Boron Isotopes as a Tracer of Subduction Zone Processes

This chapter reviews recycling of boron (B) and its isotopes in subduction zones. It discusses the profound changes in B concentrations and B isotope ratios of various materials involved in convergent margin evolution, in particular highlighting the fate and evolution of progressively dehydrating subducting slabs and the behavior of B during burial and subsequent metamorphism. We review various models used to parameterize these complex and often poorly understood processes and critically evaluate the available data from the literature. We proceed by reviewing B isotope data from mafic arc volcanic rocks and explore systematic variations with subduction zone geometry as well as familiar geochemical tracers of subduction processes. Finally, the role of serpentinisation in the mantle wedge is discussed in the light of new geochemical and petrological insights on the importance of serpentinites and subduction erosion. We provide recommendations for further research on B isotopes in subduction zones and directions where we think this exciting stable isotope tracer may make the biggest impact.