Martina Zucchi | University of Bari Italy (original) (raw)

Papers by Martina Zucchi

Research paper thumbnail of Deep Regional Fluid Pathways in an Extensional Setting: The Role of Transfer Zones in the Hot and Cold Degassing Areas of the Larderello Geothermal System (Northern Apennines, Italy)

Geochemistry, Geophysics, Geosystems

High‐temperature geothermal areas are often characterized by widespread surficial manifestations,... more High‐temperature geothermal areas are often characterized by widespread surficial manifestations, whose location is strictly controlled by sets of faults of regional relevance. The geochemical and isotopic signature of the discharged fluids can reveal key information on the geothermal fluids pathway, shedding light on the sources and fluid‐rock interaction within the geothermal reservoirs. In this paper, a geochemical and structural data set from the Larderello geothermal area and surroundings is presented and discussed. We constrain the role of transfer and normal faults in controlling the geothermal circulation enhanced by a cooling magmatic intrusion underneath the Lago area (SW of Larderello). The structural control on the fluids circulation is highlighted by both the location of the CO2 emissions along the fault segments, where permeability is enhanced, and their degassing rates, which increase moving away from the core of the Larderello geothermal system. The main results unra...

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Research paper thumbnail of The Permian-Triassic succession of the Montagnola Senese Ridge (Middle Tuscan Ridge, Italy): a perspective for late Palaeozoic magmatism and continentalisation in the western Tethys

International Geology Review

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Research paper thumbnail of Fluid flow and faulting history of the Iano tectonic window (Southern Tuscany, Italy)

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Research paper thumbnail of Use of palynology and thermal maturity in deformed geological units: A case study from the Permian succession in the Monte Leoni area (Middle Tuscan Ridge, inner Northern Apennines, Italy)

Sedimentary Geology

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Research paper thumbnail of Reconsidering the Variscan Basement of Southern Tuscany (Inner Northern Apennines)

Geosciences

The Pre-Mesozoic units exposed in the inner Northern Apennines mostly consist of Pennsylvanian-Pe... more The Pre-Mesozoic units exposed in the inner Northern Apennines mostly consist of Pennsylvanian-Permian successions unconformably deposited on a continental crust consolidated at the end of the Variscan orogenic cycle (Silurian-Carboniferous). In the inner Northern Apennines, exposures of this continental crust, Cambrian?-Devonian in age, have been described in Northern Tuscany, Elba Island (Tuscan Archipelago) and, partly, in scattered and isolated outcrops of southern Tuscany. This paper reappraises the most significant succession (i.e., Risanguigno Formation) exposed in southern Tuscany and considered by most authors as part of the Variscan Basement. New stratigraphic and structural studies, coupled with analyses of the organic matter content, allow us to refine the age of the Risanguigno Fm and its geological setting and evolution. Based on the low diversification of palynoflora, the content of sporomorphs, the structural setting and the new field study, this formation is dated a...

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Research paper thumbnail of Fossil vs. Active Geothermal Systems: A Field and Laboratory Method to Disclose the Relationships between Geothermal Fluid Flow and Geological Structures at Depth

Energies

Comparison between fossil and analogue active geothermal systems permit to obtain key-parameters ... more Comparison between fossil and analogue active geothermal systems permit to obtain key-parameters to define a conceptual model of the area under exploration. The approach is based on structural, kinematic, and fluid inclusions analyses. The fossil system is investigated to describe the distribution of the hydrothermal mineralization as witness of the fluid flow through geological structures and bodies, at depth. Structural and kinematic data (to define the preferential direction of fluid flow) are collected in structural stations and by scan lines and scan boxes on key outcrops. Distribution, length, width of fractures, and hydrothermal veins bring to evaluate permeability in the fossil system and, by analogy, in the deep roots of the active system. Fluid inclusions analysis shed light on density, viscosity, and temperature of the paleo-fluids. Data integration provides the hydraulic conductivity. In active geothermal systems, fieldwork is addressed to paleo-stress analysis with data...

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Research paper thumbnail of The Gavorrano Monzogranite (Northern Apennines): An Updated Review of Host Rock Protoliths, Thermal Metamorphism and Tectonic Setting

We review and refine the geological setting of an area located nearby the Tyrrhenian seacoast, in... more We review and refine the geological setting of an area located nearby the Tyrrhenian seacoast, in the inner zone of the Northern Apennines (southern Tuscany), where a Neogene monzogranite body (estimated in about 3 km long, 1.5 km wide, and 0.7 km thick) emplaced during early Pliocene. This magmatic intrusion, known as the Gavorrano pluton, is partially exposed in a ridge bounded by regional faults delimiting broad structural depressions. A widespread circulation of geothermal fluids accompanied the cooling of the magmatic body and gave rise to an extensive Fe-ore deposit (mainly pyrite) exploited during the past century. The tectonic setting which favoured the emplacement and exhumation of the Gavorrano pluton is strongly debated with fallouts on the comprehension of the Neogene evolution of this sector of the inner Northern Apennines. Data from a new fieldwork dataset, integrated with information from the mining activity, have been integrated to refine the geological setting of th...

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Research paper thumbnail of Geothermal Fluid Variation Recorded by Banded Ca-Carbonate Veins in a Fault-Related, Fissure Ridge-Type Travertine Depositional System (Iano, southern Tuscany, Italy)

Geofluids

Banded Ca-carbonate veins in travertine deposits are efficient recorders of the compositional flu... more Banded Ca-carbonate veins in travertine deposits are efficient recorders of the compositional fluctuations of geothermal fluids flowing (or flowed) from deep reservoirs up to the surface, within fault zones. In this view, these veins represent key tools for decoding those factors that influenced the geochemical variations. We have analyzed veins developed in fractures channeling geothermal fluids forming travertine deposits. The studied veins cut a fossil travertine fissure ridge, near the Larderello geothermal area (Iano area, southern Tuscany) where geothermal fluid circulation is favored by NE-trending strike-to-oblique-slip faults and their intersections with NW-trending normal ones. U-Th dating indicates that fluid circulation occurred from (at least) 172 ka to 21 ka. In this time span, the geothermal fluid changed in composition, and the banded Ca-carbonate veins recorded these variations in terms of mineralogical and stable isotope composition and temperature ( T ) of deposit...

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Research paper thumbnail of Geology of Las Minas: an example of an exhumed geothermal system (Eastern Trans-Mexican Volcanic Belt)

Journal of Maps

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Research paper thumbnail of Step-over fault zones controlling geothermal fluid-flow and travertine formation (Denizli Basin, Turkey)

Geothermics

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Research paper thumbnail of The cooling, deformation and exhumation history of the late Miocene syn-tectonic Porto Azzurro pluton in a regional transfer zone (Elba Island, Italy)

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Research paper thumbnail of Exhumed vs active geothermal systems: faults controlling ore deposits in Las Minas area as a key for the deep exploration in the Los Humeros geothermal field (Mexico)

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Research paper thumbnail of Skarn development in calcareous-pelitic succession affected by thermal metamorphism and fluid flow at Acquarilli beach (Elba Island, Italy)

International Journal of Earth Sciences

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Research paper thumbnail of Fracture analysis, hydrothermal mineralization and fluid pathways in the Neogene Geitafell central volcano: Insights for the Krafla active geothermal system

Journal of Volcanology and Geothermal Research

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Research paper thumbnail of Permeability and hydraulic conductivity of faulted micaschist in the eastern Elba Island exhumed geothermal system (Tyrrhenian sea, Italy): insights from Cala Stagnone

Geothermics

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Research paper thumbnail of Faults controlling geothermal fluid flow in low permeability rock volumes: An example from the exhumed geothermal system of eastern Elba Island (northern Tyrrhenian Sea, Italy)

Geothermics, 2020

Geothermal fluid circulation and storage within rock volumes are essential conditions for an effe... more Geothermal fluid circulation and storage within rock volumes are essential conditions for an effective geothermal system. Although several studies examine fluid migration through permeable rock volumes, few papers deal with fluid flow and fluid-rock interaction within the cap rocks of magma-driven geothermal systems. In this paper, I present the results of an integrated study focused on the circulation of geothermal uids and fluid-rock interaction with clayey-carbonate sedimentary rocks and interbedded tectonic slices of serpentinite, representing the cap of an exhumed geothermal system located in the south-eastern Elba Island (Acquarilli-Norsi area, Tuscan Archipelago). Structural and kinematic data highlight that the prevalent geothermal uid pathways correspond to NE- trending normal to oblique-slip faults. A Fe-amphibole + quartz + calcite ± chlorite ± epidote ± titanite mineral assemblage filled the fracture networks associated with two different fault generations. Fluid-rock interaction gave rise to skarnoids having three distinct mineralised zones, locally, crossed by the faults. Fluid inclusions data on quartz and calcite coexisting with the amphibole in the first fault generation and calcite of the second fault generation suggest that at least two paleo-geothermal uids permeated through the fault zones, at a maximum P of about 0.8 kbar. The sequence was (i) first an H2O-rich uid enriched by a volatile phase mainly made up of CO2 derived from the decarbonation and dehydration reactions of the hosting metacarbonate and metapelitic rocks. This fluid characterised by temperature up to 495 °C and salinity between 1.0 and 6.4 wt.% NaClequiv, records the residual intra-formational uid (derived from dehydration of phyllosilicate and serpentinite bodies) already present within the host rocks. This fluid was successively mobilised during the development of the fault zones and progressively cooled and CO2-depleted with time; (ii) a second fluid likely of meteoric origin, devoid of CO2 and characterised by relatively low-temperature from 146.5 to 254 °C and salinity between 1.9 and 2.9 wt.% NaClequiv related to the last uid circulation event. The main conclusions are that: (i) geothermal fluid circulation occurred within the cap rocks of the paleo-geothermal system, along fault zones; (ii) fluid circulation occurred within restricted fault-damaged volumes, developed in an extensional setting; iii) faults dissected rocks that were affected by high-temperature metamorphism induced by the cooling of a magmatic intrusion. The super-hot fluid was produced by metamorphic reactions and only in the latest stage, meteoric water infiltrated in the geothermal system due to the progressive faulting and exhumation.

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Research paper thumbnail of Fractures and mineralising fluid paths in the eastern Elba Island exhumed geothermal system (Italy)

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Research paper thumbnail of Estimating P-T metamorphic conditions on the roof of a hidden granitic pluton: an example from the Mt. Calamita promontory (Elba Island, Italy)

The metamorphic basement (i.e. Palaeozoic micaschists, Porto Azzurro Unit) cropping out in the Mt... more The metamorphic basement (i.e. Palaeozoic micaschists, Porto Azzurro Unit) cropping out in the Mt. Calamita promontory, in the southeastern Elba Island, represents the roof of the mostly unexposed late Miocene Porto Azzurro granite. A thermobarometric study was performed on micaschists and interlayered amphibolites to constrain P-T conditions during contact metamorphism. Adopted methods were based on P-T grids, conventional thermobarometry and analysis of uid inclusions. It was found that the basement was originally located at a depth of 6.5 ± 1.3 km and that the peak metamorphic conditions were close to the muscovite dehydration reaction in micaschist. Therefore, small differences of temperatures conditioned the presence or absence of K-feldspar in the eastern and western side of the Mt. Calamita promontory, respectively. A maximum peak temperature of c. 625 °C was estimated by amphibole-plagioclase thermometry in amphibolite. Fluid inclusions in micaschist quartz lenses document signi cant episodes of uid circulation during the cooling history of the metamorphic aureole. Finally, a conductive thermal model was built up to reproduce the thermal evolution during the contact metamorphic event and following cooling. Simulated temperatures resulted signi cantly lower than the observed peak values. This discrepancy is explained as the effect of the localized heat advection in zones affected by in ltration of magmatic uids and by the intrusion of numberless felsic dykes.

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Research paper thumbnail of Seismic slip recorded in tourmaline fault mirrors from Elba Island (Italy

This paper reports the first example of fault mirrors developed in an unusual protolith, consisti... more This paper reports the first example of fault mirrors developed in an unusual protolith, consisting of tourmaline crystals with interstitial goethite. The deformation mechanisms active in the fault zone have been investigated from the outcrop to the nanoscale, aiming to identify possible traces of frictional heating at seismic slip rate, as observed for other fault mirrors in different protoliths. The investigation revealed the superposition of two main deformational stages. The first was dominated by brittle processes and produced a cataclastic/ultracataclastic principal slip zone, a few mm thick; the second was associated with seismic slip and produced a sharp discontinuity (the principal slip surface) within the cataclastic/ultracataclastic zone. The mirror-like coating, a few microns thick, occurs on the principal slip surface, and is characterized by 1) absence of interstitial goethite; 2) occurrence of truncated tourmaline crystals; 3) highly variable grain size, from 200 mm to 200 nm; 4) tourmaline close packing with interlobate grain boundaries, and 5) tourmaline random crystallographic orientation. Micro and nanostructural investigations indicate the occurrence of thermally-activated processes, involving both interstitial goethite and tourmaline. In particular, close to the principal slip surface, goethite is completely decomposed, and produced an amorphous porous material, with local topotactic recrystallization of hematite. Tourmaline clasts are typically characterized by strongly lobate boundaries, indicative of reaction and partial decomposition at grain boundaries. TEM observations revealed the occurrence of tourmaline nanograins, a few tens of nm in size, characterized by rounded shape and fading amorphous boundaries, that cannot be obtained by brittle processes. Lastly, the peculiar inter-lobate microstructure of the mirror surface is interpreted as the result of grain boundary recrystallization processes taking place by deformation at high-T conditions. Our results show that tourmaline fault mirrors recorded localized high-T processes triggered by frictional heating and can be therefore considered as reliable traces of ancient earthquakes.

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Research paper thumbnail of Syn-tectonic contact aureole and metasomatic reaction zones in carbonate and pelitic host rocks (Elba Island, Italy)

Tectonophysics

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Research paper thumbnail of Deep Regional Fluid Pathways in an Extensional Setting: The Role of Transfer Zones in the Hot and Cold Degassing Areas of the Larderello Geothermal System (Northern Apennines, Italy)

Geochemistry, Geophysics, Geosystems

High‐temperature geothermal areas are often characterized by widespread surficial manifestations,... more High‐temperature geothermal areas are often characterized by widespread surficial manifestations, whose location is strictly controlled by sets of faults of regional relevance. The geochemical and isotopic signature of the discharged fluids can reveal key information on the geothermal fluids pathway, shedding light on the sources and fluid‐rock interaction within the geothermal reservoirs. In this paper, a geochemical and structural data set from the Larderello geothermal area and surroundings is presented and discussed. We constrain the role of transfer and normal faults in controlling the geothermal circulation enhanced by a cooling magmatic intrusion underneath the Lago area (SW of Larderello). The structural control on the fluids circulation is highlighted by both the location of the CO2 emissions along the fault segments, where permeability is enhanced, and their degassing rates, which increase moving away from the core of the Larderello geothermal system. The main results unra...

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Research paper thumbnail of The Permian-Triassic succession of the Montagnola Senese Ridge (Middle Tuscan Ridge, Italy): a perspective for late Palaeozoic magmatism and continentalisation in the western Tethys

International Geology Review

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Research paper thumbnail of Fluid flow and faulting history of the Iano tectonic window (Southern Tuscany, Italy)

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Research paper thumbnail of Use of palynology and thermal maturity in deformed geological units: A case study from the Permian succession in the Monte Leoni area (Middle Tuscan Ridge, inner Northern Apennines, Italy)

Sedimentary Geology

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Research paper thumbnail of Reconsidering the Variscan Basement of Southern Tuscany (Inner Northern Apennines)

Geosciences

The Pre-Mesozoic units exposed in the inner Northern Apennines mostly consist of Pennsylvanian-Pe... more The Pre-Mesozoic units exposed in the inner Northern Apennines mostly consist of Pennsylvanian-Permian successions unconformably deposited on a continental crust consolidated at the end of the Variscan orogenic cycle (Silurian-Carboniferous). In the inner Northern Apennines, exposures of this continental crust, Cambrian?-Devonian in age, have been described in Northern Tuscany, Elba Island (Tuscan Archipelago) and, partly, in scattered and isolated outcrops of southern Tuscany. This paper reappraises the most significant succession (i.e., Risanguigno Formation) exposed in southern Tuscany and considered by most authors as part of the Variscan Basement. New stratigraphic and structural studies, coupled with analyses of the organic matter content, allow us to refine the age of the Risanguigno Fm and its geological setting and evolution. Based on the low diversification of palynoflora, the content of sporomorphs, the structural setting and the new field study, this formation is dated a...

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Research paper thumbnail of Fossil vs. Active Geothermal Systems: A Field and Laboratory Method to Disclose the Relationships between Geothermal Fluid Flow and Geological Structures at Depth

Energies

Comparison between fossil and analogue active geothermal systems permit to obtain key-parameters ... more Comparison between fossil and analogue active geothermal systems permit to obtain key-parameters to define a conceptual model of the area under exploration. The approach is based on structural, kinematic, and fluid inclusions analyses. The fossil system is investigated to describe the distribution of the hydrothermal mineralization as witness of the fluid flow through geological structures and bodies, at depth. Structural and kinematic data (to define the preferential direction of fluid flow) are collected in structural stations and by scan lines and scan boxes on key outcrops. Distribution, length, width of fractures, and hydrothermal veins bring to evaluate permeability in the fossil system and, by analogy, in the deep roots of the active system. Fluid inclusions analysis shed light on density, viscosity, and temperature of the paleo-fluids. Data integration provides the hydraulic conductivity. In active geothermal systems, fieldwork is addressed to paleo-stress analysis with data...

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Research paper thumbnail of The Gavorrano Monzogranite (Northern Apennines): An Updated Review of Host Rock Protoliths, Thermal Metamorphism and Tectonic Setting

We review and refine the geological setting of an area located nearby the Tyrrhenian seacoast, in... more We review and refine the geological setting of an area located nearby the Tyrrhenian seacoast, in the inner zone of the Northern Apennines (southern Tuscany), where a Neogene monzogranite body (estimated in about 3 km long, 1.5 km wide, and 0.7 km thick) emplaced during early Pliocene. This magmatic intrusion, known as the Gavorrano pluton, is partially exposed in a ridge bounded by regional faults delimiting broad structural depressions. A widespread circulation of geothermal fluids accompanied the cooling of the magmatic body and gave rise to an extensive Fe-ore deposit (mainly pyrite) exploited during the past century. The tectonic setting which favoured the emplacement and exhumation of the Gavorrano pluton is strongly debated with fallouts on the comprehension of the Neogene evolution of this sector of the inner Northern Apennines. Data from a new fieldwork dataset, integrated with information from the mining activity, have been integrated to refine the geological setting of th...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Geothermal Fluid Variation Recorded by Banded Ca-Carbonate Veins in a Fault-Related, Fissure Ridge-Type Travertine Depositional System (Iano, southern Tuscany, Italy)

Geofluids

Banded Ca-carbonate veins in travertine deposits are efficient recorders of the compositional flu... more Banded Ca-carbonate veins in travertine deposits are efficient recorders of the compositional fluctuations of geothermal fluids flowing (or flowed) from deep reservoirs up to the surface, within fault zones. In this view, these veins represent key tools for decoding those factors that influenced the geochemical variations. We have analyzed veins developed in fractures channeling geothermal fluids forming travertine deposits. The studied veins cut a fossil travertine fissure ridge, near the Larderello geothermal area (Iano area, southern Tuscany) where geothermal fluid circulation is favored by NE-trending strike-to-oblique-slip faults and their intersections with NW-trending normal ones. U-Th dating indicates that fluid circulation occurred from (at least) 172 ka to 21 ka. In this time span, the geothermal fluid changed in composition, and the banded Ca-carbonate veins recorded these variations in terms of mineralogical and stable isotope composition and temperature ( T ) of deposit...

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Research paper thumbnail of Geology of Las Minas: an example of an exhumed geothermal system (Eastern Trans-Mexican Volcanic Belt)

Journal of Maps

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Research paper thumbnail of Step-over fault zones controlling geothermal fluid-flow and travertine formation (Denizli Basin, Turkey)

Geothermics

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Research paper thumbnail of The cooling, deformation and exhumation history of the late Miocene syn-tectonic Porto Azzurro pluton in a regional transfer zone (Elba Island, Italy)

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Exhumed vs active geothermal systems: faults controlling ore deposits in Las Minas area as a key for the deep exploration in the Los Humeros geothermal field (Mexico)

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Skarn development in calcareous-pelitic succession affected by thermal metamorphism and fluid flow at Acquarilli beach (Elba Island, Italy)

International Journal of Earth Sciences

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Research paper thumbnail of Fracture analysis, hydrothermal mineralization and fluid pathways in the Neogene Geitafell central volcano: Insights for the Krafla active geothermal system

Journal of Volcanology and Geothermal Research

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Research paper thumbnail of Permeability and hydraulic conductivity of faulted micaschist in the eastern Elba Island exhumed geothermal system (Tyrrhenian sea, Italy): insights from Cala Stagnone

Geothermics

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Research paper thumbnail of Faults controlling geothermal fluid flow in low permeability rock volumes: An example from the exhumed geothermal system of eastern Elba Island (northern Tyrrhenian Sea, Italy)

Geothermics, 2020

Geothermal fluid circulation and storage within rock volumes are essential conditions for an effe... more Geothermal fluid circulation and storage within rock volumes are essential conditions for an effective geothermal system. Although several studies examine fluid migration through permeable rock volumes, few papers deal with fluid flow and fluid-rock interaction within the cap rocks of magma-driven geothermal systems. In this paper, I present the results of an integrated study focused on the circulation of geothermal uids and fluid-rock interaction with clayey-carbonate sedimentary rocks and interbedded tectonic slices of serpentinite, representing the cap of an exhumed geothermal system located in the south-eastern Elba Island (Acquarilli-Norsi area, Tuscan Archipelago). Structural and kinematic data highlight that the prevalent geothermal uid pathways correspond to NE- trending normal to oblique-slip faults. A Fe-amphibole + quartz + calcite ± chlorite ± epidote ± titanite mineral assemblage filled the fracture networks associated with two different fault generations. Fluid-rock interaction gave rise to skarnoids having three distinct mineralised zones, locally, crossed by the faults. Fluid inclusions data on quartz and calcite coexisting with the amphibole in the first fault generation and calcite of the second fault generation suggest that at least two paleo-geothermal uids permeated through the fault zones, at a maximum P of about 0.8 kbar. The sequence was (i) first an H2O-rich uid enriched by a volatile phase mainly made up of CO2 derived from the decarbonation and dehydration reactions of the hosting metacarbonate and metapelitic rocks. This fluid characterised by temperature up to 495 °C and salinity between 1.0 and 6.4 wt.% NaClequiv, records the residual intra-formational uid (derived from dehydration of phyllosilicate and serpentinite bodies) already present within the host rocks. This fluid was successively mobilised during the development of the fault zones and progressively cooled and CO2-depleted with time; (ii) a second fluid likely of meteoric origin, devoid of CO2 and characterised by relatively low-temperature from 146.5 to 254 °C and salinity between 1.9 and 2.9 wt.% NaClequiv related to the last uid circulation event. The main conclusions are that: (i) geothermal fluid circulation occurred within the cap rocks of the paleo-geothermal system, along fault zones; (ii) fluid circulation occurred within restricted fault-damaged volumes, developed in an extensional setting; iii) faults dissected rocks that were affected by high-temperature metamorphism induced by the cooling of a magmatic intrusion. The super-hot fluid was produced by metamorphic reactions and only in the latest stage, meteoric water infiltrated in the geothermal system due to the progressive faulting and exhumation.

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Research paper thumbnail of Fractures and mineralising fluid paths in the eastern Elba Island exhumed geothermal system (Italy)

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Estimating P-T metamorphic conditions on the roof of a hidden granitic pluton: an example from the Mt. Calamita promontory (Elba Island, Italy)

The metamorphic basement (i.e. Palaeozoic micaschists, Porto Azzurro Unit) cropping out in the Mt... more The metamorphic basement (i.e. Palaeozoic micaschists, Porto Azzurro Unit) cropping out in the Mt. Calamita promontory, in the southeastern Elba Island, represents the roof of the mostly unexposed late Miocene Porto Azzurro granite. A thermobarometric study was performed on micaschists and interlayered amphibolites to constrain P-T conditions during contact metamorphism. Adopted methods were based on P-T grids, conventional thermobarometry and analysis of uid inclusions. It was found that the basement was originally located at a depth of 6.5 ± 1.3 km and that the peak metamorphic conditions were close to the muscovite dehydration reaction in micaschist. Therefore, small differences of temperatures conditioned the presence or absence of K-feldspar in the eastern and western side of the Mt. Calamita promontory, respectively. A maximum peak temperature of c. 625 °C was estimated by amphibole-plagioclase thermometry in amphibolite. Fluid inclusions in micaschist quartz lenses document signi cant episodes of uid circulation during the cooling history of the metamorphic aureole. Finally, a conductive thermal model was built up to reproduce the thermal evolution during the contact metamorphic event and following cooling. Simulated temperatures resulted signi cantly lower than the observed peak values. This discrepancy is explained as the effect of the localized heat advection in zones affected by in ltration of magmatic uids and by the intrusion of numberless felsic dykes.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Seismic slip recorded in tourmaline fault mirrors from Elba Island (Italy

This paper reports the first example of fault mirrors developed in an unusual protolith, consisti... more This paper reports the first example of fault mirrors developed in an unusual protolith, consisting of tourmaline crystals with interstitial goethite. The deformation mechanisms active in the fault zone have been investigated from the outcrop to the nanoscale, aiming to identify possible traces of frictional heating at seismic slip rate, as observed for other fault mirrors in different protoliths. The investigation revealed the superposition of two main deformational stages. The first was dominated by brittle processes and produced a cataclastic/ultracataclastic principal slip zone, a few mm thick; the second was associated with seismic slip and produced a sharp discontinuity (the principal slip surface) within the cataclastic/ultracataclastic zone. The mirror-like coating, a few microns thick, occurs on the principal slip surface, and is characterized by 1) absence of interstitial goethite; 2) occurrence of truncated tourmaline crystals; 3) highly variable grain size, from 200 mm to 200 nm; 4) tourmaline close packing with interlobate grain boundaries, and 5) tourmaline random crystallographic orientation. Micro and nanostructural investigations indicate the occurrence of thermally-activated processes, involving both interstitial goethite and tourmaline. In particular, close to the principal slip surface, goethite is completely decomposed, and produced an amorphous porous material, with local topotactic recrystallization of hematite. Tourmaline clasts are typically characterized by strongly lobate boundaries, indicative of reaction and partial decomposition at grain boundaries. TEM observations revealed the occurrence of tourmaline nanograins, a few tens of nm in size, characterized by rounded shape and fading amorphous boundaries, that cannot be obtained by brittle processes. Lastly, the peculiar inter-lobate microstructure of the mirror surface is interpreted as the result of grain boundary recrystallization processes taking place by deformation at high-T conditions. Our results show that tourmaline fault mirrors recorded localized high-T processes triggered by frictional heating and can be therefore considered as reliable traces of ancient earthquakes.

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Research paper thumbnail of Syn-tectonic contact aureole and metasomatic reaction zones in carbonate and pelitic host rocks (Elba Island, Italy)

Tectonophysics

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