scholarly journals Tracing the subducting Pacific slab to the mantle transition zone with hydrogen isotopes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Takeshi Kuritani ◽  
Kenji Shimizu ◽  
Takayuki Ushikubo ◽  
Qun-Ke Xia ◽  
Jia Liu ◽  
...  
Keyword(s):  
Transition Zone ◽  
Melt Inclusions ◽  
Hydrogen Isotopes ◽  
Volcanic Front ◽  
Mantle Transition Zone ◽  
Deep Interior ◽  
Terrestrial Water ◽  
Quantitative Understanding ◽  
Pacific Slab ◽  
Slab Dehydration

AbstractHydrogen isotopes have been widely used as powerful tracers to understand the origin of terrestrial water and the water circulation between the surface and the deep interior of the Earth. However, further quantitative understanding is hindered due to a lack of observations about the changes in D/H ratios of a slab during subduction. Here, we report hydrogen isotope data of olivine-hosted melt inclusions from active volcanoes with variable depths (90‒550 km) to the subducting Pacific slab. The results show that the D/H ratio of the slab fluid at the volcanic front is lower than that of the slab fluid just behind the volcanic front. This demonstrates that fluids with different D/H ratios were released from the crust and the underlying peridotite portions of the slab around the volcanic front. The results also show that the D/H ratios of slab fluids do not change significantly with slab depths from 300 to 550 km, which demonstrates that slab dehydration did not occur significantly beyond the arc. Our estimated δD‰ value for the slab materials that accumulated in the mantle transition zone is > − 90‰, a value which is significantly higher than previous estimates.

Intraplate and petit-spot volcanism originating from hydrous mantle transition zone

2020 ◽  
Author(s):  
Jianfeng Yang ◽  
Manuele Faccenda
Keyword(s):  
Transition Zone ◽  
Northeast China ◽  
Subduction Zones ◽  
Japan Trench ◽  
Low Velocity ◽  
Iranian Plateau ◽  
Mantle Transition Zone ◽  
Mantle Minerals ◽  
Ocean Ridges ◽  
Pacific Slab

<p>Most magmatism occurring on Earth is conventionally attributed to passive mantle upwelling at mid-ocean ridges, slab devolatilization at subduction zones, and mantle plumes. However, the widespread Cenozoic intraplate volcanism in northeast China and the peculiar petit-spot volcanoes offshore the Japan trench cannot be readily associated with any of these mechanisms. Furthermore, the seismic tomography images show remarkable low velocity zones (LVZs) sit above and below the mantle transition zone which are coincidently corresponding to the volcanism. Here we show that most if not all the intraplate/petit-spot volcanism and LVZs present around the Japanese subduction zone can be explained by the Cenozoic interaction of the subducting Pacific slab with a hydrous transition zone. Numerical modelling results indicate that 0.2-0.3 wt.% H<sub>2</sub>O dissolved in mantle minerals which are driven out from the transition zone in response to subduction and retreat of a stagnant plate is sufficient to reproduce the observations. This suggests that critical amounts of volatiles accumulated in the mantle transition zone due to past subduction episodes and/or delamination of volatile-rich lithosphere could generate abundant dynamics triggered by recent subduction event. This model is probably also applicable to the circum-Mediterranean and Turkish-Iranian Plateau regions characterized by intraplate/petit-spot volcanism and LVZs in the underlying mantle.</p>

Slab dehydration in the Earth's mantle transition zone

2006 ◽  
Vol 251 (1-2) ◽  
pp. 156-167 ◽  
Author(s):  
Guillaume Richard ◽  
David Bercovici ◽  
Shun-Ichiro Karato
Keyword(s):  
Transition Zone ◽  
Mantle Transition Zone ◽  
Earth’S Mantle ◽  
Slab Dehydration

scholarly journals Interrelation of the stagnant slab, Ontong Java Plateau, and intraplate volcanism as inferred from seismic tomography

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Masayuki Obayashi ◽  
Junko Yoshimitsu ◽  
Daisuke Suetsugu ◽  
Hajime Shiobara ◽  
Hiroko Sugioka ◽  
...  
Keyword(s):  
Transition Zone ◽  
Subduction Zones ◽  
Middle Eastern ◽  
P Wave ◽  
Ontong Java Plateau ◽  
Mantle Transition Zone ◽  
Slab Breakoff ◽  
Pacific Slab ◽  
Velocity Anomalies ◽  
Stagnant Slab

AbstractWe investigated the seismological structure beneath the equatorial Melanesian region, where is tectonically unique because an immense oceanic plateau, a volcanic chain and subduction zones meet. We conducted a multi-frequency P-wave tomography using data collected from an approximately 2-year-long seismic experiment around the Ontong Java Plateau (OJP). High-velocity anomalies were revealed beneath the center of the OJP at a depth of ~ 150 km, the middle-eastern edge of the OJP at depths of 200–300 km, and in the mantle transition zone beneath and around the OJP; low-velocity anomalies were observed along the Caroline volcanic island chain above 450 km depth. These anomalies are considered to be associated with the thick lithosphere of the OJP, remnant dipping Pacific slab, stagnant Pacific slab, and a sheet-like upwelling. The broad stagnant slab was formed due to rapid trench retreat from 48 to 25 Ma until when the OJP with thick lithosphere collided with a subduction boundary of the Pacific and Australian plates. This collision triggered slab breakoff beneath the arc where the dipping slab remained. The stagnant Pacific slab in the mantle transition zone restricted the plume upwelling from the lower mantle causing sheet-like deformed upwelling in the upper mantle.

Water flow to the mantle transition zone inferred from a receiver function image of the Pacific slab

2008 ◽  
Vol 274 (3-4) ◽  
pp. 346-354 ◽  
Author(s):  
Takashi Tonegawa ◽  
Kazuro Hirahara ◽  
Takuo Shibutani ◽  
Hikaru Iwamori ◽  
Hiroo Kanamori ◽  
...  
Keyword(s):  
Transition Zone ◽  
Water Flow ◽  
Receiver Function ◽  
Mantle Transition Zone ◽  
The Pacific ◽  
Pacific Slab

Theoretical modeling of the regular olivine intergrowths in the mimetic paramorphosis after ringwoodite and wadsleyite

2018 ◽  
pp. 3-12
Author(s):  
B. B. Shkursky
Keyword(s):  
Transition Zone ◽  
Theoretical Modeling ◽  
Mantle Transition Zone ◽  
Misorientation Angles

Theoretical modeling of regular olivine grains misorientations in mimetic paramorphoses after ringwoodite and wadsleyite, the formation of which during the ascension of matter from the Mantle Transition Zone is expected, has been carried out. The coordinates of the misorientation axes and the misorientation angles, characterizing 10 operations of alignment in the pair intergrowths of olivine grains, eight of which are twins, are calculated. Possible conditions for the formation of mimetic paramorphoses predicted here, and the chances of their persistence are discussed. The calculated orientations are compared with the known twinning laws of olivine.

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