In southern Tuscany (central Italy), deep to shallow geothermal systems were active since the Ple... more In southern Tuscany (central Italy), deep to shallow geothermal systems were active since the Pleistocene and comprise fluids carrying variable amounts of CO 2 . The Monte Amiata geothermal fields include two main reservoirs: a deep one located in the Palaeozoic metamorphic succession (1300-3000 m deep) belonging to the Tuscan metamorphic 'basement' and a shallow one hosted in the Mesozoic sedimentary succession (500-1000 m deep) belonging to the Tuscan Nappe. Multiple sets of calcite veins were investigated in some outcrops of the Tuscan Nappe succession exposed in the Monte Amiata area and surroundings. Two main fluid systems were characterized: the former related to combined diagenetic syn-tectonic processes from highly saline fluids after interaction with the Late Triassic evaporites (Burano Fm) and the latter related to a fossil geothermal system, Pleistocene in age, fed by low-salinity meteoric fluids, carrying CO 2 , radiogenic Sr and heavy O isotopes after interaction with the subsurface rocks. Comparison with the present-day hydrothermal fluids allowed to sketch the thermal evolution of the system from past to present. Geochemical data proved that portions of the vein-host rocks were reset after interaction with CO 2 -rich fluids circulating in the past. Consequently, textural and mineralogical changes are expected to have occurred with respect to the undisturbed rock masses. Understanding these modifications, their location and extension, is a prerequisite to construct (i) geochemical models addressed to the comprehension of the diagenesis induced in sediments after long-term CO 2 storage; and (ii) geological models applied to the prediction of rock heterogeneity distribution within the upper reservoirs, characterizing the shallow (500-1500 m) geothermal systems of southern Tuscany. 127 Modelling fault reactivation and fluid flow around a fault restraining step-over structure in the Laverton gold region, Yilgarn Craton, Western Australia Y. Zhang, P.M. Schaubs, H.A. Sheldon, T. Poulet and A. Karrech 140 Fluid channeling along thrust zones: the Lagonegro case history, southern Apennines, Italy T. Gabellone, M. Gasparrini, A. Iannace, C. Invernizzi, S. Mazzoli and M. D'Antonio 159 Diagenesis versus hydrothermalism and fluid-rock interaction within the Tuscan Nappe of the Monte Amiata CO 2 -rich geothermal area (Italy) M. Gasparrini, G. Ruggieri and A. Brogi 180 Diagenetic evolution of a fractured evaporite deposit (Vilobí Gypsum Unit, Miocene, NE Spain) M. Moragas, C. Martínez, V. Baqués, E. Playà, A. Travé, G. Alías and I. Cantarero 194 Geochemical simulations to assess the fluorine origin in Sierra de Gador groundwater (SE Spain) L. Daniele, M. Corbella, A. Vallejos, M. Díaz-Puga and A. Pulido-Bosch 204 Quantification of diagenesis impact on the reservoir properties of the Jurassic Arab D and C members (Offshore, U.A.E.)
In the extensional province of SW-Anatolia, the cross-cutting relationship between the NW-and NE-... more In the extensional province of SW-Anatolia, the cross-cutting relationship between the NW-and NE-oriented Neogene and Quaternary basins is an ongoing debate in the understanding of the tectonic evolution of this area. In order to contribute to this issue, we carried out a structural and kinematic study along the seismogenic NW-trending Dinar Fault Zone (DFZ). This structure was initially controlled by the sedimentary and tectonic evolution of the NE-oriented Neogene Baklan, Acıgöl and Burdur basins and, later, by the NW-oriented Quaternary Dinar Basin. On the basis of N 1000 structural and kinematic data, in conjunction with basin stratigraphy, the DFZ can be divided into three almost parallel and continuous bands, that are: (a) the Hangingwall where Quaternary sediments are deformed by normal faults with mechanical striations; (b) the Inner Zone, corresponding to the present Dinar fault scarp, where NW-trending normal faults with mechanical striations are dominant, and (c) the Outer Zone, located in the footwall of the structure comprising the area between the fault scarp and undeformed bedrock, where faults exhibit variable orientation and kinematics, from strike-slip to normal dip-slip. These kinematics are mainly indicated by calcite shear veins and superimposed mechanical striations, respectively. This suggests that the DFZ changed kinematics over time, i.e., the DFZ initiated as dominant dextral strike-slip to oblique-slip fault system and continued with a dominant normal movement. Therefore, we hypothesize that the NWtrending DFZ was initially a transfer zone during the late Miocene-Pliocene, coeval to the sedimentary and structural evolution of the NE-trending Baklan, Acigöl and Burdur basins. During the Quaternary the DFZ, representing an already weakened crustal sector, played the role of a normal fault system providing the accommodation space for the Quaternary Dinar Basin. Hydrothermal circulation and volcanism at NE-/NW-trending faults intersection implies structurally-driven conduits channeling fluids from depth to surface.
This paper deals with the tectonic control on the hydrothermal system that gave rise to Sb–Hg ore... more This paper deals with the tectonic control on the hydrothermal system that gave rise to Sb–Hg ore deposits in the Monte Amiata area that was one of the most relevant mining district for the exploitation of mercury in Italy. The study area (Selvena mining district) is located in southern Tuscany (inner Northern Apennines) one of the most important mineralized area in the western Mediterranean region. Southern Tuscany was severely affected by Middle–Late Miocene low-angle normal faults, later dissected by Pliocene–Pleistocene faults, coeval magmatism (Late Miocene–Pleistocene) and hydrothermal activity (Pliocene–Present). The Selvena mining district is located south of Middle Pleistocene Monte Amiata volcanic complex. Our structural and kinematic study is based on the integration among fieldwork, borehole and mine data. The results highlight two Pleistocene–Holocene left-lateral transtensional shear zones linked by normal faults, defining a coeval pull-apart structure. Here, the Sb–Hg mineralization, transported by meteoric hydrothermal fluids mainly, is particularly diffuse and concentrated in the cataclasites and in damage zones of the normal faults. Furthermore, a widespread mineralization also occurs in the cataclasites of Miocene low-angle normal faults. Mine evidence suggests that ore-bearing fluids percolated through structural conduits located along the fault planes and resulting parallel to the intermediate stress axis. Geological structures and ore deposit distribution are related to a single hydrothermal circuit, with meteoric water channelled to depth through conduits parallel to the intermediate stress axis of the transcurrent shear zones; then, hydrothermal fluids mainly ascended through the almost vertical deformation zones located at the intersection between normal and strike-slip faults. Thus, hydrothermal fluids permeated also the Middle–Late Miocene cataclasites. This study shed light on the relationships between geological structures and mineralization in southern Tuscany and underlines the importance to investigate mine areas to understand hydrothermal fluids path.
This paper accounts for a new finding of High Pressure-Low Temperature (HP-LT) metamorphism docum... more This paper accounts for a new finding of High Pressure-Low Temperature (HP-LT) metamorphism documented in continental-derived rocks exposed in the central part of the Middle Tuscan Range, representing the easternmost location, in the Tyrrhenian Region, where blueschist facies metamorphism has been documented. It describes the development mechanism of Mg-carpholite bearing quartz veins in the framework of the deformational events described for the inner Northern Apennines. The HP-LT peak metamorphism can be estimated in P ≥ 1.1 GPa and T = 370°-420°C as supported by the mineralogical assemblage consisting of quartz-muscovite-chloritoid-pyrophylite-hematite ± chlorite ± paragonite ± Ti-oxides, documented in the aluminous metasediments (pelites and quartzose sandstones) of the Triassic Verrucano succession. This paragenesis defines the S 1 schistosity, an axial planar tectonic foliation associated to map-and mesoscale isoclinals folds (F 1 ); S 1 schistosity is a composite foliation resulted from a non-coaxial progressive deformation associated to the DE 1 collisional event (Late Oligocene-Early Miocene). Mg-carpholite bearing quartz veins developed as tension gashes in en-échelon arrays within brittle/ductile shear zones. The development of quartz veins was guaranteed by the high volumes of Si-rich fluids produced by the dynamic recrystallization process on the siliciclastic rocks.
The Larderello geothermal field is located in the Inner Northern Apennines, in an area which has ... more The Larderello geothermal field is located in the Inner Northern Apennines, in an area which has been subject to extension since the Early Miocene. The latest extensional episode (Pliocene -Present) has resulted in the formation of NW-trending, NEdipping listric normal faults, whose geometry is controlled down to f 3 km by borehole data. In this paper, we integrate a new interpretation of seismic reflection lines with existing seismic, field, and borehole data to analyse the relations among listric normal faults, the top of the brittle -ductile transition, and the migration of geothermal fluids.
The tectonic history of Neogene-Quaternary extensional structures has been documented in the inne... more The tectonic history of Neogene-Quaternary extensional structures has been documented in the inner part of the Northern Apennines (Rapolano Terme area) from Quaternary travertines and faults relationships. In particular, structural studies, field mapping and tectono-stratigraphical considerations on the pre-Neogene, Pliocene and Quaternary units indicate two fault populations of different ages. The travertines, broadly exposed in the Rapolano Terme area, were related to hydrothermal fluid circulation and upwelling along the damage zones of Pleistocene normal faults. These structures were superimposed upon normal (mainly NNW-SSE and SW-NE oriented) and transtensional (mainly SW-NE oriented) faults, Early-Middle Pliocene in age, related to development of the Siena Basin. The age of such Pliocene normal and transtensional faults has been inferred on the basis of the relationships between tectonic elements and Pliocene deposits. In fact, Middle Pliocene marine sandy and gravelly sediments suture the faults. The Pleistocene normal faults (mainly SW-NE oriented) reactivated the oldest SW-NE transtensional faults, cut the NNW-SSE normal faults, and displaced Middle Pliocene marine deposits. Pleistocene-Holocene travertines and present-day thermal springs mainly occur at the intersection points between the Pleistocene SW-NE faults and the Pliocene NNW-SSE normal faults, or along the SW-NE Pleistocene normal faults.
Bollettino della Società geologica italiana, Jan 1, 2004
Cartographic data for the northeastern side of the Monte Amiata area suggest a very complicated g... more Cartographic data for the northeastern side of the Monte Amiata area suggest a very complicated geometric setting for the Tuscan Nappe cropping out in the Poggio Zoccolino and Campiglia d'Orcia areas. The occurrence of some outcrops consisting of «Calcare Cavernoso» and « ...
International Journal of Earth Sciences, Jan 1, 2009
In this paper we describe an example of travertine fissure-ridge development along the trace of a... more In this paper we describe an example of travertine fissure-ridge development along the trace of a normal fault with metre displacement, located in the eastern margin of the Neogene-Quaternary Siena Basin, in the Terme S. Giovanni area (Rapolano Terme, Italy). This morphotectonic feature, 250 m long, 30 m wide and 10 m high, formed from supersaturated hot waters (39.9°C) flowing from thermal springs aligned along the trace of the normal fault dissecting travertines not older than Late Pleistocene (24 ± 3 ka). A straight, continuous fissure with a maximum width of 20 cm occurs at the top of the ridge, along its crest. Hot fluids flow from cones mainly located at the extremities of the ridge, where travertine is depositing. The travertine fissure-ridge shows an asymmetrical profile since it buries the fault scarp. The difference in height of slopes corresponds to the vertical displacement of the normal fault. Fissuring of the recent travertine deposits along the strike of the crestal fissure, as well as recent hydrothermal circulation, lead us to believe that the Terme S. Giovanni normal fault may be currently active. On the whole, the Terme S. Giovanni fissure ridge can be defined as a travertine fault trace fissure-ridge, adding a helpful example for studying the relationship between faulting and travertine deposition.
Bollettino della Società geologica italiana, Jan 1, 2002
The user has requested enhancement of the downloaded file. All in-text references underlined in b... more The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately.
This paper deals with the lateral segmentation (crustal boudinage) and exhumation of the metamorp... more This paper deals with the lateral segmentation (crustal boudinage) and exhumation of the metamorphic units in the hinterland of the Northern Apennines during the Late Miocene extension. The study area (Mt. Leoni area) is part of the Middle Tuscan Ridge, a regional morpho-tectonic feature in which the deepest tectonic units of the Northern Apennines are broadly exposed. Crustal seismic profiles and deep boreholes indicate that the Middle Tuscan Ridge coincides with the outcropping part of a laterally discontinuous geological body, mainly made up of HP-LT and greenschist facies metamorphic units. Extensional detachments characterised by top-to-the-East sense of shear and staircase geometry produced the lateral segmentation of the metamorphic units. Their activity can be ascribed to Late TortonianeLate Messinian times. Geometry and kinematics of the extensional detachments have been compared with the Miocene extensional structures developed at shallow depths in the overthickened crust of the Northern Apennines, allowing understanding of the extensional tectonic evolution which reorganised the hinterland Northern Apennines collisional belt.
Bollettino della Società geologica italiana, Jan 1, 2004
The continental crust in the Mt. Amiata geothermal area was involved, in the Early-Middle Miocene... more The continental crust in the Mt. Amiata geothermal area was involved, in the Early-Middle Miocene, in widespread megaboudinage which affected all the cover tectonic units of the Northern Apennines and, in particular, the Tuscan Nappe. Field work, deep boreholes and ...
This paper deals with the structural evolution along a transect across the inner Northern Apennin... more This paper deals with the structural evolution along a transect across the inner Northern Apennines (Monte Amiata volcano-geothermal area-Monte Cetona), mainly focussing on the post-orogenic Middle Miocene-Quaternary structures. The tectonic setting of the study area derives from the superimposition of three main faulting events: the first and second events developed during the Middle-Late Miocene and Early-Middle Pliocene, respectively, and took place in response to extensional tectonics. The third faulting event developed in a transcurrent/transtensional setting during the Quaternary. Quaternary faults mainly strike NE-SW and show left-lateral kinematics with a minor dip-slip normal component. They caused the Monte Amiata volcanic eruptions (300-190 ka) and controlled the widespread Pleistocene and present hydrothermal fluids circulation. Quaternary strike-slip faults have been documented in the Monte Amiata-Monte Cetona area for the first time in this paper. Correlation with the adjoining areas (e.g. Vulsini region) identifies the Quaternary strike-slip faulting recognised in the study area as a feasible source for the seismic activity in the Monte Amiata region, where the origin of diffuse low-magnitude seismicity is still under debate and poorly understood.
Bollettino della Società geologica italiana, Jan 1, 2004
The geological research focused on the southern Tuscany continental crust and finalised on the Cr... more The geological research focused on the southern Tuscany continental crust and finalised on the Cro.P.18 Project (LAZZAROTTO & LIOTTA, 1994; MORELLI, 2000), allowed reconsideration of the geological setting for some areas located along the Cro.P.18 crustal seismic profile, ...
Studies of fracture networks and hydrothermal mineralisation of several faults affecting Jurassic... more Studies of fracture networks and hydrothermal mineralisation of several faults affecting Jurassic siliceous sedimentary rocks, exposed in the Rapolano geothermal area (hinterland of the Northern Apennines, Italy), allow us to characterise the fault zone architectures and their permeability features. The study structures are normal faults with displacements of anything up to 30e40 m, belonging to a fossil hydrothermal system, Pleistocene in age. The fault zones are characterised by asymmetrical damage zones which are thickest in the hangingwall blocks. Fracture networks mainly consist of a subvertical fracture set at about 45 with respect to the fault plane. Widespread hydrothermal alteration (illite/smectite and kaolinite) and mineralisation consisting of quartz, calcite, dolomite, malachite, azurite and iron oxides characterise the fractures of the damaged rocks. This mineralisation suggests the occurrence of extraformational fluid circulation during the latest stage of faulting. Fault cores are characterised by cemented fault rock up to 25 cm thick, consisting of protocataclasite and ultracataclasite layers, grading to crush and fine crush breccia strongly affected by minor C 1 -type shear planes. Fault cores represented barriers to fluid flow during the latest stage of faulting, whereas they acted as conduits during the initial stages. Fault zones with similar features are presently affected by hydrothermal circulation (thermal water up to 39 C, and CO 2 ). The hydrothermal fluids give rise to several thermal springs and are exploited at depth for thermal resorts and CO 2 extraction, both in the Rapolano area and surroundings. A similar scenario characterises the Larderello-Travale and Mt. Amiata geothermal areas, where hydrothermal fluids and steam are industrially exploited for electricity production. The main results of this study are that the damage zone is asymmetrical and widest in the hangingwall. This could represent a useful contribution to the prediction of hydrothermal fluid pathways and geothermal targets in all the geothermal areas with similar features to those described here.
Bollettino della Società Geologica Italiana. Volume …, Jan 1, 2005
Résumé/Abstract The integration of fieldwork, borehole and geophysical data (commercial seismic r... more Résumé/Abstract The integration of fieldwork, borehole and geophysical data (commercial seismic reflection profiles) highlighted the occurrence of syncollisional thrust structures within the Tuscan nappe cropping out in the Mt. Amiata geothermal area. These ...
In southern Tuscany (central Italy), deep to shallow geothermal systems were active since the Ple... more In southern Tuscany (central Italy), deep to shallow geothermal systems were active since the Pleistocene and comprise fluids carrying variable amounts of CO 2 . The Monte Amiata geothermal fields include two main reservoirs: a deep one located in the Palaeozoic metamorphic succession (1300-3000 m deep) belonging to the Tuscan metamorphic 'basement' and a shallow one hosted in the Mesozoic sedimentary succession (500-1000 m deep) belonging to the Tuscan Nappe. Multiple sets of calcite veins were investigated in some outcrops of the Tuscan Nappe succession exposed in the Monte Amiata area and surroundings. Two main fluid systems were characterized: the former related to combined diagenetic syn-tectonic processes from highly saline fluids after interaction with the Late Triassic evaporites (Burano Fm) and the latter related to a fossil geothermal system, Pleistocene in age, fed by low-salinity meteoric fluids, carrying CO 2 , radiogenic Sr and heavy O isotopes after interaction with the subsurface rocks. Comparison with the present-day hydrothermal fluids allowed to sketch the thermal evolution of the system from past to present. Geochemical data proved that portions of the vein-host rocks were reset after interaction with CO 2 -rich fluids circulating in the past. Consequently, textural and mineralogical changes are expected to have occurred with respect to the undisturbed rock masses. Understanding these modifications, their location and extension, is a prerequisite to construct (i) geochemical models addressed to the comprehension of the diagenesis induced in sediments after long-term CO 2 storage; and (ii) geological models applied to the prediction of rock heterogeneity distribution within the upper reservoirs, characterizing the shallow (500-1500 m) geothermal systems of southern Tuscany. 127 Modelling fault reactivation and fluid flow around a fault restraining step-over structure in the Laverton gold region, Yilgarn Craton, Western Australia Y. Zhang, P.M. Schaubs, H.A. Sheldon, T. Poulet and A. Karrech 140 Fluid channeling along thrust zones: the Lagonegro case history, southern Apennines, Italy T. Gabellone, M. Gasparrini, A. Iannace, C. Invernizzi, S. Mazzoli and M. D'Antonio 159 Diagenesis versus hydrothermalism and fluid-rock interaction within the Tuscan Nappe of the Monte Amiata CO 2 -rich geothermal area (Italy) M. Gasparrini, G. Ruggieri and A. Brogi 180 Diagenetic evolution of a fractured evaporite deposit (Vilobí Gypsum Unit, Miocene, NE Spain) M. Moragas, C. Martínez, V. Baqués, E. Playà, A. Travé, G. Alías and I. Cantarero 194 Geochemical simulations to assess the fluorine origin in Sierra de Gador groundwater (SE Spain) L. Daniele, M. Corbella, A. Vallejos, M. Díaz-Puga and A. Pulido-Bosch 204 Quantification of diagenesis impact on the reservoir properties of the Jurassic Arab D and C members (Offshore, U.A.E.)
In the extensional province of SW-Anatolia, the cross-cutting relationship between the NW-and NE-... more In the extensional province of SW-Anatolia, the cross-cutting relationship between the NW-and NE-oriented Neogene and Quaternary basins is an ongoing debate in the understanding of the tectonic evolution of this area. In order to contribute to this issue, we carried out a structural and kinematic study along the seismogenic NW-trending Dinar Fault Zone (DFZ). This structure was initially controlled by the sedimentary and tectonic evolution of the NE-oriented Neogene Baklan, Acıgöl and Burdur basins and, later, by the NW-oriented Quaternary Dinar Basin. On the basis of N 1000 structural and kinematic data, in conjunction with basin stratigraphy, the DFZ can be divided into three almost parallel and continuous bands, that are: (a) the Hangingwall where Quaternary sediments are deformed by normal faults with mechanical striations; (b) the Inner Zone, corresponding to the present Dinar fault scarp, where NW-trending normal faults with mechanical striations are dominant, and (c) the Outer Zone, located in the footwall of the structure comprising the area between the fault scarp and undeformed bedrock, where faults exhibit variable orientation and kinematics, from strike-slip to normal dip-slip. These kinematics are mainly indicated by calcite shear veins and superimposed mechanical striations, respectively. This suggests that the DFZ changed kinematics over time, i.e., the DFZ initiated as dominant dextral strike-slip to oblique-slip fault system and continued with a dominant normal movement. Therefore, we hypothesize that the NWtrending DFZ was initially a transfer zone during the late Miocene-Pliocene, coeval to the sedimentary and structural evolution of the NE-trending Baklan, Acigöl and Burdur basins. During the Quaternary the DFZ, representing an already weakened crustal sector, played the role of a normal fault system providing the accommodation space for the Quaternary Dinar Basin. Hydrothermal circulation and volcanism at NE-/NW-trending faults intersection implies structurally-driven conduits channeling fluids from depth to surface.
This paper deals with the tectonic control on the hydrothermal system that gave rise to Sb–Hg ore... more This paper deals with the tectonic control on the hydrothermal system that gave rise to Sb–Hg ore deposits in the Monte Amiata area that was one of the most relevant mining district for the exploitation of mercury in Italy. The study area (Selvena mining district) is located in southern Tuscany (inner Northern Apennines) one of the most important mineralized area in the western Mediterranean region. Southern Tuscany was severely affected by Middle–Late Miocene low-angle normal faults, later dissected by Pliocene–Pleistocene faults, coeval magmatism (Late Miocene–Pleistocene) and hydrothermal activity (Pliocene–Present). The Selvena mining district is located south of Middle Pleistocene Monte Amiata volcanic complex. Our structural and kinematic study is based on the integration among fieldwork, borehole and mine data. The results highlight two Pleistocene–Holocene left-lateral transtensional shear zones linked by normal faults, defining a coeval pull-apart structure. Here, the Sb–Hg mineralization, transported by meteoric hydrothermal fluids mainly, is particularly diffuse and concentrated in the cataclasites and in damage zones of the normal faults. Furthermore, a widespread mineralization also occurs in the cataclasites of Miocene low-angle normal faults. Mine evidence suggests that ore-bearing fluids percolated through structural conduits located along the fault planes and resulting parallel to the intermediate stress axis. Geological structures and ore deposit distribution are related to a single hydrothermal circuit, with meteoric water channelled to depth through conduits parallel to the intermediate stress axis of the transcurrent shear zones; then, hydrothermal fluids mainly ascended through the almost vertical deformation zones located at the intersection between normal and strike-slip faults. Thus, hydrothermal fluids permeated also the Middle–Late Miocene cataclasites. This study shed light on the relationships between geological structures and mineralization in southern Tuscany and underlines the importance to investigate mine areas to understand hydrothermal fluids path.
This paper accounts for a new finding of High Pressure-Low Temperature (HP-LT) metamorphism docum... more This paper accounts for a new finding of High Pressure-Low Temperature (HP-LT) metamorphism documented in continental-derived rocks exposed in the central part of the Middle Tuscan Range, representing the easternmost location, in the Tyrrhenian Region, where blueschist facies metamorphism has been documented. It describes the development mechanism of Mg-carpholite bearing quartz veins in the framework of the deformational events described for the inner Northern Apennines. The HP-LT peak metamorphism can be estimated in P ≥ 1.1 GPa and T = 370°-420°C as supported by the mineralogical assemblage consisting of quartz-muscovite-chloritoid-pyrophylite-hematite ± chlorite ± paragonite ± Ti-oxides, documented in the aluminous metasediments (pelites and quartzose sandstones) of the Triassic Verrucano succession. This paragenesis defines the S 1 schistosity, an axial planar tectonic foliation associated to map-and mesoscale isoclinals folds (F 1 ); S 1 schistosity is a composite foliation resulted from a non-coaxial progressive deformation associated to the DE 1 collisional event (Late Oligocene-Early Miocene). Mg-carpholite bearing quartz veins developed as tension gashes in en-échelon arrays within brittle/ductile shear zones. The development of quartz veins was guaranteed by the high volumes of Si-rich fluids produced by the dynamic recrystallization process on the siliciclastic rocks.
The Larderello geothermal field is located in the Inner Northern Apennines, in an area which has ... more The Larderello geothermal field is located in the Inner Northern Apennines, in an area which has been subject to extension since the Early Miocene. The latest extensional episode (Pliocene -Present) has resulted in the formation of NW-trending, NEdipping listric normal faults, whose geometry is controlled down to f 3 km by borehole data. In this paper, we integrate a new interpretation of seismic reflection lines with existing seismic, field, and borehole data to analyse the relations among listric normal faults, the top of the brittle -ductile transition, and the migration of geothermal fluids.
The tectonic history of Neogene-Quaternary extensional structures has been documented in the inne... more The tectonic history of Neogene-Quaternary extensional structures has been documented in the inner part of the Northern Apennines (Rapolano Terme area) from Quaternary travertines and faults relationships. In particular, structural studies, field mapping and tectono-stratigraphical considerations on the pre-Neogene, Pliocene and Quaternary units indicate two fault populations of different ages. The travertines, broadly exposed in the Rapolano Terme area, were related to hydrothermal fluid circulation and upwelling along the damage zones of Pleistocene normal faults. These structures were superimposed upon normal (mainly NNW-SSE and SW-NE oriented) and transtensional (mainly SW-NE oriented) faults, Early-Middle Pliocene in age, related to development of the Siena Basin. The age of such Pliocene normal and transtensional faults has been inferred on the basis of the relationships between tectonic elements and Pliocene deposits. In fact, Middle Pliocene marine sandy and gravelly sediments suture the faults. The Pleistocene normal faults (mainly SW-NE oriented) reactivated the oldest SW-NE transtensional faults, cut the NNW-SSE normal faults, and displaced Middle Pliocene marine deposits. Pleistocene-Holocene travertines and present-day thermal springs mainly occur at the intersection points between the Pleistocene SW-NE faults and the Pliocene NNW-SSE normal faults, or along the SW-NE Pleistocene normal faults.
Bollettino della Società geologica italiana, Jan 1, 2004
Cartographic data for the northeastern side of the Monte Amiata area suggest a very complicated g... more Cartographic data for the northeastern side of the Monte Amiata area suggest a very complicated geometric setting for the Tuscan Nappe cropping out in the Poggio Zoccolino and Campiglia d'Orcia areas. The occurrence of some outcrops consisting of «Calcare Cavernoso» and « ...
International Journal of Earth Sciences, Jan 1, 2009
In this paper we describe an example of travertine fissure-ridge development along the trace of a... more In this paper we describe an example of travertine fissure-ridge development along the trace of a normal fault with metre displacement, located in the eastern margin of the Neogene-Quaternary Siena Basin, in the Terme S. Giovanni area (Rapolano Terme, Italy). This morphotectonic feature, 250 m long, 30 m wide and 10 m high, formed from supersaturated hot waters (39.9°C) flowing from thermal springs aligned along the trace of the normal fault dissecting travertines not older than Late Pleistocene (24 ± 3 ka). A straight, continuous fissure with a maximum width of 20 cm occurs at the top of the ridge, along its crest. Hot fluids flow from cones mainly located at the extremities of the ridge, where travertine is depositing. The travertine fissure-ridge shows an asymmetrical profile since it buries the fault scarp. The difference in height of slopes corresponds to the vertical displacement of the normal fault. Fissuring of the recent travertine deposits along the strike of the crestal fissure, as well as recent hydrothermal circulation, lead us to believe that the Terme S. Giovanni normal fault may be currently active. On the whole, the Terme S. Giovanni fissure ridge can be defined as a travertine fault trace fissure-ridge, adding a helpful example for studying the relationship between faulting and travertine deposition.
Bollettino della Società geologica italiana, Jan 1, 2002
The user has requested enhancement of the downloaded file. All in-text references underlined in b... more The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately.
This paper deals with the lateral segmentation (crustal boudinage) and exhumation of the metamorp... more This paper deals with the lateral segmentation (crustal boudinage) and exhumation of the metamorphic units in the hinterland of the Northern Apennines during the Late Miocene extension. The study area (Mt. Leoni area) is part of the Middle Tuscan Ridge, a regional morpho-tectonic feature in which the deepest tectonic units of the Northern Apennines are broadly exposed. Crustal seismic profiles and deep boreholes indicate that the Middle Tuscan Ridge coincides with the outcropping part of a laterally discontinuous geological body, mainly made up of HP-LT and greenschist facies metamorphic units. Extensional detachments characterised by top-to-the-East sense of shear and staircase geometry produced the lateral segmentation of the metamorphic units. Their activity can be ascribed to Late TortonianeLate Messinian times. Geometry and kinematics of the extensional detachments have been compared with the Miocene extensional structures developed at shallow depths in the overthickened crust of the Northern Apennines, allowing understanding of the extensional tectonic evolution which reorganised the hinterland Northern Apennines collisional belt.
Bollettino della Società geologica italiana, Jan 1, 2004
The continental crust in the Mt. Amiata geothermal area was involved, in the Early-Middle Miocene... more The continental crust in the Mt. Amiata geothermal area was involved, in the Early-Middle Miocene, in widespread megaboudinage which affected all the cover tectonic units of the Northern Apennines and, in particular, the Tuscan Nappe. Field work, deep boreholes and ...
This paper deals with the structural evolution along a transect across the inner Northern Apennin... more This paper deals with the structural evolution along a transect across the inner Northern Apennines (Monte Amiata volcano-geothermal area-Monte Cetona), mainly focussing on the post-orogenic Middle Miocene-Quaternary structures. The tectonic setting of the study area derives from the superimposition of three main faulting events: the first and second events developed during the Middle-Late Miocene and Early-Middle Pliocene, respectively, and took place in response to extensional tectonics. The third faulting event developed in a transcurrent/transtensional setting during the Quaternary. Quaternary faults mainly strike NE-SW and show left-lateral kinematics with a minor dip-slip normal component. They caused the Monte Amiata volcanic eruptions (300-190 ka) and controlled the widespread Pleistocene and present hydrothermal fluids circulation. Quaternary strike-slip faults have been documented in the Monte Amiata-Monte Cetona area for the first time in this paper. Correlation with the adjoining areas (e.g. Vulsini region) identifies the Quaternary strike-slip faulting recognised in the study area as a feasible source for the seismic activity in the Monte Amiata region, where the origin of diffuse low-magnitude seismicity is still under debate and poorly understood.
Bollettino della Società geologica italiana, Jan 1, 2004
The geological research focused on the southern Tuscany continental crust and finalised on the Cr... more The geological research focused on the southern Tuscany continental crust and finalised on the Cro.P.18 Project (LAZZAROTTO & LIOTTA, 1994; MORELLI, 2000), allowed reconsideration of the geological setting for some areas located along the Cro.P.18 crustal seismic profile, ...
Studies of fracture networks and hydrothermal mineralisation of several faults affecting Jurassic... more Studies of fracture networks and hydrothermal mineralisation of several faults affecting Jurassic siliceous sedimentary rocks, exposed in the Rapolano geothermal area (hinterland of the Northern Apennines, Italy), allow us to characterise the fault zone architectures and their permeability features. The study structures are normal faults with displacements of anything up to 30e40 m, belonging to a fossil hydrothermal system, Pleistocene in age. The fault zones are characterised by asymmetrical damage zones which are thickest in the hangingwall blocks. Fracture networks mainly consist of a subvertical fracture set at about 45 with respect to the fault plane. Widespread hydrothermal alteration (illite/smectite and kaolinite) and mineralisation consisting of quartz, calcite, dolomite, malachite, azurite and iron oxides characterise the fractures of the damaged rocks. This mineralisation suggests the occurrence of extraformational fluid circulation during the latest stage of faulting. Fault cores are characterised by cemented fault rock up to 25 cm thick, consisting of protocataclasite and ultracataclasite layers, grading to crush and fine crush breccia strongly affected by minor C 1 -type shear planes. Fault cores represented barriers to fluid flow during the latest stage of faulting, whereas they acted as conduits during the initial stages. Fault zones with similar features are presently affected by hydrothermal circulation (thermal water up to 39 C, and CO 2 ). The hydrothermal fluids give rise to several thermal springs and are exploited at depth for thermal resorts and CO 2 extraction, both in the Rapolano area and surroundings. A similar scenario characterises the Larderello-Travale and Mt. Amiata geothermal areas, where hydrothermal fluids and steam are industrially exploited for electricity production. The main results of this study are that the damage zone is asymmetrical and widest in the hangingwall. This could represent a useful contribution to the prediction of hydrothermal fluid pathways and geothermal targets in all the geothermal areas with similar features to those described here.
Bollettino della Società Geologica Italiana. Volume …, Jan 1, 2005
Résumé/Abstract The integration of fieldwork, borehole and geophysical data (commercial seismic r... more Résumé/Abstract The integration of fieldwork, borehole and geophysical data (commercial seismic reflection profiles) highlighted the occurrence of syncollisional thrust structures within the Tuscan nappe cropping out in the Mt. Amiata geothermal area. These ...
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Papers by Andrea Brogi
the Monte Amiata area that was one of the most relevant mining district for the exploitation of mercury in
Italy. The study area (Selvena mining district) is located in southern Tuscany (inner Northern Apennines) one
of the most important mineralized area in the western Mediterranean region. Southern Tuscany was severely
affected by Middle–Late Miocene low-angle normal faults, later dissected by Pliocene–Pleistocene faults,
coeval magmatism (Late Miocene–Pleistocene) and hydrothermal activity (Pliocene–Present). The Selvena
mining district is located south of Middle Pleistocene Monte Amiata volcanic complex. Our structural and
kinematic study is based on the integration among fieldwork, borehole and mine data. The results highlight
two Pleistocene–Holocene left-lateral transtensional shear zones linked by normal faults, defining a coeval
pull-apart structure. Here, the Sb–Hg mineralization, transported by meteoric hydrothermal fluids mainly, is
particularly diffuse and concentrated in the cataclasites and in damage zones of the normal faults.
Furthermore, a widespread mineralization also occurs in the cataclasites of Miocene low-angle normal faults.
Mine evidence suggests that ore-bearing fluids percolated through structural conduits located along the fault
planes and resulting parallel to the intermediate stress axis. Geological structures and ore deposit distribution
are related to a single hydrothermal circuit, with meteoric water channelled to depth through conduits
parallel to the intermediate stress axis of the transcurrent shear zones; then, hydrothermal fluids mainly
ascended through the almost vertical deformation zones located at the intersection between normal and
strike-slip faults. Thus, hydrothermal fluids permeated also the Middle–Late Miocene cataclasites. This study
shed light on the relationships between geological structures and mineralization in southern Tuscany and
underlines the importance to investigate mine areas to understand hydrothermal fluids path.
the Monte Amiata area that was one of the most relevant mining district for the exploitation of mercury in
Italy. The study area (Selvena mining district) is located in southern Tuscany (inner Northern Apennines) one
of the most important mineralized area in the western Mediterranean region. Southern Tuscany was severely
affected by Middle–Late Miocene low-angle normal faults, later dissected by Pliocene–Pleistocene faults,
coeval magmatism (Late Miocene–Pleistocene) and hydrothermal activity (Pliocene–Present). The Selvena
mining district is located south of Middle Pleistocene Monte Amiata volcanic complex. Our structural and
kinematic study is based on the integration among fieldwork, borehole and mine data. The results highlight
two Pleistocene–Holocene left-lateral transtensional shear zones linked by normal faults, defining a coeval
pull-apart structure. Here, the Sb–Hg mineralization, transported by meteoric hydrothermal fluids mainly, is
particularly diffuse and concentrated in the cataclasites and in damage zones of the normal faults.
Furthermore, a widespread mineralization also occurs in the cataclasites of Miocene low-angle normal faults.
Mine evidence suggests that ore-bearing fluids percolated through structural conduits located along the fault
planes and resulting parallel to the intermediate stress axis. Geological structures and ore deposit distribution
are related to a single hydrothermal circuit, with meteoric water channelled to depth through conduits
parallel to the intermediate stress axis of the transcurrent shear zones; then, hydrothermal fluids mainly
ascended through the almost vertical deformation zones located at the intersection between normal and
strike-slip faults. Thus, hydrothermal fluids permeated also the Middle–Late Miocene cataclasites. This study
shed light on the relationships between geological structures and mineralization in southern Tuscany and
underlines the importance to investigate mine areas to understand hydrothermal fluids path.