Crustal Compositional Variations From Continental to Oceanic Domain: A Vp/Vs Ratio Study Across the Zhongsha Block, South China Sea.

Li, Yuhan, Grevemeyer, Ingo , Huang, Haibo, Qiu, Xuelin and Murray-Bergquist, Louisa (2022) Crustal Compositional Variations From Continental to Oceanic Domain: A Vp/Vs Ratio Study Across the Zhongsha Block, South China Sea. Journal of Geophysical Research: Solid Earth, 127 (5). e2021JB023470. DOI 10.1029/2021JB023470.

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Abstract

The VP/VS ratio is an important property for understanding magmatic and tectonic processes at passive continental margins as it is an indicator of the crustal composition. To classify the dominant lithologies in the Zhongsha Block, South China Sea (SCS), we present a detailed VP/VS crustal model based on the independent tomographic inversion of P wave and S wave data. The average VP/VS in the crust of the Zhongsha Block is ∼1.77, indicating an overall felsic to intermediate composition lacking remnant magmatic intrusive rocks. The VP-density relationship from gravity modeling suggests that the lower crust of the extended continental domain contains more greenschist and hence may have experienced metamorphism resulting from an elevated geotherm in the Northwest Sub-basin either during the syn-spreading or postspreading stage. The variability of the VP/VS ratio in the continental block is larger than that in the oceanic basin, showing distinct crustal properties. Several low VP/VS ratio anomalies (VP/VS < 1.7) were found near tectonic boundaries and are interpreted to either result from felsic metamorphism during an interval of rifting, or during the migration of magma along faults and cracks in the postrift period. VP/VS ratios occurring in concert with high VP anomalies in the continent-ocean transition zone support a mafic composition of metapelitic granulite, which was either formed by magmatic intrusions or contact with mantle melting that stem from the upwelling of the asthenospheric mantle during the initial break-up and onset of the seafloor spreading stage in the SCS.

Document Type: Article
Keywords: crustal composition, VP/VS ratio, seismic tomography, South China Sea, Zhongsha Block, magmatism
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Main POF Topic: PT3: Restless Earth
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2021JB023470
ISSN: 2169-9313
Related URLs:
Date Deposited: 12 May 2022 08:17
Last Modified: 13 May 2022 06:55
URI: https://oceanrep.geomar.de/id/eprint/55983

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