A Dual‐Level Magmatic System Beneath the East Pacific Rise, 9°N

Data from three co‐located wide‐angle ocean‐bottom seismograph experiments were used to make a new two‐dimensional tomographic image of the East Pacific Rise at 9°N. The upper half of the crustal magmatic system has a different seismic structure than the lower half, presumably corresponding with dif...

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Bibliographic Details
Published in:Geophysical research letters 2022-09, Vol.49 (18), p.n/a
Main Author: Dunn, Robert A.
Format: Article
Language:English
Subjects:
Crustal structure
Crustal thickness
East Pacific Rise
Heat loss
Isotherms
Lava
Ocean circulation
Oceanic crust
Oceans
Plates
Ridges
seismic anisotropy
seismic tomography
Seismographs
Seismology
Storage
Thickness
Upwelling
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Summary:Data from three co‐located wide‐angle ocean‐bottom seismograph experiments were used to make a new two‐dimensional tomographic image of the East Pacific Rise at 9°N. The upper half of the crustal magmatic system has a different seismic structure than the lower half, presumably corresponding with differences in melt storage and crustal cooling. The upper region is narrow (∼4.5 km wide at 2–3 km depth bsf) and estimated to contain higher melt fractions; the lower region broadens with depth and contains lower melt fractions. The shape of the system suggests steeply‐dipping isotherms and relatively stronger hydrothermal circulation in the upper gabbroic section of the crust, with moderately flattening isotherms and less circulation in the lower gabbroic section. Plain Language Summary Along mid‐ocean ridges two lithospheric plates separate, inducing mantle upwelling and pressure‐release melting. The melt buoyantly rises toward the surface where it enters a crustal magmatic system. Hydrothermal circulation and conductive heat loss cool the magmatic system and the melts solidify to form new oceanic crust. A seismological study is used to determine the size and internal structure of the crustal magmatic system, the amount of melt in the mantle as it enters the crust, and the final destination of the melt recorded by crustal thickness and crustal structure. Key Points A new seismic tomographic image of the East Pacific Rise reveals the average structure of the sub‐ridge magmatic system The upper half of the magmatic system is narrow, melt‐rich, and flanked by steeply‐dipping sub‐solidus isotherms The lower half has lower melt fractions and widens with depth as isotherms begin to flatten
ISSN:0094-8276
1944-8007
DOI:10.1029/2022GL097732