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Crustal Structure Across the Extinct Mid‐Ocean Ridge in South China Sea From OBS Receiver Functions: Insights Into the Spreading Rate and Magma Supply Prior to the Ridge Cessation
Author(s) -
Hung Tran Danh,
Yang Ting,
Le Ba Manh,
Yu Youqiang,
Xue Mei,
Liu Baohua,
Liu Chenguang,
Wang Jian,
Pan Mohan,
Huong Phan Thien,
Liu Fang,
Morgan Jason P.
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl089755
Subject(s) - geology , seafloor spreading , crust , ridge , oceanic crust , mid ocean ridge , seismology , seismometer , detachment fault , magma chamber , ultramafic rock , accretion (finance) , mid atlantic ridge , paleontology , magma , subduction , tectonics , volcano , physics , astrophysics , extensional definition
The crust near an extinct mid‐ocean ridge provides unique constraints on how its accretion and deformation responded to the cessation of spreading. Here we present crustal thickness and Vp / Vs measurements beneath 11 Ocean Bottom Seismograph sites that cross the South China Sea's extinct spreading axis. We find that the oceanic crust, which generally had only slight thickness changes once spreading started, abruptly thins at sites close to the extinct ridge axis. Abnormally high Vp / Vs ratios are obtained at several sites south of the ridge, indicating the presence of serpentine. These observations imply that, in its final stage, spreading changed to an ultraslow accretion style. As the axial crust thinned, normal faults and/or detachment faults began to form. Water could penetrate more deeply through these faults, and large fault slip could raise ultramafic peridotites to near or at the seafloor, creating favorable conditions for their enhanced serpentinization.