Geologia, Geocronologia, Geoquímica e Petrogênese das rochas ígneas cretácicas da Província Magmática do Cabo e suas relações com as unidades sedimentares da Bacia de Pernambuco (NE do Brasil)

Detalhes bibliográficos
Autor(a) principal: Nascimento, Marcos Antonio Leite do
Data de Publicação: 2003
Tipo de documento: Tese
Idioma: por
Título da fonte: Repositório Institucional da UFRN
Texto Completo: https://repositorio.ufrn.br/jspui/handle/123456789/18361
Resumo: The area studied forms a thin NNE-directed belt situated south of Recife town (Pernambuco state), northeastern Brazil. Geologically, it comprises the Pernambuco Basin (PB), which is limited by the Pernambuco Lineament to the north, the Maragogi high to the south and the Pernambuco Alagoas massif to the west, all of them with Precambrian age. This thesis reports the results obtained for the Cabo Magmatic Province (CMP), aiming the characterization of the geology, stratigraphy, geochronology, geochemistry and petrogenesis of the Cretaceous igneous rocks presented in the PB. The PB is composed of the Cabo Formation (rift phase) at the base (polymictic conglomerates, sandstones, shales), an intermediate unit, the Estiva Formation (marbles and argillites), and, at the top, the Algodoais Formation (monomictic conglomerates, sandstones, shales). The CMP is represented by trachytes, rhyolites, pyroclastics (ignimbrites), basalts / trachy-andesites, monzonites and alkali-feldspar granite, which occur as dykes, flows, sills, laccoliths and plugs. Field observations and well descriptions show that the majority of the magmatic rocks have intrusive contacts with the Cabo Formation, although some occurrences are also suggestive of synchronism between volcanism and siliciclastic sedimentation. 40Ar/39Ar and zircon fission tracks for the magmatic rocks indicate an average age of 102 r 1 Ma for the CMP. This age represents an expressive event in the province and is detected in all igneous dated materials. It is considered as a minimum age (Albian) for the magmatic episode and the peak of the rift phase in the PB. The 40Ar/39Ar dates are about 10-14 Ma younger than published palynologic ages for this basin. Geochemically, the CMP may be divided in two major groups; i) a transitional to alkaline suite, constituted by basalts to trachy-andesites (types with fine-grained textures and phenocrysts of sanidine and plagioclase), trachytes (porphyrytic texture, with phenocrysts of sanidine and plagioclase) and monzonites; ii) a alkaline suite, highly fractionated, acidic volcano-plutonic association, formed by four subtypes (pyroclastic flows ignimbrites, fine-to medium-grained rhyolites, a high level granite, and later rhyolites). These four types are distinguished essentially by field aspects and petrographic and textural features. Compatible versus incompatible trace element concentrations and geochemical modeling based on both major and trace elements suggest the evolution through low pressure fractional crystallization for trachytes and other acidic rocks, whereas basalts / trachy-andesites and monzonites evolved by partial melting from a mantle source. Sr and Nd isotopes reveal two distinct sources for the rocks of the CMP. Concerning the acidic ones, the high initial Sr ratios (ISr = 0.7064-1.2295) and the negative HNd (-0.43 to -3.67) indicate a crustal source with mesoproterozoic model ages (TDM from 0.92 to 1.04 Ga). On the other hand, the basic to intermediate rocks have low ISr (0.7031-0.7042) and positive HNd (+1.28 to +1.98), which requires the depleted mantle as the most probable source; their model ages are in the range 0.61-0.66 Ga. However, the light rare earth enrichment of these rocks and partial melting modeling point to an incompatible-enriched lherzolitic mantle with very low quantity of garnet (1-3%). This apparent difference between geochemical and Nd isotopes may be resolved by assuming that the metasomatizing agent did not obliterate the original isotopic characteristics of the magmas. A 2 to 5% partial melting of this mantle at approximately 14 kbar and 1269oC account very well the basalts and trachy-andesites studied. By using these pressure and temperatures estimates for the generation of the basaltic to trachy-andesitic magma, it is determined a lithospheric stretching (E) of 2.5. This E value is an appropriated estimate for the sub-crustal stretching (astenospheric or the base of the lithosphere?) region under the Pernambuco Basin, the crustal stretching probably being lower. The integration of all data obtained in this thesis permits to interpret the magmatic evolution of the PB as follows; 1st) the partial melting of a garnet-bearing lherzolite generates incompatible-enriched basaltic, trachy-andesitic and monzonitic magmas; 2nd) the underplating of these basaltic magmas at the base of the continental crust triggers the partial melting of this crust, and thus originating the acidic magmas; 3rd) concomitantly with the previous stage, trachytic magmas were produced by fractionation from a monzonitic to trachy-andesitic liquid; 4th) the emplacement of the several magmas in superficial (e.g. flows) or sub-superficial (e.g. dykes, sills, domes, laccoliths) depths was almost synchronically, at about 102 r 1 Ma, and usually crosscutting the sedimentary rocks of the Cabo Formation. The presence of garnet in the lherzolitic mantle does not agree with pressures of about 14 kbar for the generation of the basaltic magma, as calculated based on chemical parameters. This can be resolved by admitting the astenospheric uplifting under the rift, which would place deep and hot material (mantle plume?) at sub-crustal depths. The generation of the magmas and their subsequent emplacement would be coupled with the crustal rifting of the PB, the border (NNE-SSW directed) and transfer (NW-SE directed) faults serving as conduits for the magma emplacement. Based on the E parameter and the integration of 40Ar/39Ar and palynologic data it is interpreted a maximum duration of 10-14 Ma for the rift phase (Cabo Formation clastic sedimentation and basic to acidic magmatism) of the PB
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spelling Nascimento, Marcos Antonio Leite dohttp://lattes.cnpq.br/5356037408083015http://lattes.cnpq.br/1259445348649589Matos, Renato Marcos Darros dehttp://lattes.cnpq.br/2387084052091889Sa, Emanuel Ferraz Jardim dehttp://lattes.cnpq.br/4094827215552998Souza, Zorano Sergio de2015-02-24T19:48:43Z2014-12-102015-02-24T19:48:43Z2003-12-22NASCIMENTO, Marcos Antonio Leite do. Geologia, Geocronologia, Geoquímica e Petrogênese das rochas ígneas cretácicas da Província Magmática do Cabo e suas relações com as unidades sedimentares da Bacia de Pernambuco (NE do Brasil). 2003. 302 f. Tese (Doutorado em Geodinâmica; Geofísica) - Universidade Federal do Rio Grande do Norte, Natal, 2003.https://repositorio.ufrn.br/jspui/handle/123456789/18361The area studied forms a thin NNE-directed belt situated south of Recife town (Pernambuco state), northeastern Brazil. Geologically, it comprises the Pernambuco Basin (PB), which is limited by the Pernambuco Lineament to the north, the Maragogi high to the south and the Pernambuco Alagoas massif to the west, all of them with Precambrian age. This thesis reports the results obtained for the Cabo Magmatic Province (CMP), aiming the characterization of the geology, stratigraphy, geochronology, geochemistry and petrogenesis of the Cretaceous igneous rocks presented in the PB. The PB is composed of the Cabo Formation (rift phase) at the base (polymictic conglomerates, sandstones, shales), an intermediate unit, the Estiva Formation (marbles and argillites), and, at the top, the Algodoais Formation (monomictic conglomerates, sandstones, shales). The CMP is represented by trachytes, rhyolites, pyroclastics (ignimbrites), basalts / trachy-andesites, monzonites and alkali-feldspar granite, which occur as dykes, flows, sills, laccoliths and plugs. Field observations and well descriptions show that the majority of the magmatic rocks have intrusive contacts with the Cabo Formation, although some occurrences are also suggestive of synchronism between volcanism and siliciclastic sedimentation. 40Ar/39Ar and zircon fission tracks for the magmatic rocks indicate an average age of 102 r 1 Ma for the CMP. This age represents an expressive event in the province and is detected in all igneous dated materials. It is considered as a minimum age (Albian) for the magmatic episode and the peak of the rift phase in the PB. The 40Ar/39Ar dates are about 10-14 Ma younger than published palynologic ages for this basin. Geochemically, the CMP may be divided in two major groups; i) a transitional to alkaline suite, constituted by basalts to trachy-andesites (types with fine-grained textures and phenocrysts of sanidine and plagioclase), trachytes (porphyrytic texture, with phenocrysts of sanidine and plagioclase) and monzonites; ii) a alkaline suite, highly fractionated, acidic volcano-plutonic association, formed by four subtypes (pyroclastic flows ignimbrites, fine-to medium-grained rhyolites, a high level granite, and later rhyolites). These four types are distinguished essentially by field aspects and petrographic and textural features. Compatible versus incompatible trace element concentrations and geochemical modeling based on both major and trace elements suggest the evolution through low pressure fractional crystallization for trachytes and other acidic rocks, whereas basalts / trachy-andesites and monzonites evolved by partial melting from a mantle source. Sr and Nd isotopes reveal two distinct sources for the rocks of the CMP. Concerning the acidic ones, the high initial Sr ratios (ISr = 0.7064-1.2295) and the negative HNd (-0.43 to -3.67) indicate a crustal source with mesoproterozoic model ages (TDM from 0.92 to 1.04 Ga). On the other hand, the basic to intermediate rocks have low ISr (0.7031-0.7042) and positive HNd (+1.28 to +1.98), which requires the depleted mantle as the most probable source; their model ages are in the range 0.61-0.66 Ga. However, the light rare earth enrichment of these rocks and partial melting modeling point to an incompatible-enriched lherzolitic mantle with very low quantity of garnet (1-3%). This apparent difference between geochemical and Nd isotopes may be resolved by assuming that the metasomatizing agent did not obliterate the original isotopic characteristics of the magmas. A 2 to 5% partial melting of this mantle at approximately 14 kbar and 1269oC account very well the basalts and trachy-andesites studied. By using these pressure and temperatures estimates for the generation of the basaltic to trachy-andesitic magma, it is determined a lithospheric stretching (E) of 2.5. This E value is an appropriated estimate for the sub-crustal stretching (astenospheric or the base of the lithosphere?) region under the Pernambuco Basin, the crustal stretching probably being lower. The integration of all data obtained in this thesis permits to interpret the magmatic evolution of the PB as follows; 1st) the partial melting of a garnet-bearing lherzolite generates incompatible-enriched basaltic, trachy-andesitic and monzonitic magmas; 2nd) the underplating of these basaltic magmas at the base of the continental crust triggers the partial melting of this crust, and thus originating the acidic magmas; 3rd) concomitantly with the previous stage, trachytic magmas were produced by fractionation from a monzonitic to trachy-andesitic liquid; 4th) the emplacement of the several magmas in superficial (e.g. flows) or sub-superficial (e.g. dykes, sills, domes, laccoliths) depths was almost synchronically, at about 102 r 1 Ma, and usually crosscutting the sedimentary rocks of the Cabo Formation. The presence of garnet in the lherzolitic mantle does not agree with pressures of about 14 kbar for the generation of the basaltic magma, as calculated based on chemical parameters. This can be resolved by admitting the astenospheric uplifting under the rift, which would place deep and hot material (mantle plume?) at sub-crustal depths. The generation of the magmas and their subsequent emplacement would be coupled with the crustal rifting of the PB, the border (NNE-SSW directed) and transfer (NW-SE directed) faults serving as conduits for the magma emplacement. Based on the E parameter and the integration of 40Ar/39Ar and palynologic data it is interpreted a maximum duration of 10-14 Ma for the rift phase (Cabo Formation clastic sedimentation and basic to acidic magmatism) of the PBA área pesquisada situa-se em uma estreita faixa de direção NNE no litoral sul do Estado de Pernambuco. Geologicamente, compreende a Bacia de Pernambuco (BP), situada entre o Lineamento Pernambuco (a norte), o Alto de Maragogi (a sul) e o Terreno Pernambuco-Alagoas (a oeste), os três últimos de idade Pré-Cambriana. Esta tese compreende os resultados obtidos para a Província Magmática do Cabo (PMC), com finalidade de caracterizar as relações geológicas, estratigráficas, geocronológicas, geoquímicas e petrogenéticos de rochas ígneas cretácicas presentes na BP. A BP é composta pelas formações Cabo (fase rifte), basal (conglomerados polimícticos, arenitos, folhelhos), Estiva (calcários, argilitos) e, no topo, Algodoais (conglomerados monomícticos, arenitos, folhelhos). A PMC é representada por traquitos, riolitos, piroclásticas (ignimbritos), basaltos / traqui-andesitos, monzonitos e álcali-feldspato granito, os quais ocorrem como diques, derrames, soleiras, lacólitos e plugs. Observações de campo e descrição de dados de poços demonstram que grande parte das rochas magmáticas é intrusiva na Formação Cabo, com algumas ocorrências também sugestivas de contemporaneidade com fácies siliciclásticas desta formação. Dados geocronológicos, usando as metodologias 40Ar/39Ar e traços de fissão em zircão, revelam uma idade de cerca de 102 r 1 Ma para as rochas da PMC. Esta idade representa um evento marcante em toda a província, haja vista a sua detecção em todos os tipos de materiais ígneos datados. Ela é considerada como uma idade mínima (Albiana) para o episódio magmático e o pico da fase rifte da BP. As idades 40Ar/39Ar são cerca de 10-14 Ma mais jovens do que as idades palinológicas disponíveis para a BP. Geoquimicamente, a PMC pode ser dividida em dois grupos: (i) uma suíte transicional a alcalina, subdividida em basaltos a traqui-andesitos (tipos de textura fina, contendo fenocristais de olivina, clinopiroxênio e plagioclásio), traquitos (textura porfirítica, com fenocristais de sanidina e plagioclásio) e monzonitos; (ii) uma associação vulcano-plutônica alcalina, de composição ácida bastante fracionada, constituída de quatro subconjuntos, um formado por rochas de fluxo piroclástico (ignimbritos), o segundo por riolitos de textura fina a média, ambos com fenocristais de quartzo e sanidina, o terceiro referente ao Granito do Cabo, contendo anfibólio alcalino, e por fim riolitos tardios. A distinção entre esses quatro tipos é feita com base essencialmente em aspectos de campo e petrográficos. A coerência dos padrões de elementos terras raras e de anomalias de Eu em cada grupo corroboram a separação dos mesmos. Razões entre elementos compatíveis e incompatíveis e modelamentos geoquímicos sugerem evolução por cristalização fracionada a baixas pressões para os traquitos e demais rochas ácidas, ao passo que basaltos / traqui-andesitos e monzonitos evoluíram por mecanismos de fusão parcial. Dados isotópicos de Sr e Nd revelam duas fontes distintas para a PMC. Para as rochas ácidas, as altas razões isotópicas iniciais de Sr (ISr = 0,7064-1,2295) e o epsilo de Nd negativo (HNd = -0,43 a -3,67) caracterizam uma fonte crustal, com idade mesoproterozóica (TDM = 0,92-1,04 Ga). Para as rochas básicas a intermediárias, as baixas razões isotópicas iniciais do Sr (ISr = 0,7031-0,7042) e o epsilo de Nd positivo (HNd = +1,28 a +1,98) indicam uma fonte primordial do tipo manto empobrecido, cujos magmas teriam sido extraídos de um manto neoproterozóico (TDM = 0,61-0,66 Ga). Todavia, o fracionamento dos elementos terras raras leves dessas rochas e modelos quantitativos de fusão parcial requerem um manto lherzolítico com pequenas quantidades de granada (1-3%), porém enriquecido em elementos incompatíveis. Esta aparente incoerência de dados geoquímicos e de isótopos de Nd pode se resolvida admitindo que o agente metassomatisante não apagou as características isotópicas originais dos magmas. Usando as composições químicas dos basaltos e traqui-andesitos, estima-se que os respectivos magmas foram gerados por taxas de fusão entre 2 e 5% de uma fonte lherzolítica, a pressões e temperaturas de cerca de 14 kbar e 1269oC. Tais parâmetros físicos são compatíveis com taxas de estiramento litosférico (E) em torno de 2,5. Em um modelo de estiramento uniforme, este valor de E seria válido para a evolução da bacia como um todo. Porém, em um modelo de estiramento heterogêneo, E seria menor para a porção crustal, em comparação com a porção subcrustal / mantélica. A integração dos dados obtidos sugere a evolução do magmatismo da BP conforme segue: 1º) fusão parcial (2-5%) do manto lherzolítico com pequena quantidade de granada (1-3%), gerando magmas basálticos, traqui-andesíticos e monzoníticos, enriquecidos em elementos incompatíveis, especialmente terras raras leves; 2º) posicionamento destes magmas na base da crosta continental, provocando a fusão parcial (em graus variados e a diferentes profundidades) desta e, assim, originando os magmas ácidos; 3º) concomitante à fase prévia, magmas traquíticos seriam produzidos por fracionamento a partir de um líquido monzonítico; 4º) colocação dos diversos magmas em níveis superficiais (derrames) ou subsuperficiais / hipabissais quase que sincronicamente, em geral intrusivos no pacote de rochas sedimentares da Formação Cabo, marcando o pico (ou final) da fase rifte na BP. A suposta presença de granada na fonte lherzolítica não condiz com as profundidades de cerca de 14 kbar para a geração magma basáltico, obtida por parâmetros químicos. Isto pode ser acomodado admitindo-se o soerguimento astenosférico sob o rifte, o que colocaria material quente (pluma?) oriundos de grandes profundidades (granada lherzolito) em níveis subcrustais. A geração dos magmas e o subseqüente posicionamento de grande volume dos mesmos estariam acoplados ao processo de rifteamento da BP, com controle de falhas de borda (NNE-SSW) e de transferência (NW-SE) como sítios de colocação dos magmas. Com base no fator de estiramento (E_ e no confronto de dados geocronológicos 40Ar/39Ar e palinológicos, deduz-se que a fase rifte (sedimentação clástica a pelítica da Formação Cabo e magmatismo básico a ácido) teve uma duração máxima de 10-14 MaConselho Nacional de Desenvolvimento Científico e Tecnológicoapplication/pdfporUniversidade Federal do Rio Grande do NortePrograma de Pós-Graduação em Geodinâmica e GeofísicaUFRNBRGeodinâmica; GeofísicaGeologiaGeocronologiaProvíncia Magmática do CaboBacia de PernambucoCNPQ::CIENCIAS EXATAS E DA TERRAGeologia, Geocronologia, Geoquímica e Petrogênese das rochas ígneas cretácicas da Província Magmática do Cabo e suas relações com as unidades sedimentares da Bacia de Pernambuco (NE do Brasil)info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesisinfo:eu-repo/semantics/openAccessreponame:Repositório Institucional da UFRNinstname:Universidade Federal do Rio Grande do Norte (UFRN)instacron:UFRNORIGINALMarcosALN_TESE.pdfMarcosALN_TESE.pdfapplication/pdf15698432https://repositorio.ufrn.br/bitstream/123456789/18361/1/MarcosALN_TESE.pdf7e92d6f1dcbca85fae176743ecb064a7MD51TEXTMarcosALN_TESE.pdf.txtMarcosALN_TESE.pdf.txtExtracted texttext/plain701096https://repositorio.ufrn.br/bitstream/123456789/18361/6/MarcosALN_TESE.pdf.txt6e27782994db3d96d3fe44014dfa416eMD56THUMBNAILMarcosALN_TESE.pdf.jpgMarcosALN_TESE.pdf.jpgIM Thumbnailimage/jpeg4017https://repositorio.ufrn.br/bitstream/123456789/18361/7/MarcosALN_TESE.pdf.jpgfdcafba98b4e379f607a9b09bc255363MD57123456789/183612017-11-02 13:21:06.652oai:https://repositorio.ufrn.br:123456789/18361Repositório de PublicaçõesPUBhttp://repositorio.ufrn.br/oai/opendoar:2017-11-02T16:21:06Repositório Institucional da UFRN - Universidade Federal do Rio Grande do Norte (UFRN)false
dc.title.por.fl_str_mv Geologia, Geocronologia, Geoquímica e Petrogênese das rochas ígneas cretácicas da Província Magmática do Cabo e suas relações com as unidades sedimentares da Bacia de Pernambuco (NE do Brasil)
title Geologia, Geocronologia, Geoquímica e Petrogênese das rochas ígneas cretácicas da Província Magmática do Cabo e suas relações com as unidades sedimentares da Bacia de Pernambuco (NE do Brasil)
spellingShingle Geologia, Geocronologia, Geoquímica e Petrogênese das rochas ígneas cretácicas da Província Magmática do Cabo e suas relações com as unidades sedimentares da Bacia de Pernambuco (NE do Brasil)
Nascimento, Marcos Antonio Leite do
Geologia
Geocronologia
Província Magmática do Cabo
Bacia de Pernambuco
CNPQ::CIENCIAS EXATAS E DA TERRA
title_short Geologia, Geocronologia, Geoquímica e Petrogênese das rochas ígneas cretácicas da Província Magmática do Cabo e suas relações com as unidades sedimentares da Bacia de Pernambuco (NE do Brasil)
title_full Geologia, Geocronologia, Geoquímica e Petrogênese das rochas ígneas cretácicas da Província Magmática do Cabo e suas relações com as unidades sedimentares da Bacia de Pernambuco (NE do Brasil)
title_fullStr Geologia, Geocronologia, Geoquímica e Petrogênese das rochas ígneas cretácicas da Província Magmática do Cabo e suas relações com as unidades sedimentares da Bacia de Pernambuco (NE do Brasil)
title_full_unstemmed Geologia, Geocronologia, Geoquímica e Petrogênese das rochas ígneas cretácicas da Província Magmática do Cabo e suas relações com as unidades sedimentares da Bacia de Pernambuco (NE do Brasil)
title_sort Geologia, Geocronologia, Geoquímica e Petrogênese das rochas ígneas cretácicas da Província Magmática do Cabo e suas relações com as unidades sedimentares da Bacia de Pernambuco (NE do Brasil)
author Nascimento, Marcos Antonio Leite do
author_facet Nascimento, Marcos Antonio Leite do
author_role author
dc.contributor.authorID.por.fl_str_mv
dc.contributor.authorLattes.por.fl_str_mv http://lattes.cnpq.br/5356037408083015
dc.contributor.advisorID.por.fl_str_mv
dc.contributor.advisorLattes.por.fl_str_mv http://lattes.cnpq.br/1259445348649589
dc.contributor.advisor-co1ID.por.fl_str_mv
dc.contributor.referees1.pt_BR.fl_str_mv Sa, Emanuel Ferraz Jardim de
dc.contributor.referees1ID.por.fl_str_mv
dc.contributor.referees1Lattes.por.fl_str_mv http://lattes.cnpq.br/4094827215552998
dc.contributor.author.fl_str_mv Nascimento, Marcos Antonio Leite do
dc.contributor.advisor-co1.fl_str_mv Matos, Renato Marcos Darros de
dc.contributor.advisor-co1Lattes.fl_str_mv http://lattes.cnpq.br/2387084052091889
dc.contributor.advisor1.fl_str_mv Souza, Zorano Sergio de
contributor_str_mv Matos, Renato Marcos Darros de
Souza, Zorano Sergio de
dc.subject.por.fl_str_mv Geologia
Geocronologia
Província Magmática do Cabo
Bacia de Pernambuco
topic Geologia
Geocronologia
Província Magmática do Cabo
Bacia de Pernambuco
CNPQ::CIENCIAS EXATAS E DA TERRA
dc.subject.cnpq.fl_str_mv CNPQ::CIENCIAS EXATAS E DA TERRA
description The area studied forms a thin NNE-directed belt situated south of Recife town (Pernambuco state), northeastern Brazil. Geologically, it comprises the Pernambuco Basin (PB), which is limited by the Pernambuco Lineament to the north, the Maragogi high to the south and the Pernambuco Alagoas massif to the west, all of them with Precambrian age. This thesis reports the results obtained for the Cabo Magmatic Province (CMP), aiming the characterization of the geology, stratigraphy, geochronology, geochemistry and petrogenesis of the Cretaceous igneous rocks presented in the PB. The PB is composed of the Cabo Formation (rift phase) at the base (polymictic conglomerates, sandstones, shales), an intermediate unit, the Estiva Formation (marbles and argillites), and, at the top, the Algodoais Formation (monomictic conglomerates, sandstones, shales). The CMP is represented by trachytes, rhyolites, pyroclastics (ignimbrites), basalts / trachy-andesites, monzonites and alkali-feldspar granite, which occur as dykes, flows, sills, laccoliths and plugs. Field observations and well descriptions show that the majority of the magmatic rocks have intrusive contacts with the Cabo Formation, although some occurrences are also suggestive of synchronism between volcanism and siliciclastic sedimentation. 40Ar/39Ar and zircon fission tracks for the magmatic rocks indicate an average age of 102 r 1 Ma for the CMP. This age represents an expressive event in the province and is detected in all igneous dated materials. It is considered as a minimum age (Albian) for the magmatic episode and the peak of the rift phase in the PB. The 40Ar/39Ar dates are about 10-14 Ma younger than published palynologic ages for this basin. Geochemically, the CMP may be divided in two major groups; i) a transitional to alkaline suite, constituted by basalts to trachy-andesites (types with fine-grained textures and phenocrysts of sanidine and plagioclase), trachytes (porphyrytic texture, with phenocrysts of sanidine and plagioclase) and monzonites; ii) a alkaline suite, highly fractionated, acidic volcano-plutonic association, formed by four subtypes (pyroclastic flows ignimbrites, fine-to medium-grained rhyolites, a high level granite, and later rhyolites). These four types are distinguished essentially by field aspects and petrographic and textural features. Compatible versus incompatible trace element concentrations and geochemical modeling based on both major and trace elements suggest the evolution through low pressure fractional crystallization for trachytes and other acidic rocks, whereas basalts / trachy-andesites and monzonites evolved by partial melting from a mantle source. Sr and Nd isotopes reveal two distinct sources for the rocks of the CMP. Concerning the acidic ones, the high initial Sr ratios (ISr = 0.7064-1.2295) and the negative HNd (-0.43 to -3.67) indicate a crustal source with mesoproterozoic model ages (TDM from 0.92 to 1.04 Ga). On the other hand, the basic to intermediate rocks have low ISr (0.7031-0.7042) and positive HNd (+1.28 to +1.98), which requires the depleted mantle as the most probable source; their model ages are in the range 0.61-0.66 Ga. However, the light rare earth enrichment of these rocks and partial melting modeling point to an incompatible-enriched lherzolitic mantle with very low quantity of garnet (1-3%). This apparent difference between geochemical and Nd isotopes may be resolved by assuming that the metasomatizing agent did not obliterate the original isotopic characteristics of the magmas. A 2 to 5% partial melting of this mantle at approximately 14 kbar and 1269oC account very well the basalts and trachy-andesites studied. By using these pressure and temperatures estimates for the generation of the basaltic to trachy-andesitic magma, it is determined a lithospheric stretching (E) of 2.5. This E value is an appropriated estimate for the sub-crustal stretching (astenospheric or the base of the lithosphere?) region under the Pernambuco Basin, the crustal stretching probably being lower. The integration of all data obtained in this thesis permits to interpret the magmatic evolution of the PB as follows; 1st) the partial melting of a garnet-bearing lherzolite generates incompatible-enriched basaltic, trachy-andesitic and monzonitic magmas; 2nd) the underplating of these basaltic magmas at the base of the continental crust triggers the partial melting of this crust, and thus originating the acidic magmas; 3rd) concomitantly with the previous stage, trachytic magmas were produced by fractionation from a monzonitic to trachy-andesitic liquid; 4th) the emplacement of the several magmas in superficial (e.g. flows) or sub-superficial (e.g. dykes, sills, domes, laccoliths) depths was almost synchronically, at about 102 r 1 Ma, and usually crosscutting the sedimentary rocks of the Cabo Formation. The presence of garnet in the lherzolitic mantle does not agree with pressures of about 14 kbar for the generation of the basaltic magma, as calculated based on chemical parameters. This can be resolved by admitting the astenospheric uplifting under the rift, which would place deep and hot material (mantle plume?) at sub-crustal depths. The generation of the magmas and their subsequent emplacement would be coupled with the crustal rifting of the PB, the border (NNE-SSW directed) and transfer (NW-SE directed) faults serving as conduits for the magma emplacement. Based on the E parameter and the integration of 40Ar/39Ar and palynologic data it is interpreted a maximum duration of 10-14 Ma for the rift phase (Cabo Formation clastic sedimentation and basic to acidic magmatism) of the PB
publishDate 2003
dc.date.issued.fl_str_mv 2003-12-22
dc.date.available.fl_str_mv 2014-12-10
2015-02-24T19:48:43Z
dc.date.accessioned.fl_str_mv 2015-02-24T19:48:43Z
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dc.identifier.citation.fl_str_mv NASCIMENTO, Marcos Antonio Leite do. Geologia, Geocronologia, Geoquímica e Petrogênese das rochas ígneas cretácicas da Província Magmática do Cabo e suas relações com as unidades sedimentares da Bacia de Pernambuco (NE do Brasil). 2003. 302 f. Tese (Doutorado em Geodinâmica; Geofísica) - Universidade Federal do Rio Grande do Norte, Natal, 2003.
dc.identifier.uri.fl_str_mv https://repositorio.ufrn.br/jspui/handle/123456789/18361
identifier_str_mv NASCIMENTO, Marcos Antonio Leite do. Geologia, Geocronologia, Geoquímica e Petrogênese das rochas ígneas cretácicas da Província Magmática do Cabo e suas relações com as unidades sedimentares da Bacia de Pernambuco (NE do Brasil). 2003. 302 f. Tese (Doutorado em Geodinâmica; Geofísica) - Universidade Federal do Rio Grande do Norte, Natal, 2003.
url https://repositorio.ufrn.br/jspui/handle/123456789/18361
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dc.publisher.none.fl_str_mv Universidade Federal do Rio Grande do Norte
dc.publisher.program.fl_str_mv Programa de Pós-Graduação em Geodinâmica e Geofísica
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dc.publisher.country.fl_str_mv BR
dc.publisher.department.fl_str_mv Geodinâmica; Geofísica
publisher.none.fl_str_mv Universidade Federal do Rio Grande do Norte
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