scholarly journals Molybdenum isotopes unmask slab dehydration and melting beneath the Mariana arc

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hong-Yan Li ◽  
Rui-Peng Zhao ◽  
Jie Li ◽  
Yoshihiko Tamura ◽  
Christopher Spencer ◽  
...  

AbstractHow serpentinites in the forearc mantle and subducted lithosphere become involved in enriching the subarc mantle source of arc magmas is controversial. Here we report molybdenum isotopes for primitive submarine lavas and serpentinites from active volcanoes and serpentinite mud volcanoes in the Mariana arc. These data, in combination with radiogenic isotopes and elemental ratios, allow development of a model whereby shallow, partially serpentinized and subducted forearc mantle transfers fluid and melt from the subducted slab into the subarc mantle. These entrained forearc mantle fragments are further metasomatized by slab fluids/melts derived from the dehydration of serpentinites in the subducted lithospheric slab. Multistage breakdown of serpentinites in the subduction channel ultimately releases fluids/melts that trigger Mariana volcanic front volcanism. Serpentinites dragged down from the forearc mantle are likely exhausted at >200 km depth, after which slab-derived serpentinites are responsible for generating slab melts.

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Takeshi Kuritani ◽  
Kenji Shimizu ◽  
Takayuki Ushikubo ◽  
Qun-Ke Xia ◽  
Jia Liu ◽  
...  

AbstractHydrogen isotopes have been widely used as powerful tracers to understand the origin of terrestrial water and the water circulation between the surface and the deep interior of the Earth. However, further quantitative understanding is hindered due to a lack of observations about the changes in D/H ratios of a slab during subduction. Here, we report hydrogen isotope data of olivine-hosted melt inclusions from active volcanoes with variable depths (90‒550 km) to the subducting Pacific slab. The results show that the D/H ratio of the slab fluid at the volcanic front is lower than that of the slab fluid just behind the volcanic front. This demonstrates that fluids with different D/H ratios were released from the crust and the underlying peridotite portions of the slab around the volcanic front. The results also show that the D/H ratios of slab fluids do not change significantly with slab depths from 300 to 550 km, which demonstrates that slab dehydration did not occur significantly beyond the arc. Our estimated δD‰ value for the slab materials that accumulated in the mantle transition zone is > − 90‰, a value which is significantly higher than previous estimates.


Geology ◽  
2018 ◽  
Vol 46 (3) ◽  
pp. 239-242 ◽  
Author(s):  
Chuan-Zhou Liu ◽  
Yang Xu ◽  
Fu-Yuan Wu

Minerals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 339 ◽  
Author(s):  
Yang Xu ◽  
Chuan-Zhou Liu

Compositions of highly siderophile elements (HSEs) in forearc mantle have been little studied and effects of slab dehydration on their abundances in forearc mantle remains unclear. This study reports two different kinds of HSE patterns for peridotites from a New Caledonia forearc ophiolite. The Group-I samples show relatively flat patterns of Ir-group-platinum-group elements (IPGEs) and enrichment of Pt over Pd. Such patterns imply that interstitial sulfides were significantly removed through melt extraction, whereas sulfides enclosed within silicates were mostly unaffected. Meanwhile, Pt-Fe alloys were generated, resulting in suprachondritic Pt/Pd ratios. In contrast, the Group-II samples display convex HSE patterns and are depleted in all HSEs except for Ru, yielding strongly positive Ru anomalies. This indicates that both enclosed and interstitial sulfides were substantially consumed, whereas chromite was generated to stabilize Ru. Compared to abyssal peridotites, subduction-related peridotites commonly have stronger fractionation in the HSEs. Therefore, the HSE data of mantle peridotites are potentially able to discriminate the tectonic settings of ophiolites.


2013 ◽  
Vol 342 ◽  
pp. 94-109 ◽  
Author(s):  
Marina Martindale ◽  
Susanne Skora ◽  
Jonathan Pickles ◽  
Tim Elliott ◽  
Jonathan Blundy ◽  
...  

2010 ◽  
Vol 52 (2) ◽  
pp. 257-278 ◽  
Author(s):  
S. W. Parman ◽  
T. L. Grove ◽  
K. A. Kelley ◽  
T. Plank
Keyword(s):  

2019 ◽  
Vol 93 (S2) ◽  
pp. 17-17
Author(s):  
Chuanzhou LIU ◽  
Yang XU ◽  
Fuyuan WU

1997 ◽  
Vol 102 (B7) ◽  
pp. 14991-15019 ◽  
Author(s):  
Tim Elliott ◽  
Terry Plank ◽  
Alan Zindler ◽  
William White ◽  
Bernard Bourdon

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