Back-arc basins such as the Lau at the Australian-Pacific plate boundary are of particular interest as productive centers of crustal formation. They host a diversity of crustal structure, compositions, and processes not found at mid-ocean ridges. Using geochemical data culled from PetDB and other sources from the Eastern Lau Spreading Center and the Valu Fa Ridge, Eason and Dunn propose that slab-derived water carried in the near-arc ridge system enhances mantle melting, as well as plays a role in magmatic differentiation and crustal accretion processes. Their model successfully predicts both major element compositional trends of erupted lavas, and shows that slab-derived water close to the arc suppresses plagioclase crystallization leading to the formation of an ultramafic crust with high seismic velocities.
Fig 3. (a) Multibeam bathymetry of the ELSC and VFR showing sample locations (black dots). (b) Axial depth profile from Martinez et al. (2006). (c)–(e) Along-axis compositional variation of MgO and representative trace element ratios, color-coded by ridge segment.
Eason, D.E. and Dubb, R.A. (2015) Petrogenesis and structure of oceanic crust in the Lau back-arc basin. EPSL 429: 128-138. DOI: 10.1016/j.epsl.2015.07.065