are recurring and concerning events in Salvador, located in Northeastern Brazil, especially in densely populated urban areas with precarious infrastructure. The city, whose topography is influenced by transverse and longitudinal fault systems, including the Barra Fault System (BFS), faces challenges due to disorganized population growth and climatic conditions. These characteristics result in frequent mass movements, exposing the population and their homes to hazard. Although previous studies have contributed to the understanding of the city's structure, geology, and geomorphology, there is still a specific gap regarding the direct influence of the BFS on the generation and control of mass movements on slopes. This study analyzed the geometric and kinematic characteristics of the BFS, focusing on identifying discontinuities in natural slopes and instability mechanisms, such as planar sliding, wedge sliding, and toppling. The method included the analysis of structural lineaments using Schmidt-Lambert stereographic projection and a survey of morphostructural data to identify potentially unstable areas. The results highlighted that the BFS influences the orientation of critical discontinuities, with greater susceptibility to planar and wedge slides, especially on slopes with intersections of structural families compatible with the fault's direction. A correlation was also observed between areas with a high density of lineaments and a higher incidence of reported landslides. On the other hand, the toppling mechanism did not present critical points of instability in the analyzed scenarios. This study provides technical support for the management of urban and housing infrastructure, in addition to contributing to the implementation of public policies aimed at the safety of the most vulnerable populations in Salvador.
Copyright (c) 2025 Isaias Leal dos Santos Fernandes, Luiz César Corrêa-Gomes, João Paulo Hora Carneiro https://creativecommons.org/licenses/by-nc-sa/4.0
3D modelling and structural restoration of the deformation in deposits of the Taubaté Basin (Continental Rift of Southeastern Brazil)
The structural complexity generated by the superposition of tectonic events hinders the reconstruction of the history of deformed geological successions, making it challenging to identify deformational evolution. To address this issue, technological advances such as 3D geological modelling and structural restoration have proven to be effective tools in integrating georeferenced data, RPAS-obtained images, and field information. This study was conducted in the Taubaté Basin, part of the Continental Rift of Southeastern Brazil, a Paleogene geotectonic feature marked by multiple superimposed tectonic events. Two outcrops composed of deposits from the Pindamonhangaba Formation (Miocene-Pliocene), overlain by Neogene and Quaternary sediments, were selected, in which structural and geometric patterns related to transcurrent and extensional stresses were identified. From the integration of georeferenced aerial images with structural and stratigraphic data, a high-resolution 3D geological model was generated. Structural restoration allowed for a regression to the less deformed configuration, highlicomputaghting the superposition of tectonic events. The results indicate that the main geometries are associated with most recent extensional stresses, while previous strike-slip deformation is recorded in a negative flower structure, faults exhibiting directional striations, and significant thickness variations in layers displaced by some faults. The geological model produced contributes to understanding the tectonic evolution of the basin and will serve as a foundation for future analyses.
Copyright (c) 2025 Karina Assumpção da Costa Nóbrega, Aline Theophilo Silva, Claudio Limeira Mello https://creativecommons.org/licenses/by-nc-sa/4.0
Geochronology and considerations about the metamorphic evolution of the São João Marcos Iron Formation (Criogenian) and associated metamafic and metaultramafic rocks, interference zone between Brasília e Ribeira orogens
The study area is inserted in the context of the interference zone between the Brasília and Ribeira orogens. Based in microscopic evidence, four metamorphic stages were identified in the São João Marcos Iron Formation (SJ MIF) and associated metamafic and metaultramafic rocks. The first (E1), characterized by pyroxene relicts, marks the metamorphid peak in granulite facies. The second (E2) registers transition from granulite to amphibolite facies conditions, with the development of amphiboles (mainly hornblende) and plagioclase. The final moments of this stage is marked by the development of garnet coronas between hornblende and plagioclase, in a IBC (isobaric cooling) path. The third (E3) stage is defined by symplectites developed in a ITD (isothermal decompression) path, possibly related to the orogenic collapse. Finally, cummingtonite-grunerite appears marking the fourth (E4) stage, suggesting higher temperatures in relation to the previous stage. Regarding the geochronology, the metamafic and metaultramafic rocks present mostly archean and paleoproterozoic provenance, with subordinate neoproterozoic grains. 641,5 ± 2,9 Ma was calculated as crystallization, as well as 3 groups of metamorphic ages: 622 – 613 Ma; 599 – 598 Ma and 587 – 586 Ma. The associated metassedimentary rocks present archean to neoproterozoic provenance ages, with maximun depositional age in 686 Ma and 3 groups of metamorfic ages: 647 – 640 Ma, 609 – 605 Ma and 599 Ma. The stage E1 is related to a metamorphism between 647 – 640 Ma, contemporary to the crystallization of the metamafic and metaultramafic rocks; E2 and E3 are contemporary to metamorfic events between 622 – 598 Ma, which are related to Southern Brasília belt evolution.
Copyright (c) 2025 Ariane Felix Coelho Azevedo, Rodrigo Peternel Machado Nunes, Thadeu Henrique Silva Hoffmann, Mauro Cesar Geraldes, Beatriz Paschoal Duarte, Natália Cota de Freitas https://creativecommons.org/licenses/by-nc-sa/4.0
Osteological profile of new Mesosauridae from the Irati Formation (Paraná Basin)
Mesosaurids represent one of the oldest known groups of semi-aquatic amniotes. In Brazil, they occur in the 275 Ma Irati Formation (Paraná Basin), where three monotypic genera (Mesosaurus, Stereosternum, and Brazilosaurus) were originally described. However, recent studies propose synonymizing these under Mesosaurus Gervais, 1865. In this context, we provide osteological data based on 30 samples from the LABPALEO/UFPR and IGc/USP collections, constructing detailed profiles through morphometric analysis while accounting for ontogeny and taphonomy. While our data clarify key anatomical features, preservation artifacts in many specimens introduce ambiguity when applying traditional taxonomic characters. Comparative analysis with historical descriptions reveals both consistencies and contradictions, highlighting the need for revised diagnostic criteria in mesosaurid systematics.
Copyright (c) 2025 https://creativecommons.org/licenses/by-nc-sa/4.0
The transformation of by-products from emerald mining into soil remineralizers: the case study of the Local Production Cluster in Monte Santo/TO
Implementing Local Productive Arrangements (LPAs) based on mining and agriculture signals a new form of economic and productive synergy between two sectors that are of great importance to the Brazilian economy. The municipality of Monte Santo do Tocantins is considered an important mineral province, particularly rich in emeralds, currently exploited by small-scale miners organized under the permission for independent mining (Permissão de Lavra Garimpeira). The rocks associated with the genesis of emeralds present a great mineralogical and lithological diversity. Throughout the process of exploiting this gem, a significant amount of rock waste is generated, which can be converted into by-products, as they have characteristics that fit into the category of soil remineralizer (REM), as provided for in Law 12,890/2013 and IN 05/2016-MAPA.These products provide direct and indirect benefits to the soil and the region. The objective of this article is to evaluate the potential of the material discarded in the emerald mining process to verify its possible classification as a REM. For this purpose, samples of rocks of interest were collected in the region of the garimpos and mineralogical and chemical analyzes were performed. The results indicated that most of the analyzed samples meet the requirements established by Brazilian legislation regarding the guarantees and conditions related to this type of input. In addition, these results suggest that the strengthening of an LPA based on mining and agriculture in the region can function as a model for other localities, demonstrating the possibility of reconciling economic development, environmental preservation and integration of interests through the circular economy.
Copyright (c) 2025 Suzi Huff Theodoro, Viviane Souza Oliveira, Sanclever Freire Peixoto, Valdielly Larisse Silva, Nayara Moreira de Mesquita, Luis Carlos Nascimento, Fernanda de Paula Medeiros, Caroline Dourado Lima, Luiza Coimbra de Oliveira https://creativecommons.org/licenses/by-nc-sa/4.0
Occurrences of sedimentary phosphate in phanerozoic covers in the Arraias region - TO, west edge of the São Francisco Basin, Brazil
The region of Arraias (TO) and Campos Belos (GO) is characterized by the presence of phosphorites and phosphate siltstones interdigitated with siltstones in the basal portion of the Sete Lagoas Formation, belonging to the Bambuí Group. In the upper Phanerozoic strata, occurs partially lithified polymictic conglomerates containing variable phosphate contents, likely due to the presence of reworked clasts of phosphatic rocks derived from underlying units. This paper describes the occurrence of isolated strata of Phanerozoic sediments containing polymictic conglomerate and unconsolidated covers, which are juxtaposed to the pelitic carbonate succession of the Sete Lagoas Formation on the western edge of the São Francisco Basin (SFB). The upper lithotypes suggest a braided fluvial depositional system, similar to the Cretaceous deposits of the Urucuia Group. Field observations, semi-detailed mapping, geological and the integration of data allowed the identification of phosphatic siltstone clasts within the polymictic conglomerate, with P2O5 concentrations ranging from <1.0% to 20%. The new geological data will support future exploratory studies on phosphate deposits in the area and highlight the occurrence of phanerozoic layers with erratic phosphate contents.
Copyright (c) 2025 Alex Joaquim Choupina Andrade Silva, João Renato de Luca Rosa Franco, Juliana Okubo, Leonardo Azevedo Sá Alkmin https://creativecommons.org/licenses/by-nc-sa/4.0
Marine microplankton responses during the Cretaceous Oceanic Anoxic Events (OAEs)
Microfossils are essential components of sedimentary rocks deposited during the Cretaceous Period, providing insights to characterize Oceanic Anoxic Events (OAEs). This study aims to identify and systematize the responses of marine microplankton to OAEs during the Cretaceous based on published literature. Marine microfossils respond to OAEs through evolutionary events, preservation, and variations in abundance and diversity of the assemblages. Additionally, they export significant concentrations of chemical elements to the seafloor, impacting the global climate. Changes in the orbital cycles and large-scale paleogeographic and volcanic events are considered the main causes that promoted significant changes in Mesozoic ecosystems, resulting in the geological processes that characterize OAEs. The analysis of eight Cretaceous OAEs enables the characterization of the geochemical signals and the responses of marine microplankton to each event. Marine microfossils, especially calcareous nannofossils, radiolarians, and foraminifers, play a crucial role in the planet's biogeochemical cycles, and their evolution is closely linked to the OAEs. Further studies using material collected from the South Atlantic Ocean are necessary to better understand the impacts of OAEs on the evolution of marine biota.
Copyright (c) 2025 Mauro Daniel Rodrigues Bruno Rodrigues Bruno, Edna De Jesus Francisco Tungo, Fernanda Luft-Souza, Victória Herder Sander, Gerson Fauth https://creativecommons.org/licenses/by-nc-sa/4.0
Geotechnical evaluation and kinematic analysis of the Mascate's Waterfall as subsidy for ecotourism in Coromandel, Minas Gerais
This paper presents a geological and geotechnical evaluation combined with a kinematic analysis of Mascate Waterfall, located in the Triângulo Mineiro and Alto Paranaíba mesoregion. It also explores potential implications for regional ecotourism. The rock massif is composed exclusively of quartzite, characterized by incipient foliation and varying degrees of weathering. The quartzite beds exhibit a dip direction of 210°, with dips ranging from 16° to 54° to SW. The waterfall slope is oriented at 045° with an average dip of 75° to NE. The Rock Quality Designation (RQD) index classifies the rock mass as “Regular”, while the Rock Mass Rating (RMR) designates it as Class III (“Reasonable”). Kinematic analyses indicate potential failure types with the following probabilities: planar (9%), wedge (29%), direct toppling (26%), oblique toppling (1%), and flexural toppling (3%). Planar failures are predominantly controlled by NW-SE-oriented fractures with subvertical dips. Direct and oblique toppling failures occur along the metamorphic foliation. The calculated safety factor of 1.30 suggests stable conditions for the waterfall slope regarding different types of ruptures. However, heavy rainfall between November to March can lead to greater slope instability, increasing the likelihood of rupture. The base of the waterfall is surrounded by numerous fallen boulders, suggesting significant gravitational mass movements. Based on the geological, geotechnical, and kinematic analysis of Cachoeira do Mascate, simple actions are proposed to reduce potential geological risks.
Copyright (c) 2025 Samuel Fonseca Oliveira, Luciano Alessandretti, José Carlos Paranhos https://creativecommons.org/licenses/by-nc-sa/4.0
Genesis of the beachrocks from Trindade Island, Brazil
Beachrocks are sedimentary rocks, formed in the intertidal region from the precipitation of calcium carbonate cements, in the form of magnesium calcite and/or aragonite. Due to their genesis on beach faces, beachrocks are used as tools for coastal research. In Trindade Island (20º30'S and 29º20'W), beachrock occur on the southeast, on Tartarugas and Andrada beaches, in three-dimensional plates with plane-parallel lamination and wavy marks, with a gentle dip of ~13° towards the sea. The studied beachrocks are medium to coarse-grained sandstones, with 60 to 70% of the framework composed of bioclasts and terrigenous grains poorly sorted. The cements make up 30 to 40% of the sample, covering grains, in textures of micritic envelopes of magnesium calcite, isopach fringes of acicular aragonite and pseudo-pellets of magnesium calcite. In addition to cements, chlorite crystals and rosettes were observed in association with altered terrigenous grains. The formation of beachrocks occurred in the intertidal zones, in an active marine-phreatic environment, where marine water has a direct influence on cementation due to spreading and wave swash. In the beachrocks studied, the following diagenetic phases were identified: 1) mixture of magnesium calcite in the form of micritic envelopes by organomineralization; 2) precipitation of acicular aragonite fringes by CO2 degassing and/or evaporation; 3) dissolution of terrigenous grains and generation of a favourable microenvironment for microbiological activity; 4) precipitation and formation of magnesium calcite pseudo-pellets; and 5) precipitation of chlorite. Although the occurrence of syngenetic chlorite is not common in sediments and sedimentary rocks, its identification in the beach sandstones of Trindade Island is a very interesting record. The occurrence of biofilm on the rocks and associated with the cements suggests that the formation of beachrocks occurred as a product of physical-chemical processes, as well as by microbiological activity.
Copyright (c) 2025 Erika Kiemo Pfau Santos, Luiz Alberto Fernandes, Rodolfo José Angulo http://creativecommons.org/licenses/by-nc-sa/4.0
Geophysical diagnostics using electrical tomography to support waste landfill implementation
The correct disposal of solid waste is widely discussed in Brazil and in the world, but there is a great difficulty for its application, especially in small cities in the country. In this context, this work aimed to use the geological Resistivity Method as a tool in the geological characterization of an area intended for a waste landfill in Jaciara, state of Mato Grosso. The results obtained using the ERT technique allowed observing the variations of the resistivity values along the 2D profiles and their relationship with natural and anomalous values. Resistivity values less them 100 Ω.m indicate the presence of permeable zones, while values above 537 Ω.m indicate more resistive regions, with unsaturated sandy soils and the presence of water level varies between 5 to 30 m deep. The analysis of the resistivity variation along the sections, the geological parameters defined by the Brazilian norms and the direct tests carried out in the area, allowed classifying it as favorable for the installation of the waste landfill. The method proved to be effective applied to engineering problems, being used for litho-stratigraphic definition and variations in moisture content, ainly in large areas, with a reduction in the cost of applying direct methods, especially in municipalities with scarce resources.
Copyright (c) 2024 Isabella Nantes Nishimura, Sérgio Junior da Silva Fachin http://creativecommons.org/licenses/by-nc-sa/4.0
Copyright (c) 2024 Daniel Machado http://creativecommons.org/licenses/by-nc-sa/4.0
Metallogenic characterization of the Aguinaldo structurally-controlled Epithermal gold occurrence, Alta Floresta Gold Province (Brazil)
In the eastern-southeast sector of Alta Floresta Gold Province (Amazon Craton), the 1.78 – 1.77 Ga calc-alkaline magmatism is interpreted as answerable for ore-forming processes responsible for its disseminated, vein-type, and filonar gold occurrences hosted in 2.05 – 1.77 Ga units. The Aguinaldo structurally-controlled gold occurrence exhibits ore zones hosted in 0.5 – 1.5m thick quartz + sulfide ± carbonate veins crosscutting the porphyroblastic mylonite orthogneiss, with SHRIMP U-Pb-zircon concordia crystallization age of 1,984.9 ± 5.2 Ma. Distal to ore zones are observed high temperature, intensive, and pervasive (1) albite-rich alteration, followed by (2) K-Feldspar alteration, telescoped by lower temperature pervasive alterations: (3) sericite-muscovite alteration, (4) silicification and silica infills; (5) carbonate alteration, (6) chlorite alteration, and (7) late veinlet-type quartz. The silica injection represents one of the major hydrothermal stages due to generating barren quartz veins and quartz ± carbonate vein with chalcopyrite + pyrite ± gold ± silver ± sphalerite ± galena ± bismuthinite veins. Although the veins are partially deformed, local comb-quartz texture remains preserved. Gold occurs as small inclusions or in contact with pyrite and chalcopyrite, and subordinately, in sphalerite. Electron microprobe analysis indicates chlorite of brunsvigite composition formed between 242° and 420° C, whereas white mica shows low phengite contents. The polymetallic veins signature, the high chalcopyrite contents with galena and sphalerite inclusions, the comb-texture quartz veins, together with the hydrothermal alteration sequence, suggest low to moderate temperature, neutral to slightly alkaline pH, and moderate ƒO2 and ƒS2 conditions, possibly triggered by boiling process. This scenario indicates intermediate-sulfidation epithermal ore-forming processes as the responsible for the genesis of Aguinaldo gold occurrence.
Copyright (c) 2024 Rômulo Bortolozzo, Rafael Rodrigues de Assis, Lorenzzo Cassaro, Lays Helmer Mengal http://creativecommons.org/licenses/by-nc-sa/4.0
Gaúcha Geodiversity Path: a long-distance trail integrating geo-bio-sociocultural aspects
Long-distance trails are tools for recreation, preservation of the environment and generation of employment and sustainable income, in the form of paths followed in a sporting/tourist way, mainly on foot or bicycle, for at least one day of activity, connecting regions with notable environmental and landscape importance. In the context of the southern half of RS, some sustainable development initiatives have sought to stimulate the economy. One of the most recent was the recognition, by UNESCO, of the Caçapava Geopark, given the enormous and unique geodiversity of the region. This same characteristic motivated the preparation of this work, combining sport and tourism with geodiversity, making use of geosystemic concepts, which use bio-sociodiversity to provide an integration of the environment. The objective of this work is to propose the creation and implementation of the Gaúcha Geodiversity Path, which runs 500 km in 6 municipalities, whose vocation is the geodiversity of the region. Maps were created using remote sensing and field work was carried out, which improved the route, through joint construction with the community that lives along the route. A description of the geological, biological and social aspects is presented, which provided the distinction between 3 sectors of the path. 43 points were identified to provide logistical support and educational and environmental interest along the route. It is expected that the Gaúcha Geodiversity Path will join other sustainable development strategies in the region, bring better socioeconomic conditions and contribute to the preservation of the Pampa Biome.
Copyright (c) 2024 Ana Paula Souza Corrêa, André Weissheimer de Borba, Vinicius Matté http://creativecommons.org/licenses/by-nc-sa/4.0
Characterization of volumetric and morphological changes and the influence of anthropization on an embayed beach, Praia de Guaratuba - PR
Guaratuba beach, with dense urban occupation in the state of Paraná coast (Brazil), is an embayed beach. The beach arch extents up to. 2,440 m limited by Morro do Cristo, southward, and Morro de Caieiras, northward. Seasonal and interannual migration dynamics of sandbanks are responsible for sediment exchanges. Walls, sidewalks, and avenues, when installed over the naturally dynamic area of the beach, are subject to periodic destruction by wave action. This study aimed to identify and quantify the variations in sediments volume of Guaratuba beach. Seasonal monitoring of the beach volume was carried over 14 plan-altimetric profiles along eight campaigns, from 2012 to 2018. The sediments balance showed that the dynamics of Guaratuba beach include processes such as redirection of waves due to the presence of Morro do Cristo, and the sediments bypass, carried by the longshore current, which contours the promontory feeding the embayed beach. A decrease in sediment volumes was noticed in the emerged portion of the beach. Beach volumes and sandbanks mobility are more intense in the southern portion of the beach arch, related to wave diffraction and sediment bypass. During high wave energy events, when storm surges occur, the waves hit the walls, made for protect the sidewalk and the street, causing damage. The stabilization of the coastline by artificial means, such as the wall, limit the action of natural processes and results in the destruction of urban infrastructures.
Copyright (c) 2024 Egon Abraão de Paula Ramos, Rodolfo José Angulo, Luiz Henrique Sielski http://creativecommons.org/licenses/by-nc-sa/4.0