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Normative analysis of saline waters from the central Murray Basin, Australia
GEOCHEMISTRY OF THE EARTH'S SURFACE AND OF MINERAL FORMATION 2nd I N T E R N A T I O N A L SYMPOSIUM, July, 2-8, 1990, Aix en Provence, France.
201
N O R M A T I V E ANALYSIS OF SALINE W A T E R S F R O M T H E C E N T R A L M U R R A Y BASIN, A U S T R A L I A JONES B. F. *, HANOR J. S.** and EVANS W.R. *** * U.S. Geological Survey, MS 432 National Center, Reston, Virginia 22092 USA. ** Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana 70803, USA. *** Division of Continental Geology, Bureau of Mineral Resources, GPO Box 378, Canberra, ACT 2601, Australia.
Large areas of the Australian continent contain same regional hydrologic flow path. The ground water flow regime worked out by scattered saline lakes and salinas that are underlain by saline ground waters of regional extent. One of Macumber (1984) at Lake Tyrrell recognizes three the most important areas in which to consider the major ground water components differentiated by origin of such waters is the Murray Basin, which salinity. These include: 1) the regional Parilla Sand contains some of the most important agricultural land aquifer (TDS = 35-50 g/L), 2) Lake Tyrrell reflux on the continent. In 1987, a borehole was drilled (TDS >200 g/L) evaporatively concentration in the near Piangil in the central Murray Basin of open lake and recharging the aquifer beneath the lake northwestern Victoria through the entire thickness of by density flow; and 3) Timboram-Wahpool reflux Cenozoic basin fill. Normative calculations based on (TDS = 90-125 g/L) beneath the regional water table the composition of pore fluids extracted by of the Parilla Sand aquifer near the smaller saline squeezing cores collected during drilling, and Lakes Timboram and Wahpool, and having an comparison with results obtained from analyses of origin similar to the Lake Tyrrell reflux brine. All nearby subsurface and saline-lake brines (Teller three ground water components are roughly similar et al., 1982; Macumber, 1984) help to interpret the in overall major solute proportions, but display distribution and origin of dissolved salts in this significant variations in normative character. The salt norm is the quantitative idealized portion of the basin. Further details of sampling and equilibrium salt assemblage that would crystallize if hydrology are given by Hanor (1987). Regional sedimentation in the Murray basin a natural water were evaporated to dryness at has been dominantly continental, except for a earth-surface conditions. The salt norm is intended significant marine transgression in Oligocene- to provide a diagnostic chemical mineralogic Pliocene time, when portions of the western half of characterization of the water, to aid in the the basin were flooded with sea water. In the central interpretation of solute origin, and to be indicative of basin there are two principal aquifer systems. The the nature of water-rock interaction in subsurface Renmark Group forms the basal unit of the Cenozoic environments. For simplicity, the actual equilibrium sequence whereas the Pliocene Parilla Sand forms assemblage can be recast as simple binary salt the uppermost, near-surface aquifer. The Geera Clay combinations of the seven major ions found in is a regional conf'ming bed between the Renmark and natural water; that is Ca, Mg, Na, K, C1, SO4, and CO3 (from HCO3). The necessary computations Parilla aquifers. The Piangil drill site is situated 50 km due have been done with the computer program SNORM northeast of Lake Tyrrell, a complex saline-lake (Bodine and Jones, 1986). The results of SNORM calculations obtained ground water system which has received significant study (Macumber, 1984). Thus, Piangil and Lake from pore fluids of the Piangil Deep Bore are given Tyrrell are situated within the same regional aquifer in table 1 and are compared with similar system, though they are thus not currently on the computations for analyses of seawater and saline
202
GEOCHEMISTRY OF THE EARTH'S SURFACE AND OF MINERAL FORMATION 2nd INTERNATIONAL SYMPOSIUM, July, 2-8, 1990, Alx en Provence, France.
TABLE I : Comparison of salt norms for pore fluids extracted from core of the Piangil Deep Bore, Murray Basin, with seawater and Lake Tyrrell area ground waters (Macumber, 1984).
weight percent . . . . . . . . . . . Stratigraphic horizon or location
depth (meters)
TDS g/L
NaCI
KCI
MgCI2 CaSO4
M g S O 4 Other
Seawater
surface
35
78.2
2.2
9.2
4.0
6.1
15.3
10.1
Geera Fm.
108.7
60
75.1
0.6
6.4
6.3
1 1.6
18.0
17.9
114.1
57
75.1
0.5
9.3
6.2
8.8
18.1
15.0
122.8
52
73.8
0.7
5.3
7.6
12.6
17.9
20.2
125.2
41
80.5
0.9
2.9
9.8
5.9
8.8
15.7
129.6 . . . 171.1
53 . . 23
0.6 . . 0.5
4.0 . . . 15.1
7.2 . . 6.0
14.3 . . .
18.3
21.5
17.6
6.0
clay stud
sand Upper Renmark Group
.
.
.
.
CaCI2 1.6
total SO4 salt
178.1
23
69.2
1.0
7.9
12.1
9.8
17.7
21.9
185.7
21
68.1
1.0
t5.1
11.8
3.6
18.7
15.4
192.2
12
78.2
1.0
1 1.3
8.0
1.4
12.7
9.4
198.4
12
78.8
0.6
10.4
7.0
3.2
t3.6
10.2
15.2
9.5
219.8
clay
.
73.9 . . . 76.8
total Mg salt
14
73.6
0.8
15.2
9.5
220.1
12
71.9
1.0
15.4
11.1
227
11
73.3
1.2
14.2
10.7
227.3
14
71.1
0.9
15.7
1 1.2
230.8
17
57.0
0.2
0.2
PariUa Sand aquifer
<80
36
78.7
0.4
Tim.-Wahpooi reflux
>17
114
79.3
0.6
L. Tyrrell refl.0)
<70
230
85.1
0.5
280
90.6
. . . .
Folly Pu Spring(2) 0.5
9.2 11.0 6.0
17.9
---
CaCI2 0.4 0.1
0.3 1.0 ....... 23.5
15.4
11.1
14.5
11.0
16.7
12.2
K2SO4 1.2
23.7
42.6
16.3
11.6
17.6
9.0
0.03 13.9 Na2SO4 7.6 0.7
8.7
4.5
7.1
MgCO3 tr.
2.4
6.6
0.1
0.8
7.9
1.2
0.7
9.5
(1) Norm similar to Lake TyrreUsalt ponds at halite saturation (TDS = 328 g/L) (2) Teller, Bowler,and Macumber, 1982.
g r o u n d w a t e r s f r o m the L a k e T y r r e l l area, as g i v e n in M a c u m b e r (1984) and T e l l e r et al., (1982). T h e s e w a t e r s are all d o m i n a t e d b y s o d i u m c h l o r i d e , w i t h m a g n e s i u m salts t y p i c a l l y m a k i n g up the bulk o f the r e m a i n d e r ; p o t a s s i u m salts c o n s t i t u t e less than o n e p e r c e n t o f the n o rm . In all the p o r e f l u i d s o f the P i a n g i l B o r e the NaC1
c o n t e n t n e v e r v a r i e s m o r e than 15 p e r c e n t f r o m the s e a w a t e r v a l u e , d e s p i t e a m o r e than 7 - f o l d r a n g e in salinity. U n l i k e t h e a p p a r e n t d i f f u s i v e p r o f i l e f o r p o r e f l u i d N a o r T D S , w h i c h c u t s a c r o s s stratig r a p h i c b o u n d ar i es, the salt n o r m s a p p e a r to r ef l ect not o n l y o v e r a l l f o r m a t i o n a l differences, but specific l i t h o l o g i c c o n d i t i o n s at p a r t i c u l a r h o r i z o n s as
GEOCHEMISTRY OF THE EARTH'S SURFACE AND OF MINERAL FORMATION 2nd I N T E R N A T I O N A L SYMPOSIUM, July, 2-8, 1990, Aix en Provence, France.
well. Thus a maximum in MgSO4 corresponds to an evaporative clay layer in the Geera Formation, and the highest pore fluid sulfate proportion was in the clay of the Upper Renmark Group. The highest normative MgC12 corresponds with thin sand horizons in the lower part of the Geera. Total Mg salt is roughly constant in the Geera norms and the total sulfate salt percentages are 1.5 to 2 times higher than seawater. The pore fluids of the Geera Formation are generally higher in sulfate percent than those of the Parilla Sand, whereas total normative Mg and sulfate are both usually higher than those of the underlying Renmark Group, except for the NaCl-poor fluid at 231 m depth. Normative CaSO4 in the Piangil pore waters increases with the decreasing salinity at greater depth. The norms for the Upper Renmark Group pore fluids are similar to that for seawater in total magnesium and sulfate salts, despite salinity one-third that of the ocean, because of a higher proportion of CaSO4 accompanying the higher fraction of MgC12. The increase in calcium, largely balanced by a decrease in NaC1, leads to the appearance of small amounts of CaC12 (a diagenetic indicator) in the norms for the middle of the unit. The most anomalous norm was obtained from the pore water in the clay layer at the base of the Upper Renmark. The increased total sulfate salts in this norm, accompanied by an equivalent decrease in NaC1, are approximately double the highest value seen in the Geera Formation. The comparison of the norm for Macumber's (1984) average analysis of the regional Parilla Sand aquifer with that for seawater suggests a marine origin for the basic solute matrix in the Tyrrell system. The other norms illustrate the increase in NaC1 and decrease in sulfate salts to be expected with evaporative concentration and gypsum precipitation in an ephemeral saline lake or playa environment. Further salt depletion can be attributed to calcium added to solution by acid-sulfate hydrolysis of carbonate or Ca-bearing silicate (e.g., plagioclase) in near-surface sediments. An alkali sulfate component can result from feldspar weathering and alkaline- earth for sodium exchange on resulting clays. Compared to the surficial compositional trends, variable density-driven recharge of evaporatively concentrated, but chloride and non-Ca sulfate undersaturated brines retain the more soluble NaMg sulfate and chloride components. The extent of saturation and precipitate loss or gain of mixed calcium and sodium sulfates prior to or during
203
recharge determines the degree of normative shift toward a more magnesian assemblage. These effects can be seen (table 1) in contrasting the surficial Folly Point Spring water; average Lake Tyrrell reflux and the more dilute Timboram-Wahpool reflux brine. Except for the Parilla Sand analyses, all of the brines from the Lake Tyrrell system are more concentrated than the pore fluids of the Piangil Bore. However, the normative results suggest some distinct similarities in solute distribution and the controlling processes. The Geera Formation pore fluid norms look like those for subsurface Lake Tyrrell reflux, with a generally high MgSO4 component, as well as high total magnesium and sulfate salts. In contrast, norms of pore waters from the Upper Renmark Group, with the exception of the clay layer at 231 m, are more akin to Timboram-Wahpool reflux, e.g. high in MgC12, but usually closer to seawater in total magnesium and sulfate salts. The higher CaSO4 content of all Piangil pore fluid norms reflects lower salinity (and thus gypsum undersaturation). Also, with a single exception, the Piangil pore fluids contain normative levels of NaC1 equal to or less than seawater. Most of the Piangil results are compatible with the dilution of a variably fractionated marine bittern slightly depleted in sodium salts, which is recharged from the surface and then dissolves a variable amount of CaSO4. The association of high MgSO4 with clay seams in both the Geera and Upper Renmark Formation of the Piangil Bore can result form the dissolution of dolomite plus gypsum and the precipitation of calcite, or "dedolomitization", leaving MgSO4 in solution. Additional variation in the norms may be related to diagenetic reaction as K or Mg for Ca exchange, producing CaC12 in norms for pore fluids below clay layers. REFERENCES
Teller, J.T., Bowler, J.M., and Macumber, P.G. (1982), Modern sedimentation and hydrology in Lake Tyrrell, Victoria: Jour. Geol. So¢. Australia, v. 29, p. 159-175. Macumber, P.g. (1984) Hydrochemical processes in the regional ground water discharge zones of the Murray Basin, SE Australia: First Canadian/American Conference on Hydrology (Practical Applications of Ground Water Chemistry), Banff, Alberta, p. 47-63. Hanor, J.S. (1987) Report on rates and mechanisms of vertical fluid flow and solute transport across the Geera aquitard, central Murray basin, SE Australia, Special Rept., Bureau of Mineral Resources,Canberra, 22p.
201
N O R M A T I V E ANALYSIS OF SALINE W A T E R S F R O M T H E C E N T R A L M U R R A Y BASIN, A U S T R A L I A JONES B. F. *, HANOR J. S.** and EVANS W.R. *** * U.S. Geological Survey, MS 432 National Center, Reston, Virginia 22092 USA. ** Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana 70803, USA. *** Division of Continental Geology, Bureau of Mineral Resources, GPO Box 378, Canberra, ACT 2601, Australia.
Large areas of the Australian continent contain same regional hydrologic flow path. The ground water flow regime worked out by scattered saline lakes and salinas that are underlain by saline ground waters of regional extent. One of Macumber (1984) at Lake Tyrrell recognizes three the most important areas in which to consider the major ground water components differentiated by origin of such waters is the Murray Basin, which salinity. These include: 1) the regional Parilla Sand contains some of the most important agricultural land aquifer (TDS = 35-50 g/L), 2) Lake Tyrrell reflux on the continent. In 1987, a borehole was drilled (TDS >200 g/L) evaporatively concentration in the near Piangil in the central Murray Basin of open lake and recharging the aquifer beneath the lake northwestern Victoria through the entire thickness of by density flow; and 3) Timboram-Wahpool reflux Cenozoic basin fill. Normative calculations based on (TDS = 90-125 g/L) beneath the regional water table the composition of pore fluids extracted by of the Parilla Sand aquifer near the smaller saline squeezing cores collected during drilling, and Lakes Timboram and Wahpool, and having an comparison with results obtained from analyses of origin similar to the Lake Tyrrell reflux brine. All nearby subsurface and saline-lake brines (Teller three ground water components are roughly similar et al., 1982; Macumber, 1984) help to interpret the in overall major solute proportions, but display distribution and origin of dissolved salts in this significant variations in normative character. The salt norm is the quantitative idealized portion of the basin. Further details of sampling and equilibrium salt assemblage that would crystallize if hydrology are given by Hanor (1987). Regional sedimentation in the Murray basin a natural water were evaporated to dryness at has been dominantly continental, except for a earth-surface conditions. The salt norm is intended significant marine transgression in Oligocene- to provide a diagnostic chemical mineralogic Pliocene time, when portions of the western half of characterization of the water, to aid in the the basin were flooded with sea water. In the central interpretation of solute origin, and to be indicative of basin there are two principal aquifer systems. The the nature of water-rock interaction in subsurface Renmark Group forms the basal unit of the Cenozoic environments. For simplicity, the actual equilibrium sequence whereas the Pliocene Parilla Sand forms assemblage can be recast as simple binary salt the uppermost, near-surface aquifer. The Geera Clay combinations of the seven major ions found in is a regional conf'ming bed between the Renmark and natural water; that is Ca, Mg, Na, K, C1, SO4, and CO3 (from HCO3). The necessary computations Parilla aquifers. The Piangil drill site is situated 50 km due have been done with the computer program SNORM northeast of Lake Tyrrell, a complex saline-lake (Bodine and Jones, 1986). The results of SNORM calculations obtained ground water system which has received significant study (Macumber, 1984). Thus, Piangil and Lake from pore fluids of the Piangil Deep Bore are given Tyrrell are situated within the same regional aquifer in table 1 and are compared with similar system, though they are thus not currently on the computations for analyses of seawater and saline
202
GEOCHEMISTRY OF THE EARTH'S SURFACE AND OF MINERAL FORMATION 2nd INTERNATIONAL SYMPOSIUM, July, 2-8, 1990, Alx en Provence, France.
TABLE I : Comparison of salt norms for pore fluids extracted from core of the Piangil Deep Bore, Murray Basin, with seawater and Lake Tyrrell area ground waters (Macumber, 1984).
weight percent . . . . . . . . . . . Stratigraphic horizon or location
depth (meters)
TDS g/L
NaCI
KCI
MgCI2 CaSO4
M g S O 4 Other
Seawater
surface
35
78.2
2.2
9.2
4.0
6.1
15.3
10.1
Geera Fm.
108.7
60
75.1
0.6
6.4
6.3
1 1.6
18.0
17.9
114.1
57
75.1
0.5
9.3
6.2
8.8
18.1
15.0
122.8
52
73.8
0.7
5.3
7.6
12.6
17.9
20.2
125.2
41
80.5
0.9
2.9
9.8
5.9
8.8
15.7
129.6 . . . 171.1
53 . . 23
0.6 . . 0.5
4.0 . . . 15.1
7.2 . . 6.0
14.3 . . .
18.3
21.5
17.6
6.0
clay stud
sand Upper Renmark Group
.
.
.
.
CaCI2 1.6
total SO4 salt
178.1
23
69.2
1.0
7.9
12.1
9.8
17.7
21.9
185.7
21
68.1
1.0
t5.1
11.8
3.6
18.7
15.4
192.2
12
78.2
1.0
1 1.3
8.0
1.4
12.7
9.4
198.4
12
78.8
0.6
10.4
7.0
3.2
t3.6
10.2
15.2
9.5
219.8
clay
.
73.9 . . . 76.8
total Mg salt
14
73.6
0.8
15.2
9.5
220.1
12
71.9
1.0
15.4
11.1
227
11
73.3
1.2
14.2
10.7
227.3
14
71.1
0.9
15.7
1 1.2
230.8
17
57.0
0.2
0.2
PariUa Sand aquifer
<80
36
78.7
0.4
Tim.-Wahpooi reflux
>17
114
79.3
0.6
L. Tyrrell refl.0)
<70
230
85.1
0.5
280
90.6
. . . .
Folly Pu Spring(2) 0.5
9.2 11.0 6.0
17.9
---
CaCI2 0.4 0.1
0.3 1.0 ....... 23.5
15.4
11.1
14.5
11.0
16.7
12.2
K2SO4 1.2
23.7
42.6
16.3
11.6
17.6
9.0
0.03 13.9 Na2SO4 7.6 0.7
8.7
4.5
7.1
MgCO3 tr.
2.4
6.6
0.1
0.8
7.9
1.2
0.7
9.5
(1) Norm similar to Lake TyrreUsalt ponds at halite saturation (TDS = 328 g/L) (2) Teller, Bowler,and Macumber, 1982.
g r o u n d w a t e r s f r o m the L a k e T y r r e l l area, as g i v e n in M a c u m b e r (1984) and T e l l e r et al., (1982). T h e s e w a t e r s are all d o m i n a t e d b y s o d i u m c h l o r i d e , w i t h m a g n e s i u m salts t y p i c a l l y m a k i n g up the bulk o f the r e m a i n d e r ; p o t a s s i u m salts c o n s t i t u t e less than o n e p e r c e n t o f the n o rm . In all the p o r e f l u i d s o f the P i a n g i l B o r e the NaC1
c o n t e n t n e v e r v a r i e s m o r e than 15 p e r c e n t f r o m the s e a w a t e r v a l u e , d e s p i t e a m o r e than 7 - f o l d r a n g e in salinity. U n l i k e t h e a p p a r e n t d i f f u s i v e p r o f i l e f o r p o r e f l u i d N a o r T D S , w h i c h c u t s a c r o s s stratig r a p h i c b o u n d ar i es, the salt n o r m s a p p e a r to r ef l ect not o n l y o v e r a l l f o r m a t i o n a l differences, but specific l i t h o l o g i c c o n d i t i o n s at p a r t i c u l a r h o r i z o n s as
GEOCHEMISTRY OF THE EARTH'S SURFACE AND OF MINERAL FORMATION 2nd I N T E R N A T I O N A L SYMPOSIUM, July, 2-8, 1990, Aix en Provence, France.
well. Thus a maximum in MgSO4 corresponds to an evaporative clay layer in the Geera Formation, and the highest pore fluid sulfate proportion was in the clay of the Upper Renmark Group. The highest normative MgC12 corresponds with thin sand horizons in the lower part of the Geera. Total Mg salt is roughly constant in the Geera norms and the total sulfate salt percentages are 1.5 to 2 times higher than seawater. The pore fluids of the Geera Formation are generally higher in sulfate percent than those of the Parilla Sand, whereas total normative Mg and sulfate are both usually higher than those of the underlying Renmark Group, except for the NaCl-poor fluid at 231 m depth. Normative CaSO4 in the Piangil pore waters increases with the decreasing salinity at greater depth. The norms for the Upper Renmark Group pore fluids are similar to that for seawater in total magnesium and sulfate salts, despite salinity one-third that of the ocean, because of a higher proportion of CaSO4 accompanying the higher fraction of MgC12. The increase in calcium, largely balanced by a decrease in NaC1, leads to the appearance of small amounts of CaC12 (a diagenetic indicator) in the norms for the middle of the unit. The most anomalous norm was obtained from the pore water in the clay layer at the base of the Upper Renmark. The increased total sulfate salts in this norm, accompanied by an equivalent decrease in NaC1, are approximately double the highest value seen in the Geera Formation. The comparison of the norm for Macumber's (1984) average analysis of the regional Parilla Sand aquifer with that for seawater suggests a marine origin for the basic solute matrix in the Tyrrell system. The other norms illustrate the increase in NaC1 and decrease in sulfate salts to be expected with evaporative concentration and gypsum precipitation in an ephemeral saline lake or playa environment. Further salt depletion can be attributed to calcium added to solution by acid-sulfate hydrolysis of carbonate or Ca-bearing silicate (e.g., plagioclase) in near-surface sediments. An alkali sulfate component can result from feldspar weathering and alkaline- earth for sodium exchange on resulting clays. Compared to the surficial compositional trends, variable density-driven recharge of evaporatively concentrated, but chloride and non-Ca sulfate undersaturated brines retain the more soluble NaMg sulfate and chloride components. The extent of saturation and precipitate loss or gain of mixed calcium and sodium sulfates prior to or during
203
recharge determines the degree of normative shift toward a more magnesian assemblage. These effects can be seen (table 1) in contrasting the surficial Folly Point Spring water; average Lake Tyrrell reflux and the more dilute Timboram-Wahpool reflux brine. Except for the Parilla Sand analyses, all of the brines from the Lake Tyrrell system are more concentrated than the pore fluids of the Piangil Bore. However, the normative results suggest some distinct similarities in solute distribution and the controlling processes. The Geera Formation pore fluid norms look like those for subsurface Lake Tyrrell reflux, with a generally high MgSO4 component, as well as high total magnesium and sulfate salts. In contrast, norms of pore waters from the Upper Renmark Group, with the exception of the clay layer at 231 m, are more akin to Timboram-Wahpool reflux, e.g. high in MgC12, but usually closer to seawater in total magnesium and sulfate salts. The higher CaSO4 content of all Piangil pore fluid norms reflects lower salinity (and thus gypsum undersaturation). Also, with a single exception, the Piangil pore fluids contain normative levels of NaC1 equal to or less than seawater. Most of the Piangil results are compatible with the dilution of a variably fractionated marine bittern slightly depleted in sodium salts, which is recharged from the surface and then dissolves a variable amount of CaSO4. The association of high MgSO4 with clay seams in both the Geera and Upper Renmark Formation of the Piangil Bore can result form the dissolution of dolomite plus gypsum and the precipitation of calcite, or "dedolomitization", leaving MgSO4 in solution. Additional variation in the norms may be related to diagenetic reaction as K or Mg for Ca exchange, producing CaC12 in norms for pore fluids below clay layers. REFERENCES
Teller, J.T., Bowler, J.M., and Macumber, P.G. (1982), Modern sedimentation and hydrology in Lake Tyrrell, Victoria: Jour. Geol. So¢. Australia, v. 29, p. 159-175. Macumber, P.g. (1984) Hydrochemical processes in the regional ground water discharge zones of the Murray Basin, SE Australia: First Canadian/American Conference on Hydrology (Practical Applications of Ground Water Chemistry), Banff, Alberta, p. 47-63. Hanor, J.S. (1987) Report on rates and mechanisms of vertical fluid flow and solute transport across the Geera aquitard, central Murray basin, SE Australia, Special Rept., Bureau of Mineral Resources,Canberra, 22p.