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Campi Flegrei caldera. The dotted line is the limit of the caldera inferred from the Bouguer anomaly (after Scandone et al., 1991). White circles are the location of shallow wells drilled since 1939; red circles are the deep wells drilled during the AGIP-ENEL Joint Venture until 1980. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)
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The active volcanic zone of Ischia Island and Campi Flegrei caldera (Campania) have been the site of many geothermal investigations, since the early 20th century. These areas are characterized by very high geothermal gradient and heat flow as consequence of upward migration of magmatic sources coupled with vigorous hydrothermal circulation. After t...
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... at the Northwestern limit of the Gulf of Naples, the Campi Flegrei caldera (CFc) is roughly 12 km wide, with its centre located in the Bay of Pozzuoli, about 15 km to the west of Naples. The current caldera shape is thought as the result of two large collapses, the first of which was probably related to the Campanian Ignimbrite (CI; 150-200 km 3 dense rock equivalent [DRE]; age, 39 ky BP), and the second to the Neapolitan Yellow Tuff (NYT; 40 km 3 DRE; age, 12-15.6 ky BP) eruptions [22,[36][37][38][39] (Fig. 6). The volcanic activity has continued within the caldera, with phreatomagmatic eruptions and lava dome emplacement [36]. The last eruption occurred in 1538, with the formation of the Monte Nuovo crater, roughly in the centre of the caldera. Since Roman times, the CFc area has been characterized by slow subsidence, at a rate of about 1.1-2 cm y −1 [40,41], which has been interrupted by recurring phases of rapid uplift that are generally accompanied by intense seismicity. The study of sea-level markers on Roman coastal ruins has revealed historical ground movements, with a Roman market-place (Serapis) that was uncovered in A.D. 1750 in Pozzuoli being the subject of many studies (see for a review [40,42,43]). At least one well evident phase of uplift has been recognized to have occurred prior to the last Monte Nuovo erup- tion (A.D. 1538; 0.02 km 3 DRE) [44]. More recently, two phases of uplift have occurred, during 1970-1972 and 1982-1984, when the town of Pozzuoli was raised by 1.7 m and 1.8 m, respectively. During the 1982-1984 unrest episode, more than 15,000 shallow earthquakes (at 1-5 km in depth) with a maximum magnitude of 4.0 were recorded by the seismic stations of the Osservatorio Vesuviano [45], and the ground uplift occurred at an average rate of 0.3 cm d −1 . The last episode of unrest indicated the possibility of an imminent eruption, forcing the authorities to evacuate Pozzuoli; however, the unrest virtually ended in December 1984, without any eruption occurring ...
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... first geothermal explorations in Campi Flegrei (Lago Patria lease) were carried out by the SAFEN Company during 1939 and 1943, which drilled 19 wells (id: LA, CLV, CMV, A) with depth from few meters to 600 m [81,84] (Table 1 and Fig. 9a and b). The investigated area was characterized by a vigorous fumaroles fields, named with the local appellative of "mofete". The drillings showed the potentiality of this area (Mofete area), with the pres- ence of a water dominated system at temperature of about 200 • C and relative high pressure (Fig. 10). The methods and the technol- ogy adopted during that time, did not allow the complete defining of physical and chemical properties of geothermal fluids [85]. These fluids have an elevated salinity which caused problems during their withdrawal. For instance, within the CLV7 well, which produced a maximum water and vapor flow rate of 40th −1 , the persistence of minerals precipitation generated a self-sealing phenomenon with a consequent decreasing of flow and productivity of the well. Nev- ertheless, the CLV7 and CLV17 wells were initially productive, with a flow rate of about 7 l s −1 and temperature of water-vapor mix- ture, at well head, of about 100 • C. Furthermore, the temperature measured in the wells showed a radial decreasing from the cen- tre of the caldera. The mid term productive tests (4 months) also demonstrate that the superficial water level in the wells did not varied significantly during the fluid withdraw. In the early 1940, a new well was drilled within the crater of Monte Nuovo (CMV well) (Fig. 11). This was the result of the last volcanic activity (1538 A.D.) occurred in Campi Flegrei, for this reason the experts consid- ered that a sufficient amount of heat, for high temperature vapor production, was still contained in the shallow magmatic reservoir which fed the eruption [84,96]. The drilling, lasted about 5 months by using a direct push rig, reaching a depth of 667 m and a maxi- mum temperature of 78 • C, lower that that expected. This was due to the cooled investigated pyroclastic deposits, originated by the Mt. Nuovo phreatic eruption. At the time of this drilling, the knowl- edge of volcanic processes was not clear. At the present, it is well know that monogenic volcanoes are supplied by dikes, which cool rapidly after their emplacement. A further shallow drillings field was carried out in 1940, at Agnano (A1, A3, A6 wells), at a distance of 1.5 km from the Solfatara crater. Also in this case, the results of the drillings were not satisfactory and the exploration of this area was temporarily stopped, when a depth of about 100 m was reached and a temperature of 30 • C [84]. The geothermal exploration of the whole Campania Plain, was also suspended for the World War II occurrence, in September 1943. Later, from 1953 and 1954, a new drilling (CF23) was performed at Agnano ( Fig. 6), with a depth of 1840 m and a maximum temperature of about 300 • C at the bottom. The high temperatures recorded at shallow depth, in particular in Mofete area, stimulated further interest in the geothermal research, calling for a new regional drilling program carried out, since 1977, by the established AGIP-ENEL joint-venture, which ended in 1985. Such a program was decided by the Ministry of Industry (AGIP and ENEL were at the time State companies) in search for alternative energies because of the large peak of oil price due to the 1973, Israelo-Arab war. The aim was both to test the exploitation of high temperature fluids using an extraction/reinjection system and to monitor the perturbation of the deep geothermal system (pressure, water level and capacity) induced by the presence of active wells. Because of the substantial depth of the wells and their closeness to highly urbanized area, particular care was paid to the protection of the environment. Many surveys of micro-seismicity, deforma- tion, soil gas emission were carried out before, during and after the drillings [85]. The researches were extended to the neighbor- ing area of S. Vito, to the north of Pozzuoli, and to Licola (L1 well) located outside the north-west caldera rim. The latter was planned to evaluate the area extension of the thermal anomaly observed at Mofete (Fig. 6). In Mofete area, 7 wells (4 deviated and 3 vertical) were drilled (MF 1, 2, 3d, 5, 7d, 8d, 9d) with depth ranges from 800 to 2700 m. The deviation allowed to intercept the possible fractures and faults zones from which to obtain a better production, avoiding the extension of the wells field close to the urbanized areas [89]. At the end of 1985, the results of the drillings defined the following ...
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... first geothermal explorations in Campi Flegrei (Lago Patria lease) were carried out by the SAFEN Company during 1939 and 1943, which drilled 19 wells (id: LA, CLV, CMV, A) with depth from few meters to 600 m [81,84] (Table 1 and Fig. 9a and b). The investigated area was characterized by a vigorous fumaroles fields, named with the local appellative of "mofete". The drillings showed the potentiality of this area (Mofete area), with the pres- ence of a water dominated system at temperature of about 200 • C and relative high pressure (Fig. 10). The methods and the technol- ogy adopted during that time, did not allow the complete defining of physical and chemical properties of geothermal fluids [85]. These fluids have an elevated salinity which caused problems during their withdrawal. For instance, within the CLV7 well, which produced a maximum water and vapor flow rate of 40th −1 , the persistence of minerals precipitation generated a self-sealing phenomenon with a consequent decreasing of flow and productivity of the well. Nev- ertheless, the CLV7 and CLV17 wells were initially productive, with a flow rate of about 7 l s −1 and temperature of water-vapor mix- ture, at well head, of about 100 • C. Furthermore, the temperature measured in the wells showed a radial decreasing from the cen- tre of the caldera. The mid term productive tests (4 months) also demonstrate that the superficial water level in the wells did not varied significantly during the fluid withdraw. In the early 1940, a new well was drilled within the crater of Monte Nuovo (CMV well) (Fig. 11). This was the result of the last volcanic activity (1538 A.D.) occurred in Campi Flegrei, for this reason the experts consid- ered that a sufficient amount of heat, for high temperature vapor production, was still contained in the shallow magmatic reservoir which fed the eruption [84,96]. The drilling, lasted about 5 months by using a direct push rig, reaching a depth of 667 m and a maxi- mum temperature of 78 • C, lower that that expected. This was due to the cooled investigated pyroclastic deposits, originated by the Mt. Nuovo phreatic eruption. At the time of this drilling, the knowl- edge of volcanic processes was not clear. At the present, it is well know that monogenic volcanoes are supplied by dikes, which cool rapidly after their emplacement. A further shallow drillings field was carried out in 1940, at Agnano (A1, A3, A6 wells), at a distance of 1.5 km from the Solfatara crater. Also in this case, the results of the drillings were not satisfactory and the exploration of this area was temporarily stopped, when a depth of about 100 m was reached and a temperature of 30 • C [84]. The geothermal exploration of the whole Campania Plain, was also suspended for the World War II occurrence, in September 1943. Later, from 1953 and 1954, a new drilling (CF23) was performed at Agnano ( Fig. 6), with a depth of 1840 m and a maximum temperature of about 300 • C at the bottom. The high temperatures recorded at shallow depth, in particular in Mofete area, stimulated further interest in the geothermal research, calling for a new regional drilling program carried out, since 1977, by the established AGIP-ENEL joint-venture, which ended in 1985. Such a program was decided by the Ministry of Industry (AGIP and ENEL were at the time State companies) in search for alternative energies because of the large peak of oil price due to the 1973, Israelo-Arab war. The aim was both to test the exploitation of high temperature fluids using an extraction/reinjection system and to monitor the perturbation of the deep geothermal system (pressure, water level and capacity) induced by the presence of active wells. Because of the substantial depth of the wells and their closeness to highly urbanized area, particular care was paid to the protection of the environment. Many surveys of micro-seismicity, deforma- tion, soil gas emission were carried out before, during and after the drillings [85]. The researches were extended to the neighbor- ing area of S. Vito, to the north of Pozzuoli, and to Licola (L1 well) located outside the north-west caldera rim. The latter was planned to evaluate the area extension of the thermal anomaly observed at Mofete (Fig. 6). In Mofete area, 7 wells (4 deviated and 3 vertical) were drilled (MF 1, 2, 3d, 5, 7d, 8d, 9d) with depth ranges from 800 to 2700 m. The deviation allowed to intercept the possible fractures and faults zones from which to obtain a better production, avoiding the extension of the wells field close to the urbanized areas [89]. At the end of 1985, the results of the drillings defined the following ...
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... MF8d and MF9d) better connected with the sea, and to escape at the surface. In December 1979, a new drilling program was started in S. Vito area, few kilometers north of Pozzuoli town, with 3 wells (SV1, SV8d, SV3) (Fig. 6) of maximum depth and temperature of 3046 m and 420 • C, respectively. During the production tests a tempera- ture of 220 • C and pressure of 70 kg cm −2 were measured at wells head. The SV1 well crossed the caldera rim whose collapse was esti- mated of about 600-700 m on the basis of stratigraphic correlations between the outcropping Yellow Tuff close to the Gauro crater and its depth in the well. The highest temperatures (about 400 • C) were measured by using a zinc alloy with melt temperature of 419 • C. Before starting the measure, the drilling operations were stopped for some time, to let the temperature of the system stabilize [88]. In order to evaluate the extension of the thermal anomaly of the inves- tigated area a new drilling was carried out at Licola (L1), located outside the caldera rim, close to Cuma north of the caldera. This choice was also helpful for the reconstruction of the stratigraphic sequence which was not affected by volcano-tectonics events due to caldera formation. The recorded temperature in the L1 well was substantial lower than those measured in S. Vito zone, highlighting that the thermal anomaly is confined within the caldera rim [98] (Fig. ...
Citations
... Numerous studies have been focused on the hydrothermal system of the island, focusing on thermal fluids composition and origin, providing important information for geothermal energy exploration and volcanic risk assessment. These studies allowed refining knowledge on hydrothermal fluid circulation (De Gennaro et al., 1984;Panichi et al., 1992;Caliro et al., 1999;Celico et al., 1999;Inguaggiato et al., 2000;Lima et al., 2003;Chiodini et al., 2004;Daniele, 2004;Milano et al., 2004;Aiuppa et al., 2006;Morell et al., 2008;Di Napoli et al., 2009Carlino et al., 2012Carlino et al., , 2015. ...
Ischia is a volcanic island located NW of the Gulf of Naples (South Italy). The island of Ischia is a structurally complex hydrothermal active system that hosts a fractured aquifer system whose geometry and hydraulic properties are still partly unknown. The aquifer system of Ischia, composed mainly of Quaternary volcanic deposits and marine sediments, exhibits physically and chemically heterogeneous waters. The intense seismicity and hydrothermal activity are expressed by numerous fumaroles and thermal springs, which have been exploited since ancient times, promoting, and supporting the world-renowned tourist activities that constitute the main economic activity of the island. The aim of this study is to determine the hydrogeochemical processes in the Ischia aquifer system. Also, we calculated the proportion of seawater in the aquifer system of Ischia using historical hydrogeochemical data relative to two sampling campaigns. Sixty-nine groundwater and thermal spring samples collected in July 2000 were analyzed and compared with previously published data to identify the changes in seawater contribution. The sample analysis shows that different physicochemical processes occur in the groundwater of Ischia Island, where recharge water, seawater and deep fluids interact and overlap with different intensity. The calculated saline factor indicates a seawater content of up to 70% in some samples near the coast, suggesting that seawater intrusion is the main process in these areas. Later data show that seawater intrusion increases around the coastline with up to 93% seawater content. Finally, data analysis shows that although a change in chemical composition is observed, no variation in thermal water temperature is recorded over time.
... In a second scenario that describes the depressurization of the same magma to 130 MPa, the proportion of H 2 O in the exsolved fluid entering the country rock is specified to increase over time. All simulations use a constant, homogeneous permeability value of 1 Â 10 À 14 m 2 , roughly consistent with Campanian crustal permeability values published by Carlino et al. (2015). Output includes the mass of exsolved fluid, which is within the range of the emitted mass of fluid associated with small to moderatesize volcanic eruptions (Chiodini et al., 2012). ...
Intensive research over >200 years has contributed to a rich tectonic, geochemical, and thermophysical database on the Campanian Volcanic Zone, particularly with regard to the voluminous 39.28±0.11ka Campanian Ignimbrite. New observations on pre- and post-Campanian Ignimbrite deposits provide a basis for identifying long-term petrogenetic patterns. Recent work also stands out for its novel exploitation of diverse computational methods. Such methods are now widely accessible but are generally still not routinely applied. This review summarizes and appraises these aspects of Campanian Volcanic Zone research, highlighting major advances. New data have provided a foundation on which to test hypotheses and construct quantitatively constrained predictions. Consensus emphasizes the importance of fractional crystallization and open-system mechanisms including magma mixing and assimilation during magma evolution. Eruption triggers inherent to fractional crystallization and magma ascent have been quantified. However, debate centers on the eruptive significance of unrest signals because associated data permit more than one interpretation.
... In this work, a magnetotelluric (MT) survey was applied to the active volcanic caldera of Ischia, whose resurgence is thought to be associated to a sill intrusion, possibly developed in the form of a laccolith (Rittmann 1930;Sbrana et al. 2009;Carlino et al. 2006;Carlino 2012, and references therein). The resurgence, which is estimated as at least 800 m (Vezzoli 1988), was accompanied by volcanic activity and by the exhumation of the geothermal system (Sbrana et al. 2009), with the occurrence of a large diffuse heat flow and very high geothermal gradients (>180°C km −1 ) in the shallow crust (Vezzoli 1988;Carlino 2012;Carlino et al. 2014Carlino et al. , 2015. Although a numbers of local geophysical investigations have been performed at Ischia (Di Napoli et al. 2009, 2011Paoletti et al. 2013), a wider geophysical imaging of the island is not yet available. ...
The island of Ischia (located in the Bay of Naples, Italy) represents a peculiar case of a well-exposed caldera that has experienced a large (>800 m) and rapid resurgence, accompanied by volcanic activity. What drives the resurgence of calderas is a crucial issue to investigate, because this process is associated with potential eruptions and high risk to people living within and around such large active volcanic systems. To improve the knowledge of volcano-tectonic processes affecting the caldera of Ischia, electromagnetic imaging of the structures associated with its resurgence was performed and integrated with available geological information. A magnetotelluric (MT) survey of the island was carried out along two main profiles through the central-western sector, providing an electrical resistivity map to a depth of 3 km. These resistivity cross sections allowed us to identify the presence of a very shallow magmatic intrusion, possibly a laccolith, at a depth of about 1 km, which was responsible for both the resurgence and the volcanic activity. Furthermore, the tectonic structures bordering the resurgent area and the occurrence of a large thermal anomaly in the western sector of the caldera also provided a signature in the resistivity cross sections, with the magma intrusion producing advection of hot fluids with high geothermal gradients (>150 °C km−1) in the southern and western sectors. All of these data are fundamental for the assessment of the island’s volcano-tectonic dynamics and their associated hazards. The structure and activity of the island have been controlled by the process of resurgence associated with the arrival of new magma and the progressive intrusion of a laccolith at a shallow depth. The reactivation of such a shallow system may imply imminent eruption which would pose a major volcanic hazard.
The “reading” of an area by geologists inevitably leads to the nature of the physical processes that shaped it. It is in the variety of the landscape of Campania that one can recognize the various geological phenomena that have been operating for millions of years in this area, located on the eastern edge of the Tyrrhenian Basin and bordered by the limestone massifs of the Southern Apennines (Fig. 2.1). The two main geodynamic processes that characterize the Miocene, from 23 to 5.3 million years ago (mya), not only this area but throughout most of southern Italy, are the distension of the Tyrrhenian basin and the Apennine orogenesis (Fig. 2.2). These two processes are related to the counterclockwise rotation of the African plate to the south, converging on the Euroasian plate to the north. The border between the two plates is delimited by the Apennine chain, in the centre-south of Italy and, to the north, by the Alps, representing the zones of collision and corrugation due to convergence. The relative motion between the two plates has produced, since at least since the lower Pleistocene (between 2.5 mya and 11,700 years ago), predominantly extensional tectonic activity on the Tyrrhenian side, which becomes compressive as one moves across to the Adriatic. The Apennine is a watershed between these two different tectonic areas. The Apennine Rocks, which are Mesozoic-Tertiary in age, represent the ancient carbonate basement, formed in a shallow marine environment, and subsequently deformed by tectonic processes. Crustal relaxation on the Tyrrhenian margin during the Pleistocene is associated with a tectonic movement that incorporates a strongly vertical component, which caused the carbonate platform to sink as much as several thousand metres in the direction of the Tyrrhenian Sea. This resulted in the formation of horst and graben structures, which correspond to zones of upland topography and subsidence respectively. Within the setting of structures linked to the Tyrrenean distension system lies the Campania Plain which represents a graben, stretched in a northwesterly-southeasterly direction and filled by volcanoclastic deposits and alluvial sediments, the latter resulting from the collapse of the Apennines, for a total thickness of more than 3000 m in the area of maximum subsidence. The plain itself develops between Monte Massico to the northwest, the Campanian Apennines (the Tifatini mountains of the area around Nola and Caserta) to the east and the Lattari Mountains of the Sorrento peninsula to the southeast. Monte Massico borders to the northwest with the extinct volcano of Roccamonfina, the last eruptive activity of which dates back to about 50,000 years ago (Fig. 1.3). In the central and southern part of the plain emerge the volcanic complexes of the Campi Flegrei and Vesuvius, which together with the island of Ischia, just to the west, constitute the active volcanoes of Campania. The tectonic distension of this area, ongoing over the course of several million years, has produced a progressive stretching and thinning of the crust, with the rise of the Moho which represents the rheological discontinuity between the lower crust and the upper mantle. This process has allowed magmas in the mantle to rise through the crust, halting at a range of depths and thus feeding Neapolitan volcanism (Fig. 2.3). Open image in new window Fig. 2.1 Digital terrain model of the Campania Region with indication of the main faults (black lines) related to its Pleistocene-Holocene tectonics. The box in the right-top shows the thrust between the African and Eurasian plate that is responsible for the Apennine orogenesis (mountain building) (INGV Archive) Open image in new window Fig. 2.2 Direction of Tyrrhenian spreading and Apennine tension along the collision zone between the Africa and Eurasian plate Open image in new window Fig. 2.3 A sketch of the possible crustal structure below the Neapolitan volcanoes reconstructed using the main geological, geophysical and stratigraphic information available. The extensional (spreading) tectonics of the Tyrrhenian basin have produced a thinning of the crust and the uprising of the Moho at a depth of about 20 km beneath the volcanoes. The minimum depth, which corresponds to the maximum stretching of the crust, occurs beneath the Campi Flegrei volcanic district that is also the area with the most intense heat flow. The extension generated intense vertical tectonic activity, with the sinking of the carbonate platform toward the sea. The deep magmatic chambers that fed the larger eruptions of Neapolitan volcanoes are possibly located at a depth of 8–10 km, which may correspond to the level of neutral buoyancy. This deeper feature has not been investigated beneath the Island of Ischia. A robust geothermal system has developed within the highly fractured rocks in the Campi Flegrei and Ischia caldera, respectively. Crystalline basement is composed of metamorphic rocks, while the zone subject to sinking was filled by volcanic and alluvial deposits during the Holocene. Conglomerates and clays may be related to the intense erosional phase and sinking of the carbonate platform in the Early Pleistocene. See also Fig. 32 for Rovigliano rock
We present a numerical modeling aimed at investigating nature and role of the self-potential (SP) anomalies induced by water injection in boreholes at the Soultz-sous-Forêts (SsF) hot dry rock enhanced geothermal field. The overpressure due to the fluid stimulation is considered as source of the streaming potential effects in rocks, responsible on their turn of the SP anomalies observed at the ground surface. The numerical simulations have been realized by a combined application of the TOUGH2 and Comsol Multiphysics codes, which had already been successfully used to predict Coulomb stress changes in rocks induced by a fluid injection cycle. Two synthetic cases are investigated. At first, a simulated injection cycle in a single borehole has been modeled, consisting in the reconstruction of the overpressure and SP temporal and spatial evolutions induced by the hydraulic stimulation of the rock. The main result is that the front of the SP anomaly follows the overpressure front, with the time delay between the two fronts decreasing at increasing distance from the well. The second case takes into consideration a real injection experiment performed in 2003 at SsF, which has allowed to examine the induced seismicity. The simulated SP response to this real injection cycle shows that the SP temporal evolution is essentially a post-seismic effect. The conclusion from the simulations is that SP measurements can be used to localize the main features of the fluid flow into the reservoir.
