Hafnium isotopic variations in East Atlantic intraplate volcanism

Geldmacher, Jörg; Hoernle, Kaj; Hanan, B. B.; Blichert‐Toft, Janne; Hauff, Folkmar; Gill, James B.; Schmincke, Hans‐Ulrich

doi:10.1007/s00410-010-0580-5

Cited by 31 publications

(15 citation statements)

References 95 publications

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“…Common mantle component “C” is from Hanan and Graham [1996], with 176 Hf/ 177 Hf based on the work by Hanan et al [2000]. The trend of time‐integrated oceanic crust compositions are shown by dashed red arrow in Figure 8a, with labels for 0.5, 1.0 and 1.5 My recycled MORB, from Geldmacher et al [2010].…”

Section: Resultsmentioning

confidence: 99%

Hf isotopic evidence for small-scale heterogeneity in the mode of mantle wedge enrichment: Southern Havre Trough and South Fiji Basin back arcs

Todd

Gill

Wysoczanski

et al. 2011

Geochem. Geophys. Geosyst.

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[1] Magmas from SW Pacific back-arc basins have geochemical and isotopic signatures indicating variable mantle and subduction-derived components. Basalts from South Fiji Basin (SFB) are little influenced by subduction, but come from variably enriched mantle, resulting from mixing between enriched mantle, like FOZO, and depleted mantle, like DMM. The same components are present in the Havre Trough mantle, but Havre Trough basalts come from a mantle wedge to which a greater proportion of subduction-derived components are added. Their slab-derived components are isotopically similar to locally subducting sediment, with variable Sr and Pb from altered oceanic crust. Their compositional diversity correlates with morphology, previously described as contrasting Arc-type and Rift-type back-arc regimes. Geochemical modeling indicates that material is added as both supercritical fluids and slab melts below the back-arc, is locally distinct, and correlate with differences in the predicted slab-surface pressure and temperature conditions. Deeper slab surfaces correspond to higher-temperatures at a given distance from the volcanic front, but not necessarily with an increase in the amount of slab-derived material. Slab fluxes for rift-type basalts are consistent with predicted slab-surface temperatures at or below the water-saturated solidus. However, some are consistent with melting in equilibrium with residual rutile, zircon and monazite, so melting may have occurred by fluid fluxing of the slab surface, requiring external fluids from within the slab. Arc-type basalts are explained by thermal anomalies in the mantle wedge, which may correspond to locally hotter slab-surface temperatures and more fractionated slab-derived component signatures in their source.

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Section: Resultsmentioning

confidence: 99%

Hf isotopic evidence for small-scale heterogeneity in the mode of mantle wedge enrichment: Southern Havre Trough and South Fiji Basin back arcs

Todd

Gill

Wysoczanski

et al. 2011

Geochem. Geophys. Geosyst.

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“…In this diagram it can also be noted that bulk rocks have a less radiogenic Hf with respect to a given Nd composition than the mantle array (εHf = 1.33 εNd + 3.19 after Vervoort et al, 1999). This decoupling of Hf from Nd isotope ratios is attributed to recycling of oceanic crust and sediments (e.g., Geldmacher et al, 2011) which results in a time-integrated lowering of the 176 Hf/ 177 Hf Reported for comparison are: subducted and marine sediments (Ben Othman et al, 1989;Plank and Langmuir, 1998;Vervoort et al, 2011). DMM (Depleted MORB Mantle; Workman and Hart, 2005), EM1, and EM2 (Enriched Mantle Type-1 and Type-2; Hart, 1988), and GLOSS (Global Subducting Sediments; Plank and Langmuir, 1998).…”

Section: Nature Of the Protolith Of The Amphibolitesmentioning

confidence: 89%

Vestiges of a fore-arc oceanic crust in the Western Mediterranean: Geochemical constraints from North-East Algeria

Fernandez

Bosch

Bruguier

et al. 2020

Lithos

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The present day architecture of the Western Mediterranean mainly results from the interplay of different lithospheric plates and the Cenozoic consumption of various branches of the Alpine Tethys and Neo-Tethys Oceans. Identifying relics of these oceanic domains in the peri-Mediterranean belts enables pinpointing the earliest stages of this evolutionary framework. In NE Algeria, the Kef Lakhal Complex (Edough Massif) is composed of amphibolites and meta-gabbros metamorphosed under amphibolite facies conditions and thrust onto the northern African margin during earliest Miocene. Geochemical analyses reveal that amphibolites and metagabbros have major and trace element signatures characteristic of tholeiitic basalts and gabbros and display N-MORB (La/ Sm N = 0.7-0.9) to E-MORB (La/Sm N = 1.1-1.2) affinities. Enrichments in U and alkalis (Cs, Rb) and high 87 Sr/ 86 Sr i ratios on bulk rocks and minerals (up to 0.70856) are typical of seawater alteration and indicate that the Kef Lakhal Complex represents a piece of altered oceanic crust. Parental magmas were derived from a Depleted Mantle source (WR εNd i = 8.2-9.9 and εHf i = 10.4-14.4) that preserved some canonical MORB ratios (Ti/Eu = 5700-7600 and Y/Ho = 27.4-29.0), but which was contaminated by a component akin to recycled oceanic crust and associated sediments (Ce/Pb = 10.5-22.2; 206 Pb/ 204 Pb i = 18.41-18.74; 207 Pb/ 204 Pb i = 15.49-15.59; 208 Pb/ 204 Pb i = 37.73-38.37). The sedimentary component is consistent with a volcaniclastic origin and substantiates an intra-oceanic setting. The geochemical characteristics of the Kef Lakhal rocks are comparable to present day (Mariana, W Pacific Ocean) or fossil (Xigaze, SE Tibet) fore-arc oceanic crust. An overview of the Western Mediterranean geodynamic indicates that the most likely period for initiating formation of a fore-arc corresponds either to the Early/Late Cretaceous or to the Middle Eocene. 40 Ar/ 39 Ar dating on amphibole further indicate that after thrusting onto the African margin, the Kef Lakhal Complex cooled down to c.550°C at 18.14 ± 0.27 Ma (2σ).

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“…6), suggesting the involvement of material with excess radiogenic Hf, which, in most cases, is interpreted to reflect recycling of high Δε Hf , zircon-deficient pelagic sediments (Vervoort et al 2011) (Salters and White 1998;Chauvel and Blichert-Toft 2001;Eisele et al 2002) and representative compositions for pelagic and terrigenous sediments (Vervoort et al 2011) are plotted for comparison. Solid lines represent the isotopic evolution of modeled MORB crust of varying ages generated from the depleted MORB mantle using the average present-day Lu/Hf and Sm/Nd values for E-MORB and N-MORB (Chauvel and Blichert-Toft 2001;Chauvel et al 2008;Geldmacher et al 2011), while the dashed lines represent the mixture of N-MORB crust with associated sediments of similar age (Chauvel et al 2008). Shown for comparison are the compositional fields for the Cenozoic intraplate lavas from the Central European Volcanic Province (CEVP; Jung et al 2011;Kolb et al 2012) and the central Mediterranean (Gasperini et al 2002;Viccaro et al 2011) one of the slab-derived components.…”

Section: Source Componentsmentioning

confidence: 99%

Source components and magmatic processes in the genesis of Miocene to Quaternary lavas in western Turkey: constraints from HSE distribution and Hf–Pb–Os isotopes

Aldanmaz

Pickard

Meisel

et al. 2015

Contrib Mineral Petrol

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crystallization trends indicate distinctly lower bulk partition coefficients for IPGE in more evolved lavas, possibly reflecting a change in the fractionating assemblages. Pd and Re in the primitive melts display negative correlations with MgO, demonstrating moderately incompatible behavior of these elements during fractionation, while the significantly scattered variation in Pt against MgO may indicate the effects of micronuggets of a Pt-rich alloy. Osrich alkaline primary lavas (>50 ppt Os) exhibit a limited range of 187 Os/ 188 Os (0.1361-0.1404), with some xenolith-bearing lavas displaying depletions in 187 Os/ 188 Os (0.1131-0.1232), suggesting slight compositional modification of primitive melts through contamination with highly depleted, Os-rich mantle lithosphere. More radiogenic Os isotope ratios ( 187 Os/ 188 Os > 0.1954) in the evolved lavas reflect contamination of the magmas by high 187 Os/ 188 Os crustal material during shallow differentiation. The OIB-type lavas show limited variations in Hf and Pb isotopes with Hf ratios correlate negatively with 208 Pb*/ 206 Pb*, suggesting the effects of similar mantle processes on the evolution of time-integrated Th/U and Lu/Hf. These lavas have distinctly higher 176 Hf/ 177 Hf and lower 208 Pb*/ 206 Pb* than the Early-Middle Miocene lavas of the region, which are interpreted as melts of enriched mantle with an overprint by sediment-derived subduction component. The source region for the OIB-type alkaline melts is interpreted to be a sub-lithospheric reservoir enriched in Hf and Pb isotopes with respect to depleted MORB mantle. Combined evaluation of Hf, Pb, and Os isotopes suggests that the relative enrichment in this domain is related to mixing of ancient oceanic crust with the ambient mantle through long-term plate recycling processes.Abstract Hf-Pb-Os isotope compositions and highly siderophile element (HSE) abundance variations are used to evaluate the mantle source characteristics and possible effects of differentiation processes in lavas from western Turkey, where the eruption of Late Miocene to Quaternary OIB-type intraplate mafic alkaline lavas followed pre-Middle Miocene convergent margin-type volcanism. Concentrations of Os, Ir, and Ru (IPGE) in the OIB-type intraplate lavas decrease with fractionation for primitive melts (MgO > 10 wt%), suggesting that these elements reside predominantly in olivine and associated HSE retaining trace phases and behave compatibly during olivine-dominated fractionation. Fractional Communicated by

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Hafnium isotopic variations in East Atlantic intraplate volcanism

Cited by 31 publications

References 95 publications

Hf isotopic evidence for small-scale heterogeneity in the mode of mantle wedge enrichment: Southern Havre Trough and South Fiji Basin back arcs

Hf isotopic evidence for small-scale heterogeneity in the mode of mantle wedge enrichment: Southern Havre Trough and South Fiji Basin back arcs

Vestiges of a fore-arc oceanic crust in the Western Mediterranean: Geochemical constraints from North-East Algeria

Source components and magmatic processes in the genesis of Miocene to Quaternary lavas in western Turkey: constraints from HSE distribution and Hf–Pb–Os isotopes

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