the role of fault-zones on groundwater flow in crystalline …€¦ · the role of fault-zones on...
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The role of fault-zones on groundwater
flow in crystalline basement
Clément Roques(1), Olivier Bour (1), Luc Aquilina(1), Benoît Dewandel (2), Jean-Michel
Schroetter (3), Hélène Pauwels (4), Jean-Christophe Maréchal(2), Laurent Longuevergne(1),
Tanguy Le Borgne(1), Thierry Labasque(1), Virginie Vergnaud-Ayraud(1), Sarah Leray(1),
Rebecca Houchreutener(1), Nicolas Lavenant(1), Bruno Mougin(3), Christian Camerlynck(5)
and Stéphane Durand(6)
(1) University of Rennes 1, Rennes, France; (2) BRGM, Water Dept., New Water Resource &
Economy Unit, Montpellier, France; (3) BRGM, Regional Geological survey of French Brittany,
Rennes, France; (4) BRGM, Water Dept., Orléans, France; (5) UPMC-University of Paris 6, Paris,
France; (6) CNAM – ESGT
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Groundwater flow in crystalline media
Subsurface flow
Matrix
storage (?)
Deep flow (?)
Hydrodynamic properties of fault-zones ?
Origin of water?
Sustainability resource ?
(?)
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A multidisciplinary approach : Field site (CASPAR Project)
Structural architecture => Geology and Geophysics;
Flow => Hydrodynamic and flow logging;
Groundwater sources => Hydrogeochemistry and groundwater
dating (Anions, Cations, Traces, CFC/SF6, Noble gases).
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The field site of Saint-Brice-en-Coglès
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Normal faults in a graben structure
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GW flow controlled by the main tectonic structure
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Origin of water
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C1C2
C3
C4C5
5 sampling campaigns at different hydrological regi mes
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Hydrogeochemical compartmentalization
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Re
go
lith
Fau
lt-z
on
e
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CFC-12 vs SF6 compartmentalization
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Regolith
Fault-zone
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Paleo-water signature from noble gases concentratio ns
12°C
Regolith
7°C
Fault
High Water Level
Fault
Low Water Level
Recharge Temp. (°C)
0°C
5°C
10°C
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How do we estimate mixing and origin of water?
Conservative
tracers
End-members
composition
Principal component analysis
End-members mixing analysis
DISCHARGE FRACTIONS
from each end-members
Laaksoharju et al., 2008 11
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Dis
cha
rge
fra
ctio
n [
-]
Discharge
(C2)
Recharge
(C4)
Origin of water controlled by regional hydrological regime
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Pumping dependent on storage reservoirs
139 weeks pumping test at 45 m3/h
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Conclusion & Perspective
� Fault zone can present high hydraulic
properties to drive GW flow at depth;
� Various origins of waters controlled
by regional hydrological regimes;
� Yields of fault-zones are highly
dependent of storage reservoirs;
� It is NOT a unique case! => Regional
study of high yield fault-zones in the
Armoricain Massif (21 sites)
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LOG(k) [m2]D
ep
th [
m]
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Thank you for your
attention!