Hydrogen in diopside: Diffusion profiles

Woods, Susan Carpenter; Mackwell, S. J.; Dyar, Darby

doi:10.2138/am-2000-0409

Cited by 123 publications

(58 citation statements)

References 20 publications

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“…However, the aging of EM2 can account for our observations. This is how: very fast diffusion of hydrogen in mantle minerals (Mackwell and Kohlstedt, 1990;Wang et al, 1996;Woods et al, 2000;Stalder and Skogby, 2003) will cause recycled material with high initial water content to lose water to the drier ambient mantle during storage within the deep Earth.…”

Section: Origin Of Em2's "Dehydration"mentioning

confidence: 99%

“…It has been known for decades that the diffusion rates of most lithophile trace elements (the rare-earth-elements, for example) are so slow that mantle heterogeneities will not equilibrate for these elements over more than 10 meters during the whole age of the Earth (Hofmann and Hart, 1978;Van Orman et al, 2001). On the other hand, experimental data for the diffusion of hydrogen in upper mantle minerals (Mackwell and Kohlstedt, 1990;Wang et al, 1996;Woods et al, 2000;Stalder and Skogby, 2003) indicate that diffusive mobility of water is extremely rapid; as a result, the enhanced solid-state mobility of hydrogen can potentially shift H 2 O/La ratios in the absence of any melting or mantle-fluid interactions ( fig. 10).…”

Section: Origin Of Em2's "Dehydration"mentioning

confidence: 99%

“…Diffusion rates of water in diopside are about 5 times faster than olivine at 1600°C (Woods et al, 2000), so will help to speed the slab's equilibration times. Since much of the mantle is at temperatures higher than 1600°C, these are conservative estimates.…”

Section: Origin Of Em2's "Dehydration"mentioning

confidence: 99%

“…However, the fast diffusion of water through mantle minerals (Mackwell and Kohlstedt, 1990;Wang et al, 1996;Woods et al, 2000;Stalder and Skogby, 2003) provides a very effective means of losing water from EM2 to a water-poor ambient mantle during the long-term (~2.5 Ga) storage of EM2 -to the point of there being very similar bulk water contents (<100 ppm) in EM2 and the Depleted MORB Mantle (DMM). This finding leads credence to the idea that enriched mantle plumes are indeed "hot-spots" (Morgan, 1971;Sleep, 1990;Campbell and Griffiths, 1990) and not "wet-spots" (Schilling, et al, 1980;Green and Falloon, 1998).…”

Section: Introductionmentioning

confidence: 99%

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Volatile and trace elements in basaltic glasses from Samoa: Implications for water distribution in the mantle

Workman

Hauri

Hart

et al. 2006

Earth and Planetary Science Letters

156

146

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We report volatile (H 2 O, CO 2 , F, S, Cl) and trace element data for submarine alkalic basalt glasses from the three youngest Samoan volcanoes, Ta'u, Malumalu and Vailulu'u. Most samples are visibly sulfide saturated, so have likely lost some S during fractionation. Cl/K ratios (0.04 -0.15) extend to higher values than pristine MORBs, but are suspected to be partly due to source differences since Cl/K roughly varies as a function of 87 Sr/ 86 Sr. There are no resolvable differences in the relative enrichment of F among sources, and compatibility of F during mantle melting is established to be nearly identical to Nd. Shallow degassing has affected CO 2 in all samples, and H 2 O only in the most shallowly erupted samples from Vailulu'u. Absolute water contents are high for Samoa (0.63 -1.50 wt%), but relative enrichment of water compared to equally incompatible trace elements (Ce, La) is low and falls entirely below normal MORB values. H 2 O/Ce (58 -157) and H 2 O/La (120 -350) correlate inversely with 87 Sr/ 86 Sr compositions (0.7045 -0.7089). This leads us to believe that, because of very fast diffusion of hydrogen in mantle minerals, recycled lithospheric material with high initial water and trace element content will lose water to the drier ambient mantle during storage within the inner Earth. The net result is the counter-intuitive appearance of greater dehydration with greater mantle enrichment. We expect that subducted slabs will experience a two-stage dehydration history, first within subduction zones and then in the ambient mantle during long-term convective mixing.

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Section: Origin Of Em2's "Dehydration"mentioning

confidence: 99%

Section: Origin Of Em2's "Dehydration"mentioning

confidence: 99%

Section: Origin Of Em2's "Dehydration"mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Volatile and trace elements in basaltic glasses from Samoa: Implications for water distribution in the mantle

Workman

Hauri

Hart

et al. 2006

Earth and Planetary Science Letters

156

146

View full text Add to dashboard Cite

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“…If the difference in the H concentration of the above mentioned samples were only a matter of kinetic we should observe a concentration profile with un-or less depleted regions in the core and increasing depletion to the rim (e.g. Woods et al, 2000), which was not the case. Fig.…”

Section: Characterization Of the Samples After Heatingmentioning

confidence: 95%

Dehydration experiments on natural omphacites: qualitative and quantitative characterization by various spectroscopic methods

et al. 2007

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Originally published as:Koch-Müller, M., Abs-Wurmbach, I., Rhede, D., Kahlenberg, V., Matsyuk, S. (2007) AbstractA series of natural omphacites from a wide range of P, T occurrences were investigated by electron microprobe (EMP), infrared (IR)-, Mössbauer (MS)-and optical spectroscopy in the UV/VIS spectral range (UV/VIS), secondary ion mass spectrometry (SIMS) and single crystal structure refinement by X-ray diffraction (XRD) to study the influence of hydrogen loss on valence state and site occupancies of iron. In accordance with literature data we found Fe 2+ at M1 as well as at M2, and in a first approach assigned Fe 3+ to M1, as indicated by MS and XRD results. Hydrogen content of three of our omphacite samples were measured by SIMS. In combination with infrared spectroscopy we determined an absorption

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Pyroxenes as tracers of mantle water variations

2014

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The concentration and distribution of volatiles in the Earth's mantle influence properties such as melting temperature, conductivity, and viscosity. To constrain upper mantle water content, concentrations of H 2 O, P, and F were measured in olivine, orthopyroxene, and clinopyroxene in mantle peridotites by secondary ion mass spectrometry. Analyzed peridotites are xenoliths (Pali Aike, Spitsbergen, Samoa), orogenic peridotites (Josephine Peridotite), and abyssal peridotites (Gakkel Ridge, Southwest Indian Ridge, Tonga Trench). The comparison of fresh and altered peridotites demonstrates that low to moderate levels of alteration do not affect H 2 O concentrations, in agreement with mineral diffusion data. Olivines have diffusively lost water during emplacement, as demonstrated by disequilibrium between olivine and coexisting pyroxenes. In contrast, clinopyroxene and orthopyroxene preserve their high-temperature water contents, and their partitioning agrees with published experiments and other xenoliths. Hence, olivine water concentrations can be determined from pyroxene concentrations using mineral-mineral partition coefficients. Clinopyroxenes have 60-670 ppm H 2 O, while orthopyroxenes have 10-300 ppm, which gives calculated olivine concentrations of 8-34 ppm. The highest olivine water concentration translates to an effective viscosity of 6 × 1019 Pa s at 1250°C and~15 km depth, compared to a dry effective viscosity of 2.5 × 10 21 Pa s. Bulk rock water concentrations, calculated using mineral modes, are 20-220 ppm and correlate with peridotite indices of melt depletion. However, trace element melt modeling indicates that peridotites have too much water relative to their rare earth element concentrations, which may be explained by late-stage melt addition, during which only hydrogen diffuses fast enough for reequilibration.

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Hydrogen in diopside: Diffusion profiles

Cited by 123 publications

References 20 publications

Volatile and trace elements in basaltic glasses from Samoa: Implications for water distribution in the mantle

Volatile and trace elements in basaltic glasses from Samoa: Implications for water distribution in the mantle

Dehydration experiments on natural omphacites: qualitative and quantitative characterization by various spectroscopic methods

Pyroxenes as tracers of mantle water variations

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