Tomographic evidence for hydrated oceanic crust of the Pacific slab beneath northeastern Japan: Implications for water transportation in subduction zones

AbstractCenozoic intraplate basalts are widespread above the Big Mantle Wedge (BMW) and its front in East Asia. While the mantle source lithology and redox-hydration state have been demonstrated to be crucial in generation of the basalts above the BMW, their nature and role on the basalts above the front of the BMW is poorly constrained. To address this, we report olivine compositions of the Quaternary Datong basalts. The Datong basalts exhibit OIB-like trace-element compositions and depleted Sr-Nd isotopes with slightly enriched signatures (EMI) for tholeiitic basalts. Olivines of the Datong basalts show high Ni and Fe/Mn, and low Ca, Mn, and Mn/Zn values, pointing to a pyroxenite source. Applying V and Ca partition coefficients between olivine and whole-rock, respectively, the Datong basalts lie −0.44 to 0.64 log units above the fayalite-magnetite-quartz buffer for fO2, and contain 2.1-3.4 wt.% H2O but highly variable H2O/Ce values (265-1498). Both fO2 and H2O/Ce in the basalts vary with whole-rock and olivine compositions, indicating the source was the main control, thus, a heterogeneous redox-hydration state in the source: the EMI component being relatively reduced but extremely wet, and recycled oceanic crust being relatively oxidized but dry. The extremely wet EMI component was likely derived from the mantle transition zone. In the light of our findings, we propose a model in which mantle upwelling carried the recycled oceanic crust and EMI component from the MTZ to shallow mantle, due to the Pacific slab stagnating in the MTZ, to form pyroxenite, which subsequently melted to generate the Datong basalts.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5227668

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METAMORPHIC DEHYDRATION FROM OCEANIC CRUST PROVIDES FLUID SOURCES FOR DEEP SLOW SLIP AND TREMOR IN SUBDUCTION ZONES

10.1130/abs/2020am-357702 ◽

2020 ◽

Author(s):

Cailey Condit ◽

◽

Victor Guevara ◽

Jonathan R. Delph ◽

Melodie French

Keyword(s):

Oceanic Crust ◽

Subduction Zones ◽

Slow Slip ◽

Fluid Sources ◽

Metamorphic Dehydration

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Os isotopic composition of western Aleutian adakites: Implications for the Re/Os of oceanic crust processed through hot subduction zones

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2020.10.009 ◽

2021 ◽

Vol 292 ◽

pp. 452-467

Author(s):

Rachel Bezard ◽

Simon Turner ◽

Bruce Schaefer ◽

Gene Yogodzinski ◽

Kaj Hoernle

Keyword(s):

Isotopic Composition ◽

Oceanic Crust ◽

Subduction Zones

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Seawater-leaching Testing for Arsenic and Heavy Metals in Tsunami Deposits Produced by the 2011 off the Pacific Coast of Tohoku Earthquake, Northeastern Japan

Journal of Geography (Chigaku Zasshi) ◽

10.5026/jgeography.123.835 ◽

2014 ◽

Vol 123 (6) ◽

pp. 835-853 ◽

Cited By ~ 5

Author(s):

Takahiro WATANABE ◽

Noriyoshi TSUCHIYA ◽

Shin-ichi YAMASAKI ◽

Ryoichi YAMADA ◽

Nobuo HIRANO ◽

...

Keyword(s):

Heavy Metals ◽

Pacific Coast ◽

Tohoku Earthquake ◽

Tsunami Deposits ◽

Northeastern Japan ◽

The Pacific

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Origin of Late Cenozoic Abaga–Dalinuoer basalts, eastern China: Implications for a mixed pyroxenite–peridotite source related with deep subduction of the Pacific slab

Gondwana Research ◽

10.1016/j.gr.2016.05.014 ◽

2016 ◽

Vol 37 ◽

pp. 130-151 ◽

Cited By ~ 23

Author(s):

Maoliang Zhang ◽

Zhengfu Guo

Keyword(s):

Eastern China ◽

Late Cenozoic ◽

The Pacific ◽

Pacific Slab

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Alteration and dehydration of subducting oceanic crust within subduction zones: implications for décollement step-down and plate-boundary seismogenesis

Earth Planets and Space ◽

10.1186/s40623-017-0635-1 ◽

2017 ◽

Vol 69 (1) ◽

Cited By ~ 7

Author(s):

Jun Kameda ◽

Sayako Inoue ◽

Wataru Tanikawa ◽

Asuka Yamaguchi ◽

Yohei Hamada ◽

...

Keyword(s):

Oceanic Crust ◽

Subduction Zones ◽

Plate Boundary ◽

Step Down

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Roles of Hydrothermal Circulations on Heat Flow in the Fore-arc, Northeast Japan Subduction Zone, A Numerical Modeling Study.

10.5194/egusphere-egu21-1958 ◽

2021 ◽

Author(s):

Dongwoo Han ◽

Changyeol Lee

Keyword(s):

Heat Transfer ◽

Heat Flow ◽

Oceanic Crust ◽

Numerical Models ◽

Accretionary Prism ◽

High Heat ◽

Pacific Plate ◽

Model Calculations ◽

The Pacific ◽

Japan Subduction Zone

Heat flow in the fore-arc, Northeast Japan shows characteristic highs and lows in the seaward and landward regions of the trench axis, respectively, compared to 50 mW/m2 that is constrained from the corresponding half-space cooling model (135 Ma). For example, the high average of 70 mW/m2 at the 150-km seaward region from the trench was observed while the low average of 30 mW/m2 at the 50-km landward region was. To explain the differences between the constraints and observations of the heat flow, previous studies suggested that the high heat flow in the seaward region results from the reactivated hydrothermal circulations in the oceanic crust of the Pacific plate along the developed fractures by the flexural bending prior to subduction. The low heat flow is thought to result from thermal blanket effect of the accretionary prism that overlies the cooled subducting slab by the hydrothermal circulations. To understand heat transfer in the landward region of the trench, a series of two-dimensional numerical models are constructed by considering hydrothermal circulations in the kinematically thickening accretionary prism that overlies the converging oceanic crust of the Pacific plate where hydrothermal circulations developed prior to subduction. The model calculations demonstrate no meaningful hydrothermal circulations when the reasonable bulk permeability of the accretionary prism(<10-14m2) is used; the thermal blanket effect significantly hinders the heat transfer, yielding only the heat flow of 10 mW/m2 in the landward region, much lower than the average of 30 mW/m2. This indicates that other mechanisms such as the expelled pore fluid by compaction of the accretionary prism play important roles in the heat transfer across the accretionary prism.

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Habitat Mapping for Human Well-Being: a tool for reducing risk in disaster-prone coastal environments and human communities

Geological Society London Special Publications ◽

10.1144/sp505-2021-26 ◽

2021 ◽

pp. SP505-2021-26

Author(s):

Yuri Oki ◽

Hiroshi Kitazato ◽

Toyonobu Fujii ◽

Soichiro Yasukawa

Keyword(s):

Salt Marshes ◽

Scale Up ◽

Well Being ◽

Coastal Ecosystems ◽

Indian Ocean Tsunami ◽

Important Species ◽

Coastal Marine ◽

Coastal Species ◽

Northeastern Japan ◽

The Pacific

AbstractCoastal ecosystems consist of diverse habitats, such as reed beds, salt marshes, mangrove swamps, tidal flats, river deltas, seagrass fields, coral reefs, sandy/rocky-shore beaches and other habitats that harbour biodiversity. The Great East Japan Earthquake of March 2011 caused severe damage to one-third of the fishing communities along the Pacific Ocean of northeastern Japan. Coastal species, such as seagrasses, function as nursery areas for commercially important species. Coastal ecosystems provide natural infrastructure for the prevention and reduction of hazardous events, a process known as ecosystem-based disaster risk reduction (Eco-DRR). The preparation of topographic and thematic maps of coastal marine environments is essential to establish and visualise the concept of Eco-DRR. Experience gained following the Japanese earthquake, as well as examples from Indonesia and Thailand in the wake of 2004 Indian Ocean tsunami showed that Eco-DRR is an affordable and sustainable approach. Dissemination of habitat maps should be further promoted as a means to ‘Build Back Better’. To scale up and promote Eco-DRR, scientists must work in a transdisciplinary manner and engage with society through understanding the roles of ecosystems by monitoring and analysing, providing solutions and raising the awareness of community and policy makers, enabling them to better implement Eco-DRR.

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