Geochemical Constraints on the Origin of Volcanic Rocks from the Andean Northern Volcanic Zone, Ecuador

Bryant, J. A.; Yogodzinski, G. M.; Hall, Minard L.; Lewicki, Jennifer L.; Bailey, David G.

doi:10.1093/petrology/egl006

Cited by 101 publications

(88 citation statements)

References 103 publications

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“…Systematic across-arc increase in incompatible elements and relative decrease in fluid-mobile elements (Fig. 9), typical for arcs worldwide (Dickinson 1975;Stolper and Newman 1994;Davidson and De Silva 1995;Ryan et al 1995), suggest derivation of the Ecuadorian magmatic rocks from progressively smaller degrees of mantle melting towards the back-arc, induced by decreasing amounts of fluids released from the subducted slab (see also Barragan et al 1998;Bourdon et al 2002;Bryant et al 2006). The low degree of partial melting in the back-arc could explain the extreme enrichment in incompatible elements of Sumaco lavas (see also Barragan et al 1998).…”

Section: Across-arc Geochemical Variationsmentioning

confidence: 97%

“…6g, h) suggesting that the magmatic evolution is controlled by amphibole fractionation at depth, which lowers the Nb/Ta ratio of derivative liquids (see also Tiepolo et al 2000;AlonsoPerez 2006), or alternatively by assimilation of low Nb/Ta crustal rocks and/or their partial melts (e.g., Garrido and Bodinier 2005; see also below). The La/Yb ratio gradually increases towards the back-arc (see also Vanek et al 1994;Bryant et al 2006), which could indicate an increasing amount of residual garnet in the mantle source of the magmas of the main and back-arc. However, variable increases of La/Yb with SiO 2 (Fig.…”

Section: Across-arc Geochemical Variationsmentioning

confidence: 99%

“…For discussion, we have added the analyses of four samples of Pululagua, one of Ilalo, three of Chacana and three of Sumaco previously analyzed by Bryant et al (2006). Details of the analytical techniques used are available in the Electronic Supplementary Appendix.…”

Section: Analytical Techniquesmentioning

confidence: 99%

“…In a series of recent papers (e.g., Bourdon et al 2002Bourdon et al , 2003Samaniego et al 2002;Hidalgo et al 2007;Hoffer et al 2008), the adakite-like rocks of Ecuador have been considered the result of slab melting, but other works on the same rocks suggest the possible role played by magmatic processes at lower crustal levels (Kilian et al 1995;Arculus et al 1999;Monzier et al 1999;Garrison and Davidson 2003;Chiaradia et al 2004a;Bryant et al 2006;Garrison et al 2006), a petrogenetic process invoked also to explain the geochemical signatures of southern Colombian volcanoes (e.g., Droux and Delaloye 1996;Calvache and Williams 1997).…”

Section: Introductionmentioning

confidence: 99%

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Adakite-like volcanism of Ecuador: lower crust magmatic evolution and recycling

Chiaradia

Müntener

Beate

et al. 2009

Contrib Mineral Petrol

138

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In the Northern Andes of Ecuador, a broad Quaternary volcanic arc with significant across-arc geochemical changes sits upon continental crust consisting of accreted oceanic and continental terranes. Quaternary volcanic centers occur, from west to east, along the Western Cordillera (frontal arc), in the Inter-Andean Depression and along the Eastern Cordillera (main arc), and in the Sub-Andean Zone (back-arc). The adakite-like signatures of the frontal and main arc volcanoes have been interpreted either as the result of slab melting plus subsequent slab melt-mantle interactions or of lower crustal melting, fractional crystallization, and assimilation processes. In this paper, we present petrographic, geochemical, and isotopic (Sr, Nd, Pb) data on dominantly andesitic to dacitic volcanic rocks as well as crustal xenolith and cumulate samples from five volcanic centers (Pululagua, Pichincha, Ilalo, Chacana, Sumaco) forming a NW-SE transect at about 0°latitude and encompassing the frontal (Pululagua, Pichincha), main (Ilalo, Chacana), and back-arc (Sumaco) chains. All rocks display typical subduction-related geochemical signatures, such as Nb and Ta negative anomalies and LILE enrichment. They show a relative depletion of fluid-mobile elements and a general increase in incompatible elements from the front to the back-arc suggesting derivation from progressively lower degrees of partial melting of the mantle wedge induced by decreasing amounts of fluids released from the slab. We observe widespread petrographic evidence of interaction of primary melts with mafic xenoliths as well as with clinopyroxene-and/or amphibole-bearing cumulates and of magma mixing at all frontal and main arc volcanic centers. Within each volcanic center, rocks display correlations between evolution indices and radiogenic isotopes, although absolute variations of radiogenic isotopes are small and their values are overall rather primitive (e.g., e Nd = ?1.5 to ?6, 87 Sr/ 86 Sr = 0.7040-0.70435). Rare earth element patterns are characterized by variably fractionated light to heavy REE (La/Yb N = 5.7-34) and by the absence of Eu negative anomalies suggesting evolution of these rocks with limited plagioclase fractionation. We interpret the petrographic, geochemical, and isotopic data as indicating open-system evolution at all volcanic centers characterized by fractional crystallization and magma mixing processes at different lower-to mid-crustal levels as well as by assimilation of mafic lower crust and/or its partial melts. Thus, we propose that the adakite-like signatures of Ecuadorian rocks (e.g., high Sr/Y and La/Yb values) are primarily the result of lower-to mid-crustal processing of mantle-derived melts, rather than of slab melts and slab melt-mantle interactions. The isotopic signatures of the least evolved adakite-like rocks of the active and recent volcanoes are the same as those of Tertiary ''normal'' calc-alkaline magmatic rocks of Ecuador suggesting that the source of the magma did not change 123Contrib Mineral Petrol (2009) 1...

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Section: Across-arc Geochemical Variationsmentioning

confidence: 97%

Section: Across-arc Geochemical Variationsmentioning

confidence: 99%

Section: Analytical Techniquesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Adakite-like volcanism of Ecuador: lower crust magmatic evolution and recycling

Chiaradia

Müntener

Beate

et al. 2009

Contrib Mineral Petrol

138

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“…Pleistocene to Holocene volcanic successions of Ecuador are characterised by the frequent coexistence of conventional calc-alkaline and adakite-like compositions (Monzier et al 1997b(Monzier et al , 1999Bourdon et al 2002a, b;Samaniego et al 2002Samaniego et al , 2005Bryant et al 2006). Consequently, the Ecuadorian volcanic arc appears to be a key area in addressing problems relating to calc-alkaline and adakitic magmatism and their interactions.…”

mentioning

confidence: 99%

Evolution of the late Pleistocene Mojanda–Fuya Fuya volcanic complex (Ecuador), by progressive adakitic involvement in mantle magma sources

et al. 2008

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The Mojanda-Fuya Fuya Volcanic Complex consists of two nearby volcanoes, Mojanda and Fuya Fuya. The older one, Mojanda volcano (0.6 to 0.2 Ma), was first constructed by andesites and high-silica andesites forming a large stratovolcano (Lower Mojanda). This edifice was capped by a basaltic andesite and andesitic cone (Upper Mojanda), which collapsed later to form a 3-km-wide summit caldera, after large phreatomagmatic eruptions. The Lower Fuya Fuya edifice was constructed by the extrusion of viscous Si-rich andesitic lavas and dacitic domes, and the emission of a thick sequence of pyroclastic-flow and fallout deposits which include two voluminous rhyolitic layers. An intermediate construction phase at Fuya Fuya is represented by a mainly effusive cone, andesitic in composition (San Bartolo edifice), the construction of which was interrupted by a major sector collapse in the Late Pleistocene. Finally, a complex of thick siliceous lavas and domes was emplaced within the avalanche amphitheatre, forming the Upper Fuya Fuya volcanic centre. This paper shows that the general evolution from an effusive to an explosive eruptive style is related to a progressive adakitic contribution to the magma source. Although all the rocks of the complex are included in the medium-K field of continental arcs, the Fuya Fuya suite (61-75 wt.% SiO 2 ) shows depletion in Y and HREE and high Sr/Y and La/Yb values, compared to the less silicic Mojanda suite (55-66.5 wt.% SiO 2 ). The Mojanda calc-alkaline suite was generated by partial melting of an adakite-metasomatised mantle source that left a residue with 2% garnet, followed by fractional crystallization of dominant plagioclase + pyroxene + olivine at shallow, intra-crustal depths. For Fuya Fuya, geochemical and mineralogical data suggest either (1) partial melting of a similar metasomatised mantle with more garnet in the residue (4%), followed by fractional crystallization involving plagioclase, amphibole and pyroxene, or (2) mixing of mafic mantle-derived magma from the Mojanda suite and slab melts, followed by the same fractional crystallization process.

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Across‐arc versus along‐arc Sr‐Nd‐Pb isotope variations in the Ecuadorian volcanic arc

Ancellin

Samaniego

Vlastelić

et al. 2017

Geochem Geophys Geosyst

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International audiencePrevious studies of the Ecuadorian arc (1°N–2°S) have revealed across-arc geochemical trends that are consistent with a decrease in mantle melting and slab dehydration away from the trench. The aim of this work is to evaluate how these processes vary along the arc in response to small-scale changes in the age of the subducted plate, subduction angle, and continental crustal basement. We use an extensive database of 1437 samples containing 71 new analyses, of major and trace elements as well as Sr-Nd-Pb isotopes from Ecuadorian and South Colombian volcanic centers. Large geochemical variations are found to occur along the Ecuadorian arc, in particular along the front arc, which encompasses 99% and 71% of the total variations in 206Pb/204Pb and 87Sr/86Sr ratios of Quaternary Ecuadorian volcanics, respectively. The front arc volcanoes also show two major latitudinal trends: (1) the southward increase of 207Pb/204Pb and decrease of 143Nd/144Nd reflect more extensive crustal contamination of magma in the southern part (up to 14%); and (2) the increase of 206Pb/204Pb and decrease of Ba/Th away from ∼0.5°S result from the changing nature of metasomatism in the subarc mantle wedge with the aqueous fluid/siliceous slab melt ratio decreasing away from 0.5°S. Subduction of a younger and warmer oceanic crust in the Northern part of the arc might promote slab melting. Conversely, the subduction of a colder oceanic crust south of the Grijalva Fracture Zone and higher crustal assimilation lead to the reduction of slab contribution in southern part of the arc

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Geochemical Constraints on the Origin of Volcanic Rocks from the Andean Northern Volcanic Zone, Ecuador

Cited by 101 publications

References 103 publications

Adakite-like volcanism of Ecuador: lower crust magmatic evolution and recycling

Adakite-like volcanism of Ecuador: lower crust magmatic evolution and recycling

Evolution of the late Pleistocene Mojanda–Fuya Fuya volcanic complex (Ecuador), by progressive adakitic involvement in mantle magma sources

Across‐arc versus along‐arc Sr‐Nd‐Pb isotope variations in the Ecuadorian volcanic arc

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