Premium
Hydration of marginal basins and compositional variations within the continental lithospheric mantle inferred from a new global model of shear and compressional velocity
Author(s) -
Tesoniero Andrea,
Auer Ludwig,
Boschi Lapo,
Cammarano Fabio
Publication year - 2015
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2015jb012026
Subject(s) - geology , lithosphere , mantle (geology) , subduction , craton , geophysics , seismology , tectonics
We present a new global model of shear and compressional wave speeds for the entire mantle, partly based on the data set employed for the shear velocity model savani . We invert Rayleigh and Love surface waves up to the sixth overtone in combination with major P and S body wave phases. Mineral physics data on the isotropic δ ln V S / δ ln V P ratio are taken into account in the form of a regularization constraint. The relationship between V P and V S that we observe in the top 300 km of the mantle has important thermochemical implications. Back‐arc basins in the Western Pacific are characterized by large V P / V S and not extremely low V S at ∼150 km depth, consistently with presence of water. Most pronounced anomalies are located in the Sea of Japan, in the back‐arc region of the Philippine Sea, and in the South China Sea. Our results indicate the effectiveness of slab‐related processes to hydrate the mantle and suggest an important role of Pacific plate subduction also for the evolution of the South China Sea. We detect lateral variations in composition within the continental lithospheric mantle. Regions that have been subjected to rifting, collisions, and flood basalt events are underlain by relatively large V P / V S ratio compared to undeformed Precambrian regions, consistently with a lower degree of chemical depletion. Compositional variations are also observed in deep lithosphere. At ∼200 km depth, mantle beneath Australia and African cratons has comparable positive V S anomalies with other continental regions, but V P is ∼1% higher.