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

Lopes, Ruy Bessa; Ulbrich, Mabel N. C.

doi:10.1590/23174889201500020009

Cited by 31 publications

(14 citation statements)

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“…As these kind of oceanic islands were never totally connected to the continent (Cowie & Holland, ), peripatric speciation is far more plausible for C. insularis . Further, even though Fernando de Noronha orogenesis initiate during the Miocene (Cordani, ; Lopes & Ulbrich, ), it is also plausible that the long‐term colonization of this archipelago occurred during the Pleistocene, as suggested by our age estimative (Figure ). This is justified by the occurrence of intense volcanic activity until late Pleistocene (Cordani, ) that must have promoted recurrent extinctions and precluded the maintenance of terrestrial biota in these islands.…”

Section: Discussionmentioning

confidence: 79%

The xeric side of the Brazilian Atlantic Forest: The forces shaping phylogeographic structure of cacti

Franco

Jojima

Perez

et al. 2017

Ecology and Evolution

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In order to investigate biogeographic influences on xeric biota in the Brazilian Atlantic Forest (BAF), a biodiversity hotspot, we used a monophyletic group including three cactus taxa as a model to perform a phylogeographic study: Cereus fernambucensis subsp. fernambucensis, C. fernambucensis subsp. sericifer, and C. insularis. These cacti are allopatric and grow in xeric habitats along BAF, including isolated granite and gneiss rock outcrops (Inselbergs), sand dune vegetation (Restinga forest), and the rocky shore of an oceanic archipelago (islands of Fernando de Noronha). The nucleotide information from nuclear gene phytochrome C and plastid intergenic spacer trnS‐trnG was used to perform different approaches and statistical analyses, comprising population structure, demographic changes, phylogenetic relationships, and biogeographic reconstruction in both spatial and temporal scales. We recovered four allopatric population groups with highly supported branches in the phylogenetic tree with divergence initiated in the middle Pleistocene: southern distribution of C. fernambucensis subsp. fernambucensis, northern distribution of C. fernambucensis subsp. fernambucensis together with C. insularis, southern distribution of C. fernambucensis subsp. sericifer, and northern distribution of C. fernambucensis subsp. sericifer. Further, the results suggest that genetic diversity of population groups was strongly shaped by an initial colonization event from south to north followed by fragmentation. The phylogenetic pattern found for C. insularis is plausible with peripatric speciation in the archipelago of Fernando de Noronha. To explain the phylogeographic patterns, the putative effects of both climatic and sea level changes as well as neotectonic activity during the Pleistocene are discussed.

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Section: Discussionmentioning

confidence: 79%

The xeric side of the Brazilian Atlantic Forest: The forces shaping phylogeographic structure of cacti

Franco

Jojima

Perez

et al. 2017

Ecology and Evolution

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“…The archipelago lies at the eastern end of a linear chain of seamounts, named the Fernando de Noronha Ridge, which extends eastward from the Brazilian mainland. Magmatism situated at the westernmost end of this ridge is dated at 40 Ma, and is believed to represent the earliest activity of a mantle plume (the Fernando de Noronha plume) which later led to the formation of the archipelago of the same name (Fodor et al, 1998;Almeida, 2012;Lopes and Ulbrich, 2015).…”

Section: Fernando De Noronhamentioning

confidence: 99%

“…The geochemical evolution of the Fernando de Noronha archipelago is complex, and is summarized by Lopes et al (2014) and Lopes and Ulbrich (2015) (Figure 3G). The Remédios Formation includes two suites of rocks, each derived from a discrete parental magma, and each exhibiting continuous geochemical trends from their least to their most evolved compositions; (1) the sodic series (basanite-tephritephonotephrite-phonolite), and (2) the moderately potassic series (alkali basalt-basaltic trachyandesite-trachyandesite-trachyte).…”

Section: Fernando De Noronhamentioning

confidence: 99%

“…There exists a wide range of published studies and quantitative models which reliably recreate the compositions observed in the magmatic systems of the Atlantic, including major element, least-squares mass balance models, thermodynamic models, and trace element models (e.g., Iceland: Carmichael, 1964;Macdonald et al, 1990;Furman et al, 1992a;Sigmarsson et al, 1992;Hards et al, 2000;Prestvik et al, 2001;Martin and Sigmarsson, 2007; Azores: Widom et al, 1992;Mungall and Martin, 1995;Renzulli and Santi, 2000;Beier et al, 2006;Larrea et al, 2013Larrea et al, , 2014aZanon, 2015;Jeffery et al, 2016bJeffery et al, , 2017Canary islands: Freundt and Schmincke, 1995;Ablay et al, 1998;Neumann et al, 1999;Sliwinski et al, 2015;Tornare et al, 2016;Cape Verde: Holm et al, 2006;Kogarko, 2008;Hildner et al, 2011;Cameroon Line: Marzoli et al, 2000;Ascension Island: Harris, 1983;Kar et al, 1998;Chamberlain et al, 2016;Bouvet Island: Le Roex and Erlank, 1982;Prestvik et al, 1999; Tristan da Cunha: Le Roex et al, 1990;Harris et al, 2000;Gough Island: Le Roex, 1985;Harris et al, 2000;St. Helena: Baker, 1969; Fernando de Noronha: Weaver, 1990;Lopes and Ulbrich, 2015;…”

Section: Fractional Crystallizationmentioning

confidence: 99%

“…Although they are not ubiquitous, the occurrence of pre-eruptive magma mixing/mingling processes is well documented for many of the Atlantic Ocean islands (e.g., Iceland: Sparks et al, 1977;McGarvie et al, 1990;Azores: Storey, 1981;Jeffery et al, 2016bJeffery et al, , 2017D'Oriano et al, 2017;Madeira: Klügel and Klein, 2006;Canary Islands: Wolff, 1985;Araña et al, 1994;Edgar et al, 2002;Cape Verde;Holm et al, 2006;Eisele et al, 2016;Ascension: Weaver et al, 1996;Gough Island: Le Roex, 1985;Bouvet Island: Prestvik et al, 1999). These mixing processes are diverse in their end-members, and include direct mixing between mafic and felsic magmas (e.g., Araña et al, 1994;Lopes and Ulbrich, 2015), mixing between felsic magmas (e.g., Troll and Schmincke, 2002;Bryan, 2006;Pimentel et al, 2015), mingling of melt and crystalline mush (i.e., mush remobilisation) (e.g., Weaver et al, 1996;Sliwinski et al, 2015;D'Oriano et al, 2017;Jeffery et al, 2017), and small-scale mixing of partially melted contaminants and volumetrically superior melt (e.g., Turner et al, 2017). In peralkaline magmatic systems other than those of the Atlantic Ocean, the mixing of mafic and felsic magmas is proposed as a process responsible for the formation of intermediate magmas, which are often scarce compared to mafic and felsic compositions (e.g., Pantelleria: Ferla and Meli, 2006;Gioncada and Landi, 2010).…”

Section: Magma Mixing/minglingmentioning

confidence: 99%

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Peralkaline Felsic Magmatism of the Atlantic Islands

Jeffery

Gertisser

2018

Front. Earth Sci.

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The oceanic-island magmatic systems of the Atlantic Ocean exhibit significant diversity in their respective sizes, ages, and the compositional ranges of their eruptive products. Nevertheless, almost all of the Atlantic islands and island groups have produced peralkaline felsic magmas, implying that similar petrogenetic regimes may be operating throughout the Atlantic Ocean, and arguably elsewhere. The origins of peralkaline magmas are frequently linked to low-degree partial melting of enriched mantle, followed by protracted differentiation in the shallow crust. However, additional petrogenetic processes such as magma mixing, crustal melting, and contamination have been identified at numerous peralkaline centers. The onset of peralkalinity leads to magma viscosities lower than those typical for metaluminous felsic magmas, which has profound implications for processes such as crystal settling. This study represents a compilation of published and original data which demonstrates trends that suggest that the peralkaline magmas of the Atlantic Ocean islands are generated primarily via extended (up to ∼ 95%), open system fractional crystallization of mantle-derived mafic magmas. Crustal assimilation is likely to become more significant as the system matures and fusible material accumulates in the crust. Magma mixing may occur between various compositional end-members and may be recognized via hybridized intermediate magmas. The peralkaline magmas are hydrous, and frequently zoned in composition, temperature, and/or water content. They are typically stored in shallow crustal magma reservoirs (∼ 2-5 km), maintained by mafic replenishment. Low melt viscosities (1 × 10 1.77 to 1 × 10 4.77 Pa s) facilitate two-phase flow, promoting the formation of alkali-feldspar crystal mush. This mush may then contribute melt to an overlying melt lens via filter pressing or partial melting. We utilize a three-stage model to account for the establishment, development, and termination of peralkaline magmatism in the ocean island magmatic systems of the Atlantic. We suggest that the overall control on peralkaline magmatism in the Atlantic is magma flux rate, which controls the stability of upper crustal magma reservoirs. The abundance of peralkaline magmas in the Atlantic suggests that their development must be a common, but not inevitable, stage in the evolution of ocean islands.

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Genesis and evolution of the South Atlantic volcanic islands offshore Brazil

Mohriak

2020

Geo-Mar Lett

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

Cited by 31 publications

References 36 publications

The xeric side of the Brazilian Atlantic Forest: The forces shaping phylogeographic structure of cacti

The xeric side of the Brazilian Atlantic Forest: The forces shaping phylogeographic structure of cacti

Peralkaline Felsic Magmatism of the Atlantic Islands

Genesis and evolution of the South Atlantic volcanic islands offshore Brazil

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