Petrology, geochemistry and Sr–Nd isotopes of the Trindade and Martin Vaz volcanic rocks (Southern Atlantic Ocean)

Marques, Leila Soares; Ulbrich, Mabel N. C.; Ruberti, Excelso; Tassinari, Colombo Celso Gaeta

doi:10.1016/s0377-0273(99)00111-0

Cited by 77 publications

(58 citation statements)

References 28 publications

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“…1) are approximately 10 and 0.5 km 2 , respectively, with narrow insular shelves, extending about 3 km from the shore and composed of heterogeneous subvolcanic structures and pyroclastic deposits (MARQUES et al, 1999). The littoral zone is comprised of about 2.5 km of beaches and 14 km of narrow (<1 km) and steep (30-90º) rocky shores.…”

Section: Study Areamentioning

confidence: 99%

“…Reef fish density was assessed using a stationary visual census (n = 10 per depth strata), following the procedures of MINTE-VERA et al (2008). Fish counts were carried out at the same sites and depth strata as the benthic sampling with the use of conventional SCUBA.…”

Section: Field Proceduresmentioning

confidence: 99%

“…Despite a wealth of qualitative information from Brazilian oceanic islands (e.g. FLOETER, 2001;FLOETER et al, 2008), there are few quantitative data, either spatial or temporal (but see ROSA; MOURA, 1997;FRANCINI-FILHO et al 2000;MINTE-VERA et al, 2008), thus precluding the evaluation of their conservation status and the implementation of effective conservation and management measures.…”

Section: Introductionmentioning

confidence: 99%

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Reef fish and benthic assemblages of the Trindade and Martin Vaz Island group, southwestern Atlantic

et al. 2011

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A B S T R A C TThe Trindade and Martin Vaz island group (TMVIG) is located at about 1,120 km off the Brazilian coast. Despite its importance, highlighted by the presence of several endemic fish species, the TMVIG lacks detailed information on the structure of fish and benthic assemblages. Presented here is the first quantitative assessment of reef fish and benthic assemblages of the TMVIG in a depth gradient ranging from 5 to 45 m. Additional qualitative information on reef assemblages between 45 and 100 m was obtained using advanced gas diving techniques (TRIMIX) and a remotely operated vehicle (ROV). Similarly to other Brazilian oceanic islands, the TMVIG possesses depauperated fish and benthic assemblages, possibly due to its isolation and small size in comparison to the mainland. Depth was the most important factor affecting the structure of fish assemblages, with the density of most fish species declining with depth. Deep reefs (> 45 m) were characterized by the presence of extensive rhodolith beds and rocky reefs sparsely covered with crustose coralline algae, black coral (Cirripathes sp.) and a few massive or plate-like reef corals. Part-time or obligatory planktivorous fishes (e.g. Cephalopholis furcifer and Clepticus brasiliensis) also dominated deep reefs. Similar characteristics were recorded in mesophotic reef ecosystems across the Western Atlantic. Evidence of overfishing (obtained here and in other recent studies), the presence of four endemic and restricted range fish species, as well as the increase in number of new (and still undescribed) endemic taxa, indicates that the adoption of precautionary conservation measures are urgently needed in order to maintain the fragile and unique ecosystems of the TMVIG. R E S U M OO conjunto insular de Trindade e Martin Vaz (CITMV) está localizado a aproximadamente 1.120 km da costa brasileira. Apesar de sua importância, salientada pela presença de diversas espécies endêmicas de peixes, não existem informações detalhadas sobre as assembléias de peixes e bentos do CITMV. É apresentada aqui a primeira caracterização quantitativa das assembléias de peixes e bentos do CITMV em um gradiente de profundidade entre 5 e 45 m. Informações qualitativas adicionais sobre assembléias recifais entre 45 e 100 m foram obtidas utilizando-se técnicas avançadas de mergulho (TRIMIX) e um veículo de operação remota (VOR). Assim como outras ilhas oceânicas brasileiras, a CITMV possui assembléias depauperadas de peixes e bentos, possivelmente devido ao seu isolamento e pequeno tamanho em comparação ao continente. A profundidade foi o fator que mais afetou a estrutura das assembléias de peixes, com a densidade da maioria das espécies declinando com o aumento da profundidade. Os recifes profundos (> 45 m) foram caracterizados pela presença de bancos extensivos de rodolitos e recifes rochosos esparsamente cobertos por algas coralináceas incrustantes, corais negros (Cirripathes sp.) e alguns corais massivos e em de forma de placa. Peixes parcialmente ou obrigatoriamente planctívoros (e.g...

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Section: Study Areamentioning

confidence: 99%

Section: Field Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reef fish and benthic assemblages of the Trindade and Martin Vaz Island group, southwestern Atlantic

et al. 2011

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“…Specifically in the Atlantic Ocean, many OIB islands are known and have been extensively studied, such as the Canarias Islands (Hoernle & Schmincke 1993;Araña et al 1994;Gurenko et al 2006), the Cabo Verde Archipelago (Furnes & Stillman 1987;Dyhr & Holm 2010;Ancochea et al 2012) and the islands of Trindade and Martin Vaz (Almeida 1961;Marques et al 1999;Siebel et al 2000).…”

Section: Introductionmentioning

confidence: 99%

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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“…The region received the sporadic visit of several geologists who contributed mainly with data about geochemistry and isotope relations, thus providing information to speculate on origin and evolution of the special rock types found on the islands (cf. bibliography in [2,5,6]). This contribution on the mineral chemistry of the rockforming minerals in FN is a complement to a paper dealing with petrography and geochemistry [2].…”

Section: Introductionmentioning

confidence: 99%

The volcanic-subvolcanic rocks of the fernando de noronha archipelago, southern atlantic ocean: Mineral chemistry

Lopes

Ulbrich²,

Ulbrich³

2014

Open Geosciences

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Fernando de Noronha archipelago presents an older Remédios Formation with subvolcanic intrusions, belonging to two different alkaline series, the sodic (undersaturated: basanites, tephrites, essexites, tephriphonolites, phonolites), and potassic ones (mildly undersaturated to silicic, with alkali basalts, basaltic trachyandesites, trachyandesites, trachytes), and lamprophyres. The upper Quixaba Formation presents nephelinite flows and basanites. A third minor unit, São José, is constituted by basanites carrying mantle xenoliths. Magnesian olivines occur in the Remédios basanites and alkali basalts, and in nephelinites. Melilites are present as groundmass grains in melilite melanephelinites (MEM). Clinopyroxenes (cpx) are mostly salites to titaniferous salites (Remédios sodic series), grading into aegirines in the differentiated aphyric phonolites. Cpx in the lamprophyres show disequilibrium textures. In the Quixaba flows, cpx are salites, enriched in Mg (especially in MEM). Amphiboles, remarkably, are common in tephriphonolites and phonolites and in basaltic trachyandesites, sometimes with disequilibrum zoning textures, and a conspicuous phase in lamprophyres. Dark micas are present as groundmass plates in MEM, OLM and PYM (olivine and pyroxene melanephelinites), with compositional variety (enriched in Ti, Ba, Sr) depending on the composition of the parent rock; BaO can be as high as 16–19%. Feldspars crystallize as calcic plagioclases, sanidines and anorthoclases, depending on the rock types, as phenocrysts and in groundmass, both in Quixaba and Remédios rocks; they are absent in nephelinites. Nephelines are found in Remédios sodic series types and Quixaba rocks. Haüyne and noseane are rarely observed in Remédios rocks.

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Petrology, geochemistry and Sr–Nd isotopes of the Trindade and Martin Vaz volcanic rocks (Southern Atlantic Ocean)

Cited by 77 publications

References 28 publications

Reef fish and benthic assemblages of the Trindade and Martin Vaz Island group, southwestern Atlantic

Reef fish and benthic assemblages of the Trindade and Martin Vaz Island group, southwestern Atlantic

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

The volcanic-subvolcanic rocks of the fernando de noronha archipelago, southern atlantic ocean: Mineral chemistry

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