T52A-05
3D seismic structure of the Zhenbei-Huangyan seamount chain in the East sub-basin of the South China Sea and its mechanism of formation

Friday, 18 December 2015: 11:20
304 (Moscone South)
Minghui Zhao1, Jian Wang1, Xuelin Qiu2, Jean-Claude Sibuet3, Enyuan He1 and Jiazheng Zhang4, (1)SCSIO South China Sea Institute of Oceanology, Chinese Acaademy of Sciences, Key Laboratory of Marginal Sea Geology, Guangzhou, China, (2)SCSIO South China Sea Institute of Oceanology, Chinese Acaademy of Sciences, Guangzhou, China, (3)Ifremer Centre de Brest, 29280 Plouzané, France and 44 rue du Cloitre, 29280 Plouzané, France, Plouzané, France, (4)SCSIO South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
Abstract:
The post-spreading volcanic ridge (PSVR) is oriented approximately E-W in its western part called the Zhenbei-Huangyan seamount chain. Where is the extinct spreading ridge (ESR) of the East Sub-basin located? beneath the PSVR (Li et al., 2014)? Or intersecting with the PSVR by N055° orientation (Sibuet et al., submitted)?

A three-dimensional Ocean Bottom Seismometer (OBS) survey covered both the central extinct spreading ridge and the Zhenbei-Huangyan seamount chain, the IODP Site U1431 (Li et al., 2014) being located just north of the chain. The results of this experiment will provide the essential information to understand the emplacement of the PSVR within the previously formed oceanic crust. The comprehensive seismic record sections of 39 OBSs are of high quality and show clear and reliable P-wave seismic phases, such as Pg, Pn and PmP. These seismic arrivals provide strong constrains for modeling the detailed three-dimensional velocity structure. We will show that the crust is oceanic on each side of the Zhenbei-Huangyan seamount chain, where is the location of the ESR and what is the genetic relationship between the magma chambers and the overlying Zhenbei-Huangyan seamount chain. We suggest that the large thickness of the upper crust is possibly due to volcanic extrusions and the thickened lower crust to magmatic underplating. Combining previous geochemical study of PSVR outcropping samples, the formation mechanism of the seamount chain might be explained by a buoyancy decompression melting mechanism (Castillo et al., 2010). This research was granted by the Natural Science Foundation of China (91028002, 91428204, 41176053).

References

Sibuet J.-C., Yeh Y.-C. and Lee C.-S., 2015 submitted. Geodynamics of the South China Sea: A review with emphasis on solved and unsolved questions. Tectonophysics.

Li, C. F., et al. 2014. Ages and magnetic structures of the South China Sea constrained by deep tow magnetic surveys and IODP Expedition 349. Geochemistry, Geophysics, Geosystems, 15, 4958-4983.

Castillo, P. R., Clague, D. A., Davis, A. S., Lonsdale, P. F., 2010. Petrogenesis of Davidson Seamount lavas and its implications for fossil spreading center and intraplate magmatism in the eastern Pacific. Geochemistry, Geophysics, Geosystems, 11, Q02005, doi:10.1029/2009GC002992.

<< Previous Abstract | Next Abstract >>