Details
| Original language | English |
|---|---|
| Pages (from-to) | 3445-3450 |
| Number of pages | 6 |
| Journal | Geochimica et cosmochimica acta |
| Volume | 59 |
| Issue number | 16 |
| Publication status | Published - Aug 1995 |
Abstract
First measurements of water species in an aluminosilicate melt of haplogranitic composition at temperatures up to 800°C and at a pressure of 1500 bar determined by in situ near-infrared spectroscopy are presented. These measurements clearly show that both water molecules and hydroxyl groups are stable species in the melt. The concentration of hydroxyl groups in the melt varies strongly with temperature and is considerably higher than predicted by previous spectroscopic studies on glasses at room temperature. Changes of hydroxyl group concentration with temperature were also observed for the glassy state and are attributed to a local reaction between water molecules and bridging oxygens resulting in the formation of hydroxyl group pairs. For the studied composition with a total water content of 4.14 wt% we found contents of water present as hydroxyl groups of 1.46 wt% at 25°C, 1.61 wt% at 250°C (in the glass), and 3.23 wt% at 800°C (in the melt). Assuming an ideal behaviour of the oxygen-bearing species in the reaction, standard state enthalpies of 33.6 ± 2.0 kJ · mol-1 (melt) and 1.52 ± 0.20 kJ · mol-1 (glass), and standard state entropies of 29.8 ± 1.2 J · mol-1· K-1 (melt) and -18.6 ± 0.4 J · mol-1 · K-1 (glass) were determined for the reaction (H2O + O = 2 OH).
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
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In: Geochimica et cosmochimica acta, Vol. 59, No. 16, 08.1995, p. 3445-3450.
Research output: Contribution to journal › Letter › Research › peer review
}
TY - JOUR
T1 - The speciation of water in haplogranitic glasses and melts determined by in situ near-infrared spectroscopy
AU - Nowak, Marcus
AU - Behrens, Harald
PY - 1995/8
Y1 - 1995/8
N2 - First measurements of water species in an aluminosilicate melt of haplogranitic composition at temperatures up to 800°C and at a pressure of 1500 bar determined by in situ near-infrared spectroscopy are presented. These measurements clearly show that both water molecules and hydroxyl groups are stable species in the melt. The concentration of hydroxyl groups in the melt varies strongly with temperature and is considerably higher than predicted by previous spectroscopic studies on glasses at room temperature. Changes of hydroxyl group concentration with temperature were also observed for the glassy state and are attributed to a local reaction between water molecules and bridging oxygens resulting in the formation of hydroxyl group pairs. For the studied composition with a total water content of 4.14 wt% we found contents of water present as hydroxyl groups of 1.46 wt% at 25°C, 1.61 wt% at 250°C (in the glass), and 3.23 wt% at 800°C (in the melt). Assuming an ideal behaviour of the oxygen-bearing species in the reaction, standard state enthalpies of 33.6 ± 2.0 kJ · mol-1 (melt) and 1.52 ± 0.20 kJ · mol-1 (glass), and standard state entropies of 29.8 ± 1.2 J · mol-1· K-1 (melt) and -18.6 ± 0.4 J · mol-1 · K-1 (glass) were determined for the reaction (H2O + O = 2 OH).
AB - First measurements of water species in an aluminosilicate melt of haplogranitic composition at temperatures up to 800°C and at a pressure of 1500 bar determined by in situ near-infrared spectroscopy are presented. These measurements clearly show that both water molecules and hydroxyl groups are stable species in the melt. The concentration of hydroxyl groups in the melt varies strongly with temperature and is considerably higher than predicted by previous spectroscopic studies on glasses at room temperature. Changes of hydroxyl group concentration with temperature were also observed for the glassy state and are attributed to a local reaction between water molecules and bridging oxygens resulting in the formation of hydroxyl group pairs. For the studied composition with a total water content of 4.14 wt% we found contents of water present as hydroxyl groups of 1.46 wt% at 25°C, 1.61 wt% at 250°C (in the glass), and 3.23 wt% at 800°C (in the melt). Assuming an ideal behaviour of the oxygen-bearing species in the reaction, standard state enthalpies of 33.6 ± 2.0 kJ · mol-1 (melt) and 1.52 ± 0.20 kJ · mol-1 (glass), and standard state entropies of 29.8 ± 1.2 J · mol-1· K-1 (melt) and -18.6 ± 0.4 J · mol-1 · K-1 (glass) were determined for the reaction (H2O + O = 2 OH).
UR - http://www.scopus.com/inward/record.url?scp=0029542035&partnerID=8YFLogxK
U2 - 10.1016/0016-7037(95)00237-T
DO - 10.1016/0016-7037(95)00237-T
M3 - Letter
AN - SCOPUS:0029542035
VL - 59
SP - 3445
EP - 3450
JO - Geochimica et cosmochimica acta
JF - Geochimica et cosmochimica acta
SN - 0016-7037
IS - 16
ER -