Water content in the transition zone from electrical conductivity of wadsleyite and ringwoodite

Nature ◽  
2005 ◽  
Vol 434 (7034) ◽  
pp. 746-749 ◽  
Author(s):  
Xiaoge Huang ◽  
Yousheng Xu ◽  
Shun-ichiro Karato
Keyword(s):  
Electrical Conductivity ◽  
Water Content ◽  
Transition Zone

Electrical conductivity in the mantle transition zone beneath Eastern China derived from L1-Norm C-responses

2020 ◽  
Vol 221 (2) ◽  
pp. 1110-1124 ◽  
Author(s):  
Yanhui Zhang ◽  
Aihua Weng ◽  
Shiwen Li ◽  
Yue Yang ◽  
Yu Tang ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Objective Function ◽  
Water Content ◽  
Transition Zone ◽  
Regularization Parameter ◽  
Eastern China ◽  
Bfgs Method ◽  
L1 Norm ◽  
Mantle Transition Zone ◽  
Dehydration Reactions

SUMMARY Constraining the distribution of water in different regions of the mantle remains one of the significant challenges to comprehend the global deep water cycle. Geomagnetic depth soundings can provide such constraint through the electrical conductivity structure. Hence, this study aims to propose a regularization technique that can estimate previously unavailable C-response. In the method, the objective function comprised an L1-norm measured data prediction error and a spectral smoothness constraint term. We used the data error of C-response to weight the predicted error. The L-BFGS method was introduced to determine the minimum point of the objective function, and the regularization parameter decreased adaptively during inversion. Thus, the geomagnetic data processed yielded high-quality C-responses in 31 stations in Eastern China. In addition, we obtained 1-D electrical conductivity profiles in the mantle transition zone (MTZ) beneath Eastern China from C-responses using the L-BFGS method. Compared with the global 1-D model, the conductivity–depth profiles revealed that the MTZ beneath Eastern China is more conductive in the east but more resistive in the west. The conversion of these conductivities to water content based on the mineral physics suggested that the MTZ beneath Eastern China is characterized by a high water concentration, approximately 0.2 and 1 wt per cent in the upper and lower MTZ, respectively. Owing to the inclusion of more stations, the water-rich region could be constrained roughly to the east of the North–South Gravity Lineament (NSGL). Further considering seismic images in the same area, this water content distribution pattern suggested that the front of the stagnant Pacific Plate in the lower MTZ might have reached the NSGL. However, the dehydration reactions in the stagnant slab were more active in the eastern part. Perhaps, some of these fluids migrated into the upper MTZ and could be the source of the trapped water found in the xenoliths from the deep upper mantle beneath Eastern China.

Mantle transition zone beneath a normal seafloor in the northwestern Pacific: Electrical conductivity, seismic thickness, and water content

2017 ◽  
Vol 462 ◽  
pp. 189-198 ◽  
Author(s):  
Tetsuo Matsuno ◽  
Daisuke Suetsugu ◽  
Kiyoshi Baba ◽  
Noriko Tada ◽  
Hisayoshi Shimizu ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Water Content ◽  
Transition Zone ◽  
Northwestern Pacific ◽  
Mantle Transition Zone
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