Thermal springs and balneology in the Peri-Adriatic area ... · Some of the waters are...
Transcript of Thermal springs and balneology in the Peri-Adriatic area ... · Some of the waters are...
Thermal springs and balneology in the Peri-Adriatic area: geochemical status
and prospects
Riccardo Petrini, Pisa University
(with contributions by R. Cataldi and B. Della Vedova)
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(Picha F.J. 2002)
(Del Gaudio et al., 2007)
Epicenters of seismic events of magnitude > 2.0, from 1975 to 2005, U.S. Geological Survey Earthquake Database
The Peri-Adriatic Region
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Thermal Spas in Peri-Adriatic Region
COUNTRY Number of active SPAs
Water volume used in 2010 (m3/year, excluding pool uses)
Albania 5 140.000
Bosnia Herzegovina 20 1.290.000
Croatia 18 1.345.000
Greece > 23 (up to 50?) > 500.000
Italy 149 48.000.000
Montenegro 1 60.000
Slovenia 25 1.780.000
T O T A L > 260 > 53.115.000
Including pool uses, a flow of about 112x106 m3/year (3.55 m3/s) of thermal waters can be estimated to feed Spas of the Adriatic-Jonian Region
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(1) Data taken from different sources, they likely contain large uncertainties.
(2) Proceedings World Geothermal Congress 2010
(*) Water volumes have been estimeted starting from the Annual Energy Use of each country.
For each spring we estimated the average mean annual energy (based on the average flow) for the effective
temperature intervals (Tin –Tout), using the Annual Energy Use (TJ/yr) = Ave. flow rate (kg/s) x [inlet temp. (°C) - outlet temp. (°C)] x 0.1319
(**) Figures largely underestimated
Country N. of
SPAs
Total
average
flow rate
(kg/s)
Annual Total
average water
used (106*m3)
T (°C) Average T
(°C)
Resource
potential
capacity
(MWt)
Total
geothermal
energy used
(TJ/yr)
Estimated number
of tourists (1) Source (2)
Slovenia 26 115* 3.6 23-63 33-38 25 311 751000 (2010) ?
WGC 2010
Croatia 18 96* 3.0 25-85 42-47 33 216 400000 (2010) ? WGC 2010
Bosnia and
Herzegovina 20 79* 2.5 21-76 39-44 13 100 192000 (2009) ? WGC 2010
Montenegro 1 ? ? ? ? ? ? WGC 2010
Albania 6 21 0.7 27-60 45-50 12 8 ? WGC 2010
Greece >60 >1500 ≈ 47 18-100 ? 39?** 238?** >100000 (2010) ? WGC 2010
Serbia 59 700-800 ? ≈ 23 29-96 45-50 40 647 ? WGC 2010
TOTAL > 191 > 2.561
≈ 79,8
162 1520 >1.443.000
Thermal Spas in Peri-Adriatic Region: Q,T, V, MW, TJ
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Conceptual flow diagram for water and energy utilization in spa systems, excluding pools
Conceptual flow diagram for water and energy utilization of thermal pools associated to spa systems
Energy Potential of thermal springs and waters
Mass and energy balances are crucial for sustainable use of excess heat, up- and down-stream Spa uses, and are tools to develop the balneotherapy sector.
Geothermal reservoirs are often related to areas of active or recent magmatism, where heat is transferred from a magmatic source to the circulating fluids However, low-enthalpy waters in different tectonic settings, including aquifers in deep carbonate-rocks and metamorphic basements, are receiving much attention, in particular for bathing and swimming The Peri-Adriatic area has many favorable geothermal characteristics; however, long-term abstraction of resources should be carefully planned to avoid overexploitation
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Thermal springs and waters in peri-Adriatic context
Water geochemistry: source aquifers for a sustainable exploitation policy
The major ions chemistry gives the basic information on water-type and processes
Piper diagram
cations Ca2+, Mg2+, Na+, K+ anions HCO3
-, Cl-, SO42-
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Geothermal manifestations in the Peri-Adriatic Region belong to different hydrofacies, reflecting
different origin and nature of aquifers
They include: Thermal waters in Mesozoic carbonate-rock aquifers
Thermal waters in aquifers within the metamorphic basement
Thermal waters in porous media in sedimentary basins
Thermal waters of marine origin in coastal environments Each requires to enhance knowledge to reduce future quantitative and
qualitative threats 8
Bosnia
Hydrofacies: mostly of the Ca-HCO3 type
Some of the Ca-HCO3 waters are displaced
towards Na-Cl marine components
seawater
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Croatia
Hydrofacies: waters range from the Ca-HCO3 to the Na-Cl, Ca-SO4 type
seawater The data suggest mixing processes
between the different water-types
limited ion-exchanges
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Greece
seawater
Hydrofacies: the Na-Cl type dominate; highly variable composition, including the
Na-HCO3 type.
SO4 reduction
CaCO3 solution
CaCO3 deposition Ca-HCO3
type The data indicate that a
number of different processes are active in the
different environments, and that gases (in
particular CO2) have an active role in driving
equilibria
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Macedonia
Hydrofacies: waters range from Ca-HCO3, Na-Cl and the Na-HCO3 type
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Serbia
Most waters range from the Ca-HCO3 to the Na-HCO3 type
Ca-HCO3
type
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Slovenia
Conservative mixing between Ca-HCO3 and Na-Cl waters are absent or negligible, indicating
non-interacting reservoirs. Possible processes of
freshwater intrusion are highlighted
seawater Ca-HCO3
type
Hydrofacies: mostly waters range from the Ca-HCO3 and Na-HCO3 type Na-Cl waters are
limited
fresh water intrusion?
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Waters origin: oxygen and hydrogen stable isotopes
-90
-70
-50
-30
-10
10
-12 -10 -8 -6 -4 -2 0 2
dD
d18O
Serbia
Greece
Bosnia
Slovenia
Global Meteoric Water Line Central Mediterranean Water Line
Seawater source
Most water-types have a meteoric origin. Na-Cl waters have a marine origin. Modern or ancient seawater?
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Strontium isotopes: the modern or ancient origin of the marine Na-Cl type waters
0.7065
0.7070
0.7075
0.7080
0.7085
0.7090
0.7095
0 100 200 300 400 500
87S
r /
86 S
r
Numerical Age, Ma
Mc Arthur et al, 2001, 2007
The 87Sr/86Sr ratio in seawater
changes through geological time,
allowing the “age” of the saline
reservoir to be inferred
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The Na-HCO3 waters: extreme compositions through water-rock interaction
0.1
1
10
100
1000
10000
0.1 1 10 100 1000 10000 100000
HC
O3
(mg/
L)
Na (mg/L)
Bosnia
Croatia
Greece
Macedonia
Serbia
Slovenia
The waters from the Peri-Adriatic region show a Na vs. HCO3 scattered distribution, in some cases with high HCO3. Most waters from Greece are displaced towards low HCO3
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Some of the Na HCO3 thermal waters likely reflect silicate weathering:
silicates have low solubilities (NaAlSi3O8: 6x10-7 mol/L) and low
dissolution rates
the Na-HCO3 signature reflects long residence times of waters in deep environments
These thermal reservoirs are of particular interest
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Temperature
0
500
1000
1500
2000
2500
3000
3500
0 20 40 60 80
TD
S (
mg/L
)
Temperature (°C)
(Miosic et al., 2013)
Bosnia
the trends of increasing temperature with increasing salinity and chloride content
suggest, at least in some cases, the role of a high-thermal
component of marine origin
0
50
100
150
200
250
300
350
400
0 20 40 60 80
Cl (
mg
/L)
Temperature (°C)
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0
10
20
30
40
50
60
70
0 20 40 60 80
SiO
2 (m
g/L
)
Temperature (°C)
(Milenic et al., 2012)
0
20
40
60
80
100
120
140
0 10 20 30 40
Ca (
mg
/L)
Temperatura (°C)
Serbia
Despite some scatter, the trend of increasing temperature with
increasing silica likely indicate the role of high-thermal components
related to silicate dissolution.
The pattern of decreasing calcium with increasing temperature could
reflect the saturation state of carbonates, yielding cement
precipitation
Temperature
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0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100
SiO
2 (m
g/L
)
Temperature (°C)
(Lambrakis & Stamatis, 2008)
Greece
Also in this case, some of the waters likely reflect the role of
high-thermal, deep components related to silicate dissolution.
Trends of decreasing calcite and dolomite saturation states with
decreasing temperature are also observed, indicating the role of
CO2-mediate carbonate equilibria
Temperature
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A variety of hydrofacies characterize the active geothermal manifestations used for thermal balneology in the Peri-Adriatic region
Waters have both a meteoric origin or maintain a marine signature, likely attributable to modern or to remnants of ancient seawater. Isotopic studies would help to clarify this point
Some of the waters are diagenetically modified by long-lasting interactions with the aquifer lithologies, suggesting high residence times and/or slow flowpaths. In particular, the interactions with low-solubility silicate minerals is likely responsible for the particular Na-HCO3 signature of the thermal, deeper reservoirs. These waters would deserve further studies.
For these waters, long-term abstraction should be carefully planned
In some cases, mixing of waters with different geochemical signature occurs
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Example of application of geochemical tools
The Monfalcone (Grado – Lignano) thermal waters in the coastal area of the Friuli Plain
(NE-Italy): a case history
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Monfalcone: natural springs (34-40 °C) Grado: Grado-1 well (1100 m depth; 43 °C) Lignano: SIL well (≈2000 m depth; 53 °C)
Sites of study
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Geological framework of the Trieste Gulf
Monfalcone
Lignano Grado
After Carulli (2011) J. Geodyn. 51, 156-165 Mesozoic-Cenozoic carbonate Units
Paleogene Terrigenous Units
Quaternary alluvial sediments
A
B
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Multichannel seismic profile across the Trieste Gulf
Busetti et al 2010
Friuli Carbonate Platform
Eocene Flysch terrigenous sequence
Plio-Quaternary marine sediments
A B
Lignano Grado-1
Monfalcone
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Hydrochemistry
Monfalcone Grado-1
freshwater
Modern seawater
Wells in the FVG Low Plain
The Monfalcone, Grado-1 and Lignano deep waters have all the chemical signature like modern seawater
NOTE Some of the waters
from geothermal wells in the FGV
Low Plain are of the Na-HCO3 type
Lignano
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0
2000
4000
6000
8000
10000
12000
0 5000 10000 15000 20000
Na
(mg
/L)
Cl (mg/L)
Monfalcone
Grado-1
Lignano
Modern seawater
Waters from the Lignano well are the most representative of the marine end-member Dilution processes are active at the Monfalcone springs and Grado-1 well to a lower extent
A marine component also contributes to waters from geothermal wells in the FVG Plain (crosses)
The marine signature
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-80
-70
-60
-50
-40
-30
-20
-10
0
10
-13 -11 -9 -7 -5 -3 -1 1
dD
d18O
Monfalcone
Grado-1
Lignano
Dilution processes and origin of non-marine component
Karst-type waters
The freshwater component might be represented by karst-type groundwaters
FVG Low Plain geothermal wells
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0
500
1000
1500
2000
2500
3000
0 5000 10000 15000 20000
SO4 (
mg
/L)
Cl (mg/L)
Monfalcone
Grado-1
Lignano
Evolutionary patterns of the marine component
seawater
Sulfate depletion
Sulfate excess
Sulfate excess and mixing corrosion
3
2
4
2
322
3
2
4
2
342
4222
2222
222
2
HCOSOCaCaCOOSH
HCOSOCaCaCOSOH
SOHOSH
30
0
200
400
600
800
1000
1200
1400
1600
0 5000 10000 15000 20000
Ca
(mg
/L)
Cl (mg/L)
Monfalcone
Grado-1
Lignano
seawater
Calcium excess
Diagenetic reactions of seawater with the hosting carbonates
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Monfalcone
Grado-1 Lignano
Alpi orientali Sulfur springs in Eastern Alps
Crustal gas-water interactions
Samples deviate from the composition of air saturated water towards the admixing
of crustal gases.
This has implication on the volume of the thermal
reservoir, since the original atmospheric signature has been replaced by crustal
components:
LOW WATER VOLUME OR DISCONTINUOUS WATER
BODIES (?)
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0,7077
0,7078
0,7079
0,7080
0,7081
0,7082
0,7083
0,7084
87Sr
/86Sr
lignano monfalcone Grado-1
Modern or ancient seawater?
Sr-isotope ratio of modern seawater 0.70918
A possible common marine source for Monfalcone, Grado-1 and Lignano
The thermal waters do not have the isotopic signature of present-day seawater !
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0,7070
0,7075
0,7080
0,7085
0,7090
0,7095
0 20 40 60 80 100
87
Sr
/ 8
6 S
r
Numerical Age, Ma
reservoir
excessexcess
reservoir
excessmeasuredreservoir
Sr
SrSrSr
Sr
SrSrSrSrSr 868786878687 /1//
Deconvolving the diagenetic chemical changes and “age” of the thermal component
the marine reservoir would be represented by ancient seawaters “dated “ at Miocene
Sr isotopic changes in seawater through time
Monfalcone, Grado-1, Lignano
Mass-balance equation
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0
5000
10000
15000
20000
25000
30000
35000
40000
45000
0 10 20 30 40 50 60
EC (
uS/
cm)
T (°C)
Monfalcone
Grado-1
Lignano
Temperature
Karst waters
The thermal reservoir is best represented by the saline ancient seawater Cooling by dilution is observed; however the karst-type waters of superficial aquifers are
unsuitable as cold term
?
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60 70
80
Modern seawater
°C Lignano Grado-1
Deconvolution of the diagenetic processes of ancient seawater in the deep carbonate reservoir to estimate
temperature of the geothermal component
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65 °C is the T at about 2.0-2.5 km in carbonate
reservoir
Friuli thermal waters represent the ancient, diagenetically modified seawater of a low temperature geothermal system
Deep saline reservoir might represent remnants of seawater entrapped in Mesozoic carbonates during the late Oligocene–Miocene sea transgression
In some parts the deep thermal reservoir mixes and homogeneizes with colder kast(?)-type waters flowing in, through a deep and long-lasting circuit
Thermal reservoir might be composed by discrete aquifers, or might not be widely extended
Hydrothermal diagenesis including dolomite cementation might change the water flow dynamics at depth
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Concluding remarks
Generalized geothermal model
?
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Thank you for your attention
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Some of the waters show a Na vs. Cl linear correlation, suggesting the role of seawater or
dissolution of marine salts
On this ground, the contribution of the marine component can be removed
0.1
1
10
100
1000
10000
100000
0.1 1 10 100 1000 10000 100000
Cl (
mg
/L)
Na (mg/L)
40
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0 500 1000 1500 2000 2500 3000
Na (mg/L)
HC
O3 (
mg
/L) After correction a more clear correlation in observed, following the equimolar
distribution of Na and HCO3 ions (solid line)
This is consistent with the (incongruent) silicate dissolution to generate the Na-HCO3 waters:
2452232283 4)(22232 SiOOHOSiAlHCONaCOOHONaAlSi
as an example
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