Back-arc basins: A global view from geophysical synthesis and analysis

The present worldwide study of 31 off-shore back-arc basins and subbasins (BABs) identifies their principal characteristics based on a broad spectrum geophysical subduction-related parameters. This synthesis is next used to identify trends in evolution the for improving our understanding subduction systems general. analysis, plate configuration, demonstrates that fate are essentially controlled by nature overriding plate, which controls lithosphere thermo-compositional structure rheology. governs length extensional zone settings along trench, efficiency stretching, BAB crustal structure, its buoyancy bathymetry. Subduction dip angle apparently location slab melting roll-back with feedback link other By tectonic (the downgoing always oceanic) split into active BABs formed ocean-ocean, arc-ocean, continent-ocean convergence, extinct basins. characteristics, continental plates subdivided without seafloor spreading, Pacific, possibly oceanic plates, non-Pacific reworked or arc fragments. Six types distinctly different. Extension above steeply dipping old preferentially subducting nearly westwards, forms large deep thin oceanic-type crust. In contrast, form at small opening rates often shallow younger random orientation; these have size, bathymetry, hyperextended transitional ~20 km thick arc- continental-type crust typical passive margins. presence 2–5 high-Vp lowermost layer, characteristic all settings, indicates importance magmatic underplating growth. Conditions required initiation basin transition from stretching depend plate. evolve spreading. require long spreading duration (>8 cm/y) thinning factor 2.8–5.0 progress extension spreading; such does not happen behind (<45 o ) young (<40 My) also determines after termination extension: Pacific towards “normal” oceans, while low heat flow likely preserve affinity. do follow cooling model predictions. Distinctly different signatures mid-ocean ridges caused principally dynamics.