Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazil
Autor(a) principal: | |
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Data de Publicação: | 2000 |
Outros Autores: | , , , , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Anais da Academia Brasileira de Ciências (Online) |
Texto Completo: | http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652000000400006 |
Resumo: | Carbon isotope fluctuations in Precambrian sedimentary carbonates between 2.8 Ga and 0.60 Ga in Brazil are examined in this study. The carbonate facies of the BIF of the 2.8 Ga-old Carajás Formation, state of Pará in northern Brazil, has rather homogeneous delta13C (-5 o/ooPDB), compatible with carbonatization of a silicate protolith by a CO2-rich fluid from mantle degassing. The Paleoproterozoic Gandarela Formation, state of Minas Gerais, displays a narrow delta13C variation (-1.5 to +0.5 o/oo) compatible with carbon isotope signatures of carbonates deposited around 2.4 Ga worldwide. The Fecho do Funil Formation has probably recorded the Lomagundi delta13C positive anomaly (+6.4 to +7.1 o/ooPDB). The magnesite-bearing carbonates of the Orós mobile belt, state of Ceará, exhibit carbon isotope fluctuation within the range for carbonates deposited at 1.8 Ga. The C-isotope record of the Frecheirinha Formation, northwestern state of Ceará, shows negative delta13C values in its lower portion (-2 o/oo) and positive values up section (+1 to +3 o/oo), which suggests this sequence is a cap carbonate deposited after a glacial event around 0.95 Ga. The Jacoca and Acauã sedimentary carbonate Formations, state of Sergipe, NE Brazil, show carbon isotope fluctuations very similar to each other (average around -5 o/oo), compatible with a deposition around 0.76 Ga. The younger Olho D'Água carbonate Formation, however, also in the state of Sergipe, displays negative delta13C values at the lower portion of the Formation, changing dramatically up section to positive values as high as +10 o/oo, a characteristic compatible with a Sturtian cap carbonate deposited around 0.69 Ga. On the light of the C isotope data discussed in this study, it seems that delta13C fluctuations in Paleoproterozoic carbonates in Brazil are within the range found globally for metasedimentary carbonates of this age. Carbon isotope data proved to be very useful in establishing relative chronology of Neoproterozoic carbonate formations for which precise radiometric ages are not available. |
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Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazilcarbon isotopescarbonateschemostratigraphyArcheanPaleoproterozoicNeoproterozoicCarbon isotope fluctuations in Precambrian sedimentary carbonates between 2.8 Ga and 0.60 Ga in Brazil are examined in this study. The carbonate facies of the BIF of the 2.8 Ga-old Carajás Formation, state of Pará in northern Brazil, has rather homogeneous delta13C (-5 o/ooPDB), compatible with carbonatization of a silicate protolith by a CO2-rich fluid from mantle degassing. The Paleoproterozoic Gandarela Formation, state of Minas Gerais, displays a narrow delta13C variation (-1.5 to +0.5 o/oo) compatible with carbon isotope signatures of carbonates deposited around 2.4 Ga worldwide. The Fecho do Funil Formation has probably recorded the Lomagundi delta13C positive anomaly (+6.4 to +7.1 o/ooPDB). The magnesite-bearing carbonates of the Orós mobile belt, state of Ceará, exhibit carbon isotope fluctuation within the range for carbonates deposited at 1.8 Ga. The C-isotope record of the Frecheirinha Formation, northwestern state of Ceará, shows negative delta13C values in its lower portion (-2 o/oo) and positive values up section (+1 to +3 o/oo), which suggests this sequence is a cap carbonate deposited after a glacial event around 0.95 Ga. The Jacoca and Acauã sedimentary carbonate Formations, state of Sergipe, NE Brazil, show carbon isotope fluctuations very similar to each other (average around -5 o/oo), compatible with a deposition around 0.76 Ga. The younger Olho D'Água carbonate Formation, however, also in the state of Sergipe, displays negative delta13C values at the lower portion of the Formation, changing dramatically up section to positive values as high as +10 o/oo, a characteristic compatible with a Sturtian cap carbonate deposited around 0.69 Ga. On the light of the C isotope data discussed in this study, it seems that delta13C fluctuations in Paleoproterozoic carbonates in Brazil are within the range found globally for metasedimentary carbonates of this age. Carbon isotope data proved to be very useful in establishing relative chronology of Neoproterozoic carbonate formations for which precise radiometric ages are not available.Academia Brasileira de Ciências2000-12-01info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersiontext/htmlhttp://old.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652000000400006Anais da Academia Brasileira de Ciências v.72 n.4 2000reponame:Anais da Academia Brasileira de Ciências (Online)instname:Academia Brasileira de Ciências (ABC)instacron:ABC10.1590/S0001-37652000000400006info:eu-repo/semantics/openAccessSIAL,ALCIDES N.FERREIRA,VALDEREZ P.DEALMEIDA,AFONSO R.ROMANO,ANTONIO W.PARENTE,CLOVIS V.DACOSTA,MARCONDES L.SANTOS,VICTOR H.eng2001-01-05T00:00:00Zoai:scielo:S0001-37652000000400006Revistahttp://www.scielo.br/aabchttps://old.scielo.br/oai/scielo-oai.php||aabc@abc.org.br1678-26900001-3765opendoar:2001-01-05T00:00Anais da Academia Brasileira de Ciências (Online) - Academia Brasileira de Ciências (ABC)false |
dc.title.none.fl_str_mv |
Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazil |
title |
Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazil |
spellingShingle |
Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazil SIAL,ALCIDES N. carbon isotopes carbonates chemostratigraphy Archean Paleoproterozoic Neoproterozoic |
title_short |
Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazil |
title_full |
Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazil |
title_fullStr |
Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazil |
title_full_unstemmed |
Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazil |
title_sort |
Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazil |
author |
SIAL,ALCIDES N. |
author_facet |
SIAL,ALCIDES N. FERREIRA,VALDEREZ P. DEALMEIDA,AFONSO R. ROMANO,ANTONIO W. PARENTE,CLOVIS V. DACOSTA,MARCONDES L. SANTOS,VICTOR H. |
author_role |
author |
author2 |
FERREIRA,VALDEREZ P. DEALMEIDA,AFONSO R. ROMANO,ANTONIO W. PARENTE,CLOVIS V. DACOSTA,MARCONDES L. SANTOS,VICTOR H. |
author2_role |
author author author author author author |
dc.contributor.author.fl_str_mv |
SIAL,ALCIDES N. FERREIRA,VALDEREZ P. DEALMEIDA,AFONSO R. ROMANO,ANTONIO W. PARENTE,CLOVIS V. DACOSTA,MARCONDES L. SANTOS,VICTOR H. |
dc.subject.por.fl_str_mv |
carbon isotopes carbonates chemostratigraphy Archean Paleoproterozoic Neoproterozoic |
topic |
carbon isotopes carbonates chemostratigraphy Archean Paleoproterozoic Neoproterozoic |
description |
Carbon isotope fluctuations in Precambrian sedimentary carbonates between 2.8 Ga and 0.60 Ga in Brazil are examined in this study. The carbonate facies of the BIF of the 2.8 Ga-old Carajás Formation, state of Pará in northern Brazil, has rather homogeneous delta13C (-5 o/ooPDB), compatible with carbonatization of a silicate protolith by a CO2-rich fluid from mantle degassing. The Paleoproterozoic Gandarela Formation, state of Minas Gerais, displays a narrow delta13C variation (-1.5 to +0.5 o/oo) compatible with carbon isotope signatures of carbonates deposited around 2.4 Ga worldwide. The Fecho do Funil Formation has probably recorded the Lomagundi delta13C positive anomaly (+6.4 to +7.1 o/ooPDB). The magnesite-bearing carbonates of the Orós mobile belt, state of Ceará, exhibit carbon isotope fluctuation within the range for carbonates deposited at 1.8 Ga. The C-isotope record of the Frecheirinha Formation, northwestern state of Ceará, shows negative delta13C values in its lower portion (-2 o/oo) and positive values up section (+1 to +3 o/oo), which suggests this sequence is a cap carbonate deposited after a glacial event around 0.95 Ga. The Jacoca and Acauã sedimentary carbonate Formations, state of Sergipe, NE Brazil, show carbon isotope fluctuations very similar to each other (average around -5 o/oo), compatible with a deposition around 0.76 Ga. The younger Olho D'Água carbonate Formation, however, also in the state of Sergipe, displays negative delta13C values at the lower portion of the Formation, changing dramatically up section to positive values as high as +10 o/oo, a characteristic compatible with a Sturtian cap carbonate deposited around 0.69 Ga. On the light of the C isotope data discussed in this study, it seems that delta13C fluctuations in Paleoproterozoic carbonates in Brazil are within the range found globally for metasedimentary carbonates of this age. Carbon isotope data proved to be very useful in establishing relative chronology of Neoproterozoic carbonate formations for which precise radiometric ages are not available. |
publishDate |
2000 |
dc.date.none.fl_str_mv |
2000-12-01 |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652000000400006 |
url |
http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652000000400006 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
10.1590/S0001-37652000000400006 |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
text/html |
dc.publisher.none.fl_str_mv |
Academia Brasileira de Ciências |
publisher.none.fl_str_mv |
Academia Brasileira de Ciências |
dc.source.none.fl_str_mv |
Anais da Academia Brasileira de Ciências v.72 n.4 2000 reponame:Anais da Academia Brasileira de Ciências (Online) instname:Academia Brasileira de Ciências (ABC) instacron:ABC |
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Academia Brasileira de Ciências (ABC) |
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ABC |
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ABC |
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Anais da Academia Brasileira de Ciências (Online) |
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Anais da Academia Brasileira de Ciências (Online) |
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Anais da Academia Brasileira de Ciências (Online) - Academia Brasileira de Ciências (ABC) |
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||aabc@abc.org.br |
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1754302855429226496 |