Boron isotope compositions of coexisting kornerupine and tourmaline in high-grade metabasic rocks: an example from Akarui Point, Lützow-Holm Complex, East Antarctica

Boron isotope compositions were measured in kornerupine and tourmaline from lenses consisting primarily of kornerupine, plagioclase corundum. The occur within hornblende-gneiss or along the boundary between this gneiss an amphibolite lens at Akarui Point Lützow-Holm Complex, Prince Olav Coast, East Antarctica. peak metamorphic conditions have been estimated to be ~ 800-900 oC 8-11 kbar. δ11B which is interpreted a stable phase peak, are -11.6 ± 0.4 -7.8 0.5 ‰ -9.8 0.3 -6.1 0.2 two different samples. Grains prograde included corundum yielded = -2.1 +0.6 ‰, secondary replacing -4.6 -3.7 ‰. Therefore, isotopic fractionation tourmaline, △11BTur–Krn (= δ11BTur - δ11BKrn), average host +6.7 1.5 indicate equilibrium on basis previous studies minerals kornerupine-prismatine series. values obtained whole rock MORB mantle rocks some sedimentary rocks, similar blackwall tourmalines that crystallized during decompression stage following high-pressure metamorphism. We infer syn-metamorphic B-bearing fluid present kornerupine-plagioclase-corundum likely sourced mixture sedimentary, mafic ultramafic lithologies subduction setting. metabasic meta-ultramafic found could as remnant mixing zone Ediacaran Cambrian channel.