Lithospheric Structure near the Yangtze and Cathaysia Block, South China: Implications for Asthenosphere Upwelling and Lithosphere Modification
Abstract
The South China Block, which composes of the Yangtze and Cathaysia block, is one of the most important blocks for understanding the tectonic evolution in East Asia. Wide spread granite were produced after the orogenic process since Mesozoic, and is generally believed to be emplaced in extensional settings. However, the genesis of granites remains controversial, and the properties of the suture between the two blocks are not entirely clear.
In this study, we obtained high resolution lithospheric structure and Moho depth distribution of the Jiuyishan and its surrounding area by joint inversion of receiver functions and ambient noise data. These data are recorded from 70 seismic stations, which include 53 permanent stations from China National Seismic Network and 17 temporary broadband seismic stations of our own deployment. Our results show relatively thick crust beneath the Yangtze block ( 37 km) and thin crust beneath the Cathaysia block ( 27 km). The boundary of thin and thick Moho lies roughly along the Chenzhou-Linwu fault (CLF), with a change of about 5 km in Moho depth across it. Moreover, the three-dimension shear wave velocity structure shows prominent low velocity blocks beneath Jiuyishan and Cathaysia block near the CLF at depth of 60 km to at least 80 km. Meanwhile, the upper and middle crust beneath Jiuyishan is thicker than surrounding area. Our results suggest that the CLF is the boundary of south Yangtze and Cathaysia block. Low velocities underneath the Jiuyishan and its surrounding area indicate upwelling from asthenosphere, which may melt the lithosphere and further modify the composition of it. This process may explain the thickening of the upper and middle crust, as well as the low oxygen fugacity and low water activity of granite in Jiuyishan.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T31D0329H
- Keywords:
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- 8104 Continental margins: convergent;
- TECTONOPHYSICSDE: 8105 Continental margins: divergent;
- TECTONOPHYSICSDE: 8157 Plate motions: past;
- TECTONOPHYSICSDE: 8178 Tectonics and magmatism;
- TECTONOPHYSICS