USGS/Cascades Volcano Observatory, Vancouver, Washington

Table 4. Calculated equilibrium distributions of gas species and minerals for flash vaporization of a 22,580 Mt quantity of Pinatubo hydrothermalfluid containing 17 Mt bulk SO2


[Based on hydrothermal fluid sample from geothermal well 
PIN-2D, table 3. Units are in Mt, megatons. Only SO2 and gas 
species more abundant than SO2 are shown. ---, mineral not 
present at this temperature, degrees Celsius.]

------------------------------------------------------------
Species             800 degrees C           400 degrees C
------------------------------------------------------------

Gases:
 H2O                  22,470                   22,470
 HCl                      14.0                     13.3
 (NaCl)2                  23.6                7x10^(-6)
 NaCl                     11.5                5x10^(-6)
 KCl                       7.9                4x10^(-6)
 O2                        0.9                      0.8
 (KCl)2                    1.0                8x10^(-6)
 SO2                       0.004              6x10^(-9)

Minerals:
 Na2SO4(1)                37.7                     36.2
 MgSiO3(2)                 7.9                      8.9
 SiO2(3)                   4.2                      4.9
 (Ca,Mg)SiO3(4)            2.2                      ---
 NaCl (halite)             ---                     36.4
 KCl (sylvite)             ---                      8.9
 CaSO4 (anhydrite)         ---                      1.4
------------------------------------------------------------
(1)Hexagonal anhydrous sodium sulfate.
(2)Orthoenstatite 800 degrees C.
   Clinoenstatite 400 degrees C.
(3)Beta-quartz 800 degrees C.
   Alpha-quartz 400 degrees C.
(4)Diopside.

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