Sub‐Lithospheric Small‐Scale Convection Tomographically Imaged Beneath the Pacific Plate

Autor: Zachary C. Eilon, Lun Zhang, James B. Gaherty, Donald W. Forsyth, Joshua B. Russell
Jazyk: angličtina
Rok vydání: 2022
Předmět:
Zdroj: Geophysical Research Letters, Vol 49, Iss 18, Pp n/a-n/a (2022)
Druh dokumentu: article
ISSN: 1944-8007
0094-8276
DOI: 10.1029/2022GL100351
Popis: Abstract Small‐scale convection beneath the oceanic plates has been invoked to explain off‐axis nonplume volcanism, departure from simple seafloor depth‐age relationships, and intraplate gravity lineations. We deployed 30 broadband ocean bottom seismometer stations on ∼40 Ma Pacific seafloor in a region notable for gravity anomalies, measured by satellite altimetry, elongated parallel to plate motion. P‐wave teleseismic tomography reveals alternating upper mantle velocity anomalies on the order of ±2%, aligned with the gravity lineations. These features, which correspond to ∼300°–500°K lateral temperature contrast, and possible hydrous or carbonatitic partial melt, are—surprisingly—strongest between 150 and 260 km depth, indicating rapid vertical motions through a low‐viscosity asthenospheric channel. Coherence and admittance analysis of gravity and topography using new multibeam bathymetry soundings substantiates the presence of mantle density variations, and forward modeling predicts gravity anomalies that qualitatively match observed lineations. This study provides observational support for small‐scale convective rolls beneath the oceanic plates.
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