Characteristics of Upper Mantle Activity in the South China Sea Region and the Indochina Mantle Plume

1999 ◽  
Vol 73 (4) ◽  
pp. 464-476 ◽  
Author(s):  
WU Nengyou ◽  
ZENG Weijun ◽  
LI Zhenwu ◽  
CHEN Yizhong ◽  
WEN Xiwen ◽  
...  
Keyword(s):  
South China Sea ◽  
Mantle Plume ◽  
South China ◽  
Upper Mantle ◽  
The South China Sea ◽  
The South ◽  
China Sea

scholarly journals Supplemental Material: Crustal and upper mantle structure beneath the South China Sea and Indonesia

2020 ◽  
Author(s):  
V. Corchete
Keyword(s):  
South China Sea ◽  
Geographical Distribution ◽  
South China ◽  
Upper Mantle ◽  
The South China Sea ◽  
Mantle Structure ◽  
Inversion Process ◽  
The South ◽  
China Sea ◽  
Upper Mantle Structure

Figure S1: Geographical distribution of the 1-sigma errors arisen in computation of the S-velocities shown in Figure 3. The interval between isolines is 0.01 km/s; Figure S2. Resolution maps of the inversion process performed to calculate the S-velocities shown in Figure 3, plotted from 0 (not resolved) to 1 (perfect resolution). The interval between isolines is 0.1.

scholarly journals Post-spreading Basalts from the Nanyue Seamount: Implications for the Involvement of Crustal- and Plume-Type Components in the Genesis of the South China Sea Mantle

Minerals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 378
Author(s):  
Hao Zheng ◽  
Li-Feng Zhong ◽  
Argyrios Kapsiotis ◽  
Guan-Qiang Cai ◽  
Zhi-Feng Wan ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Upper Mantle ◽  
The South China Sea ◽  
The South ◽  
Alkali Basalts ◽  
China Sea ◽  
Isotopic Compositions ◽  
Geological Processes ◽  
Depleted Mantle

Fresh samples of basalts were collected by dredging from the Nanyue intraplate seamount in the Southwest sub-basin of the South China Sea (SCS). These are alkali basalts displaying right-sloping, chondrite-normalized rare earth element (REE) profiles. The investigated basalts are characterized by low Os content (60.37–85.13 ppt) and radiogenic 187Os/188Os ratios (~0.19 to 0.21). Furthermore, 40Ar/39Ar dating of the Nanyue basalts showed they formed during the Tortonian (~8.3 Ma) and, thus, are products of (Late Cenozoic) post-spreading volcanism. The Sr–Nd–Pb–Hf isotopic compositions of the Nanyue basalts indicate that their parental melts were derived from an upper mantle reservoir possessing the so-called Dupal isotopic anomaly. Semiquantitative isotopic modeling demonstrates that the isotopic compositions of the Nanyue basalts can be reproduced by mixing three components: the average Pacific midocean ridge basalt (MORB), the lower continental crust (LCC), and the average Hainan ocean island basalt (OIB). Our preferred hypothesis for the genesis of the Nanyue basalts is that their parental magmas were produced from an originally depleted mantle (DM) source that was much affected by the activity of the Hainan plume. Initially, the Hainan diapir caused a thermal perturbation in the upper mantle under the present-day Southwest sub-basin of the SCS that led to erosion of the overlying LCC. Eventually, the resultant suboceanic lithospheric mantle (SOLM) interacted with OIB-type components derived from the nearby Hainan plume. Collectively, these processes contributed crustal- and plume-type components to the upper mantle underlying the Southwest sub-basin of the SCS. This implies that the Dupal isotopic signature in the upper mantle beneath the SCS was an artifact of in situ geological processes rather than a feature inherited from a Southern Hemispheric, upper mantle source.

scholarly journals Coexistence of Hainan Plume and Stagnant Slab in the Mantle Transition Zone beneath the South China Sea Spreading Ridge: Constraints from Volcanic Glasses and Seismic Tomography

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 2) ◽  
Author(s):  
Shuang-Shuang Chen ◽  
Rui Gao ◽  
Zewei Wang ◽  
Tong Hou ◽  
Jie Liao ◽  
...  
Keyword(s):  
South China Sea ◽  
Oceanic Crust ◽  
Mantle Plume ◽  
South China ◽  
The South China Sea ◽  
Spreading Ridge ◽  
The South ◽  
China Sea ◽  
Volcanic Glasses ◽  
Hainan Mantle Plume

Abstract The influence of Hainan mantle plume and subducting recycled oceanic crust beneath the spreading ridge of the South China Sea (SCS) have been widely proposed recently, but still controversial and ambiguous. Here, we present seismic tomographic evidence, new major and trace element, and Pb isotopic compositions of volcanic glasses from one International Ocean Drilling Program drill core (Site U1434) in the SCS spreading ridge. The volcanic glasses are relatively enriched in alkalis and light rare earth elements (LREEs) and depleted in heavy REEs (HREEs), exhibit slightly positive anomalies in Nb, Ta, Zr, and Hf as well as a positive Nb relative to La and Th, and show relatively high 207Pb/206Pb and 208Pb/206Pb isotopic ratios, suggesting ocean island basalt- (OIB-) type and enriched mantle 2- (EM2-) type geochemical features likely related to a mantle plume. These geochemical features are consistent with those of late Cenozoic volcanic rocks in Hainan and surrounding areas associated with a mantle plume, likely providing the influence of Hainan mantle plume beneath the spreading ridge of the SCS. The SCS primary-melt and volcanic glasses indicate that the source mantle involved 18.5% eclogite (dense, recycled oceanic crust from the stagnant subducted slab) and 46.1% garnet pyroxenite (produced by the reaction between the peridotite melt and recycled oceanic crust). The existence of Hainan mantle plume and stagnant subducted slab is further supported by geophysical evidence from a recent three-dimensional P-wave seismic tomographic model.

Crustal and upper mantle structure beneath the South China Sea and Indonesia

2020 ◽  
Vol 133 (1-2) ◽  
pp. 177-184
Author(s):  
V. Corchete
Keyword(s):  
South China Sea ◽  
Continental Margin ◽  
South China ◽  
Upper Mantle ◽  
Velocity Model ◽  
The South China Sea ◽  
Mantle Structure ◽  
The South ◽  
Crust And Upper Mantle ◽  
China Sea

Abstract A three-dimensional (3-D) S-velocity model for the crust and upper mantle beneath the South China Sea and Indonesia is presented, determined by means of Rayleigh wave analysis, in the depth range from 0 km to 400 km. The crustal and lithospheric mantle structure of this study area was previously investigated using several methods and databases. Due to their low resolution, a 3-D structure for this area has not been previously determined. The determination of such a 3-D S-velocity model is the goal of the present study. The most conspicuous features of the crust and upper mantle structure include the S-velocity difference between the Java Sea and the Banda Sea regions and a transitional boundary between these two regions. This model confirms the principal structural features revealed in previous studies: an oceanic crust structure in the center of the South China Sea, crustal thinning from the northern continental margin of the South China Sea to this oceanic crust, and the existence of a high-velocity layer in the lower crust of the northern continental margin. This study concludes that the north of the South China Sea is a nonvolcanic-type continental margin, solving the open question of whether the continental margin of the northern South China Sea is volcanic or nonvolcanic. A new map of the asthenosphere’s base is also presented.

scholarly journals Supplemental Material: Crustal and upper mantle structure beneath the South China Sea and Indonesia

2020 ◽  
Author(s):  
V. Corchete
Keyword(s):  
South China Sea ◽  
Geographical Distribution ◽  
South China ◽  
Upper Mantle ◽  
The South China Sea ◽  
Mantle Structure ◽  
Inversion Process ◽  
The South ◽  
China Sea ◽  
Upper Mantle Structure

Figure S1: Geographical distribution of the 1-sigma errors arisen in computation of the S-velocities shown in Figure 3. The interval between isolines is 0.01 km/s; Figure S2. Resolution maps of the inversion process performed to calculate the S-velocities shown in Figure 3, plotted from 0 (not resolved) to 1 (perfect resolution). The interval between isolines is 0.1.

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