Geochemical modeling of magmatic gas scrubbing

L. Marini, B. Gambardella


The EQ3/6 software package, version 7.2 was successfully used to model scrubbing of magmatic gas by pure
water at 0.1 MPa, in the liquid and liquid-plus-gas regions. Some post-calculations were necessary to account
for gas separation effects. In these post-calculations, redox potential was considered to be fixed by precipitation
of crystalline a-sulfur, a ubiquitous and precocious process. As geochemical modeling is constrained by conservation
of enthalpy upon water-gas mixing, the enthalpies of the gas species of interest were reviewed, adopting
as reference state the liquid phase at the triple point. Our results confirm that significant emissions of highly
acidic gas species (SO2(g), HCl(g), and HF(g)) are prevented by scrubbing, until dry conditions are established, at
least locally. Nevertheless important outgassing of HCl(g) can take place from acid, HCl-rich brines. Moreover,
these findings support the rule of thumb which is generally used to distinguish SO2-, HCl-, and HF-bearing magmatic
gases from SO2-, HCl-, and HF-free hydrothermal gases.


magmatic gas;magma degassing;hydrothermalsystem;crater lake;meteoric water;scrubbing;reaction path modeling

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X