Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 166. New ocean crust is continuously created where tectonic plates diverge. A distinctive type of oceanic crust is formed by back-arc spreading systems that parallel oceanic island arcs on the side away from the subducting plate. Volatile-rich and spatially variable, back-arc spreading systems are a natural laboratory for multi-disciplinary studies of seafloor...