Upper Plate Stress Controls the Distribution of Mariana Arc Volcanoes

Abstract

We present a spatial analysis of volcano distribution and morphology in the young, intraoceanic Mariana Arc. Both the quality of fit to idealised models and the divergence from those ideals indicate that Mariana Arc volcanoes are arranged into five great circle segments, rather than a single small circle or multiple small circles. The alignment of magmatic centres suggests that magma transport is controlled by the stress regime in the deep crust and/or lithospheric mantle of the Philippine Sea Plate, into which the arc is emplaced, and that arc‐normal tension is the dominant process operating in the deep lithosphere along the whole arc. Volcano morphologies indicate that the stress regime in the shallow crust varies between arc‐normal tension and compression, which also implies that the stress field can vary with depth in the arc lithosphere. We show that this horizontal and vertical stress partitioning can be related to the changing dip of the subducting plate and the breadth of the zone where it is coupled with the overriding plate. The variation in stress regime is consistent with both the distribution of seismicity in the Philippine Sea Plate and with the structural fabrics of the non‐volcanic part of the plate margin to the south. Our analysis suggests that the upper plate exerts the principal control on the distribution of volcanoes in the Mariana Arc. Where tension in the deeper parts of arc lithosphere is sufficiently concentrated then a distinct volcanic front is produced.