Abstract
AbstractWe present a spatial analysis of volcano distribution and morphology in the young, intraoceanic Mariana Arc. Both the quality of fit to idealized 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 centers 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 nonvolcanic 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.
Highlights
Locations of volcanic edifices provide an opportunity to explore magma generation and transport beneath volcanic arcs (England & Katz, 2010)
The effect of including all the edifices of data set B08 is a small circle with significantly larger misfit to the Mariana Arc than previously recognized. 4.1.2
Comparison of the great and small circles for each segment with the AICc shows that segmented great circles are consistently better fitted to the arc than segmented small circles (Table 2)
Summary
Locations of volcanic edifices provide an opportunity to explore magma generation and transport beneath volcanic arcs (England & Katz, 2010). England et al (2004) approximated the distribution of arc volcanoes as small circles to define an average depth to slab (H) in each arc for comparison with other subduction dynamic parameters. This approach led them to propose that the locus of melting is related to the descent speed of slabs, from which it was inferred that the thermal structure of the mantle wedge is an additional key factor in localizing melting and, volcano location (England et al, 2004; England & Katz, 2010). Despite broadly similar H values within and between arcs (England & Katz, 2010; Jarrard, 1986; Wilson et al, 2014), with an average close to 105 km, it should be no surprise that there are wide variations, from about 60 to 200 km, in H within single subduction zones, often for volcanoes is close proximity (Pacey et al, 2013; Syracuse & Abers, 2006)
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