scholarly journals Seismological detection of low‐velocity anomalies surrounding the mantle transition zone in Japan subduction zone

2016 ◽  
Vol 43 (6) ◽  
pp. 2480-2487 ◽  
Author(s):  
Zhen Liu ◽  
Jeffrey Park ◽  
Shun‐ichiro Karato
Keyword(s):  
Subduction Zone ◽  
Transition Zone ◽  
Low Velocity ◽  
Mantle Transition Zone ◽  
Japan Subduction Zone ◽  
Velocity Anomalies

scholarly journals Teleseismic Tomography for Imaging the Upper Mantle Beneath Northeast China

2020 ◽  
Vol 10 (13) ◽  
pp. 4557
Author(s):  
Zhuo Jia ◽  
Gongbo Zhang
Keyword(s):  
Travel Time ◽  
Transition Zone ◽  
Upper Mantle ◽  
Northeast China ◽  
Time Data ◽  
Low Velocity ◽  
Mantle Transition Zone ◽  
Teleseismic Tomography ◽  
Travel Time Data ◽  
Velocity Anomalies

Tomographic imaging technology is a geophysical inversion method. According to the ray scanning, this method carries on the inversion calculation to the obtained information, and reconstructs the image of the parameter distribution rule of elastic wave and electromagnetic wave in the measured range, so as to delineate the structure of the geological body. In this paper, teleseismic tomography is applied by using seismic travel time data to constrain layered crustal structure where Fast Marching Methods (FMM) and the subspace method are considered as forward and inverse methods, respectively. Based on the travel time data picked up from seismic waveform data in the study region, the P-wave velocity structure beneath Northeast China down to 750 km is obtained. It can be seen that there are low-velocity anomalies penetrating the mantle transition zone under the Changbai volcano group, Jingpohu Volcano, and Arshan Volcano, and these low-velocity anomalies extend to the shallow part. In this paper, it is suggested that the Cenozoic volcanoes in Northeast China were heated by the heat source provided by the dehydration of the subducted Pacific plate and the upwelling of geothermal matter in the lower mantle. The low-velocity anomaly in the north Songliao basin does not penetrate the mantle transition zone, which may be related to mantle convection and basin delamination. According to the low-velocity anomalies widely distributed in the upper mantle and the low-velocity bodies passing through the mantle transition zone beneath the volcanoes, this study suggests that the Cenozoic volcanoes in Northeast China are kindred and have a common formation mechanism.

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>

scholarly journals Seismic waveform tomography of the central and eastern Mediterranean upper mantle

Solid Earth ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 669-690 ◽  
Author(s):  
Nienke Blom ◽  
Alexey Gokhberg ◽  
Andreas Fichtner
Keyword(s):  
Subduction Zone ◽  
Transition Zone ◽  
Upper Mantle ◽  
High Velocity ◽  
Eastern Mediterranean ◽  
Crust And Upper Mantle ◽  
Mantle Transition Zone ◽  
Seismic Waveform ◽  
Waveform Tomography ◽  
Seismic Waveform Tomography

Abstract. We present a seismic waveform tomography of the upper mantle beneath the central and eastern Mediterranean down to the mantle transition zone. Our methodology incorporates in a consistent manner the information from body and multimode surface waves, source effects, frequency dependence, wavefront healing, anisotropy and attenuation. This allows us to jointly image multiple parameters of the crust and upper mantle. Based on the data from ∼ 17 000 unique source–receiver pairs, gathered from 80 earthquakes, we image radially anisotropic S velocity, P velocity and density. We use a multi-scale approach in which the longest periods (100–150 s) are inverted first, broadening to a period band of 28–150 s. Thanks to a strategy that combines long-period signals and a separation of body and surface wave signals, we are able to image down to the mantle transition zone in most of the model domain. Our model shows considerable detail in especially the northern part of the domain, where data coverage is very dense, and displays a number of clear and coherent high-velocity structures across the domain that can be linked to episodes of current and past subduction. These include the Hellenic subduction zone, the Cyprus subduction zone and high-velocity anomalies beneath the Italian peninsula and the Dinarides. This model is able to explain data from new events that were not included in the inversion.

Mantle transition zone input to kimberlite magmatism near a subduction zone: Origin of anomalous Nd–Hf isotope systematics at Lac de Gras, Canada

2013 ◽  
Vol 371-372 ◽  
pp. 235-251 ◽  
Author(s):  
Sebastian Tappe ◽  
D. Graham Pearson ◽  
Bruce A. Kjarsgaard ◽  
Geoff Nowell ◽  
David Dowall
Keyword(s):  
Subduction Zone ◽  
Transition Zone ◽  
Hf Isotope ◽  
Mantle Transition Zone ◽  
Isotope Systematics

scholarly journals A ubiquitous low-velocity layer at the base of the mantle transition zone

2014 ◽  
Vol 41 (3) ◽  
pp. 836-842 ◽  
Author(s):  
Xuzhang Shen ◽  
Xiaohui Yuan ◽  
Xueqing Li
Keyword(s):  
Transition Zone ◽  
Low Velocity ◽  
Mantle Transition Zone ◽  
Low Velocity Layer ◽  
Velocity Layer
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