Detailed structure of mantle transition zone beneath southeastern China and its implications for thinning of the continental lithosphere

• Published in: Tectonophysics Vol. 789; p. 228480
• Main Authors: Han, Rubing, Li, Qiusheng, Huang, Rong, Zhang, Hongshuang
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 20-08-2020; Elsevier BV
• Subjects: Asthenosphere; Broadband; Dehydration; Discontinuity; Dynamic models; Flat-slab subduction; Geomorphology; Lithosphere; Low temperature; Magma; Mantle convection; Mantle transition zone (MTZ); Moisture content; P waves; Receiver functions; Seismic activity; Southeastern China; Stations; Subduction; Subduction (geology); Temperature anomalies; Thinning; Transition zone; Upper mantle; Water content; Water shortages; China; Temperature anomalies; Mantle transition zone (MTZ); Receiver functions; Flat-slab subduction; Southeastern China; Water content
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2020.228480

This paper presents a new study on 3-D structure, temperature and water content estimation of the mantle transition zone (MTZ) by P-wave receiver functions common conversion point (CCP) method on broadband array with 267 temporary stations and 203 permanent stations in southeastern China. The results show different structural characteristics of the MTZ to the north and south of the 29°N line. In the northern part, the 660-km discontinuity is generally deeper than globe models, and there are two independent local depressions with characteristics of high velocity, low temperature, and water shortage. We interpret them as two previous subducting plates stagnated in MTZ, possibly related to two separate subduction events at different times. While in the southern part, the 410-km discontinuity is locally depressed, resulting in thinning of the MTZ. Particularly, in the Cathaysian Block south of the 29°N line, based on the MTZ structure and the estimation of temperature and water content, we conside dehydration of the MTZ as one of the important mechanisms of lithospheric thinning through interaction with the asthenosphere. We then propose a dynamic model that combines paleo-Pacific flat-slab subduction and upper mantle convection to explain the lithospheric extension and thinning, magmatic rock distribution, weak seismic activity and basin-and-range geomorphology. This model differs from that north of the 29°N line in the North China Block.
•We presented a new study on 3-D structure, temperature and water content estimation of the mantle transition zone (MTZ) beneath southeastern China based upon a dense array data.•The results show different structural characteristics of the MTZ along the 29°N parallel.•We proposed a dynamic model combined paleo-Pacific flat subdution and upper mantle convection in Cathaysian block.