The solubility of H₂O in peralkaline and peraluminous granitic melts

authored by

D. B. Dingwell, Francois Holtz, Harald Behrens

Abstract

The solubility of H₂O in a series of 13 melts based on a haplogranitic composition (HPG8) have been determined for the conditions of 500-5000 bar pressure and 800-1000°C. The compositions represent the additions of individual components to HPG8 to generate peralkaline and peraluminous compositions, respectively. H₂O solubility increases with added excess alkali oxide. Compared on a weight percent basis, the solubility of H₂O for a given degree of peralkalinity increases in the order Cs, Rb<K<Na<Li. On a molar equivalent basis the effects of excess Bs, Rb, K, and Na on increasing the solubility of H₂O are the same, whereas the effect of Li₂O is somewhat lower. For the peraluminous compositions, the solubility of H₂O decreases with the addition of 2 wt.% Al₂O₃, to the HPG8 composition, then increases strongly with the further addition of excess Al₂O₃. The solubility of H₂O in the melt with 5 wt.% excess Al₂O₃ is significantly larger than that in HPG8. The addition of Na₂O up to levels of peralkalinity commonly encountered in glassy magmatic eruptive rocks of peralkaline volcanic provinces leads to an almsot doubling of the low pressure (500 bar) solubility of H₂O in the melt.

Organisation(s)

Institute of Mineralogy

External Organisation(s)

Centre national de la recherche scientifique (CNRS)
University of Bayreuth

Type

Article

Journal

American Mineralogist

Volume

82

Pages

434-437

No. of pages

4

ISSN

0003-004X

Publication date

01.04.1997

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Geophysics, Geochemistry and Petrology

Electronic version(s)

https://doi.org/10.2138/am-1997-3-421 (Access: Unknown)