Petrography of alkaline volcanic-subvolcanic rocks from the Brazilian Fernando de Noronha Archipelago, Southern Atlantic Ocean

Ulbrich, Mabel N. C.

doi:10.11606/issn.2316-8986.v24i0p77-94

Cited by 14 publications

(29 citation statements)

References 3 publications

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“…Some authors proposed that the São José flows may represent the culmination of the Quixaba volcanism (e.g. Lopes 2002;Ulbrich 1993), but recent radiometric dating confirmed that these rocks belong, agewise, to the Remédios volcanic event (Perlingeiro et al 2013).…”

Section: Stratigraphic Units and Geologic Occurrencesmentioning

confidence: 99%

“…To define the correspondence between the older names and the newer nomenclature, we follow mainly the discussion presented in Ulbrich (1993), Lopes (2002), and Ulbrich et al (2004), and the definitions given in Le Maitre (2002); other discussions and information on the petrography of FN rocks can be found in Gunn and Watkins (1976), Schwab and Bloch (1985), Cornen (1986), Gerlach et al (1987) and Weaver (1990).Data about mineral chemistry of these rocks can be found in a recent paper by Lopes et al (2014).…”

Section: Petrography As a Guideline For Petrogenetic Interpretationsmentioning

confidence: 99%

“…Recent detailed studies divided the FN lamprophyres into four alkaline petrographic groups (Ulbrich 1993;Maríngolo 1995), a division adopted, with some minor divergence, in Lopes (2002). Type I, similar to the typical lamprophyres of Ulbrich (1993) and the camptonite of Maríngolo (1995), has a glassy groundmass with abundant amphibole and minor clinopyroxene, altered olivine, phlogopite, opaques and clinopyroxene.…”

Section: Rocks Of the Remédios Formationmentioning

confidence: 99%

“…More recently, geologists from the University of São Paulo presented contributions on FN (two Master's thesis, one doctorate thesis : Maríngolo 1995;Lopes 1997Lopes , 2002, and several abstracts and publications on the subject (Ulbrich & Ruberti 1992;Ulbrich 1993;Ulbrich et al 1994Ulbrich et al , 2004Maríngolo & Ulbrich 1997;Lopes & Ulbrich 1997Ulbrich & Lopes 2000a, 2000b.A summary paper on the lithogeochemistry and mineral chemistry of the Quixaba Formation was published in a Brazilian journal (Lopes & Ulbrich 2006), and a more recent one on the mineral chemistry of these rocks (Lopes et al 2014). A recent study on FN was presented at Queensland as a Ph.D. thesis, dealing with geochronologic and petrogenetic aspects (Perlingeiro 2012).…”

Section: Introductionmentioning

confidence: 99%

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Geochemistry of the alkaline volcanicsubvolcanic rocks of the Fernando de Noronha Archipelago, southern Atlantic Ocean

Lopes

Ulbrich

2015

Braz. J. Geol.

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ABSTRACT:The Fernando de Noronha Archipelago presents, on its main island, a centrally-located stratigraphic unit, the Remédios Formation (age around 8 -12 Ma) constituted by basal pyroclastic rocks intruded by dikes, plugs and domes of varied igneous rocks, capped by flows and pyroclastics of mafic to ultramafic rocks of the Quixaba Formation (age around 1 -3 Ma), which is limited from the underlying unit by an extensive irregular erosion surface. A predominant sodic Remédios series (basanites, tephrites, tephriphonolites, essexite, phonolites) can be separated from a moderately potassic Remédios sequence (alkali basalts, trachyandesites, trachytes), both alkaline series showing mostly continuous geochemical trends in variation diagrams for major as well as trace elements, indicating evolution by crystal fractionation (mainly, separation of mafic minerals, including apatites and titanites). There are textural and mineralogical evidences pointing to hybrid origin of some intermediate rocks (e.g., resorbed pyroxene phenocrysts in basaltic trachyandesites, and in some lamprophyres). The primitive Quixaba rocks are mostly melanephelinites and basanites, primitive undersaturated sodic types. Geology (erosion surface), stratigraphy (two distinct units separated by a large time interval), petrography (varied Remédios Formation, more uniform Quixaba unit) and geochemistry indicate that the islands represent the activity of a protracted volcanic episode, fueled by intermittent melting of an enriched mantle, not related to asthenospheric plume activity. KEYWORDS:OIB; South Atlantic Ocean; Mafic to ultramafic volcanic-subvolcanic rocks; Sodic and potassic series. RESUMO: O Arquipélago de Fernando de Noronha mostra na sua ilha principal, na parte central, a Formação Remédios (idade em torno de 8 -12 Ma) constituída por rochas piroclásticas basais invadidas por diques, plugs e domos de variadas rochas ígneas, capeadas por derrames e piroclásticas das rochas máficas a ultramáficas da Formação Quixaba (idade de 1 a 3 Ma), separada da unidade inferior por uma superfície de erosão extensa e irregular. Uma série predominante sódica de Remédios (basanitos, tefritos, tefrifonolitos, essexito, fonolitos) pode ser diferenciada da série moderadamente potássica (álcali basaltos, traquiandesitos, traquitos), pertencente à mesma unidade. Ambas as séries mostram tendências geoquímicas geralmente contínuas em diagramas de variação de elementos maiores e traços, indicando origem por cristalização fracionada (principalmente, separação de minerais máficos, incluindo apatitas e titanitas). São encontradas evidências mineralógicas e texturais apontando

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Section: Stratigraphic Units and Geologic Occurrencesmentioning

confidence: 99%

Section: Petrography As a Guideline For Petrogenetic Interpretationsmentioning

confidence: 99%

Section: Rocks Of the Remédios Formationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Geochemistry of the alkaline volcanicsubvolcanic rocks of the Fernando de Noronha Archipelago, southern Atlantic Ocean

Lopes

Ulbrich

2015

Braz. J. Geol.

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“…Sendo diferente da ilha de Fernando de Noronha (Weave, 1990;Ulbrich, 1994), arquipélago de Abrolhos Figura 2 -Vista aérea do arquipélago de São Pedro e São Paulo. A imagem foi obtida por Thomas Ferreira da Costa Campos, um dos autores do presente trabalho.…”

Section: Introductionunclassified

Taxa de soerguimento atual do arquipélago de São Pedro e São Paulo, Oceano Atlântico Equatorial

Motoki

Sichel

Campos³

et al. 2009

Rem: Rev. Esc. Minas

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O arquipélago de São Pedro e São Paulo situa-se no Oceano Atlântico Equatorial, no topo de uma elevação morfológica submarina de 90 km de comprimento, 25 km de largura e 3.800 m de altura, composta de rochas peridotíticas do manto, denominada Cadeia Peridotítica de São Pedro e São Paulo. A morfologia submarina é altamente acidentada com escarpas subverticais de centenas de metros de altura, sugerindo ocorrência de tectonismo recente, provavelmente ativo. O mapa de seppômen do arquipélago mostra duas plataformas de abrasão marinha, com altitude respectiva de 4~5 m e de 7~9 m. As plataformas são observadas nas três ilhas maiores nas mesmas faixas de altitude, indicando que não houve basculamento ou soerguimento diferencial entre as ilhas. Considerando a plataforma superior formada durante a Transgressão Flandriana e a plataforma inferior desenvolvida por erosão recente, a taxa média de soerguimento nos últimos 6 mil anos é calculada como 1.2~1.5 mm/ano. As datações 14C para os fósseis coralígenos da ilha Belmonte indicam a taxa de soerguimento nos últimos 6.600 anos como 1.5~1.8 mm/ano. Portanto uma taxa de 1.5 mm/ano é razoável para o soerguimento atual. Interpretando a cadeia peridotítica como um megamullion tectonicamente deformado, o soerguimento total seria 1500~3000 m e o início do tectonismo seria 1~2 Ma. Se a cadeia peridotítica é originada do manto oceânico subcrustal, o soerguimento total seria, aproximadamente, 9000 m e o início do tectonismo seria cerca de 6 Ma.

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Soils of the Brazilian Volcanic Islands

Schaefer

Oliveira

Machado

et al. 2023

World Soils Book Series

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Petrography of alkaline volcanic-subvolcanic rocks from the Brazilian Fernando de Noronha Archipelago, Southern Atlantic Ocean

Cited by 14 publications

References 3 publications

Geochemistry of the alkaline volcanicsubvolcanic rocks of the Fernando de Noronha Archipelago, southern Atlantic Ocean

Geochemistry of the alkaline volcanicsubvolcanic rocks of the Fernando de Noronha Archipelago, southern Atlantic Ocean

Taxa de soerguimento atual do arquipélago de São Pedro e São Paulo, Oceano Atlântico Equatorial

Soils of the Brazilian Volcanic Islands

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