1. HYDRAULIC BINDING BETWEEN STRUCTURAL ELEMENTS AND
GROUNDWATER CIRCULATION IN A VOLCANIC AQUIFER:
INSIGHTS FROM RIANO QUARRIES DISTRICT (Rome Italy)
David Rossi
Elisabetta Preziosi, Stefano Ghergo, Daniele Parrone,
Stefano Amalfitano, Anna Bruna Petrangeli & Annamaria Zoppini
2. INTRODUCTION
As long been recognized, geological heterogeneity represents a
fundamental aspect for water circulation. In particular, meso-scale
brittle deformation elements influence the potential gradient of
water circulation and geochemical patterns related to the strain
processes.
The analysis of geological heterogeneity related to brittle
deformations is crucial to modelling surface and groundwater
dynamics. In areas characterized by intense extractive activities,
brittle deformation effects become more evident because of the
intrinsic groundwater vulnerability.
3. RATIONALE
PROBLEM: In Riano quarry District fractures show alteration bands
• Is this related to precipitation water interaction
(solution/precipitation) with fractured rocks?
OR
• Is this the result of deep thermal water upwelling?
In this case, which is the role of fracture network in the
interaction between shallow and deep aquifer circulation?
5. RIANO QUARRIES DISTRICT
• Due to the intense extractive activities the Riano quarries District
(120km2) is characterized by numerous artificial surfaces perfectly
smoothed in both horizontal and vertical orientation.
• 26 of the 32 quarries identified were selected due to their
accessibility, the presence of smooth horizontal and vertical
surfaces and the amount of logs and wells available. Fracture
distribution, orientation and length data in three dimensions
were collected. A total of 12570 fractures were measured.
• Most of the fractures shows a pervasive alteration band with
different colors and thickness around the whole fracture shape.
6. SOME EXAMPLES
Quarry A Quarry C Quarry F
Quarry D Quarry I - J
Quarry O Quarry B Quarry Q
Quarry G
14. GROUNDWATER
Earth-alkaline/alcaline
bicarbonate waters
Mean (mg/kg) ST DEV
Li 55,18 5,32
Be 12,44 0,56
Na 1317,56 282,31
Mg 671,00 663,62
Al 45851,26 4444,35
K 45632,62 6266,30
Ca 64068,29 8253,63
V 62,44 8,47
Cr 40,35 25,85
Fe 19600,12 889,82
Mn 741,79 70,72
Co 3,76 0,20
Ni 23,55 12,05
Cu 8,25 0,66
Zn 66,81 3,79
Ga 100,73 11,06
As 23,05 2,84
Se 2,34 0,93
Rb 168,41 46,83
Sr 1294,44 161,76
Mo 0,32 0,20
Ag 2,44 0,30
Cd 2,68 0,23
Sb 1,27 0,10
Cs 22,18 3,23
Ba 591,95 121,40
Tl 2,01 0,13
Pb 117,81 8,62
U 16,54 3,11
Microwave acid digestion + ICP-MS
UNALTEREDROCKS
ALTERATIONBAND
Mean mg/kg ST DEV
Li 34,59 10,77
Be 16,78 5,32
Na 733,47 1049,62
Mg 94,92 22,63
Al 36737,35 9057,75
K 42152,11 4827,28
Ca 48366,18 13357,99
V 71,96 9,45
Cr 44,59 21,63
Fe 29687,34 5247,26
Mn 1942,41 1434,14
Co 3,42 1,38
Ni 23,72 11,80
Cu 8,58 3,77
Zn 84,59 13,37
Ga 118,21 39,11
As 36,75 14,71
Se 0,47 0,37
Rb 106,48 25,46
Sr 1311,72 194,57
Mo 0,21 0,13
Ag 2,43 0,24
Cd 3,06 0,54
Sb 1,09 0,24
Cs 22,38 4,00
Ba 795,22 305,03
Tl 3,38 5,08
Pb 136,45 22,09
U 9,98 2,64
XRF %
SiO2 45,88
CaO 11,24
Na2O 0,77
Fe2O3 45,86
TiO2 0,44
Al2O3 14,97
MnO 0,11
MgO 1,51
K2O 5,84
2O5 0,15
XRF %
SiO2 48,95
CaO 8,31
Na2O 0,70
Fe2O3 48,25
TiO2 0,44
Al2O3 15,05
MnO 0,11
MgO 1,47
K2O 5,915
P2O5 0,145
I would like to thank Aida Conte for XRF analysis
and Stefano Stellino for diffractometers analysis
NO SIGNIFICATIVE DIFFERENCES WERE FOUND
15. CONCLUSIONS
• Fracture sets formed sequentially in Tuffs, with same mechanical
properties, were characterized by two main generation of
extensional fractures linked to buried extensional faults:
S1 oriented N170° and S2 oriented N27°.
• A depletion of Ca, Na, Mg, Al, U and CaO in the tuff alteration
bands could be related to the solution processes of meteoric
water circulation within fractures as also suggested by
groundwater classification
• The observed enrichment in Mn-Fe-Zn and As could be a
consequence of the earth-alcaline elements depletion
• Data do not show any evidence of deep water upwelling
processes.
