Variation in Upper Plate Crustal and Lithospheric Mantle Structure in
the Greater and Lesser Antilles from Ambient Noise Tomography
Abstract
The crust and upper mantle structure of the Greater and Lesser Antilles
Arc provides insights into key subduction zone processes in a unique
region of slow convergence of old slow-spreading oceanic lithosphere. We
use ambient noise tomography gathered from island broadband seismic
stations and the temporary ocean bottom seismometer network installed as
part of the VoiLA experiment to map crustal and upper mantle shear-wave
velocity of the eastern Greater Antilles and the Lesser Antilles Arc. We
find sediment thickness, based on the depth to the 2.0 km/s contour in
the Grenada and Tobago basins up to 15 km in the south, with thinner
sediments near the arc and to the north. We observe thicker crust, based
on the depth to the 4.0 km/s velocity contour, beneath the arc platforms
with the greatest crustal thickness of around 30 km, likely related to
crustal addition from arc volcanism through time. There are distinct low
velocity zones (4.2-4.4 km/s) in the mantle wedge (30-50 km depth),
beneath the Mona Passage, Guadeloupe-Martinique, and the Grenadines. The
Mona passage mantle anomaly may be related to ongoing extension there,
while the Guadeloupe-Martinique and Grenadine anomalies are likely
related to fluid flux, upwelling, and/or partial melt related to nearby
slab features. The location of the Guadeloupe-Martinique anomaly is
slightly to the south of the obliquely subducted fracture zones. This
feature could be explained by either three-dimensional mantle flow, a
gap in the slab, variable slab hydration, and/or melt dynamics including
ponding and interactions with the upper plate.