Dissertação

Estudos isotópicos (Pb-Pb, Sm-Nd, C e O) do depósito Cu-Au do Sossego, Província Mineral de Carajás

The Sossego deposit is located at about 25 km NW of Canaã de Carajás, southeast of Pará, at the contact zone between the Grão Pará Group and basement rocks. This deposit comprises two main ore bodies, Sequeirinho and Sossego, which were formed in an environment where deformational processes, empl...

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Autor principal: NEVES, Marcely Pereira
Grau: Dissertação
Idioma: por
Publicado em: Universidade Federal do Pará 2019
Assuntos:
Sedimentação e depósitos - Carajás, Serra dos (PA)
Isótopos
Minérios - Transporte
Sulfetos
CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA
GEOQUÍMICA E PETROLOGIA
Acesso em linha: http://repositorio.ufpa.br/jspui/handle/2011/11959
id ir-2011-11959
recordtype dspace
spelling ir-2011-119592019-10-30T05:24:15Z Estudos isotópicos (Pb-Pb, Sm-Nd, C e O) do depósito Cu-Au do Sossego, Província Mineral de Carajás NEVES, Marcely Pereira VILLAS, Raimundo Netuno Nobre http://lattes.cnpq.br/1406458719432983 Sedimentação e depósitos - Carajás, Serra dos (PA) Isótopos Minérios - Transporte Sulfetos CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA GEOQUÍMICA E PETROLOGIA The Sossego deposit is located at about 25 km NW of Canaã de Carajás, southeast of Pará, at the contact zone between the Grão Pará Group and basement rocks. This deposit comprises two main ore bodies, Sequeirinho and Sossego, which were formed in an environment where deformational processes, emplacement and cooling of intrusive bodies led to an intense hydrothermal fluid circulation. This work intended to characterize the ore host rocks, the mineralization styles and the types of hydrothermal alteration, as well as to date the sulfide mineralization and assess potential sources for metals and hydrothermal fluids. Invariably altered and deformed granitoids and mafic rocks, in addition to biotiterich rocks, hydrothermalites (magnetitites and ore bodies) and breccias occur in the deposit area. All these rocks are crosscut by mafic and felsic dikes. Albitization, epidotization, chloritization, silicification, amphibolitization and scapolitization were the main alteration processes recognized in the deposit. The first is more common in the granitoids while the last two are more typical of the mafic rocks. In these mafic rocks the concentration of actinolite increases towards the ore bodies resulting in the formation of actinolitites. A strong iron metasomatism was also identified, being responsible for the magnetitite generation. Abundant calcite-rich veinlets mark the final stage of the hydrothermal activity in the area. Although present in the Sequeirinho ore body, it was more intense in the Sossego ore body. Mineralization was subsequent to the shearing event and took place contemporaneously with the epidotization, chloritization and actinolization processes, allowing one to infer that mineralizating fluids, besides Cu, Au and P, were also enriched in Ca and Fe. Pb isotopic data in chalcopyrite from ore samples yielded ages of 2530 ± 25 Ma, 2608 ± 25 Ma (Sequeirinho ore body) and 1592 ± 45 Ma (Sossego ore body). The Archaean ages were discussed considering the hypotheses of the mineralization having or not a genetic link with the granitoids. In the first case, it could be related to the 2.76 – 2.74 Ga granitogenesis and the ages would represent the opening of the Pb isotopic system caused by subsequent thermal or deformational events. Alternatively, those ages could be related to the ~2.6 Ga magmatic event that is accounted for the dikes present at the neighboring Cu-Au 118 deposit, but its unexpressive significance in the Carajás region makes it unlikely to be responsible for the production of great cuprousauriferous deposits, like the Sossego. In the absence of a genetic link with granitoids, the mineralization could be related to metamorphic processes and the Pb-Pb ages would record the accompanying shearing event that caused the granitoid mylonitization and might have induced the infiltration of high salinity fluids, resulting in biotite-rich rocks with high Cl contents. No geological significance was given to the Mesoproterozoic age. A Sm-Nd isochron of 2578 ± 29 Ma was also obtained for ore samples. It is comparable to the Pb-Pb age of 2608 ± 25 Ma and most likely reflects an isotopic reequilibrium in response to later events. Model-ages (3.16 – 2.96 Ga) for the ore are similar to those of the deposit granitoid (3.12 – 2.98 Ga) and also to the Grão Pará Group basalts (2.76 – 3.09 Ga), suggesting that the ore could have been, at least in part, derived from these rocks. εNd values (-4.09 to -0.94) indicate an essentially crustal origin for both the host rocks and the ore. Based on the diagram εNd x t, it is plausible to admit that ore metals were derived from both granitoids and mafic rocks, especially the basalts from the Grão Pará Group. The δ 13CPDB values for calcite indicate a homogeneous source for C, probably mantle-derived. They show a negative linear correlation with the δ 18O values, suggesting a common evolution process. In terms of C and O natural reservoirs, the isotopic data are more consistent with sources of carbonatitic affiliation as indicated by the anomalous P and ETR contents found in the ore bodies. Calculation of δ 18Ofluid reveals that most values fall, respectively, in the ranges of -7.24 to -5.17‰ and +1.14‰ to +3.21‰ at 150° and 350ºC, being consistent with the participation of meteoric water in the Sossego hydrothermal system. However, higher values (+9.79‰ at 250ºC and +12.77‰ at 350ºC) suggest a magmatic or metamorphic water signature. Despite the speculations, integrating field, mineralogical, isotopic (stable and radiogenic) and fluid inclusion data allows to sustain that mineralization occurred at 2.76-2.60 Ga and was related to metamorphic-deformational processes, which triggered the migration of high saline fluids that had previously reacted with salt-rich sequences and became capable of transporting great amounts of metals, including Cu and Fe. CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior O depósito do Sossego localiza-se cerca de 25 km a NW da cidade de Canaã dos Carajás, sudeste do Pará, no contato do Grupo Grão Pará com rochas do embasamento. Este depósito compreende dois corpos principais, Sequeirinho e Sossego, que foram gerados em um ambiente onde processos deformacionais e o alojamento e resfriamento de corpos intrusivos favoreceram uma intensa circulação de fluidos hidrotermais. Este trabalho objetivou reconhecer as rochas encaixantes do minério, estilo da mineralização e tipos de alteração hidrotermal, bem como datar a mineralização de sulfetos e investigar possíveis fontes dos metais e fluidos hidrotermais. Na área do depósito ocorrem granitóides, rochas máficas, ambos invariavelmente alterados e deformados a diferentes graus, rocha rica em biotita, hidrotermalitos (magnetititos e corpos de minério) e brechas, todos cortados por diques félsicos e máficos. Os principais processos hidrotermais identificados no depósito são albitização, epidotização, cloritização, silicificação, anfibolitização e escapolitização. O primeiro é mais comum nas rochas granitóides e os dois últimos nas rochas máficas, nas quais a formação de actinolita se intensifica em direção ao minério formando actinolititos. Ocorre, também, forte metassomatismo de ferro que foi responsável pela geração de magnetititos.Vênulas tardias, dominadas por calcita, marcam o estagio final da alteração hidrotermal, o qual, embora presente no corpo Sequeirinho, foi bem mais intenso no corpo Sossego. A mineralização ocorreu contemporaneamente aos processos de epidotização, cloritização e actinolitização, o que permite inferir que os fluidos mineralizantes, além de Cu, Au e P, eram ricos em Ca e Fe. Dados de isótopos de Pb em calcopirita de amostras do minério forneceram idades de 2530±25 Ma, 2608±25 Ma (corpo Sequeirinho) e 1592±45 Ma (corpo Sossego). As idades arqueanas foram discutidas mediante as hipóteses de existir ou não elo genético da mineralização com os granitóides. No primeiro caso, a mineralização estaria ligada à granitogênese de 2,76-2,74 Ga e as idades representariam maior ou menor abertura do sistema isotópico do Pb causada por evento termal ou deformacional subseqüente. Elas poderiam, por outro lado, estar relacionadas ao mesmo evento magmático de ≈2,6 Ga que gerou os diques presentes no vizinho depósito Cu-Au do 118, porém sua pouca representatividade em Carajás torna improvável que ele seja responsável pela produção de grandes depósitos cuproauríferos, como o do Sossego. Na falta de elo genético com os granitóides, a mineralização poderia ser atribuída a processos metamórficos e essas idades registrariam o evento cisalhante que não só milonitizou os granitóides como também permitiu que eles interagissem com fluidos de elevada salinidade, vindo a produzir as rochas ricas em biotita e com altos teores de Cl. À idade mesoproterozóica não foi dado nenhum significado geológico. Com o método Sm-Nd, foi obtida a idade de 2.578±29 Ma em amostras do minério, a qual é comparável com a idade Pb-Pb de 2608±25 Ma e muito provavelmente também reflete reequilíbrio isotópico em resposta a eventos posteriores. Idades-modelo determinadas para o minério (3,16 – 2,96 Ga) são semelhantes às dos granitóides do depósito (3,12 – 2,98 Ga) e também às dos basaltos do Grupo Grão Pará (2,76-3,09 Ga), sugerindo que o minério, em parte, seja originado dessas rochas. Os valores de εNd (-4,09 a -0,94) indicam uma origem essencialmente crustal tanto das rochas hospedeiras como do próprio minério. Com base em diagrama εNd x t, fica evidente que os metais dos minérios foram derivados tanto dos granitóides como das rochas máficas, entre estas em especial os basaltos do Grupo Grão Pará. Os valores de δ13CPDB sugerem uma fonte homogênea para o C, de origem provavelmente mantélica. As amostras, em geral, revelam uma correlação linear negativa no diagrama δ13C x δ18O sugerindo um processo evolutivo comum. Em termos de reservatórios naturais de C e O, os dados isotópicos são mais consistentes com fontes de filiação carbonatítica, o que é reforçado pelos teores anômalos de P e ETR dos corpos de minério. Estimativas da composição dos fluidos mostram que a maioria dos valores de δ18O varia de -7,74‰ a -5,67‰ (a 150°C) e +0,64‰ a +2,71‰ (a 350°C), acusando participação de águas meteóricas no sistema hidrotermal do Sossego. Entretanto, valor mais elevado (+12,27‰ a 350°C) sugere assinatura de água magmática ou mesmo metamórfica naquele sistema. Apesar das especulações, a integração de dados de campo, mineralógicos, isotópicos (radiogênicos e estáveis) e de inclusões fluidas permite dizer que a mineralização ocorreu entre 2,76 e 2,60 Ga e muito provavelmente esteve ligada a processos metamórfico-deformacionais que desencadearam a migração de fluidos de elevadas salinidades, adquiridas ao reagirem com seqüências ricas em haletos, e com extraordinária capacidade de transportar grandes quantidades de metais, dentre eles Cu e Fe. 2019-10-29T13:35:03Z 2019-10-29T13:35:03Z 2006-10-30 Dissertação NEVES, Marcely Pereira. Estudos isotópicos (Pb-Pb, Sm-Nd, C e O) do depósito Cu-Au do Sossego, Província Mineral de Carajás. Orientador: Raimundo Netuno Nobre Villas. 2006. 104 f. Dissertação (Mestrado em Geologia e Geoquímica) - Instituto de Geociências, Universidade Federal do Pará, Belém, 2006. Disponível em: http://repositorio.ufpa.br/jspui/handle/2011/11959. Acesso em:. http://repositorio.ufpa.br/jspui/handle/2011/11959 por Acesso Aberto application/pdf Universidade Federal do Pará Brasil Instituto de Geociências UFPA Programa de Pós-Graduação em Geologia e Geoquímica 1 CD-ROM
institution Repositório Institucional - Universidade Federal do Pará
collection RI-UFPA
language por
topic Sedimentação e depósitos - Carajás, Serra dos (PA)
Isótopos
Minérios - Transporte
Sulfetos
CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA
GEOQUÍMICA E PETROLOGIA
spellingShingle Sedimentação e depósitos - Carajás, Serra dos (PA)
Isótopos
Minérios - Transporte
Sulfetos
CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA
GEOQUÍMICA E PETROLOGIA
NEVES, Marcely Pereira
Estudos isotópicos (Pb-Pb, Sm-Nd, C e O) do depósito Cu-Au do Sossego, Província Mineral de Carajás
topic_facet Sedimentação e depósitos - Carajás, Serra dos (PA)
Isótopos
Minérios - Transporte
Sulfetos
CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA
GEOQUÍMICA E PETROLOGIA
description The Sossego deposit is located at about 25 km NW of Canaã de Carajás, southeast of Pará, at the contact zone between the Grão Pará Group and basement rocks. This deposit comprises two main ore bodies, Sequeirinho and Sossego, which were formed in an environment where deformational processes, emplacement and cooling of intrusive bodies led to an intense hydrothermal fluid circulation. This work intended to characterize the ore host rocks, the mineralization styles and the types of hydrothermal alteration, as well as to date the sulfide mineralization and assess potential sources for metals and hydrothermal fluids. Invariably altered and deformed granitoids and mafic rocks, in addition to biotiterich rocks, hydrothermalites (magnetitites and ore bodies) and breccias occur in the deposit area. All these rocks are crosscut by mafic and felsic dikes. Albitization, epidotization, chloritization, silicification, amphibolitization and scapolitization were the main alteration processes recognized in the deposit. The first is more common in the granitoids while the last two are more typical of the mafic rocks. In these mafic rocks the concentration of actinolite increases towards the ore bodies resulting in the formation of actinolitites. A strong iron metasomatism was also identified, being responsible for the magnetitite generation. Abundant calcite-rich veinlets mark the final stage of the hydrothermal activity in the area. Although present in the Sequeirinho ore body, it was more intense in the Sossego ore body. Mineralization was subsequent to the shearing event and took place contemporaneously with the epidotization, chloritization and actinolization processes, allowing one to infer that mineralizating fluids, besides Cu, Au and P, were also enriched in Ca and Fe. Pb isotopic data in chalcopyrite from ore samples yielded ages of 2530 ± 25 Ma, 2608 ± 25 Ma (Sequeirinho ore body) and 1592 ± 45 Ma (Sossego ore body). The Archaean ages were discussed considering the hypotheses of the mineralization having or not a genetic link with the granitoids. In the first case, it could be related to the 2.76 – 2.74 Ga granitogenesis and the ages would represent the opening of the Pb isotopic system caused by subsequent thermal or deformational events. Alternatively, those ages could be related to the ~2.6 Ga magmatic event that is accounted for the dikes present at the neighboring Cu-Au 118 deposit, but its unexpressive significance in the Carajás region makes it unlikely to be responsible for the production of great cuprousauriferous deposits, like the Sossego. In the absence of a genetic link with granitoids, the mineralization could be related to metamorphic processes and the Pb-Pb ages would record the accompanying shearing event that caused the granitoid mylonitization and might have induced the infiltration of high salinity fluids, resulting in biotite-rich rocks with high Cl contents. No geological significance was given to the Mesoproterozoic age. A Sm-Nd isochron of 2578 ± 29 Ma was also obtained for ore samples. It is comparable to the Pb-Pb age of 2608 ± 25 Ma and most likely reflects an isotopic reequilibrium in response to later events. Model-ages (3.16 – 2.96 Ga) for the ore are similar to those of the deposit granitoid (3.12 – 2.98 Ga) and also to the Grão Pará Group basalts (2.76 – 3.09 Ga), suggesting that the ore could have been, at least in part, derived from these rocks. εNd values (-4.09 to -0.94) indicate an essentially crustal origin for both the host rocks and the ore. Based on the diagram εNd x t, it is plausible to admit that ore metals were derived from both granitoids and mafic rocks, especially the basalts from the Grão Pará Group. The δ 13CPDB values for calcite indicate a homogeneous source for C, probably mantle-derived. They show a negative linear correlation with the δ 18O values, suggesting a common evolution process. In terms of C and O natural reservoirs, the isotopic data are more consistent with sources of carbonatitic affiliation as indicated by the anomalous P and ETR contents found in the ore bodies. Calculation of δ 18Ofluid reveals that most values fall, respectively, in the ranges of -7.24 to -5.17‰ and +1.14‰ to +3.21‰ at 150° and 350ºC, being consistent with the participation of meteoric water in the Sossego hydrothermal system. However, higher values (+9.79‰ at 250ºC and +12.77‰ at 350ºC) suggest a magmatic or metamorphic water signature. Despite the speculations, integrating field, mineralogical, isotopic (stable and radiogenic) and fluid inclusion data allows to sustain that mineralization occurred at 2.76-2.60 Ga and was related to metamorphic-deformational processes, which triggered the migration of high saline fluids that had previously reacted with salt-rich sequences and became capable of transporting great amounts of metals, including Cu and Fe.
author_additional VILLAS, Raimundo Netuno Nobre
author_additionalStr VILLAS, Raimundo Netuno Nobre
format Dissertação
author NEVES, Marcely Pereira
title Estudos isotópicos (Pb-Pb, Sm-Nd, C e O) do depósito Cu-Au do Sossego, Província Mineral de Carajás
title_short Estudos isotópicos (Pb-Pb, Sm-Nd, C e O) do depósito Cu-Au do Sossego, Província Mineral de Carajás
title_full Estudos isotópicos (Pb-Pb, Sm-Nd, C e O) do depósito Cu-Au do Sossego, Província Mineral de Carajás
title_fullStr Estudos isotópicos (Pb-Pb, Sm-Nd, C e O) do depósito Cu-Au do Sossego, Província Mineral de Carajás
title_full_unstemmed Estudos isotópicos (Pb-Pb, Sm-Nd, C e O) do depósito Cu-Au do Sossego, Província Mineral de Carajás
title_sort estudos isotópicos (pb-pb, sm-nd, c e o) do depósito cu-au do sossego, província mineral de carajás
publisher Universidade Federal do Pará
publishDate 2019
url http://repositorio.ufpa.br/jspui/handle/2011/11959
_version_ 1787149368640405504
score 11.675088

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