The boron and lithium cycles

Hydrous fluids, which are released during the breakdown of hydrous minerals within a subducting slab, have the potential to transport elements through the mantle wedge. This process leads to characteristic geochemical features within associated volcanic rocks, which may be interpreted as slab-induced element signatures. Boron as well as lithium are typically enriched within IAB relative to MORB and mantle. In analogy to LIL-elements, the variation of B and Li and their isotopes within IAB as a function of slab depths are assumed to result from fractionation processes between B- and Li-containing minerals and fluids. To improve our understanding of geochemical processes in subduction zones and IAB-signatures and used for continuing numerical simulations, we currently perform high-pressure experiments for the determination of B-, Li-, δ¹¹B-, δ⁷Li-distributions between relevant minerals and coexisting fluids. Recently, we have made a significant progress in the prediction of B and Li isotope solid-fluid fractionation by first-principles calculation, which result in excellent agreement to experimentally determined fractionation data.
 

Contact: B. Wunder, W. Heinrich, R.L. Romer, S. Jahn