Geology and petrology of the Frade alkaline mafic-ultramafic layered complex in the São Sebastião Island, Southeastern, Brazil

Detalhes bibliográficos
Autor(a) principal: Giraldo Arroyave, Maria Isabel
Data de Publicação: 2020
Tipo de documento: Tese
Idioma: eng
Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
Texto Completo: https://www.teses.usp.br/teses/disponiveis/44/44143/tde-26012021-163726/
Resumo: The Frade Alkaline Mafic-Ultramafic Layered Complex crops out to south of the São Sebastião Island on the north coast of the state of São Pablo State (Brazil). It is a small plutonic intrusive with a ring sill-like shape and a maximum thickness estimated in 350 m, associated with younger ultramafic and felsic dikes, and - micro olivine clinopyroxenites and micro (mela) gabbros as dikes, sills and enclaves. Geochronological estimations indicate that emplacement took place at 88 Ma at shallow crustal level, around 2-3 km, liquidus temperature about 1050°C; the late crystallization suggests close-to-solidus temperature of ~870°C in average. The high temperature promoted a contact aureole in the host porphyritic granodiorites, evidenced in the development of recrystallization textures and granophyric intergrowths as well as orthopyroxene development and chemical and isotopic exchange in the contact zone. The mafic intrusive displays well-developed layered structures at the base of the sequence that vary to a strong mineral lamination upwards. The structures, textures, as well as the cumulus and intercumulus mineralogy allow recognizing 4 main gabbroic units, which, from the bottom to the top, are: 1) Lower Gabbro Sequence (LGS); 2) Intermediate Gabbro Sequence (IGS); 3) Upper Gabbro Sequence (UGS); 4) Massive Leucogabbros (MLG). It is thought that the rocks from the LGS, IGS, and UGS were formed from the same magma batch undergoing fractional crystallization and modification of the main ferromagnesian minerals by interaction with the intercumulus liquid. Crystallization is accompanied by minor crustal contamination reflected in the progressive increase in the 87Sr/86Sri isotope composition in plagioclase and apatite through stratigraphy coupled with depletion in the 143Nd/144Ndi over apatite. The Massive Leucogabbros represent a period of recharge by a less evolved and less contaminated magma keeping the chemical and isotopic signatures of the common source with the Frade Intrusive. In this rock, the intercumulus mafic assemblage probably was formed by the interaction of the resident magma with the primitive melt. Associated to the Frade Intrusion, ultramafic (picrite and micro peridotite) and melanocratic porphyritic subvolcanic rocks have been recognized in the form of dikes, sills and enclaves. The relationship of these porhyritic melanocratic rocks and the main intrusive is given by the similarities in the chemical characteristics of the main mineral phases, but also the isotopic Sr composition of plagioclase. Detailed chemical analysis allowed to characterize the different crystal population. Macrocryst of pyroxene were defined as MC1 and MC2. In the porphyritic clinopyroxenites, MC1 cores are mostly antecryst Crdiopsides recycled from a source located at a depth of ~8 km. MC2 macrocryst are Al-diopsides phenocryst crystallized in a magma chamber located at a depth of ~6 km, which is probably the same magmatic source of the Frade Intrusive. MC2 phenocrysts define an evolutionary trend with rims and groundmass pyroxenes by progressive fractional crystallization during magma ascent and emplacement in a shallow magma chamber located ~3 km depth, the Frade magma chamber. Olivine macrocryst show a well differentiation path with the groundmass crystals. If they were antecryst they re-equilibrated with the host magma that formed the Frade Mafic Intrusive. The chemical and isotopic differences in the picrite and micro peridotite, indicate a complex evolution in the magmatic plumbing system involving deeper zones of a heterogeneous mantle source. The picrite probably formed by mixing with a magma with a more primitive H2O and CO2 rich melt emplaced at 86 Ma ( 40Ar/39Ar data in amphibole). Contemporaneous trachytes, phonolites and alkali-feldspar dikes and SiO2-undersaturated and oversaturated syenite varieties, were emplaced into the upper crust cross cutting the Frade Layered Intrusive. All the described lithologies belong to the north sector of the Serra do Mar Province an represent a spatial and temporal association of a continuous bimodal magmatism that occurred in a short period of about 5 Ma.
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spelling Geology and petrology of the Frade alkaline mafic-ultramafic layered complex in the São Sebastião Island, Southeastern, Brazilnot availableAlkaline magmatismGeochemistryIgneous PetrologyLayered mafic intrusionMafic-Ultramafic cumulatesnot availableThe Frade Alkaline Mafic-Ultramafic Layered Complex crops out to south of the São Sebastião Island on the north coast of the state of São Pablo State (Brazil). It is a small plutonic intrusive with a ring sill-like shape and a maximum thickness estimated in 350 m, associated with younger ultramafic and felsic dikes, and - micro olivine clinopyroxenites and micro (mela) gabbros as dikes, sills and enclaves. Geochronological estimations indicate that emplacement took place at 88 Ma at shallow crustal level, around 2-3 km, liquidus temperature about 1050°C; the late crystallization suggests close-to-solidus temperature of ~870°C in average. The high temperature promoted a contact aureole in the host porphyritic granodiorites, evidenced in the development of recrystallization textures and granophyric intergrowths as well as orthopyroxene development and chemical and isotopic exchange in the contact zone. The mafic intrusive displays well-developed layered structures at the base of the sequence that vary to a strong mineral lamination upwards. The structures, textures, as well as the cumulus and intercumulus mineralogy allow recognizing 4 main gabbroic units, which, from the bottom to the top, are: 1) Lower Gabbro Sequence (LGS); 2) Intermediate Gabbro Sequence (IGS); 3) Upper Gabbro Sequence (UGS); 4) Massive Leucogabbros (MLG). It is thought that the rocks from the LGS, IGS, and UGS were formed from the same magma batch undergoing fractional crystallization and modification of the main ferromagnesian minerals by interaction with the intercumulus liquid. Crystallization is accompanied by minor crustal contamination reflected in the progressive increase in the 87Sr/86Sri isotope composition in plagioclase and apatite through stratigraphy coupled with depletion in the 143Nd/144Ndi over apatite. The Massive Leucogabbros represent a period of recharge by a less evolved and less contaminated magma keeping the chemical and isotopic signatures of the common source with the Frade Intrusive. In this rock, the intercumulus mafic assemblage probably was formed by the interaction of the resident magma with the primitive melt. Associated to the Frade Intrusion, ultramafic (picrite and micro peridotite) and melanocratic porphyritic subvolcanic rocks have been recognized in the form of dikes, sills and enclaves. The relationship of these porhyritic melanocratic rocks and the main intrusive is given by the similarities in the chemical characteristics of the main mineral phases, but also the isotopic Sr composition of plagioclase. Detailed chemical analysis allowed to characterize the different crystal population. Macrocryst of pyroxene were defined as MC1 and MC2. In the porphyritic clinopyroxenites, MC1 cores are mostly antecryst Crdiopsides recycled from a source located at a depth of ~8 km. MC2 macrocryst are Al-diopsides phenocryst crystallized in a magma chamber located at a depth of ~6 km, which is probably the same magmatic source of the Frade Intrusive. MC2 phenocrysts define an evolutionary trend with rims and groundmass pyroxenes by progressive fractional crystallization during magma ascent and emplacement in a shallow magma chamber located ~3 km depth, the Frade magma chamber. Olivine macrocryst show a well differentiation path with the groundmass crystals. If they were antecryst they re-equilibrated with the host magma that formed the Frade Mafic Intrusive. The chemical and isotopic differences in the picrite and micro peridotite, indicate a complex evolution in the magmatic plumbing system involving deeper zones of a heterogeneous mantle source. The picrite probably formed by mixing with a magma with a more primitive H2O and CO2 rich melt emplaced at 86 Ma ( 40Ar/39Ar data in amphibole). Contemporaneous trachytes, phonolites and alkali-feldspar dikes and SiO2-undersaturated and oversaturated syenite varieties, were emplaced into the upper crust cross cutting the Frade Layered Intrusive. All the described lithologies belong to the north sector of the Serra do Mar Province an represent a spatial and temporal association of a continuous bimodal magmatism that occurred in a short period of about 5 Ma.O Complexo Máfico-ultramáfico do Frade está localizado ao sul da Ilha de São Sebastião, na costa norte do estado de São Paulo (Brasil). Trata-se de um pequeno corpo intrusivo plutônico de forma arqueada com espessura máxima estimada em 350 m, associado a diques ultramáficos e félsicos mais jovens e olivina clinopiroxênitos, e micro mela-gabbros colocados em forma de diques, sills e enclaves. Dados geocronológicos indicam que a colocação ocorreu há 88 Ma em um nível superficial da crosta, em torno de 3 km, a uma temperatura magmática máxima de 1050 ° C e cristalização magmática tardia em torno de 871 ° C. A alta temperatura da intrusão do complexo promoveu uma auréola de contato nos granodioritos porfiríticos hospedeiros, evidenciada pelo desenvolvimento de texturas de recristalização e crescimentos granófricos, além de trocas químicas e isotópicas na zona do contato. O corpo intrusivo máfico de Frade exibe estruturas de sedimentação bem desenvolvidas, especialmente na base da sequência que varia para uma laminação mineral para o topo. A mineralogia cumulus e intercumulus permitem o reconhecimento de 4 unidades principais: 1. sequência gabro inferior (LGS): 2. sequência intermediaria do gabro (IGS); 3. sequência gabro superior (UGS); 4. Leucogabro massivo (MLG). Pensa-se que as rochas do LGS, IGS e UGS são formadas a partir do mesmo pulso magmático, sofrendo cristalização fracionada e modificação dos principais minerais ferromagnesianos por interação com o líquido intercumulus. A cristalização é acompanhada por contaminação crustal refletida pelo aumento progressivo a longo da estratigrafia da composição 87Sr/86Sri, juntamente com a depleção na ração 143Nd/144Ndi. Já os leucogabbros massivos (MLG) representam um período de recarga por um magma menos evoluído e menos contaminado, mantendo as assinaturas químicas e isotópicas da fonte comum com o intrusivo de Frade. Nesta rocha (MLG), a assembleia máfica intercumulus provavelmente foi formada pela interação do magma residente com o líquido primitivo. Associadas à intrusivo de Frade, rochas melanocraticas porfirticas sub-vulcânicas e ultramáficas (picritos e micro peridotitos) foram reconhecidas na forma de diques, sills e enclaves. A relação dessas rochas porfiriticas com o corpo intrusivo principal é dada pelas similaridades nas características químicas das principais fases minerais, mas também pela composição isotópica do Sr no plagioclásio. Análises químicas detalhadas permitiram caracterizar as diferentes populações de cristais. Nos clinopiroxenitos porfiríticos, os núcleos MC1 são principalmente antecristais de Cr-diópsidos reciclados de uma fonte localizada a mais de 8 Km de profundidade. Os acrocristais MC2 são fenocristais de Al-diopsído cristalizados em uma câmara magmática localizada a uma profundidade aproximada de 6,5 km e provavelmente da mesma fonte magmática do Intrusivo do Frade. Os fenocristais MC2 definem uma tendência evolutiva com as bordas e a matriz de piroxênio por cristalização fracionada progressiva durante a ascensão e colocação numa câmara magma rasa localizada entre 5 a 3 km de profundidade, e a câmara de magma Frade. Os macrocristais de olivina mostram uma tendência de diferenciação junto com os cristais da matriz. Se eles eram antecristais, eles se reequilibravam com o magma hospedeiro que formou o intrusivo máfico. As diferenças químicas e isotópicas do picrito e do peridotito indicam uma evolução complexa no sistema magmático envolvendo zonas mais profundas de uma fonte heterogênea. O picrito foi formado pela mistura de um magma mais primitivo rico em H2O e CO2, colocado há 86 Ma. Traquitos, fonólitos e diques de alcali-feldspato sienito contemporâneos e variedades de sienito saturado e super saturado foram colocados na crosta superior, cortando a o intrusivo máfico do Frade. Todas as litologias descritas pertencem ao setor norte da província da Serra do Mar e representam uma associação espacial e temporal de um magmatismo bimodal contínuo que ocorreu em um período curto de 5 Ma.Biblioteca Digitais de Teses e Dissertações da USPVlach, Silvio Roberto FariasGiraldo Arroyave, Maria Isabel 2020-04-23info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesisapplication/pdfhttps://www.teses.usp.br/teses/disponiveis/44/44143/tde-26012021-163726/reponame:Biblioteca Digital de Teses e Dissertações da USPinstname:Universidade de São Paulo (USP)instacron:USPLiberar o conteúdo para acesso público.info:eu-repo/semantics/openAccesseng2021-02-01T21:36:01Zoai:teses.usp.br:tde-26012021-163726Biblioteca Digital de Teses e Dissertaçõeshttp://www.teses.usp.br/PUBhttp://www.teses.usp.br/cgi-bin/mtd2br.plvirginia@if.usp.br|| atendimento@aguia.usp.br||virginia@if.usp.bropendoar:27212021-02-01T21:36:01Biblioteca Digital de Teses e Dissertações da USP - Universidade de São Paulo (USP)false
dc.title.none.fl_str_mv Geology and petrology of the Frade alkaline mafic-ultramafic layered complex in the São Sebastião Island, Southeastern, Brazil
not available
title Geology and petrology of the Frade alkaline mafic-ultramafic layered complex in the São Sebastião Island, Southeastern, Brazil
spellingShingle Geology and petrology of the Frade alkaline mafic-ultramafic layered complex in the São Sebastião Island, Southeastern, Brazil
Giraldo Arroyave, Maria Isabel
Alkaline magmatism
Geochemistry
Igneous Petrology
Layered mafic intrusion
Mafic-Ultramafic cumulates
not available
title_short Geology and petrology of the Frade alkaline mafic-ultramafic layered complex in the São Sebastião Island, Southeastern, Brazil
title_full Geology and petrology of the Frade alkaline mafic-ultramafic layered complex in the São Sebastião Island, Southeastern, Brazil
title_fullStr Geology and petrology of the Frade alkaline mafic-ultramafic layered complex in the São Sebastião Island, Southeastern, Brazil
title_full_unstemmed Geology and petrology of the Frade alkaline mafic-ultramafic layered complex in the São Sebastião Island, Southeastern, Brazil
title_sort Geology and petrology of the Frade alkaline mafic-ultramafic layered complex in the São Sebastião Island, Southeastern, Brazil
author Giraldo Arroyave, Maria Isabel
author_facet Giraldo Arroyave, Maria Isabel
author_role author
dc.contributor.none.fl_str_mv Vlach, Silvio Roberto Farias
dc.contributor.author.fl_str_mv Giraldo Arroyave, Maria Isabel
dc.subject.por.fl_str_mv Alkaline magmatism
Geochemistry
Igneous Petrology
Layered mafic intrusion
Mafic-Ultramafic cumulates
not available
topic Alkaline magmatism
Geochemistry
Igneous Petrology
Layered mafic intrusion
Mafic-Ultramafic cumulates
not available
description The Frade Alkaline Mafic-Ultramafic Layered Complex crops out to south of the São Sebastião Island on the north coast of the state of São Pablo State (Brazil). It is a small plutonic intrusive with a ring sill-like shape and a maximum thickness estimated in 350 m, associated with younger ultramafic and felsic dikes, and - micro olivine clinopyroxenites and micro (mela) gabbros as dikes, sills and enclaves. Geochronological estimations indicate that emplacement took place at 88 Ma at shallow crustal level, around 2-3 km, liquidus temperature about 1050°C; the late crystallization suggests close-to-solidus temperature of ~870°C in average. The high temperature promoted a contact aureole in the host porphyritic granodiorites, evidenced in the development of recrystallization textures and granophyric intergrowths as well as orthopyroxene development and chemical and isotopic exchange in the contact zone. The mafic intrusive displays well-developed layered structures at the base of the sequence that vary to a strong mineral lamination upwards. The structures, textures, as well as the cumulus and intercumulus mineralogy allow recognizing 4 main gabbroic units, which, from the bottom to the top, are: 1) Lower Gabbro Sequence (LGS); 2) Intermediate Gabbro Sequence (IGS); 3) Upper Gabbro Sequence (UGS); 4) Massive Leucogabbros (MLG). It is thought that the rocks from the LGS, IGS, and UGS were formed from the same magma batch undergoing fractional crystallization and modification of the main ferromagnesian minerals by interaction with the intercumulus liquid. Crystallization is accompanied by minor crustal contamination reflected in the progressive increase in the 87Sr/86Sri isotope composition in plagioclase and apatite through stratigraphy coupled with depletion in the 143Nd/144Ndi over apatite. The Massive Leucogabbros represent a period of recharge by a less evolved and less contaminated magma keeping the chemical and isotopic signatures of the common source with the Frade Intrusive. In this rock, the intercumulus mafic assemblage probably was formed by the interaction of the resident magma with the primitive melt. Associated to the Frade Intrusion, ultramafic (picrite and micro peridotite) and melanocratic porphyritic subvolcanic rocks have been recognized in the form of dikes, sills and enclaves. The relationship of these porhyritic melanocratic rocks and the main intrusive is given by the similarities in the chemical characteristics of the main mineral phases, but also the isotopic Sr composition of plagioclase. Detailed chemical analysis allowed to characterize the different crystal population. Macrocryst of pyroxene were defined as MC1 and MC2. In the porphyritic clinopyroxenites, MC1 cores are mostly antecryst Crdiopsides recycled from a source located at a depth of ~8 km. MC2 macrocryst are Al-diopsides phenocryst crystallized in a magma chamber located at a depth of ~6 km, which is probably the same magmatic source of the Frade Intrusive. MC2 phenocrysts define an evolutionary trend with rims and groundmass pyroxenes by progressive fractional crystallization during magma ascent and emplacement in a shallow magma chamber located ~3 km depth, the Frade magma chamber. Olivine macrocryst show a well differentiation path with the groundmass crystals. If they were antecryst they re-equilibrated with the host magma that formed the Frade Mafic Intrusive. The chemical and isotopic differences in the picrite and micro peridotite, indicate a complex evolution in the magmatic plumbing system involving deeper zones of a heterogeneous mantle source. The picrite probably formed by mixing with a magma with a more primitive H2O and CO2 rich melt emplaced at 86 Ma ( 40Ar/39Ar data in amphibole). Contemporaneous trachytes, phonolites and alkali-feldspar dikes and SiO2-undersaturated and oversaturated syenite varieties, were emplaced into the upper crust cross cutting the Frade Layered Intrusive. All the described lithologies belong to the north sector of the Serra do Mar Province an represent a spatial and temporal association of a continuous bimodal magmatism that occurred in a short period of about 5 Ma.
publishDate 2020
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