Solubility of water-hydrogen fluid in haplogranite,albite, and sodium disilicate melts |
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| Authors: | N I Bezmen V O Zavel’sky T P Salova |
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| Institution: | 1.Institute of Experimental Mineralogy,Russian Academy of Sciences,Chernogolovka, Moscow obl.,Russia;2.Institute of Physiologically Active Substances,Russian Academy of Sciences,Chernogolovka, Moscow obl.,Russia |
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| Abstract: | Solubility curves of water-hydrogen fluid were studied using a high-pressure gas apparatus at a pressure of 200 MPa under
variable fluid composition in haplogranite (Ab
39
Or
32
Qtz
29, 950°C), Na-disilicate (Na2Si2O5, 950°C), and albite melts (1200°C). The mole fraction of hydrogen in experiments was controlled directly by Ar-H2 mixtures using a specially designed cell with a Shaw membrane. $
X_{H_2 }^{Ar - H_2 }
$
X_{H_2 }^{Ar - H_2 }
ranged from 0 to 1. In some experiments with haplogranite and Na-disilicate melts under oxidizing conditions, in order to
increase the accuracy of experimental parameters, the fugacities of oxygen and hydrogen were controlled using the double-capsule
technique and the solid-phase buffer mixtures Ni-NiO (NNO) and Co-CoO (CCO). The addition of H2 to the H2O-saturated systems ($
X_{H_2 }^{H_2 O - H_2 }
$
X_{H_2 }^{H_2 O - H_2 }
≥ 0.012) results in the appearance of a distinct maximum on the solubility curves at $
X_{H_2 }^{H_2 O - H_2 }
$
X_{H_2 }^{H_2 O - H_2 }
= 0.05–0.07 (H2 mole fractions were calculated for real H2O-H2 mixtures of real gases), and the maximum content of H2O-H2 fluid increases relative to the H2O-saturated melts by 1.51 wt % for haplogranite melt at $
X_{H_2 }
$
X_{H_2 }
= 0.063, 2.68 wt % for albite melt at $
X_{H_2 }
$
X_{H_2 }
= 0.066, and 3.54 wt % for Na-disilicate melt at $
X_{H_2 }
$
X_{H_2 }
= 0.067. A further increase in H2 content in the gas mixture decreases the solubility of H2O-H2 fluid in the melts, and under pure H2 pressure, the contents of fluid components are 0.08 wt % in haplogranite melt and 0.06 wt % in albite melt. The 1H NMR study of aluminosilicate and Na-silicate glasses obtained under the pressure of H2O and H2O-H2 fluids suggests different mechanisms of the dissolution of H2O and H2O-H2 fluids in magmatic melts. In addition to the spectra of dissolved water fluid, the spectra of quenched glasses synthesized
under H2O-H2 fluid pressure exhibited a narrow line of molecular hydrogen with a width at half height of 1.8–2.0 kHz at $
X_{H_2 }
$
X_{H_2 }
≥ 0.653 for albite and $
X_{H_2 }
$
X_{H_2 }
≥ 0.063 for Na-disilicate and two lines at $
X_{H_2 }
$
X_{H_2 }
≥ 0.063 for the haplogranite composition. |
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| Keywords: | |
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