Experimental investigation of antigorite dehydration fabrics at high pressure and high temperature

2020 ◽  
Author(s):  
Junfeng Zhang ◽  
Wenlong Liu ◽  
Yongfeng Wang
Keyword(s):  
Mantle Wedge ◽  
Seismic Anisotropy ◽  
Coarse Grained ◽  
Anisotropic Fluid ◽  
Plate Boundaries ◽  
Intermediate Depth ◽  
Fine Grained ◽  
Serpentinized Peridotite ◽  
Type C ◽  
Convergent Plate Boundaries

<p>Antigorite dehydration is well known as a key process in convergent boundaries for the genesis of mantle wedge partial melting and intermediate-depth earthquakes. However, the crystallographic preferred orientations (CPOs) of prograde minerals from antigorite dehydration and its effects on seismic anisotropy of subducting slabs remain ambiguous and controversial. Here we report hydrostatic dehydration experiments on foliated serpentinized peridotite at pressures of 0.3-6 GPa and temperatures of 700-900 °C. Our results show that the orientations of prograde olivine inherit orientations from adjacent olivine grains in the olivine-rich layer by epitaxial growth. In contrast, olivine CPOs evolved with the grain size from fiber-[001] featuring clear [100] point maxima and [001] girdles for fine-grained olivine to orthorhombic patterns characterized by clear [100] and [001] point maxima for coarse-grained olivine, i.e., type-C CPO. We propose that the fine-grained fiber-[001] CPO is developed by topotactic growth at the onset of dehydration, while the orthorhombic type-C CPO for the coarse-grained olivine, especially the [001] point maximum along the lineation, is mainly developed by anisotropic growth resulting from anisotropic fluid flow during the dehydration. The developed olivine type-C CPO in the antigorite-rich layer after antigorite dehydration could explain the trench or strike parallel seismic anisotropy observed at convergent plate boundaries.</p>

Boron isotope systematics of Higashi-akaishi mantle wedge peridotites (Sanbagawa belt, Japan): implications for fluid recycling in subduction zones

2021 ◽  
Author(s):  
Cees-Jan De Hoog ◽  
Keiko Hattori ◽  
Eleri Clarke
Keyword(s):  
Isotopic Composition ◽  
Subduction Zones ◽  
Isotope Fractionation ◽  
Mantle Wedge ◽  
Greenschist Facies ◽  
Coarse Grained ◽  
High Concentration ◽  
Fine Grained ◽  
Dynamic Recrystallisation ◽  
Mantle Olivine

<p>Boron provides an efficient tracer of fluids in subduction zones, due to its high concentration in surface reservoirs, low concentration in the mantle, and large isotope fractionation. The Higashi-akaishi peridotite body in Sanbagawa UHP belt, Japan, is composed of partially serpentinised dunites and harzburgites, which are interpreted to be exhumed mantle wedge peridotites. Compositions of olivine (Fo90-94, NiO 0.28-0.48 wt%, MnO 0.10-0.16 wt%) and chromite (Cr# >0.7, TiO<sub>2</sub> <0.4 wt%) confirm its origin as highly refractory fore-arc mantle. Several generations of olivine and serpentine can be recognised in the samples, and were analysed in-situ for their B content and B isotopic composition by SIMS. Coarse-grained primary mantle olivine has low [B] (1-3 µg/g), but is still significantly B-enriched compared to typical mantle olivine, and has δ<sup>11</sup>B of -10 to -3 ‰. Lower B contents in olivine cores compared to rims suggests diffusive incorporation of B from slab-derived fluids at high temperature.  Later fine-grained olivine neoblasts, products of dynamic recrystallization, have higher [B] (3-11 µg/g) and higher δ<sup>11</sup>B (-7 to +2‰). Platy antigorite associated with the olivine neoblasts have similar [B] (4-12 µg/g) but higher δ<sup>11</sup>B (-4 to +6‰). Late-stage greenschist-facies overprint resulted in lizardite veining with high [B] (18-52 µg/g) and a narrow range of δ<sup>11</sup>B (-2 to -1‰).</p><p>We envisage the following scenario. Coarse-grained mantle olivine acquired B from slab-derived fluids when the peridotites were dragged down by mantle corner flow and positioned near the slab-mantle interface. The values of δ<sup>11</sup>B (-10 to -3‰) are consistent with fluids from dehydrating slab at ca. 110-150 km depth, but are potentially affected by diffusion-controlled kinetic isotope fractionation. High temperatures (> 650-700°C) prevented the peridotites from serpentinisation. Subsequently the rocks were down-dragged in a subduction channel where olivine neoblasts formed first and platy antigorite crystallized later when temperature dropped below 650°C. Both phases show heavier δ<sup>11</sup>B than coarse-grained olivine; the values are consistent with fluids from dehydrating slab at ca. 70-100 km depth. Finally, the peridotites were exposed to crust-derived B-rich fluids with low δ<sup>11</sup>B during exhumation and amalgamation with crustal units, forming lizardite veining during greenschist-facies overprint.</p><p>This study shows that mantle olivine may scavenge significant amounts of B from percolating fluids by diffusive re-equilibration or dynamic recrystallisation, lowering the B content of such fluids and potentially modifying their B isotopic composition.</p>

scholarly journals Thermo-Structural Evolution of the Val Malenco (Italy) Peridotite: A Petrological, Geochemical and Microstructural Study

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 962
Author(s):  
Wenlong Liu ◽  
Yi Cao ◽  
Junfeng Zhang ◽  
Yanfei Zhang ◽  
Keqing Zong ◽  
...  
Keyword(s):  
Strain Localization ◽  
Structural Evolution ◽  
Coarse Grained ◽  
Prograde Metamorphism ◽  
Fine Grained ◽  
Tectonic History ◽  
Serpentinized Peridotite ◽  
Geochemical Study ◽  
Dissolution And Precipitation

The Val Malenco peridotite massif is one of the largest exposed ultramafic massifs in Alpine orogen. To better constrain its tectonic history, we have performed a comprehensive petro-structural and geochemical study. Our results show that the Val Malenco serpentinized peridotite recorded both pre-Alpine extension and Alpine convergence events. The pre-Alpine extension is recorded by microstructural and geochemical features preserved in clinopyroxene and olivine porphyroblasts, including partial melting and refertilisation, high-temperature (900–1000 °C) deformation and a cooling, and fluid-rock reaction. The following Alpine convergence in a supra-subduction zone setting is documented by subduction-related prograde metamorphism features preserved in the coarse-grained antigorite and olivine grains in the less-strained olivine-rich layers, and later low-temperature (<350 °C) serpentinization in the fine-grained antigorite in the more strained antigorite-rich layers. The strain shadow structure in the more strained antigorite-rich layer composed of dissolving clinopyroxene porphyroblast and the precipitated oriented diopside and olivine suggest dissolution and precipitation creep, while the consistency between the strain shadow structure and alternating less- and more-strained serpentinized domains highlights the increasing role of strain localization induced by the dissolution-precipitation creep with decreasing temperature during exhumation in Alpine convergence events.

scholarly journals Microstructural Evolution of Amphibole Peridotites in Åheim, Norway, and the Implications for Seismic Anisotropy in the Mantle Wedge

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 345 ◽  
Author(s):  
Sejin Jung ◽  
Haemyeong Jung ◽  
Håkon Austrheim
Keyword(s):  
Mantle Wedge ◽  
Seismic Anisotropy ◽  
Microstructural Analysis ◽  
Dislocation Creep ◽  
Hydrous Minerals ◽  
Fine Grained ◽  
Lattice Preferred Orientation ◽  
Initial Stage ◽  
Dominant Deformation Mechanism ◽  
Rich Condition

The microstructure of amphibole peridotites from Åheim, Norway were analyzed to understand the evolution of the lattice-preferred orientation (LPO) of olivine throughout the Scandian Orogeny and its implication for the seismic anisotropy of the subduction zone. The Åheim peridotites had a porphyroclastic texture and some samples contained an abundant amount of hydrous minerals such as tremolite. Detailed microstructural analysis on the Åheim peridotites revealed multiple stages of deformation. The coarse grains showed an A-type LPO of olivine, which can be interpreted as the initial stage of deformation. The spinel-bearing samples showed a mixture of B-type and C-type LPOs of olivine, which is considered to represent the deformation under water-rich conditions. The recrystallized fine-grained olivine displays a B-type LPO, which can be interpreted as the final stage of deformation. Microstructures and water content of olivine indicate that the dominant deformation mechanism of olivine showing a B-type LPO is a dislocation creep under water-rich condition. The observation of the B-type LPO of olivine is important for an interpretation of trench-parallel seismic anisotropy in the mantle wedge. The calculated seismic anisotropy of the tremolite showed that tremolite can contribute to the trench-parallel seismic anisotropy in the mantle wedge.

scholarly journals Influence of convergent plate boundaries on upper mantle flow and implications for seismic anisotropy

2007 ◽  
Vol 8 (8) ◽  
pp. n/a-n/a ◽  
Author(s):  
Julian P. Lowman ◽  
Laura T. Pinero-Feliciangeli ◽  
J.-Michael Kendall ◽  
M. Hosein Shahnas
Keyword(s):  
Upper Mantle ◽  
Seismic Anisotropy ◽  
Mantle Flow ◽  
Plate Boundaries ◽  
Convergent Plate Boundaries

Deformation microstructure of amphibole peridotite from Aheim, Norway and its implication for the seismic anisotropy of the mantle wedge

2020 ◽  
Author(s):  
Sejin Jung ◽  
Haemyeong Jung ◽  
Håkon Austrheim
Keyword(s):  
Mantle Wedge ◽  
Seismic Anisotropy ◽  
Microstructural Analysis ◽  
Localized Deformation ◽  
Western Gneiss Region ◽  
Hydrous Minerals ◽  
Fine Grained ◽  
Rich Condition ◽  
Fabric Strength ◽  
The One

&lt;p&gt;The microstructures of amphibole peridotites from the &amp;#197;heim, Norway were studied to understand the evolution of microstructures of olivine through the Scandian Orogeny and the subsequent exhumation process. The Western Gneiss Region, Norway had undergone UHP metamorphism and subsequent retrogression associated with the Scandian Orogeny. The &amp;#197;heim amphibole peridotite shows clear porphyroclastic texture, abundant hydrous minerals such as tremolite or chlorite, and much evidence of localized deformation. LPOs of olivine and amphibole were determined by using electron back-scattered diffraction (EBSD) system attached to the scanning electron microscope (SEM).&lt;/p&gt;&lt;p&gt;Detailed microstructural analysis on the &amp;#197;heim amphibole peridotites revealed the evidence of the multiple stages of deformation during the Scandian Orogeny. The coarse grains of olivine including porphyroclasts showed the A-type LPO of olivine (Jung &amp; Karato, 2001), which is interpreted as an initial stage of deformation. The recrystallized-fine grains of olivine showed the B-type LPO of olivine (Jung &amp; Karato, 2001), which is interpreted as a late-stage deformation in amphibolite facies condition. Observation of abundant hydrous minerals, hydrous inclusions in olivine, as well as high dislocation density of olivine in the fine-grained olivines suggest that fabric transition of olivine from the A-type to B-type LPO was resulted from the deformation in a water-rich condition during the exhumation process. The B-type LPO of olivine is important because it is the one of the possible mechanisms for causing the trench-parallel seismic anisotropy in the mantle wedge. A partial fabric transition from the A-type to the B-type LPO of olivine associated with the localized deformation in a water-rich condition might explain a weak seismic anisotropy observed in NE Japan or Mexico. Amphiboles in the amphibole-rich layer showed the Type-III LPO of amphibole (Ko &amp; Jung, 2015). It is found that strong fabric strength and the resultant seismic anisotropy of amphibole can perform a similar role as other hydrous minerals such as serpentine or chlorite on the trench-parallel seismic anisotropy with the flow dipping along the subducting slab in the mantle wedge.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Jung, H., Karato, S., 2001, Science, 293, 1460-1463.&lt;/p&gt;&lt;p&gt;Ko, B., Jung, H., 2015, Nature Communications, 6: 6586.&lt;/p&gt;

Correlation between dislocation, grain boundary and interface of duplex SS in stress corrosion cracking(SCC)

1990 ◽  
Vol 48 (4) ◽  
pp. 928-929
Author(s):  
Wang Zheng-fang ◽  
Z.F. Wang
Keyword(s):  
Stainless Steel ◽  
Thermal Cycle ◽  
Secondary Phase ◽  
Corrosion Cracking ◽  
Coarse Grained ◽  
Test Environment ◽  
Fine Grained ◽  
Evaluation Test ◽  
Welding Thermal Cycle ◽  
Micro Analysis

The main purpose of this study highlights on the evaluation of chloride SCC resistance of the material,duplex stainless steel,OOCr18Ni5Mo3Si2 (18-5Mo) and its welded coarse grained zone(CGZ).18-5Mo is a dual phases (A+F) stainless steel with yield strength:512N/mm2 .The proportion of secondary Phase(A phase) accounts for 30-35% of the total with fine grained and homogeneously distributed A and F phases(Fig.1).After being welded by a specific welding thermal cycle to the material,i.e. Tmax=1350°C and t8/5=20s,microstructure may change from fine grained morphology to coarse grained morphology and from homogeneously distributed of A phase to a concentration of A phase(Fig.2).Meanwhile,the proportion of A phase reduced from 35% to 5-10°o.For this reason it is known as welded coarse grained zone(CGZ).In association with difference of microstructure between base metal and welded CGZ,so chloride SCC resistance also differ from each other.Test procedures:Constant load tensile test(CLTT) were performed for recording Esce-t curve by which corrosion cracking growth can be described, tf,fractured time,can also be recorded by the test which is taken as a electrochemical behavior and mechanical property for SCC resistance evaluation. Test environment:143°C boiling 42%MgCl2 solution is used.Besides, micro analysis were conducted with light microscopy(LM),SEM,TEM,and Auger energy spectrum(AES) so as to reveal the correlation between the data generated by the CLTT results and micro analysis.

scholarly journals Balanced Sparsity for Efficient DNN Inference on GPU

2019 ◽  
Vol 33 ◽  
pp. 5676-5683 ◽  
Author(s):  
Zhuliang Yao ◽  
Shijie Cao ◽  
Wencong Xiao ◽  
Chen Zhang ◽  
Lanshun Nie
Keyword(s):  
Deep Neural Networks ◽  
General Purpose ◽  
Coarse Grained ◽  
Efficient Computation ◽  
Model Accuracy ◽  
Sparse Model ◽  
Model Inference ◽  
Fine Grained ◽  
Practical Inference ◽  
Speed Up

In trained deep neural networks, unstructured pruning can reduce redundant weights to lower storage cost. However, it requires the customization of hardwares to speed up practical inference. Another trend accelerates sparse model inference on general-purpose hardwares by adopting coarse-grained sparsity to prune or regularize consecutive weights for efficient computation. But this method often sacrifices model accuracy. In this paper, we propose a novel fine-grained sparsity approach, Balanced Sparsity, to achieve high model accuracy with commercial hardwares efficiently. Our approach adapts to high parallelism property of GPU, showing incredible potential for sparsity in the widely deployment of deep learning services. Experiment results show that Balanced Sparsity achieves up to 3.1x practical speedup for model inference on GPU, while retains the same high model accuracy as finegrained sparsity.

scholarly journals Submarine lava deltas of the 2018 eruption of Kīlauea volcano

2021 ◽  
Vol 83 (4) ◽  
Author(s):  
S. Adam Soule ◽  
Michael Zoeller ◽  
Carolyn Parcheta
Keyword(s):  
Grain Size ◽  
Pore Pressure ◽  
Mechanistic Model ◽  
Large Fraction ◽  
Volcanic Hazards ◽  
Lava Flows ◽  
Coarse Grained ◽  
Fine Grained ◽  
Fine Grain ◽  
Delta Formation

AbstractHawaiian and other ocean island lava flows that reach the coastline can deposit significant volumes of lava in submarine deltas. The catastrophic collapse of these deltas represents one of the most significant, but least predictable, volcanic hazards at ocean islands. The volume of lava deposited below sea level in delta-forming eruptions and the mechanisms of delta construction and destruction are rarely documented. Here, we report on bathymetric surveys and ROV observations following the Kīlauea 2018 eruption that, along with a comparison to the deltas formed at Pu‘u ‘Ō‘ō over the past decade, provide new insight into delta formation. Bathymetric differencing reveals that the 2018 deltas contain more than half of the total volume of lava erupted. In addition, we find that the 2018 deltas are comprised largely of coarse-grained volcanic breccias and intact lava flows, which contrast with those at Pu‘u ‘Ō‘ō that contain a large fraction of fine-grained hyaloclastite. We attribute this difference to less efficient fragmentation of the 2018 ‘a‘ā flows leading to fragmentation by collapse rather than hydrovolcanic explosion. We suggest a mechanistic model where the characteristic grain size influences the form and stability of the delta with fine grain size deltas (Pu‘u ‘Ō‘ō) experiencing larger landslides with greater run-out supported by increased pore pressure and with coarse grain size deltas (Kīlauea 2018) experiencing smaller landslides that quickly stop as the pore pressure rapidly dissipates. This difference, if validated for other lava deltas, would provide a means to assess potential delta stability in future eruptions.

scholarly journals A cooperative DDoS attack detection scheme based on entropy and ensemble learning in SDN

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Shanshan Yu ◽  
Jicheng Zhang ◽  
Ju Liu ◽  
Xiaoqing Zhang ◽  
Yafeng Li ◽  
...  
Keyword(s):  
Ensemble Learning ◽  
Denial Of Service ◽  
Attack Detection ◽  
Coarse Grained ◽  
Communication Overhead ◽  
Detection Scheme ◽  
Fine Grained ◽  
Ddos Attack ◽  
Network Status ◽  
Ddos Attack Detection

AbstractIn order to solve the problem of distributed denial of service (DDoS) attack detection in software-defined network, we proposed a cooperative DDoS attack detection scheme based on entropy and ensemble learning. This method sets up a coarse-grained preliminary detection module based on entropy in the edge switch to monitor the network status in real time and report to the controller if any abnormality is found. Simultaneously, a fine-grained precise attack detection module is designed in the controller, and a ensemble learning-based algorithm is utilized to further identify abnormal traffic accurately. In this framework, the idle computing capability of edge switches is fully utilized with the design idea of edge computing to offload part of the detection task from the control plane to the data plane innovatively. Simulation results of two common DDoS attack methods, ICMP and SYN, show that the system can effectively detect DDoS attacks and greatly reduce the southbound communication overhead and the burden of the controller as well as the detection delay of the attacks.

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