Liquid-vapor fractionation of boron and boron isotopes: Experimental calibration at 400°C/23 MPa to 450°C/42 MPa

Trace element partitioning between vapor, brine and halite under extreme phase separation conditions

“…7a). At lower bulk chloride composition, boron does indeed appear to partition weakly into the brine, in general agreement with previous investigations (Berndt and Seyfried, 1990;Liebscher et al, 2005). Apparently, B is strongly immiscible in high-salinity fluid and mineral phases, allowing B vapor /B initial ratios to reach values higher than unity.…”

“…A similar approach involving the departure of the actual pressure conditions from the critical curve has been successfully adopted to study hydrogen and boron isotopic systematics under two-phase conditions (Berndt et al, 1996;Liebscher et al, 2005). This approach for boron, however, reveals an excellent linear correlation over the full range of conditions investigated during the present and previous studies, which, as noted, tended to emphasize more narrow compositional conditions (Fig.…”

“…5) support a volatile-like behavior of boron owing the enhanced stability of B(OH) 3(aq) in low pH and low-density aqueous fluids (Schmidt et al, 2005), although previous experimental studies indicate otherwise for some conditions (Berndt and Seyfried, 1990;Liebscher et al, 2005). The extensive range of chemical and physical conditions examined during the present study, however, confirm fractionation of boron into vapor, especially for phase separation conditions far removed from the two-phase boundary of the NaCl-H 2 O system.…”

“…Previous experimental studies conducted to investigate the distribution of Li, Br and B in supercritical/subcritical vapors and brines (Bischoff and Rosenbauer, 1987;Berndt and Seyfried, 1990;Berndt and Seyfried, 1997;Liebscher et al, 2005) were restricted in temperature and pressure, as well as limited by the close-system experimental approaches adopted. The relatively high contrast in density and composition between coexisting vapors and brines anticipated for physical conditions deep in the two-phase region (Bischoff, 1991;Berndt et al, 2001), presents serious experimental challenges for a closed and fixed volume gold reaction cell (Seyfried et al, 1987).…”

Isotope Fractionation Processes of Selected Elements

“…Experimental studies of boron isotope fractionation between hydrous fluids, melts and minerals have shown that 11 B preferentially partitions into the fluid relative to minerals or melts (Palmer et al 1987;Williams et al 2001;Wunder et al 2005;Liebscher et al 2005), ranging from about 33 ‰ for fluid-clay (Palmer et al 1987), to about 6 ‰ for fluid-muscovite at 700°C (Wunder et al 2005) and to a few ‰ for fluid-melt above 1000°C (Hervig et al 2002). The main fractionation effect seems to be due to the change from trigonal boron in neutral pH hydrous fluid to tetrahedrally coordinated boron in most rock forming minerals.…”