Source lithology and crustal assimilation recorded in low δ18O olivine from Okinawa Trough, back-arc basin

Lithos ◽  
2020 ◽  
Vol 360-361 ◽  
pp. 105444 ◽  
Author(s):  
Xiaohui Li ◽  
Zhigang Zeng ◽  
Wei Dan ◽  
Huixin Yang ◽  
Xiaoyuan Wang ◽  
...  
Keyword(s):  
Okinawa Trough ◽  
Crustal Assimilation ◽  
Back Arc

A highly diverse silicic end member of a bimodal magma suite formed in an active continental back arc, Okinawa Trough

2021 ◽  
Author(s):  
Arran Murch ◽  
Kenichiro Tani ◽  
Takashi Sano ◽  
Shigekazu Yoneda
Keyword(s):  
Magma Mixing ◽  
Okinawa Trough ◽  
Fractional Crystallisation ◽  
Chemical Diversity ◽  
Crustal Assimilation ◽  
Arc Volcanism ◽  
The North ◽  
The Okinawa Trough ◽  
Formation Conditions ◽  
Back Arc

<p>The Okinawa Trough (OT) is an incipient continental back-arc basin that extends from Kyushu in the north to Taiwan in the south. The Okinawa Trough can be split in to three segments, the Northern (NOT), Middle (MOT), and Southern (SOT) with active back-arc volcanism restricted to volcanic centres located in en-echelon grabens the MOT and SOT. Previous studies have shown magmatism in the OT is bimodal (basaltic to rhyolitic), with at least two types of silicic melts inferred to form through pure fractional crystallisation from basalt and by fractional crystallisation along with minor crustal assimilation (Shinjo and Kato, 2000).</p><p>Here we present petrological descriptions, along with major, trace element and Sr–Nd isotopic data for 75 silicic end member samples recovered as both lava and pumice, collected during the R/V Sonne HYDROMIN1 and 2 cruises in 1988 and 1990, respectively. Samples were dredged from various seafloor knolls and ridges located in the Io and Iheya grabens and from Izena Hole in the MOT, and from a single volcanic ridge in the Yaeyama graben and a single isolated knoll in the SOT.</p><p>Results show a chemically highly diverse silicic end member magmas, with at least four identifiable groups based on differences in the degree of enrichment of incompatible elements (LREE, K, Rb, Ba, etc.). Each group contains at least one dense lava sample suggesting the chemical diversity is a primary feature of magmatism in the Okinawa Trough rather than a result of the floating in of pumiceous material from various locations.</p><p>Using petrological descriptions and the chemistry of samples along with MELTS modelling we plan to calculate magma formation conditions and identify any evidence of magma mixing or crustal assimilation. In doing so we hope to provide a model to explain the diversity of silicic magma chemistry in the MOT and SOT.</p><p> </p><p>Shinjo, R., and Kato, Y. (2000). Geochemical constraints on the origin of bimodal magmatism at the Okinawa Trough, an incipient back-arc basin. Lithos 54, 117–137. doi:10.1016/S0024-4937(00)00034-7.</p>

Active tectonics and volcanism in the southernmost Okinawa Trough back-arc basin derived from deep-towed sonar surveys

2021 ◽  
pp. 229047
Author(s):  
Ching-Hui Tsai ◽  
Shu-Kun Hsu ◽  
Song-Chuen Chen ◽  
Shiou-Ya Wang ◽  
Lien-Kai Lin ◽  
...  
Keyword(s):  
Okinawa Trough ◽  
Active Tectonics ◽  
Back Arc

scholarly journals Seismic structure of the crust and uppermost mantle in the incipient stage of back arc rifting - northernmost Okinawa Trough

2004 ◽  
Vol 31 (2) ◽  
Author(s):  
Kazuo Nakahigashi ◽  
Masanao Shinohara ◽  
Sadaomi Suzuki ◽  
Ryota Hino ◽  
Hajime Shiobara ◽  
...  
Keyword(s):  
Okinawa Trough ◽  
Seismic Structure ◽  
Uppermost Mantle ◽  
Incipient Stage ◽  
Back Arc

scholarly journals Diversity of fluid geochemistry affected by processes during fluid upwelling in active hydrothermal fields in the Izena Hole, the middle Okinawa Trough back-arc basin

2014 ◽  
Vol 48 (4) ◽  
pp. 357-369 ◽  
Author(s):  
JUN-ICHIRO ISHIBASHI ◽  
TAKUROH NOGUCHI ◽  
TOMOHIRO TOKI ◽  
SHUNSUKE MIYABE ◽  
SHOSEI YAMAGAMI ◽  
...  
Keyword(s):  
Okinawa Trough ◽  
Fluid Geochemistry ◽  
Back Arc ◽  
Hydrothermal Fields

scholarly journals Moho Geometry of the Okinawa Trough Based on Gravity Inversion and Its Implications on the Crustal Nature and Tectonic Evolution

2021 ◽  
Vol 9 ◽  
Author(s):  
Liang Zhang ◽  
Xiwu Luan
Keyword(s):  
Early Stage ◽  
Okinawa Trough ◽  
High Heat ◽  
Crustal Thickness ◽  
Moho Depth ◽  
Gravity Inversion ◽  
The Okinawa Trough ◽  
Oceanic Spreading ◽  
Thickness Variations ◽  
Back Arc

The Okinawa Trough (OT) is an incipient back-arc basin, but its crustal nature is still controversial. Gravity inversion along with sediment and lithospheric mantle density modeling are used to map the regional Moho depth and crustal thickness variations of the OT and its adjacent areas. The gravity inversion result shows that the crustal thicknesses are 17–22 km at the northern OT, 11–19 km at the central OT, and 7–19 km at the southern OT. Because of the crust with a thickness larger than 17 km, the slow southward arc movement, and scarce contemporaneous volcanisms, the northern OT should be in the stage of early back-arc extension. All of the moderate crustal thickness, high heat flow, and intense volcanism at the central OT indicate that this region is probably in the transitional stage from the back-arc rifting to the oceanic spreading. A crust that is only 7 km thick, lithosphere strength as low as the mid-ocean ridge, and MORB-similar basalts at the southern OT demonstrate that the southern OT is at the early stage of seafloor spreading.

scholarly journals Lithium, Oxygen and Magnesium Isotope Systematics of Volcanic Rocks in the Okinawa Trough: Implications for Plate Subduction Studies

2021 ◽  
Vol 10 (1) ◽  
pp. 40
Author(s):  
Zhigang Zeng ◽  
Xiaohui Li ◽  
Yuxiang Zhang ◽  
Haiyan Qi
Keyword(s):  
Basaltic Andesite ◽  
Subduction Zones ◽  
Okinawa Trough ◽  
Volcanic Rocks ◽  
Philippine Sea Plate ◽  
Material Transfer ◽  
Magma Compositions ◽  
Subduction Input ◽  
Back Arc ◽  
Plate Subduction

Determining the influence of subduction input on back-arc basin magmatism is important for understanding material transfer and circulation in subduction zones. Although the mantle source of Okinawa Trough (OT) magmas is widely accepted to be modified by subducted components, the role of slab-derived fluids is poorly defined. Here, major element, trace element, and Li, O and Mg isotopic compositions of volcanic lavas from the middle OT (MOT) and southern OT (SOT) were analyzed. Compared with the MOT volcanic lavas, the T9-1 basaltic andesite from the SOT exhibited positive Pb anomalies, significantly lower Nd/Pb and Ce/Pb ratios, and higher Ba/La ratios, indicating that subducted sedimentary components affected SOT magma compositions. The δ7Li, δ18O, and δ26Mg values of the SOT basaltic andesite (−5.05‰ to 4.98‰, 4.83‰ to 5.80‰ and −0.16‰ to −0.09‰, respectively) differed from those of MOT volcanic lavas. Hence, the effect of the Philippine Sea Plate subduction component, (low δ7Li and δ18O and high δ26Mg) on magmas in the SOT was clearer than that in the MOT. This contrast likely appears because the amounts of fluids and/or melts derived from altered oceanic crust (AOC, lower δ18O) and/or subducted sediment (lower δ7Li, higher δ18O and δ26Mg) injected into magmas in the SOT are larger than those in the MOT and because the injection ratio between subducted AOC and sediment is always >1 in the OT. The distance between the subducting slab and overlying magma may play a significant role in controlling the differences in subduction components injected into magmas between the MOT and SOT.

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