Slab steepening and rapid mantle wedge replacement during back-arc rifting in the New Hebrides

The effects of the composition and angle of the subducting slab and mantle wedge flow on tectonic and magmatic processes in island arcs and associated back-arcs are poorly understood. Here we analyse the ages and compositions of submarine lavas from the flanks and the floor of the back-arc Futuna Trough some 50 km east of Tanna Island in the New Hebrides arc front. Whereas >2.5 Ma-old back-arc lavas formed from an enriched mantle source strongly metasomatized by a slab component, the younger lavas show less slab input into a depleted mantle wedge. The input of the slab component decreased over the past 2.5 million years while the enriched mantle was replaced by depleted peridotite. The change of Futuna Trough lava compositions indicates rapid (10 s of km/million years) replacement of the mantle wedge by corner flow and slab steepening due to rollback, causing extensional stress and back-arc rifting in the past 2.5 million years.

Physical applications of GPS geodesy: a review

Geodesy, the oldest science, has become an important discipline in the geosciences, in large part by enhancing Global Positioning System (GPS) capabilities over the last 35 years well beyond the satellite constellation's original design. The ability of GPS geodesy to estimate 3D positions with millimeter-level precision with respect to a global terrestrial reference frame has contributed to significant advances in geophysics, seismology, atmospheric science, hydrology, and natural hazard science. Monitoring the changes in the positions or trajectories of GPS instruments on the Earth's land and water surfaces, in the atmosphere, or in space, is important for both theory and applications, from an improved understanding of tectonic and magmatic processes to developing systems for mitigating the impact of natural hazards on society and the environment. Besides accurate positioning, all disturbances in the propagation of the transmitted GPS radio signals from satellite to receiver are mined for information, from troposphere and ionosphere delays for weather, climate, and natural hazard applications, to disturbances in the signals due to multipath reflections from the solid ground, water, and ice for environmental applications. We review the relevant concepts of geodetic theory, data analysis, and physical modeling for a myriad of processes at multiple spatial and temporal scales, and discuss the extensive global infrastructure that has been built to support GPS geodesy consisting of thousands of continuously operating stations. We also discuss the integration of heterogeneous and complementary data sets from geodesy, seismology, and geology, focusing on crustal deformation applications and early warning systems for natural hazards.

The coral sea: physical environment, ecosystem status and biodiversity assets

The Coral Sea, located at the southwestern rim of the Pacific Ocean, is the only tropical marginal sea where human impacts remain relatively minor. Patterns and processes identified within the region have global relevance as a baseline for understanding impacts in more disturbed tropical locations. Despite 70 years of documented research, the Coral Sea has been relatively neglected, with a slower rate of increase in publications over the past 20 years than total marine research globally. We review current knowledge of the Coral Sea to provide an overview of regional geology, oceanography, ecology and fisheries. Interactions between physical features and biological assemblages influence ecological processes and the direction and strength of connectivity among Coral Sea ecosystems. To inform management effectively, we will need to fill some major knowledge gaps, including geographic gaps in sampling and a lack of integration of research themes, which hinder the understanding of most ecosystem processes.