Water and magmas: insights about the water solution mechanisms in alkali silicate melts from infrared, Raman, and 29Si solid-state NMR spectroscopies

Progress in Earth and Planetary Science

Table 2 Water concentration of glasses

Glass	nom. mol % H₂O	Conditions of synthesis	FTIR values					RAMAN
Glass	nom. mol % H₂O	Conditions of synthesis	A₄₂₀₀	A₅₂₀₀	[OH]	[H₂O_mol]	[H₂O^TOT]	[H₂O^TOT]
LS4	3.28	1650 °C	151 (12)	93 (9)	2.11 (35)	1.04 (22)	3.15 (41)	3.08 (60)
	9.40	1.5 GPa	325 (18)	452 (21)	4.56 (70)	5.06 (42)	9.61 (81)	10.09 (60)
	17.64	1.5 GPa	447 (21)	1109 (33)	6.26 (94)	12.42 (55)	18.68 (1.09)	18.74 (60)
NS4	3.28	1500 °C	155 (12)	3 (2)	3.85 (40)	0.07 (3)	3.92 (40)	3.44 (67)
	9.40	1.5 GPa	301 (17)	86 (9)	7.35 (63)	1.89 (20)	9.24 (66)	9.46 (67)
	17.64		403 (20)	440 (21)	9.52 (80)	9.35 (60)	18.87 (1.00)	17.54 (67)
KS4	3.28	1550 °C	-	-	3.98 (70)^a	0.00 (0)^a	-	3.98 (74)
	9.40	1.5 GPa	-	-	8.89 (70)^a	0.73 (7)^a	-	9.62 (74)
	17.64		-	-	13.65 (70)^a	2.30 (24)^a	-	15.95 (74)

Nom. refers to the nominal water concentrations. [H₂O_mol], [OH], and [H₂O^TOT] concentrations are in mol %. A₄₅₀₀ and A₅₂₀₀ are the integrated intensities of the IR peaks at ~4500 and ~5200 cm⁻¹ that have been used to quantify the content of [OH] and [H₂O_mol] for the LS4 and NS4 glasses. FTIR and Raman values are from Le Losq et al. (2015a). Errors are given at the 1σ confidence interval
^aCalculated with the calibration linking ¹H MAS NMR sideband area to H₂O_mol content shown in Fig. 1; the concentration of OH is estimated by difference to [H₂O_mol] measured with using Raman spectroscopy