scholarly journals Alkali basalt from the Seifu seamount of the Japan Sea: post-spreading magmatism in the back-arc region

2019 ◽  
Author(s):  
Tomoaki Morishita ◽  
Naoto Hirano ◽  
Hirochika Sumino ◽  
Hiroshi Sato ◽  
Tomoyuki Shibata ◽  
...  
Keyword(s):  
Early Stage ◽  
Japan Sea ◽  
Spinel Peridotite ◽  
Stability Field ◽  
Alkaline Basalt ◽  
Trace Element Pattern ◽  
Low Degree ◽  
Element Pattern ◽  
The Japan Sea ◽  
Back Arc

Abstract. We report geochemical characteristics and Ar-Ar dating of a basalt dredged from the Seifu Seamount (SSM-basalt), located at northeast of the Tsushima Basin in the southwest Japan Sea, which is one of the western Pacific back-arc basin swarm. A plateau age of 8.33 ± 0.15 Ma (2σ) was obtained by the 40Ar-39Ar age spectrum of SSM-basalt. The SSM-basalt (8.3 Ma) was formed at an early stage after the termination of the Japan Sea back-arc opening. The SSM-basalt is high-K to shoshonitic alkaline basalt and is characterized by enrichment of light rare earth element (REE). The trace element pattern of the SSM-basalt is similar to Ocean island-type basalt (OIB) whereas YbPM (= 6) is distinctively higher than that of OIB, indicating of its formation by the low degree melting of the source mantle under spinel peridotite stability field. The Nd-Sr and Pb isotope compositions of the SSM-basalt are offset from the compositional trend of the Japan Sea back-arc basin basalts. The Sr-Nd isotope relationship of the SSM-basalt suggest its source can be formed by deplete MORB mantle source mixing with EM1-like component. The SSM basalt was formed as a post-back-arc spreading magmatism by low degree of partial melting of a portion that is easily melted in the upwelling asthenosphere associated with the main back-arc magmatism.

scholarly journals Alkali basalt from the Seifu Seamount in the Sea of Japan: post-spreading magmatism in a back-arc setting

Solid Earth ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 23-36
Author(s):  
Tomoaki Morishita ◽  
Naoto Hirano ◽  
Hirochika Sumino ◽  
Hiroshi Sato ◽  
Tomoyuki Shibata ◽  
...  
Keyword(s):  
Partial Melting ◽  
Sea Of Japan ◽  
Alkali Basalt ◽  
Spinel Peridotite ◽  
The Sea Of Japan ◽  
Low Degree ◽  
Tsushima Basin ◽  
Arc Setting ◽  
Element Enrichment ◽  
Back Arc

Abstract. We present geochemical and 40Ar∕39Ar age data for a peridotite xenolith-bearing basalt dredged from the Seifu Seamount (SSM basalt) in the northeast Tsushima Basin, southwest Sea of Japan. An 40Ar∕39Ar plateau age of 8.33±0.15 Ma (2σ) was obtained for the SSM basalt, indicating that it erupted shortly after the termination of back-arc spreading in the Sea of Japan. The SSM basalt is a high-K to shoshonitic alkali basalt that is characterized by light rare earth element enrichment. The trace element features of the basalt are similar to those of ocean island basalt, although the Yb content is much higher, indicating formation by the low-degree partial melting of spinel peridotite. The Nd, Sr, and Pb isotopic compositions of the SSM basalt differ from those of back-arc basin basalts in the Sea of Japan. The Sr–Nd isotopic composition of the SSM basalt suggests its source was depleted mid-ocean ridge mantle containing an enriched mantle (EM1) component. The SSM basalt was formed in a post-back-arc extension setting by the low-degree partial melting of an upwelling asthenosphere that had previously been associated with the main phase of back-arc magmatism.

scholarly journals Last stage of the Japan Sea back-arc opening deduced from the seismic velocity structure using wide-angle data

2006 ◽  
Vol 7 (6) ◽  
pp. n/a-n/a ◽  
Author(s):  
Takeshi Sato ◽  
Narumi Takahashi ◽  
Seiichi Miura ◽  
Gou Fujie ◽  
Dong-Hyo Kang ◽  
...  
Keyword(s):  
Velocity Structure ◽  
Seismic Velocity ◽  
Japan Sea ◽  
Wide Angle ◽  
Seismic Velocity Structure ◽  
Angle Data ◽  
The Japan Sea ◽  
Last Stage ◽  
Back Arc

U–Pb ages of Miocene near-trench granitic rocks of the Southwest Japan arc: implications for magmatism related to hot subduction

2019 ◽  
Vol 158 (1) ◽  
pp. 47-71 ◽  
Author(s):  
Hironao Shinjoe ◽  
Yuji Orihashi ◽  
Ryo Anma
Keyword(s):  
Middle Miocene ◽  
Japan Sea ◽  
Wide Distribution ◽  
Granitic Rocks ◽  
Philippine Sea Plate ◽  
Kii Peninsula ◽  
The Japan Sea ◽  
Igneous Activity ◽  
Mariana Arc ◽  
Back Arc

AbstractWe present a new dataset of zircon U–Pb ages that document igneous activity in the SW Japan arc during middle Miocene time and discuss its relationship with the opening of the Japan Sea, Philippine Sea plate migration, and subduction of the young hot lithosphere of the Shikoku Basin. Precursory magmatism, characterized by dike and stock intrusions, started c. 15.6 Ma in both Kyushu and the Kii Peninsula. Most plutonism occurred between 15.5 and 13.5 Ma in an area 600 km long and 150 km wide. No along-arc trend was recognized in the U–Pb ages of igneous activity near the trench. Our data indicate that all near-trench middle Miocene igneous activity occurred immediately after the opening of the Japan Sea ceased, i.e. after 16 Ma, implying that melt extraction and the emplacement of granites in the near-trench region had some influence on the back-arc opening. Our data also imply that the trench–trench–trench-type triple junction between the Japan arc and the Izu–Bonin–Mariana arc must have reached the east side of the Kii Peninsula by 15.6 Ma. The wide distribution of contemporaneous magmatic activity along the arc requires a trench-parallel heat source, such as the subduction of a trench-parallel ridge or a young and highly segmented ridge–fracture zone system in addition to the hot wedge mantle condition related to the opening of Japan Sea.

Neogene deformation of the back-arc shelf of Southwest Japan and its impact on the palaeoenvironments of the Japan Sea

1997 ◽  
Vol 281 (1-2) ◽  
pp. 71-82 ◽  
Author(s):  
Yasuto Itoh ◽  
Takeshi Nakajima ◽  
Atsushi Takemura
Keyword(s):  
Japan Sea ◽  
Southwest Japan ◽  
The Japan Sea ◽  
Back Arc

Low-Ti gabbroic pluton in Dali, SW China: new evidence for back-arc lithospheric melting inducing the early-stage magmatism of the Emeishan large igneous province

2021 ◽  
pp. jgs2020-224
Author(s):  
Bei Zhu ◽  
Zhaojie Guo ◽  
Shaonan Zhang ◽  
Ning Ye ◽  
Ziye Lu ◽  
...  
Keyword(s):  
Early Stage ◽  
Large Igneous Province ◽  
Spinel Peridotite ◽  
Heavy Rare Earth Element ◽  
Content Type ◽  
Igneous Province ◽  
Supplementary Material ◽  
Back Arc ◽  
Emeishan Lip ◽  
Yangtze Plate

The latest studies proved contribution of the Emeishan mantle plume (the widely-regarded origin of the Emeishan LIP in the western Yangtze Plate. LIP: large igneous province) to the Palaeo-Tethys subduction. However, whether the Palaeo-Tethys subduction oppositely affected the formation of the Emeishan LIP remains poorly understood. Here, we report geochronological, petrological, geochemical and isotopic studies of a gabbroic intrusion in this LIP, located in Jiangwei, the Dali area. The gabbro has a weighted mean SHRIMP U-Pb age of ∼262 Ma. Key geochemical features include Nb, Ta and Ti depletion; Th, U and Sr enrichment, low light/heavy rare earth element ratios and ∼0.707 87Sr/86Sr(t) and ∼-0.21 εNd(t) values. We conducted pMELTS thermodynamic modeling and batch melting calculations to evaluate the origin and evolution of the gabbro, based on real components of low-Ti picrites and xenolith of the Yangtze lithosphere. The results support 3% melting of a hydrated spinel peridotite source from the Yangtze lithosphere can produce magma equivalent to the gabbro components. Integrating this conclusion with tectonic background of the western Yangtze Plate and volcano-stratigraphic record of the Emeishan LIP, we infer the early-stage magmatism of the Emeishan LIP was triggered by Paleo-Tethys back-arc extension with fluid modification from subductional slab.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5433267

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