Metal concentrations in groundwater around disturbed and undisturbed massive sulfide deposits H. Pauwels, A.
Download ReportTranscript Metal concentrations in groundwater around disturbed and undisturbed massive sulfide deposits H. Pauwels, A.
Slide 1
Metal concentrations in groundwater around
disturbed and undisturbed massive sulfide
deposits
H. Pauwels, A. Lassin , J.C. Foucher,Y.
Deschamps, M. L. Tercier-Waeber, F.
Graziottin, R. Castroviejo, J. Samper, A.
López
Slide 2
Objectives
To determine water-rock interactions
around VMS deposits with application to
two VMS ore deposits from Iberian Pyrite
Belt:
– the effect of a deeply buried orebody on the
composition of groundwaters
– metal speciation and solubility controlling role of
complexants
Applications in exploration and baseline
studies
Slide 3
La Zarza and Masa Valverde VMS
La Zarza
Nearly outcropping to more
than 500 m depth
Masa Valverde
Buried at 400-600 m depth
Mined between 1853 and 1991 Unworked
Remaining reserves: 110 Mt
Reserves : 100 Mt
Low to very low permeability
of host-rock
Low to very low permeability of
host-rock
Located in an area of
hydrogeological recharge
Located in a hydrogeological
discharge zone
Slide 4
Hydrogeology and Chemistry
Eh: Masa Valverde : -285 to -230 mV
La Zarza : -30 to + 400 mV
SCO2
Masa Valverde
La Zarza
Deep groundwater flow
400
2
R = 0.94
300
Na (mg/l
La Zarza
200
Masa Valverde .
100
Surroundings
2
R = 0.80
0
Cl
0
25
50
75
SO4
100
0
50
Infiltrating waters
100
150
Cl (mg/l)
200
Local groundwater flow
Different chemical characteristics strengthened
by occurrence of two mixing trends
Slide 5
Metal determination: VIP and ICP-MS
Voltammetric In-situ Profiling System ( VIP):
Submersible voltammetric probe
+ Calibration deck unit
+ Surface deck unit + PC
Specificity: measures only the concentration
of the mobile fraction of trace metals ( free
metal ions + small labile complexes
• Analysis by VIP for Cu, Pb, Zn, Cd, Mn
• Analysis by ICP-MS for Cu, Pb, Zn, Cd,
Fe, Mn, Co, Ni, Al, As
IDRONAUT s.r.l
Slide 6
-1
S( Zn+Cu+Pb+Cd+As+Ni+Co)
in a concentration range of
the same order at both sites,
despite :
- very reducing conditions at
Masa Valverde
-very low solubility of
sulphide minerals
S metals (µg l )
Metal contents
120
La Zarza
100
Masa Valverde
80
60
40
20
0
0
100
200
300
SO4 (mg l-1)
Impossible distinction between La Zarza and Masa
Valverde G.W. using any particular metal
400
Slide 7
Metal Speciation: Comparison VIP / ICP-MS
150
1.5
Cu (ppb)
100
1
50
0.5
0
0
0
100
80
60
40
20
0
1000
2000
3000
% of concentration
measured by VIP with
respect to ICP-MS :
0
50
400
Cd (ppb)
La Zarza G.W. :
Zn (ppb)
100
Pb (ppb)
300
Cu : less than 6%
Zn : 0.5 to 21 %
Cd : less than 27 %
200
Pb: 8 to 100%
100
0
0
500
1000
1500
0
500
1000
1500
ICP-MS
Cu, Zn and Cd present as macromolecules and/or adsorbed on
colloids/small particles
Pb presents as free ions + small labile complexes
Slide 8
Metal Speciation: Geochemical Modelling
Using EQ3NR:
- Estimation of undetectable
H2S from equilibrium with
respect to pyrite
- Estimation of Cu, Pb, Zn
concentrations expected
from equilibrium with respect
to chalcopyrite, galena and
sphalerite
1.E+03
Calculated conc. (ng.l -1 )
Masa Valverde G.W.
1.E+01
Cu
1.E-01
1.E-03
Pb
1.E-05
1.E-07
Zn
1.E-09
1.E-11
1.E-02
1.E-01
1.E+00 1.E+01 1.E+02
Measured conc. (ng.l-1)
Cu and Pb present as macromolecules and/or adsorbed on
colloids/small particles
Zn presents as free ions + small labile complexes
Slide 9
Conclusions and Perspectives
Two major observations :
• Similar total metal concentrations at
both disturbed and deep buried
unworked deposits
• Enhancement of total metal
concentrations in GW by the formation
of complexes or by metal adsorption on
colloids or small particles
Slide 10
Conclusions and Perspectives :
Mineral exploration
These results:
• Enlarge the field of potential applications for
deep orebody exploration using
hydrogeochemical methods at local scale
not only restricted in case of acid mine drainage
despite low solubility of sulphide minerals
• Contribute to support the possible role of
G.W.-rock interactions in the formation of
surface geochemical anomalies identified by
enzyme leach, MMI selective digestions and
others...
Slide 11
Conclusions and Perspectives :
Environmental Assessment
These results:
• Confirm the importance of a natural
baseline study in order to determine realistic
achievable targets for remediation.
• Pose the problem of suitable methods for
estimating natural background total metal
concentration at abandoned mine sites:
Predictive modeling constitutes an upper limit in the
case of acid mine drainage and a lower limit in the
absence of significant oxidation.
Metal concentrations in groundwater around
disturbed and undisturbed massive sulfide
deposits
H. Pauwels, A. Lassin , J.C. Foucher,Y.
Deschamps, M. L. Tercier-Waeber, F.
Graziottin, R. Castroviejo, J. Samper, A.
López
Slide 2
Objectives
To determine water-rock interactions
around VMS deposits with application to
two VMS ore deposits from Iberian Pyrite
Belt:
– the effect of a deeply buried orebody on the
composition of groundwaters
– metal speciation and solubility controlling role of
complexants
Applications in exploration and baseline
studies
Slide 3
La Zarza and Masa Valverde VMS
La Zarza
Nearly outcropping to more
than 500 m depth
Masa Valverde
Buried at 400-600 m depth
Mined between 1853 and 1991 Unworked
Remaining reserves: 110 Mt
Reserves : 100 Mt
Low to very low permeability
of host-rock
Low to very low permeability of
host-rock
Located in an area of
hydrogeological recharge
Located in a hydrogeological
discharge zone
Slide 4
Hydrogeology and Chemistry
Eh: Masa Valverde : -285 to -230 mV
La Zarza : -30 to + 400 mV
SCO2
Masa Valverde
La Zarza
Deep groundwater flow
400
2
R = 0.94
300
Na (mg/l
La Zarza
200
Masa Valverde .
100
Surroundings
2
R = 0.80
0
Cl
0
25
50
75
SO4
100
0
50
Infiltrating waters
100
150
Cl (mg/l)
200
Local groundwater flow
Different chemical characteristics strengthened
by occurrence of two mixing trends
Slide 5
Metal determination: VIP and ICP-MS
Voltammetric In-situ Profiling System ( VIP):
Submersible voltammetric probe
+ Calibration deck unit
+ Surface deck unit + PC
Specificity: measures only the concentration
of the mobile fraction of trace metals ( free
metal ions + small labile complexes
• Analysis by VIP for Cu, Pb, Zn, Cd, Mn
• Analysis by ICP-MS for Cu, Pb, Zn, Cd,
Fe, Mn, Co, Ni, Al, As
IDRONAUT s.r.l
Slide 6
-1
S( Zn+Cu+Pb+Cd+As+Ni+Co)
in a concentration range of
the same order at both sites,
despite :
- very reducing conditions at
Masa Valverde
-very low solubility of
sulphide minerals
S metals (µg l )
Metal contents
120
La Zarza
100
Masa Valverde
80
60
40
20
0
0
100
200
300
SO4 (mg l-1)
Impossible distinction between La Zarza and Masa
Valverde G.W. using any particular metal
400
Slide 7
Metal Speciation: Comparison VIP / ICP-MS
150
1.5
Cu (ppb)
100
1
50
0.5
0
0
0
100
80
60
40
20
0
1000
2000
3000
% of concentration
measured by VIP with
respect to ICP-MS :
0
50
400
Cd (ppb)
La Zarza G.W. :
Zn (ppb)
100
Pb (ppb)
300
Cu : less than 6%
Zn : 0.5 to 21 %
Cd : less than 27 %
200
Pb: 8 to 100%
100
0
0
500
1000
1500
0
500
1000
1500
ICP-MS
Cu, Zn and Cd present as macromolecules and/or adsorbed on
colloids/small particles
Pb presents as free ions + small labile complexes
Slide 8
Metal Speciation: Geochemical Modelling
Using EQ3NR:
- Estimation of undetectable
H2S from equilibrium with
respect to pyrite
- Estimation of Cu, Pb, Zn
concentrations expected
from equilibrium with respect
to chalcopyrite, galena and
sphalerite
1.E+03
Calculated conc. (ng.l -1 )
Masa Valverde G.W.
1.E+01
Cu
1.E-01
1.E-03
Pb
1.E-05
1.E-07
Zn
1.E-09
1.E-11
1.E-02
1.E-01
1.E+00 1.E+01 1.E+02
Measured conc. (ng.l-1)
Cu and Pb present as macromolecules and/or adsorbed on
colloids/small particles
Zn presents as free ions + small labile complexes
Slide 9
Conclusions and Perspectives
Two major observations :
• Similar total metal concentrations at
both disturbed and deep buried
unworked deposits
• Enhancement of total metal
concentrations in GW by the formation
of complexes or by metal adsorption on
colloids or small particles
Slide 10
Conclusions and Perspectives :
Mineral exploration
These results:
• Enlarge the field of potential applications for
deep orebody exploration using
hydrogeochemical methods at local scale
not only restricted in case of acid mine drainage
despite low solubility of sulphide minerals
• Contribute to support the possible role of
G.W.-rock interactions in the formation of
surface geochemical anomalies identified by
enzyme leach, MMI selective digestions and
others...
Slide 11
Conclusions and Perspectives :
Environmental Assessment
These results:
• Confirm the importance of a natural
baseline study in order to determine realistic
achievable targets for remediation.
• Pose the problem of suitable methods for
estimating natural background total metal
concentration at abandoned mine sites:
Predictive modeling constitutes an upper limit in the
case of acid mine drainage and a lower limit in the
absence of significant oxidation.