Effects of Al content on water partitioning between orthopyroxene and olivine: Implications for lithosphere–asthenosphere boundary

Sakurai, Masahiro; Tsujino, Noriyoshi; Sakuma, Hiroshi; Kawamura, Katsuyuki; Takáhashi, Eiichi

doi:10.1016/j.epsl.2014.05.041

Cited by 23 publications

(44 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Under relatively low water content (water fugacity), water is partitioned more to orthopyroxene than to olivine (Dai and Karato 2009a;Sakurai et al 2014). In these cases, orthopyroxene would have much higher electrical conductivity than olivine, and therefore, the volume fraction and the connectivity of orthopyroxene will have an important effect on the bulk electrical conductivity.…”

Section: Conductivity Of the Lithosphere: Can Olivine Explain It?mentioning

confidence: 99%

Some remarks on hydrogen-assisted electrical conductivity in olivine and other minerals

Karato

2019

Prog Earth Planet Sci

View full text Add to dashboard Cite

Electrical conductivity in minerals is sensitive to hydrogen content, and therefore, it is a potentially important property from which one can infer hydrogen (water) distribution in the mantle. However, there has been much confusion in the reported results on hydrogen-assisted conductivity. In this paper, I review the existing experimental observations on hydrogenenhanced electrical conductivity in olivine and other minerals to identify the causes of confusion. Hydrogen loss as well as hydrogen gain could occur during a conductivity measurement at high pressures and temperatures. Particularly important is the unrecognized hydrogen gain during an experiment that could lead to a large degree of error. Many experiments were conducted under the conditions where specimens were super-saturated with hydrogen making the validity of those results unclear. A model for hydrogen loss is developed showing a strategy by which hydrogen loss can be minimized. When one selects the experimental results in which the influence of hydrogen loss/gain are carefully examined, there is no major discrepancy among the results from different laboratories except differences between the results from low and high temperatures. Differences between low-temperature and high-temperature results are caused by the change in conduction mechanism. At low temperatures, conduction is due to the migration of interstitial ("free") proton and is nearly isotropic, whereas conduction at high temperatures is due to the migration of two protons at M-site that is highly anisotropic. There is no evidence for substantial concentration dependence of activation enthalpy. Observed exceptionally large concentration dependence reported by Poe et al. (Phys Earth Planet Inter 181:103-111, 2010) is inconsistent with all other reports and is likely caused by some experimental artifact. Experimental results in the high-temperature regime explain a majority of geophysical observations on the conductivity of the oceanic asthenosphere: partial melting is not needed in most regions and is rather inconsistent with the observations on the matured oceanic mantle. Exception is the asthenosphere near the ridge and/or near the trench where very high conductivity (~0.1 S/m) is reported at the top of the asthenosphere. Partial melting might play some role in these regions. Electrical conductivity in the continental lithosphere cannot be attributed entirely to olivine. An important role of orthopyroxene and/or other minor materials (graphite, sulfide) is needed to explain high conductivity reported in some regions such as Bushveld in South Africa. The largest remaining uncertainty is the degree to which hydrogen affects electrical conductivity in the lower mantle minerals. Determining the influence of hydrogen on electrical conductivity in lower mantle minerals is critical to make progress in understanding the global water circulation.

show abstract

Section: Conductivity Of the Lithosphere: Can Olivine Explain It?mentioning

confidence: 99%

Some remarks on hydrogen-assisted electrical conductivity in olivine and other minerals

Karato

2019

Prog Earth Planet Sci

View full text Add to dashboard Cite

show abstract

“…Total vacuum‐type FTIR microscope by JASCO Company (FT‐IR‐6100) located at the SKLaBIG‐GIGCAS were used. Because of the vacuum system, LOD for H 2 O in this system is less than 0.1 ppmw . The samples were cut into tabular rhomboids of 500 to 3000 μm thick and polished on both sides.…”

Section: Samples and Analytical Methodsmentioning

confidence: 99%

Section: Samples and Analytical Methodsmentioning

confidence: 99%

“…Because of the vacuum system, LOD for H 2 O in this system is less than 0.1 ppmw. 19 The samples were cut into tabular rhomboids of 500 to 3000 μm thick and polished on both sides. Samples were heated in an oven at 80°C for at least an hour prior to analysis in order to remove potential surface contaminated water.…”

Section: Analysis Methodsmentioning

confidence: 99%

“…Typically, up to 800 scans were performed for each measurement at 2 cm −1 nominal resolution to obtain spectra with a signal to noise ratio of >1000. The method has been described in detail by Sakurai et al 19 After FTIR analyses, all the samples were placed on a doublesided adhesive type and enclosed in tin-based alloy, same as the method described by Zhang et al 10 The alloy mount was photographed under reflected light with an optical microscope and then gold-coated (approximately 30 nm thick) before the SIMS analysis.…”

Section: Analysis Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Optimization of SIMS analytical parameters for water content measurement of olivine

Zhang

Xia

Takáhashi

et al. 2019

Surface & Interface Analysis

View full text Add to dashboard Cite

Secondary ion mass spectrometry (SIMS) has a wide range of applications in Earth Science research, thanks to its high precision and sensitivity, and its capacity in direct insitu micromeasurement. The technique is operated in ultra‐high vacuum (UHV) conditions, especially for the measurement of volatiles such as hydrogen, or the water content in nominally anhydrous minerals (NAMs). To minimize the water background and obtain accurate and precise water contents in NAMs (eg, olivine) critical parameters such as presputtering time, field aperture (FA), dynamic transfer on/off, and primary beam current intensity were investigated for a CAMECA IMS 1280‐HR system. When the chamber vacuum reaches approximately 2 × 10−9 mbar, we set the DTOS OFF, raster size to 50 μm and primary beam current to 5 nA, and used 2000 μm FA and 170‐second presputtering time. Consequently, an approximately 1.2 ppmw water background and 3.6 ppmw limit of detection (LOD) were yielded, from analyzing the San Carlos olivine. Meanwhile, the water content and homogeneity of a range of olivine minerals were characterized for potential use as reference materials for SIMS water content measurement. Olivine water content calibration curve was also established by comparing the Fourier transform infrared (FTIR) results with the SIMS‐measured 16O1H−/16O− ratios. Accuracy and precision of water content measurement were estimated to be better than approximately 10% in this study.

show abstract

Regional heterogeneity in the water content of the Cenozoic lithospheric mantle of Eastern China

et al. 2016

View full text Add to dashboard Cite

The major and trace elements and H2O contents of minerals in peridotite xenoliths hosted by the Cenozoic basalts in Northeast China (NEC) were evaluated using electron microprobe, laser‐ablation inductively coupled plasma–mass spectrometry and Fourier transform infrared spectroscopy, respectively. Although a potential loss of H during the xenoliths' ascent cannot be excluded for olivine, orthopyroxene (opx) and clinopyroxene (cpx) largely preserved the H2O contents of their mantle source in all of the samples, as inferred from (1) the homogenous H2O contents within single pyroxene grains and (2) the equilibrium H2O partitioning between cpx and opx. No OH was detected for pyroxenes of peridotite xenoliths from the north part of NEC (NNEC). Combined with previously published data from the North China Craton (NCC) and the South China Block (SCB), the regional heterogeneity in the water contents in the Cenozoic lithospheric mantle beneath the whole Eastern China has been revealed. The lithospheric mantle beneath the NNEC is completely dry. The “bulk” water contents of the lithospheric mantle of the south part of NEC and the NCC have similar ranges and average values, whereas those of the SCB are much higher (12–195 ppm, average 90 ± 45 ppm for whole rock). The regional variations in the H2O content of the Cenozoic lithospheric mantle of Eastern China cannot be caused by partial melting, mantle metasomatism, or variations in redox state. We propose that the lithospheric mantle beneath the different regions of Eastern China may have distinct origins and may have undergone distinct geodynamic processes.

show abstract

Effects of Al content on water partitioning between orthopyroxene and olivine: Implications for lithosphere–asthenosphere boundary

Cited by 23 publications

References 33 publications

Some remarks on hydrogen-assisted electrical conductivity in olivine and other minerals

Some remarks on hydrogen-assisted electrical conductivity in olivine and other minerals

Optimization of SIMS analytical parameters for water content measurement of olivine

Regional heterogeneity in the water content of the Cenozoic lithospheric mantle of Eastern China

Contact Info

Product

Resources

About