This study highlights a new by-product source for cobalt by recycling Paleoproterozoic Mn deposits.We present a geochemical modeling approach utilizing Principal Component Analysis(PCA)for available geochemical data o...This study highlights a new by-product source for cobalt by recycling Paleoproterozoic Mn deposits.We present a geochemical modeling approach utilizing Principal Component Analysis(PCA)for available geochemical data of Paleoproterozoic manganese deposits found in Africa and Brazil,which exhibit anomalous cobalt contents(up to 1200 ppm)along with other metals such as copper,nickel,and vanadium.The PCA results for the correlation coefficient matrix of the Enrichment Factor(_(EF))values of major and trace elements from samples of eight Mn deposits found in Africa and Brazil(Kisenge-Kamata,Moanda,Nsuta in Africa,and Azul,Buritirama,Lagoa do Riacho,Morro da Mina,and Serra do Navio in Brazil)yielded a cumulative variance of 53.3%for PC1(34%)and PC2(19.3%).In PC1,the highest positive loadings correspond to the variables Mn_(EF),Ni_(EF),and Co_(EF),while the highest negative loadings correspond to the variables Si_(EF),Fe_(EF),K_(EF),Ti_(EF),Cr_(EF),and Zr_(EF).PC2 exhibits the highest positive loadings for the variables Ca_(_(EF)),Mg_(EF),and P_(EF),while the highest negative loadings are for Cu_(EF)and V_(EF).The biplot diagram representation showed that clusters of vectors Mn_(EF),Ni_(EF),Co_(EF),V_(EF),and Cu_(EF)influence samples of Mn-carbonate rock,Mn-carbonate-silicate rock,Mn-silicate rock,and Mn-carbonate-siliciclastic rock,all with high Co_(EF)values(up to 414).The cluster of vectors Ca_(_(EF)),Mg_(EF),and P_(EF)significantly influence carbonate rock and dolomite marble,which have low Co_(EF)values(close to 0).The cluster of vectors Si_(EF),Fe_(EF),K_(EF),Ti_(EF),Cr_(EF),and Zr_(EF)strongly influences siliciclastic rock,which exhibits low Co_(EF)values.On the other hand,the cluster of vectors Cu_(EF)and V_(EF)influences oxidized Mn ore,which exhibits Co_(EF)values of up to 108.The results reveal a dichotomy regarding the origin of cobalt and other metal enrichments in these deposits linked to the Mn redox cycle.This process involves the formation of Mn-oxyhydroxides with the adsorption of Co and other metals under oxic conditions,followed by the burial of these Mn oxides in an anoxic diagenetic environment,where microbial sulfate reduction leads to the nucleation of Mn-carbonates and the formation of metal-rich sulfides(Fe,Co,Ni,V).Additionally,detrital input and sulfide phases(e.g.,framboidal pyrite)for the formation of Mn-rich siliciclastic rocks associated with Mn-carbonate rocks are evidenced by proxies Si_(EF),Fe_(EF),K_(EF),Ti_(EF),Cr_(EF),and Zr_(EF).This new exploration approach,supported by geochemical modeling through PCA,enhances our understanding of the genesis of these Paleoproterozoic manganese deposits and highlights a new route for cobalt exploration.In the increasing global demand for cobalt,particularly in applications involving electric vehicle batteries and energy storage,exploring these deposits emerges as an alternative source to produce these critical metals.展开更多
The paleogeographic reconstruction of fragmented and dispersed continents often poses a challenge due to the lack of information regarding the nature of that extend beneath passive margin basins.To define the width of...The paleogeographic reconstruction of fragmented and dispersed continents often poses a challenge due to the lack of information regarding the nature of that extend beneath passive margin basins.To define the width of the continental crust beneath passive margin basins and its implications for paleogeographic reconstruction of conjugate continental margins,this study investigates the architecture of the stretched continental crust of the southern South Atlantic conjugate margin.The investigated region encompasses South Africa,Namibia,southern Brazil,and Uruguay,which were formed during the Mesozoic rifting of SW Gondwana.Employing a multi-tool approach combining seismic interpretation,gravity,magnetometry,and U-Pb isotopic data,the research aims to quantify the extension of stretched continental crust and its implications for plate reconstructions.The study reveals that the restored stretched crust spans at least 150 km,emphasizing the significance of considering connections between both margins for realistic paleogeographic reconstructions.Furthermore,the distinct U-Pb zircon age distribution patterns between SW Africa and SE South America reinforce the lack of direct connections despite their Gondwanan origin.The missing link estimated in this study is around 150 km,comparable in size to major mountain ranges such as the Andean or Urals.This work sheds light on critical aspects of Earth’s dynamic crustal evolution and emphasizes the need for comprehensive reconstructions considering stretched and eroded crust in the South Atlantic conjugate margin.展开更多
The present work analyzes the monotypic Taenidium barretti ichnofabric developed in abandoned channels and floodplains to understand its paleoecological significance in highly seasonal fluvial systems.The data come fr...The present work analyzes the monotypic Taenidium barretti ichnofabric developed in abandoned channels and floodplains to understand its paleoecological significance in highly seasonal fluvial systems.The data come from the Cretaceous paleosols of the Marília Formation(Bauru Basin,SE Brazil),in which the T.barretti ichnofabric and rhizoliths represent the biotic record.Beetle larvae are considered to be the most likely T.barretti tracemakers in these paleosols.The intensity and recurrence of bioturbation suggest that the windows of opportunity for beetle population growth were very short and controlled by the progressive substrate desiccation after flood cessation.The characteristics of the trace fossil assemblage suggest soil colonization by r-strategic organisms triggered by flooding events that provided the resource inputs necessary for their living during rainy seasons.The results also show that in fluvial systems with high discharge variations,the boundaries between a“pre-desiccation suite”and a“desiccation suite”in the Scoyenia ichnofacies can be diffuse due to the short duration of colonization windows and progressive terrestrialization of floodplains and channels.Therefore,the frequency of flooding events,the lowered water table,and the rapidity of substrate desiccation constrained colonization by other burrowers and may be considered as firstorder factors controlling the generation of a monotypic T.barretti ichnofabric.Thus,the monotypic Taenidium ichnofabric in the Scoyenia ichnofacies context is an ichnomarker of brief windows for colonization in highly seasonal environments.展开更多
基金the Department of Geology at the Federal University of Ceará(DEGEO-UFC)and Prof.Dr.Felipe Holanda dos Santos for their support and guidance during the research process.FHS would like to thank the Society of Economic Geologists(SEG)for the Student Research Grant.WAS is funded by CNPq,under grant number(407255/2022-2).
文摘This study highlights a new by-product source for cobalt by recycling Paleoproterozoic Mn deposits.We present a geochemical modeling approach utilizing Principal Component Analysis(PCA)for available geochemical data of Paleoproterozoic manganese deposits found in Africa and Brazil,which exhibit anomalous cobalt contents(up to 1200 ppm)along with other metals such as copper,nickel,and vanadium.The PCA results for the correlation coefficient matrix of the Enrichment Factor(_(EF))values of major and trace elements from samples of eight Mn deposits found in Africa and Brazil(Kisenge-Kamata,Moanda,Nsuta in Africa,and Azul,Buritirama,Lagoa do Riacho,Morro da Mina,and Serra do Navio in Brazil)yielded a cumulative variance of 53.3%for PC1(34%)and PC2(19.3%).In PC1,the highest positive loadings correspond to the variables Mn_(EF),Ni_(EF),and Co_(EF),while the highest negative loadings correspond to the variables Si_(EF),Fe_(EF),K_(EF),Ti_(EF),Cr_(EF),and Zr_(EF).PC2 exhibits the highest positive loadings for the variables Ca_(_(EF)),Mg_(EF),and P_(EF),while the highest negative loadings are for Cu_(EF)and V_(EF).The biplot diagram representation showed that clusters of vectors Mn_(EF),Ni_(EF),Co_(EF),V_(EF),and Cu_(EF)influence samples of Mn-carbonate rock,Mn-carbonate-silicate rock,Mn-silicate rock,and Mn-carbonate-siliciclastic rock,all with high Co_(EF)values(up to 414).The cluster of vectors Ca_(_(EF)),Mg_(EF),and P_(EF)significantly influence carbonate rock and dolomite marble,which have low Co_(EF)values(close to 0).The cluster of vectors Si_(EF),Fe_(EF),K_(EF),Ti_(EF),Cr_(EF),and Zr_(EF)strongly influences siliciclastic rock,which exhibits low Co_(EF)values.On the other hand,the cluster of vectors Cu_(EF)and V_(EF)influences oxidized Mn ore,which exhibits Co_(EF)values of up to 108.The results reveal a dichotomy regarding the origin of cobalt and other metal enrichments in these deposits linked to the Mn redox cycle.This process involves the formation of Mn-oxyhydroxides with the adsorption of Co and other metals under oxic conditions,followed by the burial of these Mn oxides in an anoxic diagenetic environment,where microbial sulfate reduction leads to the nucleation of Mn-carbonates and the formation of metal-rich sulfides(Fe,Co,Ni,V).Additionally,detrital input and sulfide phases(e.g.,framboidal pyrite)for the formation of Mn-rich siliciclastic rocks associated with Mn-carbonate rocks are evidenced by proxies Si_(EF),Fe_(EF),K_(EF),Ti_(EF),Cr_(EF),and Zr_(EF).This new exploration approach,supported by geochemical modeling through PCA,enhances our understanding of the genesis of these Paleoproterozoic manganese deposits and highlights a new route for cobalt exploration.In the increasing global demand for cobalt,particularly in applications involving electric vehicle batteries and energy storage,exploring these deposits emerges as an alternative source to produce these critical metals.
基金supported by the UNISINOS-PETROBRAS and UNISINOS-CNODC Cooperation Agreements.
文摘The paleogeographic reconstruction of fragmented and dispersed continents often poses a challenge due to the lack of information regarding the nature of that extend beneath passive margin basins.To define the width of the continental crust beneath passive margin basins and its implications for paleogeographic reconstruction of conjugate continental margins,this study investigates the architecture of the stretched continental crust of the southern South Atlantic conjugate margin.The investigated region encompasses South Africa,Namibia,southern Brazil,and Uruguay,which were formed during the Mesozoic rifting of SW Gondwana.Employing a multi-tool approach combining seismic interpretation,gravity,magnetometry,and U-Pb isotopic data,the research aims to quantify the extension of stretched continental crust and its implications for plate reconstructions.The study reveals that the restored stretched crust spans at least 150 km,emphasizing the significance of considering connections between both margins for realistic paleogeographic reconstructions.Furthermore,the distinct U-Pb zircon age distribution patterns between SW Africa and SE South America reinforce the lack of direct connections despite their Gondwanan origin.The missing link estimated in this study is around 150 km,comparable in size to major mountain ranges such as the Andean or Urals.This work sheds light on critical aspects of Earth’s dynamic crustal evolution and emphasizes the need for comprehensive reconstructions considering stretched and eroded crust in the South Atlantic conjugate margin.
基金the Sao Paulo Research Foundation(FAPESP)for supporting and funding this work(grant 2015/17632-5)The Brazilian National Council for Scientific and Technological Development(CNPq)is also thanked for the Ph.D.grant provided to DLN(140807/2017-9)+3 种基金the post-doctoral fellowship grant to DS(159548/2018-7)the research grants to AB(310734/2020-7)RGN(310377/2019-6)FSBL(307951/2018-9,303977/2021-3).
文摘The present work analyzes the monotypic Taenidium barretti ichnofabric developed in abandoned channels and floodplains to understand its paleoecological significance in highly seasonal fluvial systems.The data come from the Cretaceous paleosols of the Marília Formation(Bauru Basin,SE Brazil),in which the T.barretti ichnofabric and rhizoliths represent the biotic record.Beetle larvae are considered to be the most likely T.barretti tracemakers in these paleosols.The intensity and recurrence of bioturbation suggest that the windows of opportunity for beetle population growth were very short and controlled by the progressive substrate desiccation after flood cessation.The characteristics of the trace fossil assemblage suggest soil colonization by r-strategic organisms triggered by flooding events that provided the resource inputs necessary for their living during rainy seasons.The results also show that in fluvial systems with high discharge variations,the boundaries between a“pre-desiccation suite”and a“desiccation suite”in the Scoyenia ichnofacies can be diffuse due to the short duration of colonization windows and progressive terrestrialization of floodplains and channels.Therefore,the frequency of flooding events,the lowered water table,and the rapidity of substrate desiccation constrained colonization by other burrowers and may be considered as firstorder factors controlling the generation of a monotypic T.barretti ichnofabric.Thus,the monotypic Taenidium ichnofabric in the Scoyenia ichnofacies context is an ichnomarker of brief windows for colonization in highly seasonal environments.
