-
as
highly concentrated carbonate brines,
100 ee
=
=
50 £2.
California,
is
an
intermittent
Se
no
|
7
°
31d ht
ve
»
“\
mo
Lake Magadi, Kenya
& Ioke area
)
oe ~~
10
B4
86
;
BB
7
’
/
4
90
92
94
@ Abert Lake basin, Ore.
% Alkali Valley, Ore.
‘
ui Closed sug pond
Deep Springs Valley, Calif.
;
6
Springs
98
pH —
100
|
i
104
102
_& bake and inflow creas
L
106
108
TO
Fig. 1. Silica in solution versus pH. The three solid curves are (from low to high SiOz)
for Si(OH) ,, SiO(OH)., and Si0,(OH). ~~ Areas a—d are discussed in text.
saline water body in a small basin (9);
about a third of its 13-km? area is cov-
.
ered by saline crusts. Inflow is chiefly
groups of springs
|
™
(8).
Deep Springs Lake, in Deep Springs
MMe
ET
Samples came from several potholes
Valley,
ea
500
.
and the main playa pond.
a
f
1000
which apparently
result fro
-term
PP:
tly &s
from long
evaporation of artesian waters at a rate
roughly equivalent to discharge
J
from a prominent zone of recent fault-
+
4+ Aqua de Ney Springs, Colif.
x
ing. Also within the fault zone are two
sag ponds, one of which has no outlet
TTT
|
—
TT
a
5000 ;
discharging
1
and 1 m or more in depth; the largest
contain masses of crystalline sodium
salts, chiefly carbonate. Many of them
also contain extremely variable and
;
!
More than half the playa area contains
numerous circular depressions or pot-
1
i
|
\
\
ately north of the Abert basin (7).
from
1
I
Alkali Lake, in Alkali Valley, is a
holes, some as much as 9m across
at low stage. Carbonate species pre-
1000
Baker
(/0)
has
sum-
geochemistry of the area; the lake lies
in the Gregory Rift Valley and contains a vast deposit of trona (Na.CO,-
NaHCo,-2H.O0). It is intermittently
dry, but has a number of perennial
brine pools (lagoons) near the margins;
it has no visible outlet and is fed
marily by a number of perennial
springs and by runoff during rainy
sons. Samples were collected from
prihot
seahot
springs, open brine pools, and brines
interstitial to trona crusts.
500
|
studied.
Lake Nokuru, Kenya
+
Owens
+ Lake,
Calif.
100
i]
were
marized the geology, mineralogy, and
me
1
50
=
Figure 1 shows that the silica content
increases drastically for brines having
a pH greater than 9.2; this finding
agrees with the reported increase in
a
& Lake Magadi, Kenya
(2). With the exception of those for
plotted in Fig. 1 are based on field
measurements at ambient temperature;
1
|
|
eo Abert Lake basin, Ore.
o
f
]
* Alkali Valley, Ore.
|
solubility of amorphoussilica with pH
the interstitial solutions, most pH values
Ob
from Oregon and California, several
samples from Lake Magadi in Kenya
.
TTT)
dominate in the ponds and springs but
are subordinate to sulfate in the lake
area.
In addition to the alkaline waters
SiO, IN PARTS PER MILLION
“
1
5000 —
LL
brine.
playa of approximately 13 km? immedi.
J
pedite 71
1/100th the concentration, feeds a pool
of highly concentrated chlorocarbonate
SiO, IN PARTS PER MILLION
‘
10,000 CF
Ko
BD
lake; here a small seep similar to the
lake in solute composition, but of
=|os bin!
pad we ast
_
woe
\
7
>
'
*
+
4
bow testtallies ae AATCoke a ate eet ahd,
\
Ee
1
DeepSprings Valley, Calif.
10
1000
1
1]
5000
LELd
10,000
'
1
Nat IN PARTS PER MILLION
1
m cresed sag pond]
{pee
50,000
100,000
for samples not in immediate contact
Fig. 2. Sodium versus SiOz for alkaline brines from Kenya, Oregon, and California.
as 1 unit during subsequent storage.
Small dots represent samples for which pH and total CO2 data were not obtained.
with muds, pH may change by as much
8 DECEMBER 1967
Regression lines have been derived independently for the Oregon and Magadi points.
1311
JOA