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 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 Mesozoic Northward Subduction Along the SE Asian Continental Margin Inferred from Magmatic Records in the South China Sea

Minerals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 598 ◽  
Author(s):  
Guanqiang Cai ◽  
Zhifeng Wan ◽  
Yongjian Yao ◽  
Lifeng Zhong ◽  
Hao Zheng ◽  
...  
Keyword(s):  
South China Sea ◽  
Continental Margin ◽  
South China ◽  
Oceanic Lithosphere ◽  
The South China Sea ◽  
The South ◽  
Late Mesozoic ◽  
China Sea ◽  
Depleted Mantle ◽  
T Values

During the Mesozoic, Southeast (SE) Asia (including South China and the South China Sea (SCS)) was located in a transitional area between the Tethyan and Pacific geotectonic regimes. However, it is unclear whether geodynamic processes in the SE Asian continental margin were controlled by Tethyan or paleo-Pacific Ocean subduction. Herein, we report ~124 Ma adakitic granodiorites and Nb-enriched basalts from the Xiaozhenzhu Seamount of the SCS. Granodiorites have relatively high Sr/Y (34.7–37.0) and (La/Yb)N (13.8–15.7) ratios, as well as low Y (9.67–9.90 μg/g) and Yb (0.93–0.94 μg/g) concentrations, typical of adakites. Their Sr/Y and (La/Yb)N values coupled with their relatively low initial 87Sr/86Sr ratios (0.70541–0.70551), relatively high K2O contents (3.31–3.38 wt%), high Th/La ratios (0.33–0.40), negative εNd(t) values (−3.62 to −3.52), and their variable zircon εHf(t) values (−3.8 to +5.2) indicate that these rocks were formed by melting of subducted oceanic crust and sediments. The Nb-enriched basalts show enrichment in high field strength elements (HFSE) and have εNd(t) values of +2.90 to +2.93, as well as relatively low initial 87Sr/86Sr ratios of 0.70341–0.70343, demonstrating that they were derived from a depleted-mantle (DM) source metasomatized by silicate magmas originating from melting of a subducted oceanic lithospheric slab. By combining our findings with data from other Late Mesozoic arc-related magmatic rocks and adakites from the broader study area, we propose a geotectonic model involving subduction of young oceanic lithosphere during the Late Jurassic and northward subduction of the proto-South China Sea (PSCS) along the SE Asian continental margin during the Early Cretaceous. This conceptual model better explains the two-period Mesozoic magmatism, commonly reported for the SE Asian continental margin.

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 Calcium Isotopic Compositions of Neogene Dolomites in the South China Sea and Its Implications for Paleoclimate Changes

2021 ◽  
Author(s):  
Xiaofeng Liu ◽  
Xiaoming Liu ◽  
Shikui Zhai ◽  
Cheng Cao ◽  
Dongjie Bi ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Isotopic Compositions

Boron isotopic compositions in growing corals from the South China Sea

2013 ◽  
Vol 62 ◽  
pp. 561-567 ◽  
Author(s):  
Jun Xiao ◽  
Yingkai Xiao ◽  
Zhangdong Jin ◽  
Congqiang Liu ◽  
Maoyong He
Keyword(s):  
South China Sea ◽  
South China ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Isotopic Compositions

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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