The boron and lithium isotopic composition of mid-ocean ridge basalts and the mantle

Marschall, Horst R.; Wanless, V. D.; Shimizu, Nobumichi; Strandmann, Philip A.E. Pogge von; Elliott, Tim; Monteleone, B. D.

doi:10.1016/j.gca.2017.03.028

Cited by 230 publications

(173 citation statements)

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“…Today, the best estimate for the d 11 B of uncontaminated MORB is −7.1 ± 0.9‰, and it is homogenous in boron isotopes on the level of current analytical precision and accuracy. It is further concluded that assimilation of seawater or seawater-altered materials produces elevated d 11 B values as observed in a number of MORB glass samples (Chaussidon and Jambon 1994;Marschall et al 2017; Fig. 8.1).…”

Section: Mid-ocean Ridge Basaltsmentioning

confidence: 59%

“…The authors use a d 11 B reference value of −3 ± 3‰ for MORB-source mantle and interpret all observed values higher than that as due to assimilation of altered Hawai'ian crust into the magma (Kobayashi et al 2004). Values lower than −6‰ are taken as evidence for deeply recycled ancient subducted crust; however, there are no data that are significantly lower than the more recently suggested d 11 B value for the MORB-source mantle (−7.1 ± 0.9‰; Marschall et al 2017), suggesting that all data may be explained by melts derived from mantle without an unusual B isotopic composition, and that the observed range may be due to various degrees of assimilation of altered crust. Kobayashi et al (2004) also report a wide range of Li isotopes in the melt inclusions, but these would have to be revisited in the light of kinetic isotope fractionation during diffusion of Li in and out of the melt inclusions after entrapment.…”

Section: St Helena Mcdonald Afarmentioning

confidence: 70%

“…Their two MORB samples with 187 Os/ 188 Os\0:135 have a d 11 B value of −10.3 ± 2.2‰, which they take as representative of the uncontaminated mantle, following Chaussidon and Marty (1995). Gannoun et al (2007) Marschall et al (2017), the most recent and comprehensive study so far, investigated 56 MORB samples from the northern and southern MAR, the SWIR and from three sections of the EPR. Magma assimilation of altered crust (or seawater, or brines) was identified through elevated chlorine contents and Cl/K ratio.…”

Section: Mid-ocean Ridge Basaltsmentioning

confidence: 99%

“…'n' refers to the number of samples analyzed in each study, including analyses of matrix glass, melt inclusions, and whole-rock samples. MORB range from Marschall et al (2017) component. This model has to be reversed, however, if a d 11 B value for the MORB-source mantle of approximately −7.1‰ is accepted, and a component with isotopically heavy B is required, instead, to explain the data for all three Hawai'ian volcanic centers.…”

Section: St Helena Mcdonald Afarmentioning

confidence: 99%

“…However, fresh basaltic glasses erupted at mid-ocean ridges have been used to indirectly determine the boron elemental and isotopic composition of the convecting mantle, and ocean-island basalts have been investigated to identify possible recycled crustal materials in the mantle (Chaussidon and Jambon 1994;Chaussidon and Marty 1995;Marschall et al 2017). …”

Section: Introductionmentioning

confidence: 99%

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Boron Isotopes in the Ocean Floor Realm and the Mantle

Marschall

2017

Advances in Isotope Geochemistry

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This chapter reviews the boron isotopic composition of the ocean floor, including pristine igneous oceanic crust such as mid-ocean ridge basalts and ocean island basalts and their implications for the B isotopic composition of the mantle. The chapter further discusses the B isotopic effects of assimilation of altered crustal materials in mantle-derived magmas. The systematics of seawater alteration on oceanic rocks are discussed, including sediments, igneous crust and serpentinization of ultramafic rocks and the respective marine hydrothermal vent fluids. The chapter concludes with a discussion of the secular evolution of the B isotopic composition of seawater.

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Section: Mid-ocean Ridge Basaltsmentioning

confidence: 59%

Section: St Helena Mcdonald Afarmentioning

confidence: 70%

Section: Mid-ocean Ridge Basaltsmentioning

confidence: 99%

Section: St Helena Mcdonald Afarmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Boron Isotopes in the Ocean Floor Realm and the Mantle

Marschall

2017

Advances in Isotope Geochemistry

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New insights into the source of the boron memory effect and implications for accurate boron isotope measurements

Cai

Chen

et al. 2023

Rapid Comm Mass Spectrometry

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Rationale:The boron (B) memory effect is a concern for B isotope analysis in inductively-coupled plasma mass spectrometry and a potential cause of poor data comparability between laboratories. It is widely assumed that the memory resides in water droplets on the surface of the spray chamber. However, even without the use of the spray chamber, background subtractions are still required to generate accurate data, therefore additional causes for the memory effect exist, which are investigated here.Methods: Different parts of the mass spectrometer were examined to pinpoint the source of a particularly high B background. After identifying the torch as the source of the background, different parts of the torch were soaked in dilute nitric acid, which was analyzed for B over time.Results: B was leached out of the tip of the outer quartz tube of the torch in a fashion similar to borosilicate glass, which suggests the incorporation of B into the silica structure of the torch at high temperatures. Running 3% nitric acid washes effectively reduces the background. B background compositions change based on the solutions run beforehand, therefore different blank subtraction methods generate systematic differences. A new background subtraction method that utilizes B isotope ratios improved the precision by up to 0.14‰. The addition of a water wash step before sample elution led to smaller eluent volumes and improved matrix matching without causing a B breakthrough.Conclusions: An important part of the B memory derives from the torch glass, which incorporates B from sample solutions at high temperatures. Multiple nitric acid washes, matrix matching, blank subtraction, and standard sample bracketing generated accurate B isotope analyses with background/signal ratios as high as 10%, without the need for hazardous chemicals as washes. B isotope values of two sediment standards that represent average post-Archean continental crust were reported. | INTRODUCTIONBoron (B) is highly soluble in water. Its two isotopes, 10 B and 11 B, partition differently between borate and boric acid, the two dominant species of boron in aqueous solutions. [1][2][3][4][5] Because the proportion of borate and boric acid changes according to the pH of the environment, the 10 B/ 11 B ratio is widely used to investigate processes that involve water, including the weathering process, 6-8 ocean pH changes, 9-11 tectonic processes, 12-14 and ore formation. [15][16][17] Multicollector inductively-coupled plasma mass spectrometry (MC-ICP-MS) permits high throughput of B isotope measurements. However, relatively elevated and persistent instrumental B background between samples, or the B memory effect, remains a common concern. This memory effect is generally attributed to B(OH) 3 vapor from previously nebulized solutions that become entrained in droplets coating the walls of the spray chambers. [18][19][20] The use of demountable

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Isotope Fractionation Processes of Selected Elements

Hoefs¹

2021

Springer Textbooks in Earth Sciences, Geography and Environment

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The boron and lithium isotopic composition of mid-ocean ridge basalts and the mantle

Abstract: The global set of samples investigated here were produced at various degrees of partial melting and in-

Cited by 230 publications

References 175 publications

Boron Isotopes in the Ocean Floor Realm and the Mantle

Boron Isotopes in the Ocean Floor Realm and the Mantle

New insights into the source of the boron memory effect and implications for accurate boron isotope measurements

Isotope Fractionation Processes of Selected Elements

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