Brazilian Journal of Geology最新文献_第3页

Artisanal and small-scale gold mining in the Southern Espinhaço Range, Brazil, using time-domain electromagnetic induction: prospecting, efficiency, and environmental aspects 巴西南埃斯帕纳帕拉索山脉的手工和小规模金矿，利用时域电磁感应:勘探、效率和环境方面

4区地球科学

Brazilian Journal of Geology Pub Date : 2023-01-01 DOI: 10.1590/2317-488920232022090

Henrique Borgatti, Aline Tavares Melo, Luiz Guilherme Knauer

{"title":"Artisanal and small-scale gold mining in the Southern Espinhaço Range, Brazil, using time-domain electromagnetic induction: prospecting, efficiency, and environmental aspects","authors":"Henrique Borgatti, Aline Tavares Melo, Luiz Guilherme Knauer","doi":"10.1590/2317-488920232022090","DOIUrl":"https://doi.org/10.1590/2317-488920232022090","url":null,"abstract":"Gold mining has profound ties to the history of Brazilian colonization and still takes place with many communities involved in artisanal and small-scale gold mining. The most relevant gold deposits in the Southern Espinhaço Range are related to the occurrence of shear zones in the region between the cities of Diamantina and Gouveia, Minas Gerais, Brazil. Former colonial-dated gold mines were depleted; however, the use of newer prospecting practices has brought new interest in these areas. In this context, this study assesses the efficiency, environmental impacts, and economic viability of time-domain electromagnetic induction as a gold exploration method for small-scale prospecting in Gouveia county. Additionally, this study provides a characterization of the local gold mineralization and brings awareness to the prospecting community regarding environmental and legal aspects of gold mining. This article presents the results of a field campaign of prospecting efforts in which 114 metallic targets were located, 35 of which were identified as native gold. The gold samples have specific morphology, depth, and weight that suggest a hypogenic origin with a low degree of transport at eluvial levels. From an environmental perspective, the time-domain electromagnetic induction method has presented fewer impacts, related mostly to site-specific remobilization of the soil.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136202432","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}

引用次数: 0

Sodic alkaline magmatism in Eastern Paraguay revisited: geochemical and petrological implications 巴拉圭东部的钠碱性岩浆活动:地球化学和岩石学意义

4区地球科学

Brazilian Journal of Geology Pub Date : 2023-01-01 DOI: 10.1590/2317-4889202320220095

Celso de Barros Gomes, Piero Comin-Chiaramonti, Victor Fernandez Velázquez

{"title":"Sodic alkaline magmatism in Eastern Paraguay revisited: geochemical and petrological implications","authors":"Celso de Barros Gomes, Piero Comin-Chiaramonti, Victor Fernandez Velázquez","doi":"10.1590/2317-4889202320220095","DOIUrl":"https://doi.org/10.1590/2317-4889202320220095","url":null,"abstract":"Associated with subordinate potassic rocks, Mesozoic to Cenozoic sodic alkaline rocks are represented by four distinct provinces in Eastern Paraguay: Alto Paraguay, Central, Misiones, and Asunción; additional Rio Apa and Amambay provinces are exclusively of potassic affinity. Alkaline magmatism is clearly controlled by a tectonic extensional regime that generated NW-SE-trending faults and grabens. It varies in composition, with the intrusive sodic rocks mainly composed of foid syenites and quartz-bearing syenites and the potassic ones of syenites, syenogabbros, and gabbros, all of which are accompanied by fine-grained hypoabissal and volcanic counterparts. In the Central Province, potassic and sodic rocks occur together and are represented by two distinct magmatic series: basanites-phonolites and alkali basalts-trachytes/trachyphonolites. Ultramafic sodic rocks (ankaratrites and nephelinites) are uniquely found in the Misiones and Asunción provinces. In general, the sodic rocks exhibit LILE enrichment, high field strength elements depletion, and Nb-Ta positive anomalies in the mantle's normalized incompatible elements (IE) distribution. Chondrite-normalized rare earth element (REE) diagrams point to strong REE enrichment and high light/heavy rare earth element fractionation in different subparallel patterns. Conversely, the potassic rocks display negative anomalies of Nb-Ta and are fractionated in REE. In the initial Sri versus Ndi diagram, the sodic rocks approach to bulk earth, whereas the potassic ones plot into the Sr-enriched quadrant. Sr-Nd-Pb isotope data suggest that a high U/Pb mantle component played an important role in the genesis of the Late Early Cretaceous and Tertiary sodic magmas, while an enriched mantle component dominated the Early Cretaceous potassic magmas. The close association of potassic and sodic rocks implies that their parental magmas derived from a subcontinental mantle variable in composition enriched in IE.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136305741","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}

引用次数: 0

Structural controls on the Bonsucesso Zinc-Lead Deposit, Vazante Group, Brazil 巴西Vazante集团bonsuccesso铅锌矿床的构造控制

4区地球科学

Brazilian Journal of Geology Pub Date : 2023-01-01 DOI: 10.1590/2317-4889202320190135

Edson Ricardo Maia Ferraz, George Luiz Luvizotto, Juliana Okubo, Denis Antonio Batiston

{"title":"Structural controls on the Bonsucesso Zinc-Lead Deposit, Vazante Group, Brazil","authors":"Edson Ricardo Maia Ferraz, George Luiz Luvizotto, Juliana Okubo, Denis Antonio Batiston","doi":"10.1590/2317-4889202320190135","DOIUrl":"https://doi.org/10.1590/2317-4889202320190135","url":null,"abstract":"The Bonsucesso zinc-lead (Zn-Pb) sulfide deposit is hosted in carbonate rocks from the Vazante Group (transition of the Mesoproterozoic to the Neoproterozoic time), northwest of Minas Gerais State, Brazil. Regional deformation is associated with the thin-skinned tectonics that led to the formation of the foreland zone of the Brasília Orogen during the Neoproterozoic. These orogenic processes are the trigger of Zn-Pb mineralization in many base-metal deposits in the Vazante Group. Here, we describe the ore textures and the structures of the deposit to define its structural controls in deposit scale and formulate hypotheses about its forming process in the context of other Vazante Zn-Pb deposits. Mineralization distribution is controlled by a high-angle fault zone striking NNW and dipping 60° to WSW. Fault-related fractures functioned as pathways for Zn-Pb-rich fluids to be redistributed and crystallize where chemical conditions were adequate. Mineralization was likely formed in an extensional setting in breccia zones controlled by flexurally induced normal faults related to development of the foreland basin of Brasília Orogen. Later, the entire Vazante sequence underwent an inversion process and extensional structures were reactivated or obliterated. Finally, an understanding of local controls may be of good use to target exploration for new orebodies in the district scale.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135660425","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}

引用次数: 0

Paleokarst features in the Aptian carbonates of the Barra Velha Formation, Santos Basin, Brazil 巴西Santos盆地Barra Velha组Aptian碳酸盐岩古岩溶特征

4区地球科学

Brazilian Journal of Geology Pub Date : 2023-01-01 DOI: 10.1590/2317-4889202320220073

David Chibuzor Nworie, Guilherme Furlan Chinelatto, Alexandre Campane Vidal

{"title":"Paleokarst features in the Aptian carbonates of the Barra Velha Formation, Santos Basin, Brazil","authors":"David Chibuzor Nworie, Guilherme Furlan Chinelatto, Alexandre Campane Vidal","doi":"10.1590/2317-4889202320220073","DOIUrl":"https://doi.org/10.1590/2317-4889202320220073","url":null,"abstract":"Seismic data, borehole image logs, and conventional well logs were used to investigate the distribution and characteristics of paleokarst features in the Aptian carbonates of the Barra Velha Formation in a pilot area of the Santos Basin, Brazil. Multiple seismic attributes were used to enhance details on the seismic data and highlight key seismic parameters including strata deformation and geometry, continuity of seismic events, and fault patterns. The study found that karst structures are controlled by faults and fractures along structural highs, which served as a conduit for the flow of dynamic fluids that dissolved the carbonate materials. Several closed, circular depressions and bright spots identified in the northeastern portion of the study area represent possible sinkhole structures. Epigenic and hypogenic processes due to the action of meteoric water, hydrothermal activity, and intra-formation acidity along regional unconformities in the Barremian-Aptian may have been responsible for the dissolution. Limitations of this study are related to the difficulty of integrating multiple datasets with various scales. However, the higher confidence for the occurrence of the karst features is provided by borehole images at the sub-seismic scale. The findings of this study hold significant relevance for the strategic planning of energy development and carbon sequestration initiatives in the Brazilian continental margins, thereby aiding in informed decision-making.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135784271","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}

引用次数: 1

Mineral chemistry from the Alfeu-I lamproite (Southern Brazil) and its contribution to understand the mantle heterogeneity under South American Plate during the Gondwana breakup 巴西南部alfeu - 1煌斑岩的矿物化学特征及其对冈瓦纳破裂时期南美板块地幔非均质性的贡献

4区地球科学

Brazilian Journal of Geology Pub Date : 2023-01-01 DOI: 10.1590/2317-4889202320220092

Larissa Colombo Carniel, Rommulo Vieira Conceição, Carlos Augusto S. Provenzano, Andrea Sander, Felipe Padilha Leitzke, Andrea Brum da Silva, Jasper Berndt, Stephan Klemme

{"title":"Mineral chemistry from the Alfeu-I lamproite (Southern Brazil) and its contribution to understand the mantle heterogeneity under South American Plate during the Gondwana breakup","authors":"Larissa Colombo Carniel, Rommulo Vieira Conceição, Carlos Augusto S. Provenzano, Andrea Sander, Felipe Padilha Leitzke, Andrea Brum da Silva, Jasper Berndt, Stephan Klemme","doi":"10.1590/2317-4889202320220092","DOIUrl":"https://doi.org/10.1590/2317-4889202320220092","url":null,"abstract":"The Alfeu-I lamproite is one of the few alkaline rock occurrences in the South of Brazil that represents the alkaline event related to the South Atlantic opening and the enormous magmatic activity that formed the Paraná basalts. Alfeu-I lamproite is a diatreme facies and exhibits an inequigranular texture with macrocrysts of mica, spinel, garnet, and ilmenite and microcrysts of mica, pyroxene, and rare olivine, all immersed in a groundmass of pyroxene, spinel, perovskite, rutile, ilmenite, and, more rarely, olivine. Major element compositions of Alfeu-I pyroxene, garnet, ilmenite, mica, and olivine were determined by electron microprobe analyses, and trace element concentrations of clinopyroxene, garnet, ilmenite, and mica were measured using laser-ablation inductively coupled plasma mass spectrometry techniques. Temperature, pressure, and oxygen fugacity (fO2) conditions during the crystallization of Alfeu-I lamproite were calculated with the geothermobarometers and olivine, spinel, garnet, and orthopyroxene. The resulting mean equilibrium temperature ranges from 1375°C at 4 GPa to 1395°C at 5 GPa, whereas the fO2 points to ΔFMQ = +2.4 (at 4 GPa) and ΔFMQ = +2.2 (at 5 GPa). Rb-Sr and Sm-Nd isotopic data together with the trace element concentrations of minerals suggest that melting of a mantle source enriched in incompatible elements and volatiles due to previous subduction events occurred during the Gondwana breakup around 125 Ma ago. Fluids that may have originated from subducting slabs in the old subduction zone are probably the cause of the high fO2 conditions in Alfeu-I lamproite.","PeriodicalId":9221,"journal":{"name":"Brazilian Journal of Geology","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135107407","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}

引用次数: 0

Depositional systems, sequence stratigraphy, and sedimentary provenance of the Palaeoproterozoic Minas Supergroup and Itacolomi Group, Quadrilátero Ferrífero, Brazil 巴西Quadrilátero Ferrífero古元古代Minas超群和Itacolomi群沉积体系、层序地层学及物源研究

IF 1.4 4区地球科学

Brazilian Journal of Geology Pub Date : 2022-01-01 DOI: 10.1590/2317-4889202220210081

Gabriel Gonçalves, A. Uhlein

引用次数: 2

Mineral potential re-evaluation of the Seis Lagos Carbonatite Complex. Amazon. Brazil Seis - Lagos碳酸盐岩杂岩的矿物潜力再评价。亚马逊。巴西

IF 1.4 4区地球科学

Brazilian Journal of Geology Pub Date : 2022-01-01 DOI: 10.1590/2317-4889202120210031

J. P. P. Bento, C. Porto, L. Takehara, F. A. D. Silva, Artur Cezar Bastos Neto, Matheus Lamas Machado, Ana Carolina Duarte

引用次数: 0

Magnetic petrology of the Neoarchean granitoids in the Vila Jussara Suite, Carajás Province, Amazonian Craton 亚马逊克拉通Carajás省Vila Jussara Suite新太古代花岗岩类的磁岩石学研究

IF 1.4 4区地球科学

Brazilian Journal of Geology Pub Date : 2022-01-01 DOI: 10.1590/2317-4889202220210071

Luan Alexandre Martins de Sousa, R. Dall’Agnol, Ingrid Roberta Viana da Cunha, F. F. Silva, D. Oliveira

引用次数: 0

Microbialitic deposits of the Yacoraite Formation, NW Argentina: distribution, environments, paleoecology, and economic implications 阿根廷西北部雅长岩组微生物沉积:分布、环境、古生态和经济意义

IF 1.4 4区地球科学

Brazilian Journal of Geology Pub Date : 2022-01-01 DOI: 10.1590/2317-4889202220210088

P. G. Villafañe, Rocío del Cielo Frías-Saba, Micaela Della-Vedova, P. Citton, I. Díaz-Martínez, S. Valais, F. Aceñolaza, R. A. Marquillas, Carlos Cónsole-Gonella

引用次数: 1

Post-Cretaceous brittle tectonics in the Tunas Alkaline Complex, Paraná, Brazil 巴西帕拉纳<e:1>图纳斯碱性复合体的后白垩纪脆性构造

IF 1.4 4区地球科学

Brazilian Journal of Geology Pub Date : 2022-01-01 DOI: 10.1590/2317-4889202220210041

T. F. Farias, Eduardo Salamuni, W. Peyerl, V. Gimenez

引用次数: 0