Mapping water content in the upper mantle

2003 ◽  
pp. 135-152 ◽  
Author(s):  
Shun-ichiro Karato
Keyword(s):  
Water Content ◽  
Upper Mantle

Pyroxenes can be used to estimate upper mantle water content

Eos ◽  
2014 ◽  
Vol 95 (36) ◽  
pp. 332-332
Author(s):  
JoAnna Wendel
Keyword(s):  
Water Content ◽  
Upper Mantle

On the fate of water in the formation of rocky planets

2021 ◽  
Author(s):  
Lindy Elkins-Tanton ◽  
Jenny Suckale ◽  
Sonia Tikoo
Keyword(s):  
Water Content ◽  
Upper Mantle ◽  
Lower Mantle ◽  
Plate Tectonics ◽  
Solidus Temperature ◽  
Magma Ocean ◽  
Excess Water ◽  
Low Degree ◽  
Giant Impacts ◽  
Rocky Planets

<p>Rocky planets go through at least one and likely multiple magma ocean stages, produced by the giant impacts of accretion. Planetary data and models show that giant impacts do not dehydrate either the mantle or the atmosphere of their target planets. The magma ocean liquid consists of melted target material and melted impactor, and so will be dominated by silicate melt, and also contain dissolved volatiles including water, carbon, and sulfur compounds.</p><p>As the magma ocean cools and solidifies, water and other volatiles will be incorporated into the nominally anhydrous mantle phases up to their saturation limits, and will otherwise be enriched in the remaining, evolving magma ocean liquids. The water content of the resulting cumulate mantle is therefore the sum of the traces in the mineral grains, and any water in trapped interstitial liquids. That trapped liquid fraction may in fact be by far the largest contributor to the cumulate water budget.</p><p>The water and other dissolved volatiles in the evolving liquids may quickly reach the saturation limit of magmas near the surface, where pressure is low, but degassing the magma ocean is likely more difficult than has been assumed in some of our models. To degas into the atmosphere, the gases must exsolve from the liquid and form bubbles, and those bubbles must be able to rise quickly enough to avoid being dragged down by convection and re-dissolved at higher pressures. If bubbles are buoyant enough (that is, large enough) to decouple from flow and rise, then they are also dynamically unstable and liable to be torn into smaller bubbles and re-entrained. This conundrum led to the hypothesis that volatiles do not significantly degas until a high level of supersaturation is reached, and the bubbles form a buoyant layer and rise in diapirs in a continuum dynamics sense. This late degassing would have the twin effects of increasing the water content of the cumulates, and of speeding up cooling and solidification of the planet.</p><p>Once the mantle is solidified, the timeclock until the start of plate tectonics begins. Modern plate tectonics is thought to rely on water to lower the viscosity of the asthenosphere, but plate tectonics is also thought to be the process by which water is brought into the mantle. Magma ocean solidification, however, offers two relevant processes. First, following solidification the cumulate mantle is gravitationally unstable and overturns to stability, carrying water-bearing minerals from the upper mantle through the transition zone and into the lower mantle. Upon converting to lower-mantle phases, these minerals will release their excess water, since lower mantle phases have lower saturation limits, thus fluxing the upper mantle with water. Second, the mantle will be near its solidus temperature still, and thus its viscosity will be naturally low. When fluxed with excess water, the upper mantle would be expected to form a low degree melt, which if voluminous enough with rise to help form the earliest crust, and if of very low degree, will further reduce the viscosity of the asthenosphere.</p>

The electrical conductivity of upper-mantle rocks: water content in the upper mantle

2007 ◽  
Vol 35 (3) ◽  
pp. 157-162 ◽  
Author(s):  
Duojun Wang ◽  
Heping Li ◽  
Li Yi ◽  
Baoping Shi
Keyword(s):  
Electrical Conductivity ◽  
Water Content ◽  
Upper Mantle

Water content in natural eclogite and implication for water transport into the deep upper mantle

Lithos ◽  
2006 ◽  
Vol 86 (3-4) ◽  
pp. 245-259 ◽  
Author(s):  
I KATAYAMA ◽  
S NAKASHIMA ◽  
H YURIMOTO
Keyword(s):  
Water Content ◽  
Water Transport ◽  
Upper Mantle

scholarly journals Origins of water content variations in the suboceanic upper mantle: Insight from Southwest Indian Ridge abyssal peridotites

2017 ◽  
Vol 18 (3) ◽  
pp. 1298-1329 ◽  
Author(s):  
Wei Li ◽  
Vincent Soustelle ◽  
Zhenmin Jin ◽  
Huaiming Li ◽  
Tao Chen ◽  
...  
Keyword(s):  
Water Content ◽  
Upper Mantle ◽  
Southwest Indian Ridge ◽  
Indian Ridge

Effect of H2O on upper mantle phase transitions in MgSiO3: Is the depth of the seismic X-discontinuity an indicator of mantle water content?

2010 ◽  
Vol 183 (1-2) ◽  
pp. 234-244 ◽  
Author(s):  
Steven D. Jacobsen ◽  
Zhenxian Liu ◽  
Tiziana Boffa Ballaran ◽  
Elizabeth F. Littlefield ◽  
Lars Ehm ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Water Content ◽  
Upper Mantle

Electrical conductivity of omphacite and garnet in eclogite: implications for water recycling in the mantle

2020 ◽  
Author(s):  
Hanyong Liu ◽  
Xiaozhi Yang
Keyword(s):  
Electrical Conductivity ◽  
Water Content ◽  
Deep Water ◽  
Upper Mantle ◽  
Critical Role ◽  
High Resistivity ◽  
Water Recycling ◽  
Structural Water ◽  
Crust And Upper Mantle ◽  
Water Contents

<p>Eclogite is an important constituent of subduction slabs and plays a critical role in transporting surface materials (e.g., water) into the deep Earth. Eclogite consists mainly of omphacite and garnet. Although nominally anhydrous, omphacite and garnet contain some amount of structural water (OH) in the lattice, which is up to >1500 ppm wt. H<sub>2</sub>O. This is virtually the highest content in nominally anhydrous minerals (NAMs) derived from the crust and upper mantle (Ingrin and Skogby, 2000). The electrical property of NAMs is very sensitive to water content and a small amount of water could dramatically enhance the conductivity. Thus, laboratory measured conductivity data of omphacite and garnet may help to understand the deep water recycling by eclogitized slab.</p><p>In this study, we have systemically determined the conductivity of omphacite and garnet with different water contents. The experiments were carried out at 350-800 °C, 1 GPa (note that the effect of pressure itself on conductivity is very small) and Ni-NiO buffered conditions. The data show that the conductivity of both omphacite and garnet increases with water content or temperature. The bulk conductivity is then modeled for different mineral compositions and water contents over a range of conditions (Liu et al., 2019). In combination with the geophysically documented high resistivity of the crustal part in deep subducted slabs, we suggest that the water content in omphacite and garnet in the deep-subducted eclogites should not be high at mantle depths. This provides new insights into the deep water recycling by subducted eclogites.</p><p> </p><p><strong>References:</strong></p><p>Ingrin, J., and Skogby, H., 2000, Hydrogen in nominally anhydrous upper-mantle minerals: Concentration levels and implications: European Journal of Mineralogy, 12, 543–570.</p><p>Liu, H., Zhu, Q., and Yang, X., 2019, Electrical conductivity of OH-bearing omphacite and garnet in eclogite: the quantitative dependence on water content: Contributions to Mineralogy and Petrology, 174, doi:10.1007/s00410-019-1593-3.</p><p></p><p></p><p></p><p></p>

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