Geochemical
Journal,Vol. 30, pp. 339to 354, 1996
Empirical
expressionsofquartzsolubilityin H2O,H2O + CO2,
and H2O+ NaClfluids
YASUHIROSHIBUE
-cho,Kato-gun,Hyogo 673-l4,Japan
GeoscienceInstitute,HyogoUniversityofTeacher
Education,Yashiro
(ReceivedSeptember29,1995;AcceptedAugust7, 1996)
(up to 10 kb
AnempiricalequationofquartzsolubilityinH2O at elevatedpressuresandtemperatures
results
. Theresultantsolubilityequationis as
and900'C)isobtainedbasedon thepublishedexperimental
- 2636.78T-1 + 0.00387766T+
0.0198582PT
-1,where Swater,
follows:lnSwater=-1.519l4+l.99970lnPwater
Pwater, T,and P stand for quartzsolubility(mol/kgH20), density(g/cm3)of pure water,temperature
(Kelvin),andpressure(bar),respectively
. Densitiesof purewaterarecalculatedby the equationofHaar
is
thenmodified
for describingthe solubilitybehaviorof quartz in
et al. (1984). The solubilityequation
thisstudyusestheweightfractionof waterinthe
H2O+ CO2 or H2O + NaClfluid. Forthemodification,
solvent (F),densityofthe aqueousfluid(Paq),and anempiricalconstant(Æ) as theadditionalterms. The
-temratioof quartzsolubilityin aqueousfluid(Saq) to that in pure water(Swater) at the same pressure
+
=
Densities
of
H2O
CO2
and
H2O
c
ondition
i
s
then
expressed
asln(Saq/Swater)
Oln(PaqF/Pwater)
.
perature
+ NaClfluidsarecomputedwiththeequations of Kerrickand Jacobs (1981) and Anderkoand Pitzer
. For
(l993a),respectively
. Theempiricalconstantfor quartzsolubilityin H2O + CO2 fluid is 1.49063
to
600'
experimentalresultsdoneat
l.5
kb
5
kb,
obtainingthe constant,thisstudyconsidersthepublished
of
CO2
The
0
valueforquartz
700'C,and
up
to
71
wt%
CO2
concentration
(molefraction
0.505)
.
to
solubilitiesconsistentwith the
solubilityin H20 + NaClfluid is 3.24740,which gives thecalculated
.
experimentalresultsdoneat 0.2 kb to 2 kb,200' to 700'C,andup to 33.6wt% NaClconcentration