Water in peralkaline aluminosilicate melts to 2 GPa and 1400 degrees C

摘要

The solubility of H2O in melts along the join CaSi4O4-Ca(Ca0.5Al)(4)O-9 (0, 3, and 6 mol% Al2O3) has been determined at 0.8 to 2.0 GPa and 1200 to 1400degreesC and compared with the solubility of H2O in melts along the joins Na2Si4O9-Na-2(NaAl)(4)O-9 and K2Si4O9-K-2(KAl)(4)O-9. The H2O solubility is a positive function of pressure and a negative function of temperature and Al2O3 content so that solubility, X-H2Omelt(mol%), is X-H2O(melt)(CAS) = 19 +/- 2 - 0.7 +/- 0.1.X-Al2O3 + 0.06 +/- 0.02.(X-Al2O3)(2) + 13.3 +/- 0.2.P(GPa) - 0.011 +/- 0.001.T(K). In alkali aluminosilicate melts, the solubility is considerably more sensitive to pressure, Al2O3, and temperature. The H2O solubility data in the 0.8- to 2.0-GPa and 1200 to 1400degreesC pressure and temperature range are consistent with constant activity coefficient of H2O in the melt. The partial molar volume of H2O, (V) over bar (melt)(H2O), derived from the solubility data, ranges between 12.4 cm(3)/mol for Al-free CaSi4O9 melt and 10.4 cm(3)/mol for CaSi4O9 + 6 mol% Al2O3. This decrease in (V) over bar (melt)(H2O) with increasing Al2O3 is similar to that reported for H2O in melts along the two alkali aluminosilicate joins (Na2Si4O9-Na-2(NaAl)(4)O-9 and K2Si4O9-K-2(KAl)(4)O-9). The (V) over bar (melt)(H2O) is invariant with temperature in contrast to (V) over bar (melt)(H2O) along the joins, Na2Si4O9-Na-2(NaAl)(4)O-9 and K2Si4O9-K-2(KAl)(4)O-9, wherein both cases (V) over bar (melt)(H2O) decreases with increasing temperature. Copyright (C) 2002 Elsevier Science Ltd. [References: 59]