Cosmogenic Be-10 and the Solid Earth: Studies in Geomagnetism, Subduction Zone Processes, and Active Tectonics

Morris, Julie; Gosse, John C.; Brachfeld, Stefanie; Tera, F.

doi:10.2138/rimg.2002.50.5

Cited by 31 publications

(20 citation statements)

References 290 publications

(406 reference statements)

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“…The abundance of 10 Be in some arc volcanic rocks provides evidence that subducted ocean-floor material is transferred to the mantle wedge, entrained into arc magmas, transported through the lithosphere, and erupted at the surface all within ∼ 5 million years [44]. The mantle wedge plume model meets this time constraint for a range of parameters, because the plumes and diapirs are predicted to rise from the slab to the magma source region in a timeframe of 10 4 to 10 6 years [32, 36].…”

Section: Temperature and Time Constraintsmentioning

confidence: 99%

“…Important restrictions on the timescales involved in material cycling in subduction zones comes from isotope geochemistry, most importantly 10 Be and U-Th disequilibrium chronology [44,45]. The abundance of 10 Be in some arc volcanic rocks provides evidence that subducted ocean-floor material is transferred to the mantle wedge, entrained into arc magmas, transported through the lithosphere, and erupted at the surface all within ∼ 5 million years [44].…”

Section: Temperature and Time Constraintsmentioning

confidence: 99%

“…This allows temperatures in the mantle wedge to remain high, and explains the along-strike distribution of the volcanic activity in clusters [32, 35, 36]. Mantle wedge diapirs also explain significant differences in temperature and composition of magmas that are erupted from spatially closely related volcanoes [39].Important restrictions on the timescales involved in material cycling in subduction zones comes from isotope geochemistry, most importantly 10 Be and U-Th disequilibrium chronology [44,45]. The abundance of 10 Be in some arc volcanic rocks provides evidence that subducted ocean-floor material is transferred to the mantle wedge, entrained into arc magmas, transported through the lithosphere, and erupted at the surface all within ∼ 5 million years [44].…”

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Arc magmas sourced from mélange diapirs in subduction zones

2012

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At subduction zones, crustal material is recycled back into the mantle. A certain proportion, however, is returned to the overriding plate via magmatism. The magmas show a characteristic range of compositions that have been explained by three-component mixing in their source regions: hydrous fluids derived from subducted altered oceanic crust and components derived from the thin sedimentary veneer are added to the depleted peridotite in the mantle beneath the volcanoes. However, currently no uniformly accepted model exists for the physical mechanism that mixes the three components and transports them from the slab to the magma source.Here we present an integrated physico-chemical model of subduction zones that emerges from a review of the combined findings of petrology, modelling, geophysics, and geochemistry: Intensely mixed metamorphic rock formations, so-called mélanges, form along the slab-mantle interface and comprise the characteristic trace-element patterns of subduction-zone magmatic rocks. We consider mélange formation the physical mixing process that is responsible for the geochemical three-component pattern of the magmas. Blobs of low-density mélange material, so-called diapirs, rise buoyantly from the surface of the subducting slab and provide a means of transport for well-mixed materials into the mantle beneath the volcanoes, where they produce melt. Our model provides a consistent framework for the interpretation of geophysical, petrological and geochemical data of subduction zones.Geochemical studies of volcanic rocks erupted at convergent plate margins have identified element and isotopic ratios that seem to require material present in their source that is absent in volcanic rocks from other settings, such as mid-ocean ridge basalts [1]. This subduction zone geochemical fingerprint has led to the establishment of three-component mixing models to explain the composition of magmatic rocks produced at continental and island arcs [2, 3]. Their trace-element characteristics are believed to have originated from two distinct sources added to the depleted mantle source: hydrous fluids derived from subducted altered ocean crust and a component derived from the thin sedimentary veneer of the slab. However, the details of the physical process that allows the mixing of these components within the * Corresponding author. Tel: +1-508-289-2776. Fax: +1-508-457- E-mail: hmarschall@whoi.eduEmail address: hmarschall@whoi.edu (Horst R. Marschall)."subduction factory" are unknown. Current models propose that a hydrous component, enriched in incompatible trace elements, is released from the subducting slab and migrates into the overlying mantle wedge. The wedge is at much higher temperatures than the slab due to the 'corner flow' of the asthenospheric mantle, driven by viscous coupling of the mantle to the subducting slab [4]. Mantle-wedge peridotite partial melting is thought to be promoted by the influx of slab-derived fluids [5]. Yet, no uniformly accepted model exists for the actual physical mechanism tha...

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Section: Temperature and Time Constraintsmentioning

confidence: 99%

Section: Temperature and Time Constraintsmentioning

confidence: 99%

mentioning

confidence: 99%

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Arc magmas sourced from mélange diapirs in subduction zones

2012

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“…Therefore, any input of fluid or melt from the subducting slab into the overlying mantle has a strong impact on the light element budget and isotopic composition of the mantle wedge, and on the magmas generated there. Island arc volcanic rocks consequently display strong enrichments of Li, Be and B with respect to MORB (Ryan and Langmuir, 1987Smith et al, 1997;Sano et al, 2001;Ryan, 2002) and specific Be and B isotopic signatures (Ishikawa and Nakamura, 1994;Ishikawa and Tera, 1997;Clift et al, 2001;Morris et al, 2002;Palmer and Swihart, 2002;Straub and Layne, 2002). Detailed knowledge on budget and partitioning of light elements within different materials of the subducting slab are essential for the modelling of Li, Be and B transfer and isotopic evolution in subduction zones.…”

Section: Introductionmentioning

confidence: 99%

Partitioning and budget of Li, Be and B in high-pressure metamorphic rocks

Marschall

Altherr

Ludwig

et al. 2006

Geochimica et Cosmochimica Acta

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Partitioning and budget of Li, Be and B in high-pressure metamorphic rocks from the island of Syros (Greece) were studied, using secondary ion mass spectrometry, inductively coupled plasma optical emission spectrometry and prompt gamma neutron activation analysis. Partitioning between coexisting mineral phases was found to be rather constant and independent of element concentrations. For several mineral pairs, apparent partition coefficients vary in a narrow range, while concentrations vary by more than an order of magnitude. Hence, it was possible to establish sets of inter-mineral partition coefficients for Li, Be and B among 15 different high-pressure minerals. This data set provides important information on the behaviour of the light elements in different lithologies within subducting slabs from the onset of metamorphism to the eclogite stage. It is essential for modelling trace-element and isotope fractionation during subduction and dehydration of oceanic crust.

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“…The 10 Be in the seawater is scavenged and concentrated in marine sediments. Because 10 Be does not exist in the Earth's interior, its presence in volcanic rocks derived from island-arc volcanism is direct evidence of the contribution of subducted sediment to arc-derived magmas; its abundance is a useful tracer to understand the behavior of slab-derived fluid in island-arc systems (Morris et al, 2002). However, 10 Be abundance can be modified by magmatic processes such as partial melting and fractional crystallization.…”

Section: Introductionmentioning

confidence: 99%

Determination of 9Be in geological standard samples, JA-2 and JB-2, and of 9Be and 10Be in a basaltic rock sample for evaluation of uncertainty involved in 10Be/9Be ratio measurements

2008

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We determined the concentrations of 9 Be in JB-2 and JA-2 geological standard samples using an inductively coupled plasma mass spectrometer (ICP-MS). We determined 9 Be abundance in standard samples of JA-2 and JB-2 as 2.26 ± 0.10 and 0.241 ± 0.010 ppm, respectively, after comparing and selecting 9 Be concentration data obtained by the internal standard method, the standard addition method and the column separation method. In the course of comparison, we identified a problem in the internal standard method, which is usually used for abundance analyses using an ICP-MS.Repeated analyses of a basalt lava gave a standard deviation of 10 Be abundance of 9% (1σ, n = 5). From the results, we estimated the uncertainty of 10 Be/ 9 Be ratio as 10% (1σ), considering a law of propagation of errors.

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Cosmogenic Be-10 and the Solid Earth: Studies in Geomagnetism, Subduction Zone Processes, and Active Tectonics

Cited by 31 publications

References 290 publications

Arc magmas sourced from mélange diapirs in subduction zones

Arc magmas sourced from mélange diapirs in subduction zones

Partitioning and budget of Li, Be and B in high-pressure metamorphic rocks

Determination of 9Be in geological standard samples, JA-2 and JB-2, and of 9Be and 10Be in a basaltic rock sample for evaluation of uncertainty involved in 10Be/9Be ratio measurements

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