Effects of aseismic ridge subduction on the geochemistry of frontal arc magmas

Chiaradia, Massimo; Müntener, Othmar; Beate, Bernardo

doi:10.1016/j.epsl.2019.115984

Cited by 29 publications

(35 citation statements)

References 64 publications

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“…The abundance of volcanic arc activity suggests that flat slab subduction that might be associated with the downgoing Carnegie Ridge must be relatively recent. A number of studies point to petrological changes along the arc to suggest that a shallowly subducting Carnegie Ridge may affect arc magmatism at the surface, either by affecting the depth of melting (e.g., Chiaradia et al, 2020) or through the melting of overthickened oceanic crust due to adjacent tears in the downgoing plate (e.g., Gutscher et al, 1999a;Bourdon et al, 2003;Rosenbaum et al, 2018). One way or the other, 5 Ma of subduction would still imply a substantial amount of subducted ridge, certainly sufficient to be responsible for the observed seismic gap within uncertainties.…”

Section: Cocos and Carnegie Ridgesmentioning

confidence: 99%

Effects of Oceanic Crustal Thickness on Intermediate Depth Seismicity

et al. 2020

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The occurrence of intermediate depth seismicity (70-300 km) is commonly attributed to the dehydration of hydrous phases within the downgoing oceanic plate. While some water is incorporated into the oceanic crust at formation, a significant amount of water is introduced into the plate immediately before subduction along outer-rise faults. These faults have been shown to extend to depths of over 30 km and can channel water to depths of 20 km or more beneath the seafloor. However, the amount of water introduced into the oceanic mantle lithosphere, and the role of that water in the formation of intermediate depth seismicity, has been the topic of ongoing research.Here we compile evidence from areas where the subducted oceanic crust is likely thicker than the penetration depth of water into the downgoing plate. These regions comprise aseismic plateaus and ridges (hot spot tracks) that can be compared directly to adjacent segments of the oceanic plate where oceanic crust of normal thickness is subducted. Regions with thick oceanic crust show little to no seismicity at intermediate depths, whereas adjacent regions with normal oceanic crust (∼6-8 km thick) have significant seismicity at similar depths and distances from the trench. We hypothesize that intermediate depth earthquakes observed in regions with thinner oceanic crust are caused by mantle dehydration reactions that are not possible in regions where the oceanic mantle was never hydrated because the thickness of the oceanic crust exceeded the penetration depth of water into the plate. We compare our observations to phase diagrams of hydrous basalt and hydrated depleted peridotite to determine pressures and temperatures that would be consistent with our observations. These can provide valuable constraints, not only on the degree of hydration and dehydration in the downgoing plate, but also as ground-truth for thermal models of these regions, all of which have complex, three-dimensional, time-variant subduction geometries and thermal histories.

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Section: Cocos and Carnegie Ridgesmentioning

confidence: 99%

Effects of Oceanic Crustal Thickness on Intermediate Depth Seismicity

et al. 2020

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“…In addition, the three‐dimensional geometry of slab edges influences the pattern of asthenospheric flow, which can lead to asthenospheric upwelling and associated decompression melting (Faccenna et al., 2010; Jadamec & Billen, 2010; Strak & Schellart, 2014). Lastly, the nature of melt generated, and the manner in which magmas are transferred and emplaced, are influenced by structural and compositional heterogeneities, both in the overriding plate (Acocella & Funiciello, 2010) and in the subducting plate (e.g., Chiaradia et al., 2020; Cruz‐Uribe et al., 2018). Accordingly, to fully understand the spatio‐geochemical distribution of arc magmatism, one must obtain detailed information on the local architecture and composition of the crust and mantle.…”

Section: Discussionmentioning

confidence: 99%

Spatially and Geochemically Anomalous Arc Magmatism: Insights From the Andean Arc

Rosenbaum

Caulfield

Ubide

et al. 2021

Geochem Geophys Geosyst

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While most volcanic arcs show a distinctive spatial relationship to subducting plates, there are many examples where volcanoes occur in anomalous locations. These are commonly also geochemically anomalous relative to the composition of more typical subduction‐related rocks. Using Holocene volcanoes in South America as a case study, we document the spatial and geochemical patterns along the Andean volcanic belt. To determine whether spatial variations are also geochemically anomalous, we assess a series of geochemical indices that provide information on the depth and degree of melting, and the role of metasomatic subduction inputs in melt generation. We use these parameters to develop a scoring system, with the lowest and highest scores indicating “typical” and “anomalous” arc melting processes, respectively. Typical arc magmatism is defined as melts generated in the sub‐arc mantle wedge through slab‐derived fluid metasomatism, with or without contributions from subducted sediments. In contrast, we show that anomalous volcanism in South America appears to relate to geometric anomalies in the subducting Nazca plate (e.g., beneath Sumaco, Laguna Blanca and Payun Matru), or to areas affected by variations in mantle flow due to the proximity to the slab edge (Crater Basalt Volcanic Field). By establishing relationships between anomalous magmatism and slab structure, we propose that similar geochemical fingerprints could be used to explore the magmatic response to slab deformation and/or tearing in older arc systems, particularly in cases where the three‐dimensional slab structure is no longer detectable.

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“…Mélange diapirs melt at increasing depths because of changes in the slab and crustal architectures. (Gorring & Kay, 2001), or in promoting magma stagnation and contamination at different depths (Chiaradia et al, 2020). In the case of the PB, however, the rugged bathymetry created by ridge structures impacted ocean circulation and sedimentation, which in turn controlled the kind of sediments feeding the subduction zone across the ridge axes.…”

Section: Discussionmentioning

confidence: 99%

“…The Hf isotopic composition shown in panel (d) is an estimate based on the compositional similarity with Lesser Antilles sediments. still represent viable explanations for the isotopic and trace element enrichments of typical continental arc rocks like those from the NVP (Annen et al, 2006;Chiaradia et al, 2020;Hildreth & Moorbath, 1988).…”

Section: Ruling Out Intra-crustal Processesmentioning

confidence: 99%

“…And yet, it has recently been shown that the similarly parabolic-shaped compositional trends in Th (or Th/ La ratios) and Nd isotopes found in Ecuadorian volcanoes may still be governed by assimilation of compositionally distinct crustal segments that reside at different depths, due to the influence of the subducted Carnegie ridge (Chiaradia et al, 2020). As in Ecuador, the lower crust in Colombia has lower Th/La ratios and is isotopically less evolved than the locally exposed upper crustal peraluminous granites (Figures 4 and 5), compositions that could in principle be transferred to magmas that stagnate and contaminate at different crustal levels.…”

Section: Ruling Out Intra-crustal Processesmentioning

confidence: 99%

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A Biogeochemical Imprint of the Panama Basin in the North Andean Arc

Errázuriz-Henao

Gómez-Tuena

Parolari

et al. 2021

Geochem Geophys Geosyst

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The biological and sedimentological surface-processes recorded in the compositions of seafloor sediments are transferred to the Earth's interior at convergent margins. These materials can be either recycled into the deep mantle forming long-term compositional heterogeneities (Stracke et al., 2005), or be reworked shallowly into arc magmas giving shape to the continental masses (Behn et al., 2011). While it has been long recognized that subducted sediments exert an important control in the compositions of island arcs (Plank, 2005), less is known about the geochemical imprint of the oceanic realm in thick-crusted continental arc sections. This is because subducting sediments (i.e., GLOSS; Plank, 2013) are compositionally very similar to the overriding continental crust with which ascending magmas may interact, and because forearc subduction erosion may introduce a volumetrically higher crustal influx at most continental margins that could overwhelm the oceanic inputs (Straub et al., 2020).

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Effects of aseismic ridge subduction on the geochemistry of frontal arc magmas

Abstract: The following manuscript entitled 'Effects of aseismic ridge subduction on geochemistry of frontal arc magmas' has been submitted for publication in Earth and Planetary Science Letters.

Cited by 29 publications

References 64 publications

Effects of Oceanic Crustal Thickness on Intermediate Depth Seismicity

Effects of Oceanic Crustal Thickness on Intermediate Depth Seismicity

Spatially and Geochemically Anomalous Arc Magmatism: Insights From the Andean Arc

A Biogeochemical Imprint of the Panama Basin in the North Andean Arc

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