Seismic Velocity Structure of the Magnetic Quiet Zone and Continent‐Ocean Boundary in the Northeastern South China Sea

Wan, Xiao; Li, Chun‐Feng; Zhao, Minghui; He, Enhui; Liu, Siqing; Qiu, Xuelin; Lu, Yu; Chen, Nan

doi:10.1029/2019jb017785

Cited by 40 publications

(13 citation statements)

References 72 publications

(169 reference statements)

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“…If so, it would have cooled rapidly, making it hard to retain low-velocity in the long term. Yet, the cooled magma would have generated a high-velocity zone which, however, has not been resolved in our case nor in other reports [18]. Though not improbably, it is less likely an active magma chamber.…”

Section: Analysis Of the Hill H110 And The Low-velocity Zonecontrasting

confidence: 60%

“…On the whole, the northern margin of South China Sea is magma-poor, but there are enhanced young magmatism locally, particularly around the southern CSD, in expressions of volcanoes, shallow intrusive, and lower crust underplating, featuring high-velocity (7.0-7.5 km/s) [13,17,18]. However, the impact of magmatism on the petroleum system in the CSD is less known.…”

Section: Geological Settingmentioning

confidence: 99%

“…The seismic survey line L2016-2 was initially designed to explore the magmatism over the DS water. Wan, et al [18] has used the OBS data to construct forward and inversion velocity models and found two lower crust high-velocity (7.0-7.5 km/s) zones beneath the middle and lower slope, in the southeast, close to the CSD. Both zones were interpreted as formed by magma underplating.…”

Section: Geological Settingmentioning

confidence: 99%

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Velocity Structure Revealing a Likely Mud Volcano off the Dongsha Island, the Northern South China Sea

Yan

Liao

et al. 2021

Energies

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The Dongsha Island (DS) is located in the mid-northern South China Sea continental margin. The waters around it are underlain by the Chaoshan Depression, a relict Mesozoic sedimentary basin, blanketed by thin Cenozoic sediments but populated with numerous submarine hills with yet less-known nature. A large hill, H110, 300 m high, 10 km wide, appearing in the southeast to the Dongsha Island, is crossed by an ocean bottom seismic and multiple channel seismic surveying lines. The first arrival tomography, using ocean bottom seismic data, showed two obvious phenomena below it: (1) a low-velocity (3.3 to 4 km/s) zone, with size of 20 × 3 km2, centering at ~4.5 km depth and (2) an underlying high-velocity (5.5 to 6.3 km/s) zone of comparable size at ~7 km depth. MCS profiles show much-fragmented Cenozoic sequences, covering a wide chaotic reflection zone within the Mesozoic strata below hill H110. The low-velocity zone corresponds to the chaotic reflection zone and can be interpreted as of highly-fractured and fluid-rich Mesozoic layers. Samples dredged from H110 comprised of illite-bearing authigenic carbonate nodules and rich, deep-water organisms are indicative of hydrocarbon seepage from deep source. Therefore, H110 can be inferred as a mud volcano. The high-velocity zone is interpreted as of magma intrusion, considering that young magmatism was found enhanced over the southern CSD. Furthermore, the origin of H110 can be speculated as thermodynamically driven, i.e., magma from the depths intrudes into the thick Mesozoic strata and promotes petroleum generation, thus, driving mud volcanism. Mud volcanism at H110 and the occurrence of a low-velocity zone below it likely indicates the existence of Mesozoic hydrocarbon reservoir, which is in favor of the petroleum exploration.

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Section: Analysis Of the Hill H110 And The Low-velocity Zonecontrasting

confidence: 60%

Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

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Velocity Structure Revealing a Likely Mud Volcano off the Dongsha Island, the Northern South China Sea

Yan

Liao

et al. 2021

Energies

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“…However, this was not revealed in the northwestern margin (Huang, Qiu, Pichot et al., 2019; Huang et al., 2021; Qiu et al., 2001), which makes the situation of magmatism still enigmatic. In the COT, except for one wide‐angle seismic study in the northeastern margin which reveals possible exhumed mantle (Wan et al., 2019), most of the seismic and drilling data indicate a rapid transition (Larsen et al., 2018; Li, Huang, Grevemeyer et al., 2021). In the oceanic basin, the Northwest Sub‐basin and East Sub‐basin mainly show typical oceanic crust, but whether the Southwest Sub‐basin shows typical or thinned oceanic crust with serpentinized mantle is still a matter of debate (e.g., Li, Huang, Grevemeyer et al., 2021).…”

Section: Geological Settingmentioning

confidence: 99%

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

Grevemeyer

Huang

et al. 2022

JGR Solid Earth

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At passive continental margins, magmatism and tectonics are two important factors that control the fluid, thermal, and rheological conditions in the lithosphere, from continental rifting to break-up. As a result, different extension modes may occur in the continental crust, such as pure shear, simple shear, and depth independent stretching (Franke et al., 2011;Lister et al., 1986;McKenzie, 1978;Wernicke, 1981). Different architectures are also found in the continent-ocean transition zone (COT), such as wide domains of exhumed continental mantle (e.g., Dean et al., 2000;Grevemeyer et al., 2022) versus rapid transition from continental to oceanic crust (e.g., Larsen et al., 2018). After break-up, the crustal thickness in oceanic basins may vary widely depending on magma

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“…At the SCS passive margin, the role of magmatism in the processes of rifting and seafloor spreading is still a matter of debate. MCS and OBS data were used to infer a mantle exhumation model for the COT (Franke et al, 2014;Wan et al, 2019), while the IODP drilling results yielded a rapid transition from continental crust to seafloor spreading and characterized it as an intermediate-type rifted margin (Larsen et al, 2018). Spatial and temporal variations of the magmatic budget in the SCS basin (Yu et al, 2018(Yu et al, , 2021 demonstrated the unstable magmatic supply, especially before and after the ridge jump events, leading the architecture of COT in the SCS becomes an open problem and need more evidence.…”

mentioning

confidence: 99%

Seismic Constraint From V_p/V_s Ratios on the Structure and Composition Across the Continent‐Ocean Transition Zone, South China Sea

Grevemeyer

Huang

et al. 2021

Geophysical Research Letters

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At passive non-volcanic rifted continental margins, the interrelation between rifting, un-roofing of continental mantle in a broad continent-ocean transition zone (COT), and the onset of seafloor spreading is even after decades of geological and geophysical investigations still poorly understood (e.g., Sun et al., 2018). Deep drilling at two non-volcanic margins revealed that at the Iberia-Newfoundland margin the COT is characterized by a wide domain of exhumed mantle (Dean et al., 2000;Whitmarsh et al., 2001), while the mid-northern South China Sea (SCS) margin shows fast break-up without mantle exhumation (Larsen et al., 2018). However, without deep drilling and hence sampling the type of basement rocks, constraints from geophysical imaging alone, are usually too tenuous to uniquely outline the detailed crustal structure forming the seafloor. In seismic exploration, multi-channel seismic data (MCS) provide exquisite basement geometry and shallow crustal characteristics (e.g., Dean et al., 2015;Minshull et al., 2014), while the P wave velocity structure derived from seismic refraction and wide-angle data helps to define the crustal nature (e.g., Dean et al., 2000). However, these traditional approaches are inadequate to reveal the enigmatic structure and composition of the COT. For example, serpentinization of exhumed mantle can hardly be unscrambled from crustal rocks since the P wave velocity overlap at ∼6.5-7.2 km/s of gabbro and partially serpentinized peridotite (Christensen, 2004;Grevemeyer, Hayman, et al., 2018). Further, reflection energy

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Seismic Velocity Structure of the Magnetic Quiet Zone and Continent‐Ocean Boundary in the Northeastern South China Sea

Cited by 40 publications

References 72 publications

Velocity Structure Revealing a Likely Mud Volcano off the Dongsha Island, the Northern South China Sea

Velocity Structure Revealing a Likely Mud Volcano off the Dongsha Island, the Northern South China Sea

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

Seismic Constraint From V_p/V_s Ratios on the Structure and Composition Across the Continent‐Ocean Transition Zone, South China Sea

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Seismic Velocity Structure of the Magnetic Quiet Zone and Continent‐Ocean Boundary in the Northeastern South China Sea

Cited by 40 publications

References 72 publications

Velocity Structure Revealing a Likely Mud Volcano off the Dongsha Island, the Northern South China Sea

Velocity Structure Revealing a Likely Mud Volcano off the Dongsha Island, the Northern South China Sea

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

Seismic Constraint From Vp/Vs Ratios on the Structure and Composition Across the Continent‐Ocean Transition Zone, South China Sea

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

Seismic Constraint From V_p/V_s Ratios on the Structure and Composition Across the Continent‐Ocean Transition Zone, South China Sea