Re-examination of the boron isotopic composition of tourmaline from the Lavicky granite, Czech Republic, by secondary ion mass spectrometry: back to normal. Critical comment on “Chemical and boron isotopic compositions of tourmaline from the Lavicky leucogranite, Czech Republic” by S.-Y. Jiang et al., Geochemical Journal, 37, 545-556, 2003

Abstract

A re-examination of tourmaline from the Lavicky leucogranite by secondary ion mass spectrometry revealed a very homogeneous boron isotopic composition both on grain scale and on the outcrop scale. Tourmaline from tourmaline-quartz-feldspar orbicules and from tourmaline-quartz-feldspar veins show identical boron isotopic compositions of δ11B=-10.77 ± 1.24‰. This value is similar to the value for average continental crust. A comparison of the Lavicky tourmaline with δ11B values of magmatic tourmaline available in the literature additionally demonstrates its rather ordinary character. The extremely negative δ11B values and the boron isotopic fractionation during the magmatic-hydrothermal transition proposed in an earlier study (Jiang et al., 2003) are not supported by our data. The source region of the Lavicky granite and its geochemical evolution did probably not involve any evaporitic material.