Brazilian Journal of Geology最新文献

{"title":"Origin of the reduced, amethyst-mineralized lower tier of the Cordillera Flow, southern Paraná Volcanic Province","authors":"Léo Afrâneo Hartmann, Leonardo Cardoso Renner","doi":"10.1590/2317-4889202520250007","DOIUrl":"https://doi.org/10.1590/2317-4889202520250007","url":null,"abstract":"Abstract The structure of two superposed layers within a redox-altered basaltic flow is restricted to the Paraná Volcanic Province among large igneous provinces. World-class amethyst-geode and agate-geode deposits occur in reduced Tier 1 of the Cordillera Flow (> 100 km long). Satellite and drone-sourced imagery, several field surveys, and 11 new geochemical analyses were used in this study. The lower Tier 1 (10 m thick) consists of massive rocks without cooling joints, whereas the barren Tier 2 is massive with colonnade. The flow is identified from the stratigraphy and chemical composition (e.g., 1.3 wt.% TiO2). The presence of poikilitic microphenocrysts of magnetite (mostly plagioclase inclusions) is a distinctive feature. Tier 2 rocks are chemically similar to the original lava; Tier 1 displays a decrease in SiO2 and K2O contents and an increase in Fe2O3T. Reducing and acidic hot water formed amethyst and agate deposits in Tier 1. Curved shapes (erosional remnants with agate) were formed by silicification of the lower portion of the flow. The interaction of the Guarani Paleoaquifer with the lava flow formed the two layers: the geodes and the curved portions. Other provinces may have similar features where hot aquifer water was available below the basalt.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.scielo.br/j/bjgeo/a/mMQ3WJHyNcyMDV44SMLPBqM/?lang=en&format=pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147882882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Integrated hydrothermal evolution of a Botucatu paleodune and a blanketing lava flow from the Serra Geral Group, Uruguaiana","authors":"Léo Afrâneo Hartmann, Felipe Padilha Leitzke, Cassiana Roberta Lizzoni Michelin, Melissa Johner, Cristiano Lana","doi":"10.1590/2317-4889202420240018","DOIUrl":"https://doi.org/10.1590/2317-4889202420240018","url":null,"abstract":"Abstract The integrated hydrothermal evolution of the large Santa Otília Paleodune from the Botucatu paleoerg and the cover Catalán Flow from the Serra Geral Group is here evaluated in Uruguaiana, southern Paraná Basin. Methods included satellite images, field surveying, petrography, and U-Pb geochronology of detrital and volcanic zircon. The tops of the compound linear-barchan paleodunes are exposed in the topographic highs. Rhombi and bowls at the top of the silicified sandstone units are significant, as is the poor preservation of eolian layering. The fishbone-shaped dune tops are surrounded by the lavas. The oxidized top of the flow (upper Tier 2) overlies the reduced base (Tier 1), which consists of exposed, massive rocks in creek beds that are light gray-colored and contain small (10 cm) agate geodes and numerous silicified sandstone dikes. The youngest dated zircon grains from the sandstone are 225–300 Ma old (one 175 Ma age), and the main older age peaks are 450–600 Ma (predominant), 900–975 Ma, 1800–1900 Ma, and 2500 Ma; few Archean 2.5 Ga ages. The strongly altered volcanic zircon preserved in the reddened Catalán Flow yields a concordia-intercept age of 137.3 ±7.6 Ma. Complex processes are thus constrained in the evolution of the Botucatu Formation and the first Serra Geral lava flow.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147922695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Calcareous nannofossils, biostratigraphy, and paleobiogeography of the Aptian/Albian Romualdo Formation in the Araripe Basin, North-Eastern Brazil","authors":"Flávia A.P. Lemos, Yumi Asakura, Rogério Loureiro Antunes, Rilda C. Araripe, L. Prado, Maria Emília Travassos Rios Tomé, D. Oliveira, L. R. Nascimento, Christiano Ng, A. Barreto","doi":"10.1590/2317-4889202320220054","DOIUrl":"https://doi.org/10.1590/2317-4889202320220054","url":null,"abstract":"Abstract The objectives of this study were the biostratigraphic and paleobiogeographic interpretations of the calcareous nannofossil records of the Romualdo Formation (Aptian-Albian) in the south-central portion of the Araripe Basin. The methods used to process the samples were decanting, smear slide, centrifugation, and ultra-thin section confection. The taxonomic and biostratigraphic interpretations were carried out through qualitative and quantitative investigations. A total of 11 genera and 17 species of calcareous nannofossils, namely, Biscutum constans, Biscutum sp., Braarudosphaera africana, Braarudosphaera sp., Calculites sp., Discorhabdus ignotus, Hayesites albiensis, Hayesites sp., Nannoconus bucheri, Nannoconus sp., Retecapsa surirella, Rhagodiscus sp., Thoracosphaera sp., Watznaueria barnesiae, Watznaueria sp., Zeughrabdotus erectus, and Zeughrabdotus noeliae were identified. The integrated analysis of three outcrops suggests two distinct marine phases: the first in the Aptian, recognized in two outcrops, and during the Albian age. The genera Hayesites and Nannoconus suggest a strong Tethyan affinity. Differently, other calcareous nannofossils such as Watznaueria, Thoracosphaera, and Braarudosphaera recorded here are considered more resistant, cosmopolitan, and/or opportunistic species. Biscutum and Zeughrabdotus are sensitive calcareous nannofossils because they are more susceptible to dissolution and cannot be surely used to define this paleobiogeography and biostratigraphic range.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"60 3","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72442886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A review of mineral assemblages of agpaitic rocks from the Poços de Caldas alkaline massif, southeastern Brazil","authors":"Celso de Barros Gomes, A. A. Azzi, Daniel Atencio","doi":"10.1590/2317-4889202320220076","DOIUrl":"https://doi.org/10.1590/2317-4889202320220076","url":null,"abstract":"Abstract This study revises the early-magmatic, late-magmatic, and hydrothermal mineral assemblages occurring in rocks of agpaitic affinity, mainly represented by nepheline syenites and phonolites, from the Poços de Caldas alkaline massif. Mostly composed of different types of silicates, these rocks include rare minerals of of distinct groups, such as sulfides, oxides, carbonates, phosphates, sulfates, niobates, and notably halides, with villiaumite (NaF) as an important phase indicative of extreme alkali enrichment. Hydrothermal alteration products of nepheline and alkali feldspar typically consist of feldspathoids and zeolites. The rare minerals are of varied origin, from magmatic crystallization to hydrothermal and weathering processes. In general, they tend to occur interstitially or form euhedral crystals, especially when filling cavities or growing out from their walls. Petrological conditions involving the formation of the agpaitic rocks and their mineral assemblages are discussed.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"49 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88168916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrology of volcanic rocks of the Serra Sul mine, Carajás Province, Pará","authors":"Hélio Junior Lima Monteiro, Artur Corval, D. Roldão, Benevides Aires Filho, Luighi Santos Rinaldi, L. Martins, G. D. Oliveira","doi":"10.1590/2317-4889202320220053","DOIUrl":"https://doi.org/10.1590/2317-4889202320220053","url":null,"abstract":"The Parauapebas Formation and Igarapé Cigarra Formation constitute two Neoarchean extrusive units inserted in the metavolcanosedimentary sequence (~2.76 Ga) of the Grão Pará Group, Itacaiúnas Supergroup, being represented by basaltic seeps underlain and overlain by jaspillites, rhyolites, volcanoclastic rocks, and gabbro dikes/sills, thus being inserted in the Serra Sul district in the Mineral Province of Carajás, Pará. This study aimed to understand the igneous processes involved in the genesis of these basalts from both geological formations, supported by field, petrographic, and geochemical data. Inserted in the metavolcanosedimentary sequence of the Grão Pará Group (Carajás Domain), the basalts and basalt andesites, the most abundant types of the Parauapebas and Igarapé Cigarra Formations, occur as successions of massive and amygdaloidal lava flows. The study of core samples from nine stratigraphic holes that intersected basaltic rocks of the two geological formations in body S11D (Serra Sul) showed that these rocks reach thick layers with different characteristics, ranging from aphanitic to phaneritic. The ba-salts are dark green, aphanitic, phaneritic, thin to medium, and hypocrystalline. They show preserved igneous texture being commonly seriated as inequigranular, intersertal, ophitic, subophytic, intergranular, branching, and swallow tail. Its essential primary constituents are plagioclase, orthopyroxene, and clinopyroxene, and its accessory constituents are titanite and apatite. Chlorite, epidote, quartz, and calcite occur as secondary phases and are interpreted as the products of ocean-bottom hydrothermal alteration and/or incipient metamorphism. In general, the studied volcanic rocks stand out for SiO 2 content between 47.00 and 56.04%, high alkali contents (4.70–7.50%), K 2 O contents between 0.40 and 3.97%, TiO 2 (< 1.0%), and MgO between 4.90 and 8.16%. In the classification diagrams, the samples are situated in the fields of basalts, basalt andesites, trachyandesite, and trachybasalt basalts, in the transition of the toleitic and calc-alkaline series. The basalts of the Parauapebas and Igarapé Cigar-ra Formations were probably formed in an intraplate continental environment influenced by subduction zones. Therefore, the Grão-Pará Basin was probably formed in a convergent regime related to a subduction-type environment. The geochemical data indicate that the studied rocks of the Parauapebas Formation and the Igarapé Cigarra Formation correspond to basalts of calc-alkaline affinity. Two facies were identified in the Parauapebas Formation, namely, the Amendoim and Violão facies. In the Igarapé Cigarra Formation as well, the following facies were identified: Jacaré and Três Marias. Based on the geochemical interpretation, it is assumed that the rocks studied are arc-like continental basalts, which are formed in a subduction environment with influence from a possible asthenospheric source and modified by crustal contamination.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"158 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73496988","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The missing mats: MISS diversity and influence on life preservation in the late Ediacaran of the Tandilia System, Argentina","authors":"M. Arrouy, L. Warren, Fernanda Quaglio, L. Gómez-Peral, L. Inglez, Victoria Penzo, M. Simões, D. Poiré","doi":"10.1590/2317-4889202320220093","DOIUrl":"https://doi.org/10.1590/2317-4889202320220093","url":null,"abstract":"The terminal Ediacaran fossil record includes microbial mats and body fossils characterized by simple morphologies, which represents a challenge to understand several aspects related to the paleoecology of the emerging complex life. The marine siliciclastic deposits of the Cerro Negro Formation (~560–550 Ma) contain evidence of different styles of microbially induced sedimentary structures (MISS) and discoidal forms associated with them. Different types of MISS, such as Kinneyia and wrinkle structures, elephant skin, and Arumberia , are reported and related to shallow marine depositional environments . These morphologies are commonly associated with the high quality of preservation of body fossils in Ediacaran deposits. The preservation of Aspidella discoidal holdfast is related to biotic and abiotic processes involving substrate sealing by microbial mats, fluidization, and probably organic matter decay. Both abiotic factors (tidal currents and waves, added to liquefaction and sand injection) and biotic factors (substrate biostabilization by microbial mats favoring sediment cohesion) are considered the main ones responsible for the preservation style in the Cerro Negro Formation. This formation constitutes a remarkable example in SW-Gondwana of how preservation dynamics took place on a seabed sealed by microbial mats and is an important deposit conserving diverse Ediacaran forms of life in South America.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"71 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79956107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Carbonate reservoir quality and permoporosity obliteration due to silicification processes in the Barra Velha Formation, Santos Basin, Southeastern Brazil","authors":"Igor Lima de Jesus, Francisco Romeiro Abrantes Jr., D. Ferreira, W. Lupinacci","doi":"10.1590/2317-4889202320220086","DOIUrl":"https://doi.org/10.1590/2317-4889202320220086","url":null,"abstract":"Silicification is a diagenetic process commonly observed in sedimentary sections of the Aptian carbonate deposits of the Santos Basin that involves the replacement of carbonate minerals with silica. It is mostly associated with hydrothermal fluids percolating through faults and fractures. CO 2 degassing favors an increase in acidity. Consequently, the fluids became subsaturated with calcite and supersaturated with silica. Given the increase in silica content, two distinct behaviors were identified: reduction and enhancement of permoporous properties. The aim of this work is to identify permoporous alteration due to silicification in the Barra Velha Formation. To accomplish this, a qualitative analysis was conducted correlating acoustic borehole images, nuclear magnetic resonance porosity and permeability, and elemental capture spectroscopy logs were performed, followed by a quantitative analysis based on crossplot evaluation. The Barra Velha Formation was divided into three intervals with respect to silica content. The common behavior observed is permoporosity reduction associated with silica increase, but locally, permoporosity enhancement associated with silica increase was also identified. Finally, we established a direct relationship be-tween calcite dissolution and silica precipitation, a well-defined trend characterized by sonic log (DT) reduction and density increase, and an inverse relationship between acoustic impedance and permoporous properties. Finally, the quantitative analysis also favored improving the lack of reservoir qualities of the intrusive igneous interval.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"11 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88743711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deformational sequence of inversion in the Paramirim Aulacogen, northern region of the intracontinental sector of the Araçuaí Orogen","authors":"Caroline Novais Bitencourt, S. Cruz","doi":"10.1590/2317-4889202320220069","DOIUrl":"https://doi.org/10.1590/2317-4889202320220069","url":null,"abstract":"The Paramirim Aulacogen was filled by the Espinhaço and São Francisco supergroups in the period from 1.75 to 0.69 Ga, and suffered partial inversion during the Ediacaran. In the northern sector of the intracontinental domain of the Araçuaí-WestCongo Orogen, six compressive deformational phases were interpreted and associated with the frontal inversion of the Paramirim Aulacogen. Three structural domains were identified: Jacaraci Fold-Thrust Belt, Caetité Nappe, and Transpressive Domain. The nucleation of deformational structures is related to a maximum stress field with general WSW-ENE orientation. The first deformational phase (D 1 ), found in the Jacaraci Fold-Thrust Belt and the Transpressional Domain, is related to the evolution of the Rio Pardo Salient. A dextral transpressional system nucleated the Caetité Nappe. This system also juxtaposed amphibolite facies rocks over lower temperature facies, as well as Statherian over Tonian rocks. Furthermore, this system was responsible for deformation in the transpressional domains and late deformation in the Jacaraci Fold-Thrust Belt. The region presents a variety of structures and is, therefore, an excellent natural laboratory for studying positive inversion in aulacogens.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"69 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86325866","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Volcaniclastic rocks and reconstruction of a volcanosedimentary paleoenvironment in Campos Basin, SE Brazil","authors":"Yara Veloso Magalhães Frank, S. Valente","doi":"10.1590/2317-4889202320220089","DOIUrl":"https://doi.org/10.1590/2317-4889202320220089","url":null,"abstract":"Santonian-Campanian tuffaceous siltstone, epiclastic siltstone, arkose, and fossiliferous mudstone occur in a 45-m-thick section of well 1-BR-SA-37-RJS drilled in the southern Campos Basin, offshore SE Brazil. Well log data and petrographic and lithogeochemical data obtained from cutting samples were used to propose a schematic model of the volcano’s sedimentary paleoenvironment. The volcaniclasts in the tuffaceous siltstone and epiclastic siltstone are scoria basalts, typical of spatter cones associated with monogenetic fields worldwide. The combination of these features with the petrographic ones of the arkoses found in the same well interval is likely to be related to volcaniclastic processes taking place on the continental shelf. Ratios between the immobile trace elements of the volcaniclastic rocks can be explained by mixing between sources in the upper continental crust adjacent to southern Campos and the scoria basalts extruded in the monogenetic fields. The little differentiated, olivine-rich basalts extruded from the scoria and spatter cones suggest a rising asthenosphere mantle extending from hundreds of kilometers eastwards till southern Campos in the Santonian-Campanian. This may have resulted in regional discordances in the Santonian, both in the Campos and Santos basins, and also places the petroleum systems in the southern Campos Basin under the thermal influence of such a rising asthenosphere in the Santonian-Campanian.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"30 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83105833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A guide for microscopic description of fossil stromatolites","authors":"E. Sanchez, G. R. Romero, F. Callefo, A. Cardoso, T. Fairchild","doi":"10.1590/2317-4889202220220031","DOIUrl":"https://doi.org/10.1590/2317-4889202220220031","url":null,"abstract":"Stromatolites are laminated biosedimentary structures of great importance for paleobiological, paleoecological, and paleoenvironmental analyses, mainly in Precambrian rocks. Their value is related to the glimpse of past life recorded in their lamination, fabric, and, eventually, due to the preservation of organic matter, including microfossils, and because their deposition is directly influenced by environmental conditions. Although stromatolites are widely described in microscopic scale, there is a lack of standardization of their nomenclature, precluding better paleoenvironmental and paleobiological interpretations. In this study, we propose a guide for the microscopic analysis of fossil stromatolites and, possibly, thrombolites, and provide a review of specialized literature and the bibliometric context of main terms. The goal is to contribute to the improvement of their application through systematization of microscopic data, in the face of novel paleoecological and paleobiological approaches and for astrobiological prospection for microbialites in therock record of Mars.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"25 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74871250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}