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Shunichiro Karato - One of the best experts on this subject based on the ideXlab platform.
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seismic evidence for water transport out of the mantle Transition Zone beneath the european alps
Earth and Planetary Science Letters, 2018Co-Authors: Zhen Liu, Jeffrey Park, Shunichiro KaratoAbstract:Abstract The mantle Transition Zone has been considered a major water reservoir in the deep Earth. Mass transfer across the Transition-Zone boundaries may transport water-rich minerals from the Transition Zone into the water-poor upper or lower mantle. Water release in the mantle surrounding the Transition Zone could cause dehydration melting and produce seismic low-velocity anomalies if some conditions are met. Therefore, seismic observations of low-velocity layers surrounding the Transition Zone could provide clues of water circulation at mid-mantle depths. Below the Alpine orogen, a depressed 660-km discontinuity has been imaged clearly using seismic tomography and receiver functions, suggesting downwellings of materials from the Transition Zone. Multitaper-correlation receiver functions show prominent ∼0.5–1.5% velocity reductions at ∼750–800-km depths, possibly caused by partial melting in the upper part of lower mantle. The gap between the depressed 660-km discontinuity and the low-velocity layers is consistent with metallic iron as a minor phase in the topmost lower mantle reported by laboratory studies. Velocity drops atop the 410-km discontinuity are observed surrounding the Alpine orogeny, suggesting upwelling of water-rich rock from the Transition Zone in response to the downwelled materials below the orogeny. Our results provide evidence that convective penetration of the mantle Transition Zone pushes hydrated minerals both upward and downward to add hydrogen to the surrounding mantle.
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water content in the Transition Zone from electrical conductivity of wadsleyite and ringwoodite
Nature, 2005Co-Authors: Yousheng Xu, Xiaoge Huang, Shunichiro KaratoAbstract:The distribution of water in the Earth's interior reflects the way in which the Earth has evolved, and has an important influence on its material properties. Minerals in the Transition Zone of the Earth's mantle (from ∼410 to ∼660 km depth) have large water solubility1,2,3, and hence it is thought that the Transition Zone might act as a water reservoir. When the water content of the Transition Zone exceeds a critical value, upwelling flow might result in partial melting at ∼410 km, which would affect the distribution of certain elements in the Earth4. However, the amount of water in the Transition Zone has remained unknown. Here we determined the effects of water and temperature on the electrical conductivity of the minerals wadsleyite and ringwoodite to infer the water content of the Transition Zone. We find that the electrical conductivity of these minerals depends strongly on water content but only weakly on temperature. By comparing these results with geophysically inferred conductivity5,6,7, we infer that the water content in the mantle Transition Zone varies regionally, but that its value in the Pacific is estimated to be ∼0.1–0.2 wt%. These values significantly exceed the estimated critical water content in the upper mantle3,8,9, suggesting that partial melting may indeed occur at ∼410 km depth, at least in this region.
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water content in the Transition Zone from electrical conductivity of wadsleyite and ringwoodite
Nature, 2005Co-Authors: Xiaoge Huang, Shunichiro KaratoAbstract:The distribution of water in the Earth's interior reflects the way in which the Earth has evolved, and has an important influence on its material properties. Minerals in the Transition Zone of the Earth's mantle (from ∼410 to ∼660 km depth) have large water solubility1,2,3, and hence it is thought that the Transition Zone might act as a water reservoir. When the water content of the Transition Zone exceeds a critical value, upwelling flow might result in partial melting at ∼410 km, which would affect the distribution of certain elements in the Earth4. However, the amount of water in the Transition Zone has remained unknown. Here we determined the effects of water and temperature on the electrical conductivity of the minerals wadsleyite and ringwoodite to infer the water content of the Transition Zone. We find that the electrical conductivity of these minerals depends strongly on water content but only weakly on temperature. By comparing these results with geophysically inferred conductivity5,6,7, we infer that the water content in the mantle Transition Zone varies regionally, but that its value in the Pacific is estimated to be ∼0.1–0.2 wt%. These values significantly exceed the estimated critical water content in the upper mantle3,8,9, suggesting that partial melting may indeed occur at ∼410 km depth, at least in this region.
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plastic deformation of silicate spinel under the Transition Zone conditions of the earth s mantle
Nature, 1998Co-Authors: Shunichiro Karato, Catherine Dupasbruzek, David C RubieAbstract:The dynamics of the Earth's deep interior are controlled to a large extent by rheological properties1,2. Until recently, however, experimental studies on the rheological properties of materials thought to be present in the Earth's deep interior have been limited to relatively low pressures. Most previous estimates of rheology have therefore been based on either large extrapolations of low-pressure experimental data3,4 or inferences from geodynamical observations5,6,7. Such studies have provided only weak constraints on the complicated rheological structure expected in the Transition Zone of the Earth's mantle (between 410 and 660 km depth) where a series of phase transformations occur in silicate minerals8. Here we report the results of a direct experimental study of deformation, under Transition-Zone conditions, of the spinel phase of (Mg,Fe)2SiO4 (ringwoodite; thought to be present in the Earth's Transition Zone). Relatively coarse-grained samples show evidence of dislocation creep with dislocation structures similar to those observed in oxide and germanate spinels9,10, which have significantly higher creep strengths than olivine10,11. In contrast, a fine-grained sample shows evidence for grain-size-sensitive creep. These observations suggest that a ringwoodite-rich layer of the Transition Zone is likely to have a higher viscosity than the olivine-rich upper mantle3, whereas a subducting slab in the deep Transition Zone may lose its strength if significant grain-size reduction occurs12,13,14.
Tomoo Katsura - One of the best experts on this subject based on the ideXlab platform.
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high water solubility of ringwoodite at mantle Transition Zone temperature
Earth and Planetary Science Letters, 2020Co-Authors: Tomoo KatsuraAbstract:Abstract The mantle Transition Zone, a potential water reservoir in the Earth's interior, is suggested to contain more than 1 wt.% of H2O, at least locally, by the natural water-rich ringwoodite inclusion ( Pearson et al., 2014 ) and the mineral viscosity ( Fei et al., 2017 ). It is against the low H2O solubility of ringwoodite ( Ohtani et al., 2000 ). We revisited the H2O solubility in ringwoodite at 1600-2000 K, showing that both iron-free and iron-bearing ringwoodite can store about 0.8-1.2 wt.% of H2O under mantle Transition Zone conditions. Temperature has a relatively small effect on the H2O solubility in iron-bearing system, but much larger in iron-free one. The high H2O solubility of ringwoodite is compatible with the water-rich mantle Transition Zone. The relatively low values reported previously is probably due to insufficient H2O source or unbuffered by SiO2.
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dry mantle Transition Zone inferred from the conductivity of wadsleyite and ringwoodite
Nature, 2008Co-Authors: Takashi Yoshino, Geeth Manthilake, Takuya Matsuzaki, Tomoo KatsuraAbstract:A large amount of water could potentially reside in the Earth's mantle Transition Zone, as two minerals there, wadsleyite and ringwoodite, can store significant amounts of water in their crystal structure. This paper reports the electrical conductivity measurements of these minerals, and finds that they can explain observed conductivity-depth profiles without introducing a significant amount of water into the mantle Transition Zone. The Earth’s mantle Transition Zone could potentially store a large amount of water, as the minerals wadsleyite and ringwoodite incorporate a significant amount of water in their crystal structure1,2. The water content in the Transition Zone can be estimated from the electrical conductivities of hydrous wadsleyite and ringwoodite, although such estimates depend on accurate knowledge of the two conduction mechanisms in these minerals (small polaron and proton conductions), which early studies have failed to distinguish between3,4. Here we report the electrical conductivity of these two minerals obtained by high-pressure multi-anvil experiments. We found that the small polaron conductions of these minerals are substantially lower than previously estimated. The contributions of proton conduction are small at temperatures corresponding to the mantle Transition Zone and the conductivity of wadsleyite is considerably lower than that of ringwoodite for both mechanisms. The dry model mantle shows considerable conductivity jumps associated with the olivine–wadsleyite, wadsleyite–ringwoodite and post-spinel Transitions. Such a dry model explains well the currently available conductivity–depth profiles5 obtained from geoelectromagnetic studies. We therefore conclude that there is no need to introduce a significant amount of water in the mantle Transition to satisfy electrical conductivity constraints.
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dry mantle Transition Zone inferred from the conductivity of wadsleyite and ringwoodite
Nature, 2008Co-Authors: Takashi Yoshino, Geeth Manthilake, Takuya Matsuzaki, Tomoo KatsuraAbstract:The Earth's mantle Transition Zone could potentially store a large amount of water, as the minerals wadsleyite and ringwoodite incorporate a significant amount of water in their crystal structure. The water content in the Transition Zone can be estimated from the electrical conductivities of hydrous wadsleyite and ringwoodite, although such estimates depend on accurate knowledge of the two conduction mechanisms in these minerals (small polaron and proton conductions), which early studies have failed to distinguish between. Here we report the electrical conductivity of these two minerals obtained by high-pressure multi-anvil experiments. We found that the small polaron conductions of these minerals are substantially lower than previously estimated. The contributions of proton conduction are small at temperatures corresponding to the mantle Transition Zone and the conductivity of wadsleyite is considerably lower than that of ringwoodite for both mechanisms. The dry model mantle shows considerable conductivity jumps associated with the olivine-wadsleyite, wadsleyite-ringwoodite and post-spinel Transitions. Such a dry model explains well the currently available conductivity-depth profiles obtained from geoelectromagnetic studies. We therefore conclude that there is no need to introduce a significant amount of water in the mantle Transition to satisfy electrical conductivity constraints.
Hedvig Hricak - One of the best experts on this subject based on the ideXlab platform.
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Transition Zone prostate cancers features detection localization and staging at endorectal mr imaging
Radiology, 2006Co-Authors: Oguz Akin, Evis Sala, Chaya S Moskowitz, Kentaro Kuroiwa, Nicole Ishill, Darko Pucar, Peter T Scardino, Hedvig HricakAbstract:PURPOSE: To retrospectively evaluate the accuracy of endorectal magnetic resonance (MR) imaging in the detection and local staging of Transition Zone prostate cancers, with pathologic analysis serving as the reference standard, and to assess MR imaging features of these cancers. MATERIALS AND METHODS: The institutional review board approved this HIPAA-compliant retrospective study and waived the informed consent requirement. An institutional database of 986 patients who underwent MR imaging before radical prostatectomy yielded 148 consecutive patients with at least one Transition Zone cancer at step-section pathologic analysis. An additional 46 patients without Transition Zone cancer were randomly selected as a control group. Two readers independently reviewed MR studies to identify patients with Transition Zone cancers and determine the location and local extent of these cancers. Imaging features that helped in the identification of Transition Zone cancers were recorded. Descriptive and kappa statistics, as well as receiver operating characteristic and multivariate logistic regression analyses, were used. RESULTS: For identification of patients with Transition Zone cancers, sensitivity and specificity were 75% and 87%, respectively, for reader 1 and 80% and 78%, respectively, for reader 2. Interreader agreement was fair. For detection of the location of Transition Zone cancer, the area under the receiver operating characteristic curve was 0.75 for reader 1 and 0.73 for reader 2. Interreader agreement was fair. The readers' accuracy in detecting Transition Zone cancer foci increased significantly (P=.001) as tumor volume increased. In the detection of extraprostatic extension of Transition Zone cancers, sensitivity and specificity were 56% and 94%, respectively, for reader 1 and 28% and 93%, respectively, for reader 2. Homogeneous low T2 signal intensity (P=.001 for reader 1, P<.001 for reader 2) and lenticular shape (P=.017 for reader 1) were significantly associated with the presence of Transition Zone cancer. CONCLUSION: MR imaging can be used to detect, localize, and stage Transition Zone prostate cancers.
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Transition Zone prostate cancers features detection localization and staging at endorectal mr imaging
Radiology, 2006Co-Authors: Oguz Akin, Evis Sala, Chaya S Moskowitz, Kentaro Kuroiwa, Nicole Ishill, Darko Pucar, Peter T Scardino, Hedvig HricakAbstract:Purpose: To retrospectively evaluate the accuracy of endorectal magnetic resonance (MR) imaging in the detection and local staging of Transition Zone prostate cancers, with pathologic analysis serving as the reference standard, and to assess MR imaging features of these cancers. Materials and Methods: The institutional review board approved this HIPAA-compliant retrospective study and waived the informed consent requirement. An institutional database of 986 patients who underwent MR imaging before radical prostatectomy yielded 148 consecutive patients with at least one Transition Zone cancer at step-section pathologic analysis. An additional 46 patients without Transition Zone cancer were randomly selected as a control group. Two readers independently reviewed MR studies to identify patients with Transition Zone cancers and determine the location and local extent of these cancers. Imaging features that helped in the identification of Transition Zone cancers were recorded. Descriptive and κ statistics, as ...
Xiaoge Huang - One of the best experts on this subject based on the ideXlab platform.
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water content in the Transition Zone from electrical conductivity of wadsleyite and ringwoodite
Nature, 2005Co-Authors: Yousheng Xu, Xiaoge Huang, Shunichiro KaratoAbstract:The distribution of water in the Earth's interior reflects the way in which the Earth has evolved, and has an important influence on its material properties. Minerals in the Transition Zone of the Earth's mantle (from ∼410 to ∼660 km depth) have large water solubility1,2,3, and hence it is thought that the Transition Zone might act as a water reservoir. When the water content of the Transition Zone exceeds a critical value, upwelling flow might result in partial melting at ∼410 km, which would affect the distribution of certain elements in the Earth4. However, the amount of water in the Transition Zone has remained unknown. Here we determined the effects of water and temperature on the electrical conductivity of the minerals wadsleyite and ringwoodite to infer the water content of the Transition Zone. We find that the electrical conductivity of these minerals depends strongly on water content but only weakly on temperature. By comparing these results with geophysically inferred conductivity5,6,7, we infer that the water content in the mantle Transition Zone varies regionally, but that its value in the Pacific is estimated to be ∼0.1–0.2 wt%. These values significantly exceed the estimated critical water content in the upper mantle3,8,9, suggesting that partial melting may indeed occur at ∼410 km depth, at least in this region.
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water content in the Transition Zone from electrical conductivity of wadsleyite and ringwoodite
Nature, 2005Co-Authors: Xiaoge Huang, Shunichiro KaratoAbstract:The distribution of water in the Earth's interior reflects the way in which the Earth has evolved, and has an important influence on its material properties. Minerals in the Transition Zone of the Earth's mantle (from ∼410 to ∼660 km depth) have large water solubility1,2,3, and hence it is thought that the Transition Zone might act as a water reservoir. When the water content of the Transition Zone exceeds a critical value, upwelling flow might result in partial melting at ∼410 km, which would affect the distribution of certain elements in the Earth4. However, the amount of water in the Transition Zone has remained unknown. Here we determined the effects of water and temperature on the electrical conductivity of the minerals wadsleyite and ringwoodite to infer the water content of the Transition Zone. We find that the electrical conductivity of these minerals depends strongly on water content but only weakly on temperature. By comparing these results with geophysically inferred conductivity5,6,7, we infer that the water content in the mantle Transition Zone varies regionally, but that its value in the Pacific is estimated to be ∼0.1–0.2 wt%. These values significantly exceed the estimated critical water content in the upper mantle3,8,9, suggesting that partial melting may indeed occur at ∼410 km depth, at least in this region.
Oguz Akin - One of the best experts on this subject based on the ideXlab platform.
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Transition Zone prostate cancers features detection localization and staging at endorectal mr imaging
Radiology, 2006Co-Authors: Oguz Akin, Evis Sala, Chaya S Moskowitz, Kentaro Kuroiwa, Nicole Ishill, Darko Pucar, Peter T Scardino, Hedvig HricakAbstract:PURPOSE: To retrospectively evaluate the accuracy of endorectal magnetic resonance (MR) imaging in the detection and local staging of Transition Zone prostate cancers, with pathologic analysis serving as the reference standard, and to assess MR imaging features of these cancers. MATERIALS AND METHODS: The institutional review board approved this HIPAA-compliant retrospective study and waived the informed consent requirement. An institutional database of 986 patients who underwent MR imaging before radical prostatectomy yielded 148 consecutive patients with at least one Transition Zone cancer at step-section pathologic analysis. An additional 46 patients without Transition Zone cancer were randomly selected as a control group. Two readers independently reviewed MR studies to identify patients with Transition Zone cancers and determine the location and local extent of these cancers. Imaging features that helped in the identification of Transition Zone cancers were recorded. Descriptive and kappa statistics, as well as receiver operating characteristic and multivariate logistic regression analyses, were used. RESULTS: For identification of patients with Transition Zone cancers, sensitivity and specificity were 75% and 87%, respectively, for reader 1 and 80% and 78%, respectively, for reader 2. Interreader agreement was fair. For detection of the location of Transition Zone cancer, the area under the receiver operating characteristic curve was 0.75 for reader 1 and 0.73 for reader 2. Interreader agreement was fair. The readers' accuracy in detecting Transition Zone cancer foci increased significantly (P=.001) as tumor volume increased. In the detection of extraprostatic extension of Transition Zone cancers, sensitivity and specificity were 56% and 94%, respectively, for reader 1 and 28% and 93%, respectively, for reader 2. Homogeneous low T2 signal intensity (P=.001 for reader 1, P<.001 for reader 2) and lenticular shape (P=.017 for reader 1) were significantly associated with the presence of Transition Zone cancer. CONCLUSION: MR imaging can be used to detect, localize, and stage Transition Zone prostate cancers.
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Transition Zone prostate cancers features detection localization and staging at endorectal mr imaging
Radiology, 2006Co-Authors: Oguz Akin, Evis Sala, Chaya S Moskowitz, Kentaro Kuroiwa, Nicole Ishill, Darko Pucar, Peter T Scardino, Hedvig HricakAbstract:Purpose: To retrospectively evaluate the accuracy of endorectal magnetic resonance (MR) imaging in the detection and local staging of Transition Zone prostate cancers, with pathologic analysis serving as the reference standard, and to assess MR imaging features of these cancers. Materials and Methods: The institutional review board approved this HIPAA-compliant retrospective study and waived the informed consent requirement. An institutional database of 986 patients who underwent MR imaging before radical prostatectomy yielded 148 consecutive patients with at least one Transition Zone cancer at step-section pathologic analysis. An additional 46 patients without Transition Zone cancer were randomly selected as a control group. Two readers independently reviewed MR studies to identify patients with Transition Zone cancers and determine the location and local extent of these cancers. Imaging features that helped in the identification of Transition Zone cancers were recorded. Descriptive and κ statistics, as ...
