Hydrothermal activity and volcano distribution along the Mariana arc

[1] Submarine volcanic arcs extend for fully a third of the length of the mid-ocean ridge system, but systematic investigation of hydrothermal venting on those arcs is sparse. Here we report on the distribution of hydrothermal activity along the intraoceanic Mariana arc. We identify 76 volcanic edifices along 1370 km of arc, grouped into 60 "volcanic centers,'' of which at least 26 (20 submarine) are hydrothermally or volcanically active. The overall volcanic center density is 4.4/100 km of arc, and that of active centers is 1.9/100 km. An equal length of the Tonga-Kermadec arc holds fewer centers, 2.9/100 km, but a similar density of active centers, 1.8/100 km. The lower percentage of active centers on the Mariana arc results from its having both fewer caldera volcanoes, since on both arcs calderas are twice as likely as cones to be active, and a lower percentage of active calderas and cones. Active centers are found from 80 to 230 km above the subducting Pacific slab, and a quarter lie behind the arc front. The frequency distribution of center spacing along the arc front peaks between 20 and 30 km and shows the asymmetric, long-tail shape typical for many other arcs, especially those with volcano populations >similar to 20. There is no evidence for a regular spacing of volcanic centers. Using the new Mariana data and recent data from the Tonga-Kermadec arc, we estimate that all intraoceanic arcs combined may contribute hydrothermal emissions equal to similar to 10% of that from the global mid-ocean ridge.