Evaluating the role of the overriding-plate tectonics on the position of arc volcanism

The mechanisms that have been proposed to control the position of volcanic arcs in subduction zones can be broadly divided into two categories. Geophysical and geodynamical studies emphasize a “deep-thermal control” related to the thermal state of the subducting plate and the mantle wedge, whereas field-based regional studies highlight a “tectonic control” driven by deformation and the tectonic configuration of the overriding plate. While the deep-thermal controls have been widely investigated statistically at the global scale, the influence of overriding-plate tectonics on arc position remains underexplored. 

In this study, we investigate both perspectives for the majority of present-day subduction zones, with a particular focus on tectonic controls. We first build an accurate dataset of the position of the Holocene arc volcanoes, using the Smithsonian Institution Global Volcanism Program, with respect to the subducting plate as defined by the Slab2.0 model (Hayes et al., 2018). We then construct a dataset describing the mean tectonic regime of arc regions by inverting the stress state from focal mechanisms compiled from global and regional catalogs, complemented by information on major active geological structures near the arc. These two datasets, arc location relative to the subducting plate and tectonic regime in the arc vicinity, are combined to address the dominant control on the volcanic arc position. 

In regions such as those spanning from the Mariana Islands to the southern Kuril Islands and the Tonga-Kermadec subduction zones, we find that slab-top depth beneath the volcanic front (i.e., the volcanoes closest to the trench, H_VF) increases with slab age and decreases with increasing subduction velocity. These trends are consistent with the volcanic front position being primarily controlled by the thermal state near the slab top or within the proximal mantle wedge. 

In contrast, in regions lacking trends indicative of deep-thermal controls (i.e., Indonesia), another control likely dominates. In particular, we show that in Mexico-Central America and the Ryukyu-Nankai subduction zones, H_VF values vary with the tectonic regime: H_VF tends to be slightly lower in extensional settings than in compressional ones. Our interpretation is that, in these regions, deep-thermal controls are overprinted by the tectonic regime of the overriding plate. 

For a large subset of regions, including the Andes and the Alaska-Aleutian subduction zones, we do not identify any clear signal.

At the global scale, arcs governed by deep-thermal controls seem to occur mostly where the overriding plate is oceanic, whereas those whose position varies with the tectonic regime are mainly found in continental settings, suggesting the influence of the overriding-plate nature.