Author: Angharad Hills
Last saved by: Tamzin Anderson

A. Analytical Methods

Compositions of Tur were determined using a Cameca SX 51 electron microprobe equipped with five wavelength-dispersive spectrometers (Mineralogisches Institut, Heidelberg). Operating conditions were 20 nA beam current and 15 kV acceleration voltage. The electron beam was defocused to 5 μm. A modified matrix correction was applied assuming stoichiometric oxygen and all non-measured components to be B_2O_3. The accuracy of the electron microprobe analyses of Tur and the correction procedure was checked by measuring three samples of reference tourmaline (98144: elbaite, 108796: dravite, 112566: schorl, Dyar et al., 1998, 2001). Under the described conditions, analytical errors on all analyses are ±1% relative for major elements and ±5 % relative for minor elements. A detailed description of the applied electron microprobe techniques for Tur analysis is given in Kalt et al. (2001).

Concentrations of H, Li, Be and B in Tur were measured by secondary ion mass spectrometry (SIMS) with a modified Cameca IMS 3f ion microprobe at the Mineralogisches Institut, Heidelberg, equipped with a primary beam mass filter. Secondary ions ^7Li, ^9Be and ^11B were collected under an ion-imaged field of 150 μm diameter (Kalt et al., 2001). Hydrogen was analysed with a nominal imaged field of 25 μm, reduced to ~12 μm by using field aperture #2 (d = 750 μm). Magnetic field coils were used to compensate for (stray) magnetic fields and water contamination was further reduced using a cold-trap cooled with liquid nitrogen attached to the sample chamber of the IMS 3f . Due to the high H concentration in tourmalines the H analyses were performed at a constant beam current of 20 nA. Except for the constant beam current the method is described in Ludwig & Stalder (2007).

The relative ion yields (RIY) for H and B were determined using three different tourmalines as reference material: elbaite (98144), dravite (108796) and schorl (112566). The relative reproducibility (1σ) of the analyses of B was <1 %. For Li the reference material was NIST SRM 610 (Pearce et al., 1997) with a relative reproducibility of <1 %. The accuracy is limited by matrix effects and the uncertainty of the element concentrations in the reference material; the relative uncertainty is estimated to be <25 % for H, <20 % for Li and <10 % for B (Kalt et al., 2001). Between 6 and 17 Li, Be and B analyses and 3 to 6 H analyses were performed on Tur in each sample. However, note that the determination of the accurate amount of B cations per formula unit requires a full chemical analysis including H_2O and Li_2O contents and Fe^2+/Fe^3+ ratios. The amount of B calculated with all Fe as Fe^2+ decreases by 0.01 cpfu per 1 wt% FeO converted to Fe_2O_3.

Boron isotope ratios of Tur were also measured with the Heidelberg Cameca IMS 3f. Primary ion beam was ^16O^− accelerated to 10 keV with a beam current of 1 nA, resulting in count rates for ^11B of ~2 x 10^5 s^−1 and ~5 x 10^4 s^−1 for ^10B on Tur, collected by a single electron multiplier. Diameter of the 1 nA spot was 5 − 10 μm. The energy window was set to 50 eV and no offset was applied. 50 cycles were measured on each analysis spot with counting times of 3.307 s and 1.660 s on ^10B and ^11B, respectively. Presputtering lasted for 5 min and settling time between two different masses was 200 ms, resulting in total analysis time for one spot of approximately 10 min. Internal precision of a single analysis was ~1 ‰ (2σ). Boron isotopic compositions of samples are reported in delta notation (δ^11B in ‰) relative to the NBS-SRM 951 accepted value (Catanzaro et al., 1970). Instrumental mass fractionation was corrected by using three samples of proposed reference tourmaline (98114: elbaite, 108796: dravite, 112566: schorl; Leeman & Tonarini, 2001). Reproducibility of measured isotope ratios during the analytical session (eight days) was ±1.0 ‰ (2σ).

Raman spectra were obtained by means of a Horiba Jobin Yvon LabRam-HR800 spectrometer equipped with Olympus BX41 optical microscope, a grating with 1800 grooves per mm, and Peltier-cooled charge-coupled device (CCD) detector. Spectra were excited with the He-Ne 632.8 nm emission. The laser power was ~8 mW, which is well below the threshold for any heating effects that hypothetically could be caused by intense local absorption of the laser light. With confocal arrangement of the optical beam path, and using the Olympus 100x objective (numerical aperture 0.9), the lateral resolution was on the order of 1.5 μm. Wavenumber calibration was done using the Rayleigh line and neon lamp emissions. The wavenumber accuracy was better than 0.5 cm^−1 and the spectral resolution was ~0.8 cm^−1. For reference spectra and band assignment of coesite see Sharma et al. (1981) and Boyer et al. (1985), and for a description of the α-quartz spectrum see Etchepare et al. (1974). More experimental details are given in Nasdala et al. (2006).

References
Boyer, H., Smith, D.C., Chopin, C. & Lasnier, B. 1985. Raman microprobe (RMP) determinations of natural and synthetic coesite. Physics and Chemistry of Minerals, 12, 45–48.
Catanzaro, F.J., Champion, C.E., Garner, E.L., Marinenko, G., Sappenfield, K.M. & Shields, W.R. 1970. Boric acid: isotopic and assay standard reference materials. In: Boric Acid. National Bureau of Standards (US) Special Publications Series 206, 17, 1–70.
Dyar, M.D., Taylor, M.E., Lutz, T.M., Francis, C.A., Guidotti, C.V. & Wise, M. 1998. Inclusive chemical characterization of tourmaline: Mössbauer study of Fe valence and site occupancy. American Mineralogist, 83, 848–864.
Dyar, M.D., Wiedenbeck, M., Robertson, D., et al. 2001. Reference minerals for the microanalysis of light elements. Geostandards Newsletter, 25, 441–463.
Etchepare, J., Merian, M. & Smetankine, L. 1974. Vibrational normal modes of SiO_2. I. α & β quartz. Journal of Chemical Physics, 60, 1873–1876.
Kalt, A., Schreyer, W., Ludwig, T., Prowatke, S., Bernhardt, H.-J. & Ertl, A. 2001. Complete solid solution between magnesian schorl and lithian excess-boron olenite in a pegmatite from the Koralpe (eastern Alps, Austria). European Journal of Mineralogy, 13, 1191–1205.
Leeman, W.P. & Tonarini, S. 2001. Boron isotopic analysis of proposed borosilicate mineral reference samples. Geostandards Newsletter, 25, 399–403.
Liu, L. & Mernagh, T.P. 1992. High-pressure Raman study of the -quartz forms of SiO_2 and GeO_2 at room temperature. High Temperatures–High Pressures, 24, 13–21.
Ludwig, T. & Stalder, R. 2007. A new method to eliminate the influence of in situ contamination in SIMS analysis of hydrogen. Journal of Analytical Atomic Spectrometry, 22, 1415–1419.
Nasdala, L., Widner, M., Wirth, R., Groschopf, N., Pal, D.C. & Möller, A. 2006. Alpha particle haloes in chlorite and cordierite. Mineralogy and Petrology, 86, 1–27.
Pearce, N.J.G., Perkins, W.T., Westgate, J.A., Gorton, M.P., Jackson, S.E., Neal, C.R. & Chenery, S.P. 1997. A compilation of new and published major and trace element data for NIST SRM 610 and NIST SRM 612 glass reference materials. Geostandards Newsletter, 21, 115–144.
Sharma, S.K., Mammone, J.F. & Nicol, M.F. 1981. Raman investigation of ring configurations in vitrous silica. Nature, 292, 140–141.