Back-Arc Spreading Centers and Superfast Subduction: The Case of the Northern Lau Basin (SW Pacific Ocean)

Abstract

The Lau Basin is a back-arc region formed by the subduction of the Pacific plate below the Australian plate. We studied the regional morphology of the back-arc spreading centers of the Northern Lau basin, and we compared it to their relative spreading rates. We obtained a value of 60.2 mm/year along the Northwest Lau Spreading Centers based on magnetic data, improving on the spreading rate literature data. Furthermore, we carried out numerical models including visco-plastic rheologies and prescribed surface velocities, in an upper plate-fixed reference frame. Although our thermal model points to a high temperature only near the Tonga trench, the model of the second invariant of the strain rate shows active deformation in the mantle from the Tonga trench to ~800 km along the overriding plate. This explains the anomalous magmatic production along all the volcanic centers in the Northern Lau Back-Arc Basin.

Imaging the Plumbing System of the Asymmetric Vavilov Spreading Ridge (Tyrrhenian Sea Back‐Arc Basin) From Combined Bathymetry and Magnetic Data

“…The lack of a clear symmetry of the magnetic strips of VBAB as well as the occurrence of younger rocks on the eastern side of the BAB suggest that the N-S ridge structures of VBAB represent basaltic injections occurring along dikes formed in discrete time phases rather than associated with an active seafloor spreading as observed in other BABs (i.e., Marsili basin and North Lau Basin; Cocchi et al, 2009;Palmiotto, Ficini, et al, 2022). This agrees with more general geodynamic models suggesting that VBAB is not a classical, symmetric BAB but a basin dominated by mantle-exhumation processes related to the eastward migration of the subducting slab (Magrini et al, 2022;Manu-Marfo et al, 2019;Milia et al, 2017;Prada et al, 2016).…”

Modeling subduction with extremely fast trench retreat

“…A common assumption is that numerical models will produce reasonable results as long as the convergence rate is held constant while changing the velocity of the subducting plate. For example, some recent studies applied the convergence rate to the subducting plate while keeping the trench and overriding plate stationary to model the Tonga slab subduction (Palmiotto et al, 2022). To challenge this assumption, we ran three models with varying Pacific Plate velocities and trench retreat rates, maintaining a total convergence rate of 23 cm/yr (Fig.…”

Editorial of Special Issue “Tectonics and Morphology of Back-Arc Basins”

“…Palmiotto et al [1] focus on the back-arc spreading centers of the Northern Lau basin (Tonga subduction system). Based on the regional morphology and magnetic data, they improved our knowledge on spreading center velocities.…”