Papers by Angelo Minissale
Journal of Geochemical Exploration, 2023
This paper presents and discusses the water and gas geochemistry of a large number of thermal spr... more This paper presents and discusses the water and gas geochemistry of a large number of thermal springs occurring along the N-S trending Strymon Valley, from its source, near Sofia (Bulgaria), to the Aegean Sea (Greece). In Bulgaria springs have markedly alkaline pH, relatively low Total Dissolved Solids and prevalent Na-HCO 3 to Na-Cl(SO 4) in composition while the associated gas phase is mostly N 2-dominated. When moving to the Greek sector, the thermal springs, Ca(Mg)-HCO 3 to Na-HCO 3 , become less alkaline and more saline whereas the associated gas phase is CO 2-dominated. The abrupt geochemical change in the Greek sector is caused by a variation in the thickness and nature of the sediments filling the Strymon Valley, the latter being characterized by a relevant amount of Neogene marine material. Such changes occur south of an important E-W lineament named Middle Mesta, south of which marble formations extensively crop out and are likely occurring below the sedimentary succession. The presence of these carbonate sequences embedded in the Neogene sediments is explaining the CO 2-rich gases associated to the Greek springs. Water isotopes indicate a meteoric origin for the studied waters. From a geothermometric point of view, solute (previous studies) and gas (this work) geothermometers suggest that no high enthalpy systems occur in the Bulgaria and northern sector of Greece with estimated temperatures <120 • C. Consequently, these thermal springs can be regarded as tectonically-derived along the many fault systems that border the Strymon Valley. The convective circuits are thus originated from rainfall in the crystalline massifs that border the valley, i.e. the Serbo-Macedonian to the west and the Rhodope to the east.
Bollettino Della Societa Geologica Italiana, 2011
This paper presents geothermal exploration in the western part of Yemen. Geologically this volcan... more This paper presents geothermal exploration in the western part of Yemen. Geologically this volcanic province totals approximately 45,000 km 2 . Tectonically the study area is considered as one of the most active areas in the Arabian Plate boundaries and affected by the opening of the Red Sea and the Gulf of Aden as well as by the African rift valley. Extensive field work had been carried out to evaluate the geothermal characteristics of this area. Water and gas samples were collected from hundreds of thermal springs and shallow domestic wells and geochemically analyzed and reported. Temperatures and PH values ranged from 35 to 96.3 °C and from 4.5 to 8.5 respectively. Deep geothermal gradient indicated that the geothermal gradients in the western part of the province (Red Sea coast) were relatively high, up to 182 °C at the depth of 3290 m. Volcanic units were affected by hydrothermal processes and were intensively altered. By applying geothermometric methods, four geothermal fields...
Chinese Science Bulletin, 1998
In the period 1998-2002 thermal spring discharges of Rincon de la Vieja volcano (NW Costa Rica) h... more In the period 1998-2002 thermal spring discharges of Rincon de la Vieja volcano (NW Costa Rica) have been sampled and analyzed for major, trace and isotopic (18 O/ 16 O and D/H in waters and 3 He/ 4 He and 13 C/ 12 C in CO 2 in gases) composition. The boiling pools hosted inside the summit crater (Active Crater) are characterized by high contents of magmatic-related compounds (SO 2 , HCl and HF) that strongly affect the chemistry of the crater lake. These chemical features are not shown by the thermal discharges seeping out in the surrounding area of the volcano. Here, the shallow aquifer apparently masks any possible clues related to the magmatic system. This suggests that the fluid vents located inside the Active Crater are likely to represent the most appropriate sampling sites for geochemical surveillance purposes, although the high gas discharge rate from the lake may occasionally prevent any fluid sampling. Alternatively, as already suggested by recent studies on the behavior of light hydrocarbons in different volcanic environments, the compositional features of the organic gas fraction in the more accessible outer flank thermal discharges could usefully be utilized, at least, to assess the thermodynamic conditions of the volcanichydrothermal system, since these compounds are affected by secondary processes only at limited extent.
In this paper a relatively inexpensive and efficient strategy for geothermal exploration by using... more In this paper a relatively inexpensive and efficient strategy for geothermal exploration by using geochemical prospecting tools to determine the placement of initial exploratory well(s) is proposed. The method involves categorizing the hierarchy of thermal manifestations from which the presence of a buried thermal anomaly can be identified in a given geothermal area, and then locating the centre of the thermal anomaly. This is done by using simple, easy to obtain data on the depth, temperature, and some common chemical parameters determined in wells of the shallow unconfined aquifer, from which thermal gradients can be calculated if the temperature of the local rainfall is known. The proposed strategy was applied by the author in Yemen; on a national scale in 2001-2006 (Minissale et al., 2007), and a local scale in 2007-2010 in the Dhamar region (Minissale et al., 2013). In the paper about the Dhamar area, briefly summarized here, how the placement of its first exploratory well was determined is described. The methodology proposed is particularly effective and convenient in developing countries, such as those located along the African Rift, e.g. Zambia and Malawi, where geothermal exploration is still in its infancy, and where waiting for expensive geophysical investigations might postpone the development of geothermal resources for decades.
This paper reports how travertine of central-southern Italy, formed in response to the extensive ... more This paper reports how travertine of central-southern Italy, formed in response to the extensive circulation of waters inside the regional aquifer hosted in the Mesozoic carbonate sequences, can be used as a tool for paleoclimatic, neotectonic and paleohydrological investigations. CO 2-rich thermal springs, CO 2 vents and travertine are frequent occurrences of the peri-Tyrrhenian sector of central-southern Italy. In a crust affected by mantle magmas triggering fluids motion, among others CO 2 from several horizons at variable depth, the δ 13 C of CO 3-ions of dissolved travertine suggests the type of circulation and the prevalent CO 2 source involved. More negative values suggest "normal" topographically driven circulation in karstic circuits, where CO 2 derives from soil (bacteria); more positive values suggest the inflow into the karstic circuits of deep CO 2. Such rising CO 2 , together with other acidic gases (e.g. H 2 S) greatly enhances limestone dissolution. Accordingly, the travertine formed at the surface (metheogene vs thermogene) reflects the type of "mother" CO 2 involved in the dissolution process. In this way, travertine can be used to trace the evolution of paleohydrothermal systems in areas where there are no thermal features at surface. In terms of tectonic tool, since active and fossil travertine in the Apennines can be found at very different elevations, their formation age reflects the difference in elevation between the present and the past karstic circulation. Being the Apennines a young, very active orogen, the described methodology of using travertine as a benchmark for paleohydrology, suggests for a vertical isostatic rate of 0.7 mm/y. Being very sensitive to environmental conditions, travertine can also be used as a tracer for paleoclimate. The parallel investigation on the stable isotopic composition (δ 18 O, δ 13 C) of the dissolved CO 3-ions, and palynological profiles in two Pleistocene deposits of central Italy (Serre di Rapolano and Tivoli, the latter in progress), allowed to describe variations in the last ca 120 kyrs. The correspondence between observed environmental fluctuations in pollen and isotopes, as well as with other proxies in nearby terrestrial deposits, and with more global proxies (ice-core and foraminifera) seems possible and demonstrates that travertine can be used to investigate the paleoclimate of the late Quaternary. This is in line with the observation that most of dated travertine in central Italy cluster in interglacial periods. This coincidence seems reasonable: 1) because the deposition of travertine is depending upon rainfall amounts, and 2) because in glacial periods, the lower level of the oceans also lowers the base level of karstic circulation.
Geothermics, 2018
Abstract Thermal springs lined up for about 350 km along the Western coast of Maharashtra, India,... more Abstract Thermal springs lined up for about 350 km along the Western coast of Maharashtra, India, have been studied for major, minor, trace and rare earth elements, along with the boron isotope ratios for selected samples, to understand their evolution pattern. These alkaline springs have discharge temperatures varying from 40 to 72 °C. Based on the major ion composition, it is established that most of the thermal springs are of Na(Ca)-Cl or Ca(Na)-Cl type, with a few of Na-Cl(SO 4 ) type. Only one thermal spring at Rajapur is Na-HCO 3 type behavior. Trace elements concentration vary significantly e.g., Li (19–386 ppb), B (104–1362 ppb), Sr (16–13560 ppb), Rb (13–220 ppb), Cs (0.75–44 ppb) and Ba (3–2077 ppb). Chondrite-normalized REE patterns indicate a pronounced ‘Eu’ anomaly probably due to the involvement of plagioclase, but the effect of temperature reaching more than 250 °C cannot be ruled out in case of some springs. First-time study of δ 11 B isotope (range between 2.5‰ to 27.0‰) of the West Coast thermal fluid suggests role of leaking marine sediments in their evolution. Water-rock interaction experiments with granite, basalt and diluted seawater at elevated temperatures and pressures have given an insight into the evolution of the thermal springs. Based on all the findings, a conceptual model has been prepared, which gives an overview of the evolution of the thermal springs.
Journal of Volcanology and Geothermal Research, 2017
In this study, the occurrence, chemical composition, origin and geothermal significance of therma... more In this study, the occurrence, chemical composition, origin and geothermal significance of thermal springs and fumaroles naturally discharging in the area located north of the Lake Abaya (western margin of the Main Ethiopian Rift, East Africa) are reviewed in relation with recent tectonics. All thermal springs showed a dominantly Na-HCO 3 composition, consistent with observations dating from at least 1972, and most of them displayed a narrow range of δD and δ 18 O isotopic compositions for water similar to regional meteoric origins. These observations suggest that water-rock interaction processes occur in all aquifers and dominate the contributions of water that actively circulate within thermal fluids, and also suggest a similar elevation of groundwater recharge throughout the study area. Most of the thermal springs are dominated by a CO 2-rich gas phase and discharge along the active faults bordering the western edge of the Main Ethiopian Rift valley. The δ 13 C values of CO 2 and the 3 He/ 4 He isotopic ratios are consistent with the presence of mantle-derived fluids similar to what is observed in many other areas along the kinematically active African Rift, especially within Ethiopia. The application of geothermometric techniques in the liquid and the gas phases suggests the presence of a deep reservoir in which the fluids equilibrated at a maximum temperature of approximately 180°C. Additionally, the presence of fumaroles at boiling temperatures and water/mud boiling pools in several places suggests that the geothermal reservoir is positioned at a relatively shallow depth and likely located in the western side of the study area. The analysis of data collected throughout time reveals that the waters of Lake Abaya have experienced an increase in salinity of 20% paralleled contemporaneously with a decrease in pH and δ 18 O and δD of water in the last 40 years; these changes do not appear to be related to climate changeinduced increases in temperature or evaporation at the global scale.
Earth-Science Reviews, 2017
Abstract Low-to-medium temperature fluid reservoirs hosted in carbonate rocks are some of the mos... more Abstract Low-to-medium temperature fluid reservoirs hosted in carbonate rocks are some of the most promising and unknown geothermal systems. Western Sicily is considered a key exploration area. This paper illustrate a multidisciplinary and integrated review of the existing geological, geochemical and geophysical data, mainly acquired during oil and gas explorations since the 1950s, specifically re-analyzed for geothermal purposes, has led to understanding the western Sicily geothermal system as a whole, and to reconstructing the modalities and particular features of the deep fluid circulation within the regional reservoir. The data review suggests the presence of wide groundwater flow systems in the reservoir beneath impervious cap rocks. We identified the main recharge areas, reconstructed the temperature distribution at depth, recognized zones of convective geothermal flow, and depicted the main geothermal fluid flow paths within the reservoir. We believe that our reconstruction of geothermal fluid circulation is an example of the general behavior of low-to-medium enthalpy geothermal systems hosted in carbonate units on a regional scale. Due to the recent technological developments of binary plants, these systems have become more profitable, not only for geothermal direct uses but also for power production.
Geothermics, 2016
Abstract Carbonate aquifers in foreland tectonic settings can host important thermal springs alth... more Abstract Carbonate aquifers in foreland tectonic settings can host important thermal springs although located in areas commonly not characterized by regional high heat flow values. In these cases, when thermal springs are located close or along the coastlines the subaerial and/or submarine thermal springs constitute the outflow of marine groundwater, flowing through localized fractures and karsitic rock-volumes. This is the case of springs occurring along the south-easternmost portion of the Apulia region (Southern Italy) where few sulphurous and warm waters (22–33 °C) outflow in partially submerged caves located along the shoreline, thus supplying the historical spas of Santa Cesarea Terme. Here, with the aim to define the origin of the thermal fluids and their deep path, we carried out the geo-structural survey of the area and detailed hydrogeological and geochemical analyses of the thermal spring fluids. In particular, the isotopes δ18O, δD, 13C in DIC, 34Ssulphate, 34Ssulphide, 3He/4He ratio and 13C in CO2 were used to define the origin of the thermal water and the recharge mechanism of the geothermal system while the isotopes 3H and 14C were determined for estimating the age of the thermal waters, resulting in older than roughly twenty thousands years BP. The results indicate that the thermal springs are fed by marine water, having reached Santa Cesarea Terme through a localized fracture network. This affects the evaporitic and carbonatic rocks that characterize the substratum of the Adriatic Sea in the offshore.
Geothermics, 2015
ABSTRACT This paper describes a data integration tool used to identify potentially undiscovered g... more ABSTRACT This paper describes a data integration tool used to identify potentially undiscovered geothermal resources in the island of Sicily. The factors facilitating the recovery of exploitable geothermal energy were defined, and their spatial correlation established by Geographic Information System (GIS) models.
Oil exploration in western Sicily started in the late 1950s when several exploration wells were d... more Oil exploration in western Sicily started in the late 1950s when several exploration wells were drilled, and continued with the acquisition of many seismic reflection profiles and the drilling of new wells in the1980s. The geological interpretation of these data mainly provided new insights for the definition of geometric relationships between tectonic units and structural reconstruction at depth. Although it has not produced completely satisfactory results for oil industry, this hydrocarbon exploration provided a great amount of data, resulting very suitable for geothermal resource assessment. From a geothermal point of view western Sicily is, indeed, a very promising area, with the manifestation at surface of several thermal springs, localized areas of high heat flux and thick carbonates units uninterruptedly developing from surface up top great depths. These available data were often collected with the modalities and purposes typical of oil exploration, not always the finest for geothermal exploration as in the case of temperature measurements. The multidisciplinary and integrated review of these data, specifically corrected for geothermal purposes, and the integration with new data acquired in particular key areas such as the Mazara Del Vallo site in the southern part of western Sicily, allowed us to better understand this medium-enthalpy geothermal system, to reconstruct the modalities and peculiarities of fluids circulation, and to evaluate the geothermal potentialities of western Sicily. We suggest that western Sicily can be taken as a reference for the understanding of geothermal systems developed at a regional scale within carbonate rocks. This study was performed within the framework of the VIGOR project (http://www.vigor-geotermia.it).
The Chiavenna Valley (Sondrio, Northern Italy) is located in the Central Alps and is elongated al... more The Chiavenna Valley (Sondrio, Northern Italy) is located in the Central Alps and is elongated along a NNW-SSE direction. Geologically, it consists of a poly-metamorphic sequence, which includes metasediments, metagranitoids, and ophiolites, intruded by Tertiary granitoid rocks.This work describes a geochemical investigation carried out in the Chiavenna Valley (Sondrio, Northern Italy) in 2000-2002, during which more than 200 running and ground waters were collected and analysed for major, trace elements, and Sr isotopes.The great majority of the analysed waters are of good quality and have low contents of those elements considered as contaminants or undesirable substances. Thus, the Chiavenna Valley can be regarded as a mostly low-pollution area. A few metals, i.e. As, Cd, Cr, and Pb, as well as the nitrogen species, are enriched close to urban centres or/and industrial areas, suggesting an anthropogenic source. Furthermore, Sr isotopes were used to evaluate the input due to the leaching of the country rocks.
Geothermal Energy Resources for Developing Countries, 2002
Geochemical survey on thermal spring areas all over the World have been largely used in the past ... more Geochemical survey on thermal spring areas all over the World have been largely used in the past to assess the potentiality of a promising region for the development of geothermal energy. Before conducting any expensive geochemical and geophysical prospecting campaign, a preliminary reconnaissance survey describing the location, geological setting of thermal emergences, and type of manifestation should be conducted. Once the occurrence and type of thermal manifestations is known, a strategy on what type of chemical prospecting is better for the area under investigation should be planned. Chemical investigation of steam condensates, thermal waters, gas vents and mineral phases, precipitated at the orifice of thermal discharges should include both isotopic and chemical analysis, whose number is limited by the available budget. The geochemical prospecting of natural thermal (and for comparison cold) fluids discharged at the surface of a promising area should precede any future geophysical investigation. Among possible geophysical investigations, geoelectrical prospecting and the drilling of shallow wells to measure the geothermal gradient seem to be the more useful tools to decide if a potential geothermal area deserve to be investigated by deep drillings
Journal of Volcanology and Geothermal Research, 2003
Most thermal spring discharges of Rajasthan and Gujarat in northwestern India have been sampled a... more Most thermal spring discharges of Rajasthan and Gujarat in northwestern India have been sampled and analysed for major and trace elements in both the liquid and associated gas phase, and for 18 O/ 16 O, D/H (in water), 3 He/ 4 He and 13 C/ 12 C in CO 2 (in gas) isotopic ratios. Most thermal springs in Rajasthan are tightly associated to the several regional NE^SW strike-slip faults bordering NE^SW ridges formed by Archaean rocks at the contact with Quaternary alluvial and aeolian sedimentary deposits of the Rajasthan desert. Their Ca^HCO 3 immature character and isotopic composition reveals: (1) meteoric origin, (2) relatively shallow circulation inside the crystalline Archaean formations, (3) very fast rise along faults, and (4) deep storage temperatures of the same order of magnitude as discharging temperatures (50^90 ‡C). Thermal spring discharges in Gujarat are spread over a larger area than in Rajasthan and are associated both with the NNW^SSE fault systems bordering the Cambay basin and the ENE^WSW strike-slip fault systems in the Saurashtra province, west of the Cambay basin. Chemical and isotopic compositions of springs in both areas suggest a meteoric origin of deep thermal waters. They mix with fresh or fossil seawater entering the thermal paths of the spring systems through both the fault systems bordering the Cambay basin, as well as faults and fractures occurring inside the permeable Deccan Basalt Trap in the Saurashtra province. The associated gas phase, at all sampled sites, shows similar features: (1) it is dominated by the presence of atmospheric components (N 2 and Ar), (2) it has high crustal 4 He enrichment, (3) it shows crustal 3 He/ 4 He signature, (4) it has low CO 2 concentration, and (5) the only analysed sample for 13 C/ 12 C isotopic ratio in CO 2 suggests that CO 2 has a strong, isotopically light organic imprint. All these features and chemical geothermometer estimates of spring waters suggest that any active deep hydrothermal system at the base of the Cambay basin (about 2000^3000 m) has low-to-medium enthalpy characteristics, with maximum deep temperature in the storage zone of about 150 ‡C. In a regional overview, both thermal emergences of Rajasthan and Gujarat could be controlled by the counterclockwise rotation of India.
Journal of Volcanology and Geothermal Research, 2005
... Permissions &amp;amp;amp;amp;amp;amp;amp;amp; Reprints. The hydrothermal-volcanic system ... more ... Permissions &amp;amp;amp;amp;amp;amp;amp;amp; Reprints. The hydrothermal-volcanic system of Rincon de la Vieja volcano (Costa Rica): A combined (inorganic and organic) geochemical approach to understanding the origin of the fluid discharges and its possible application to volcanic surveillance. ...
Journal of Volcanology and Geothermal Research, 1997
The Mt. Amiata volcano in central Italy is intimately related to the post-orogenic magmatic activ... more The Mt. Amiata volcano in central Italy is intimately related to the post-orogenic magmatic activity which started in Pliocene times. Major, trace elements, and isotopic composition of thermal and cold spring waters and gas manifestations indicate the occurrence of three main reservoir of the thermal and cold waters in the Mt. Amiata region. The deepest one is located in an extensive carbonate reservoir buried by thick sequences of low-permeability allochthonous and neo-autochthonous formations. Thermal spring waters discharging from this aquifer have a neutral Ca-SO composition due to the 4 presence of anhydrite layers at the base of the carbonate series and, possibly, to absorption of deep-derived H S with 2 2y . subsequent oxidation to SO in a system where pH is buffered by the calcite-anhydrite pair Marini and Chiodini, 1994 . 4 Isotopic signature of these springs and N -rich composition of associated gas phases suggest a clear local meteoric origin of 2 the feeding waters, and atmospheric O may be responsible for the oxidation of H S. The two shallower aquifers have 2 2 different chemical features. One is Ca-HCO in composition and located in several sedimentary formations above the 3 Mesozoic carbonates. The other one has a Na-Cl composition and is hosted in marine sediments filling many post-orogenic NW-SE-trending basins. Strontium, Ba, F, and Br contents have been used to group waters associated with each aquifer. Although circulating to some extent in the same carbonate reservoir, the deep geothermal fluids at Latera and Mt. Amiata and thermal springs discharging from their outcropping areas have different composition: Na-Cl and Ca-SO type, 4 respectively. Considering the high permeability of the reservoir rock, the meteoric origin of thermal springs and the two different composition of the thermal waters, self-sealed barriers must be present at the boundaries of the geothermal systems. The complex hydrology of the reservoir rocks greatly affects the reliability of geothermometers in liquid phase, which understimate the real temperatures of the discovered geothermal fields. More reliable temperatures are envisaged by using gas composition-based geothermometers. Bulk composition of the 67 gas samples studied seems to be the result of a continuous mixing between a N -rich component of meteoric origin related to the Ca-SO aquifer and a deep CO -rich 2 4 2 component rising largely along the boundaries of the geothermal systems. Nitrogen-rich gas samples have nearly
Geological Society, London, Special Publications, 2006
This paper presents the results of an extensive chemical and isotopic investigation on natural th... more This paper presents the results of an extensive chemical and isotopic investigation on natural thermal and cold fluids (spring waters and associated gases) discharging throughout the main geological domains of Morocco. The chemical features of the thermal springs are mainly dependent on rock dissolution involving Triassic evaporite formations, producing either Na-Cl or Ca-SO4 composition, although mixing with shallower connate high-saline waters in Neogene post-orogenic sedimentary layers cannot be ruled out. Only in the Moroccan Meseta and Anti-Atlas domains have spring discharges probably undergone equilibration as a result of water-rock interaction in granites. Of the chemical and isotopic features of the gas seeps, 3He/4He ratios and δ13C-CO2 values indicate the occurrence of a significant contribution of mantle-derived gas, especially at Oulmès (Moroccan Meseta) and Tinejdad-Erfoud (Anti-Atlas), where associated waters are found to equilibrate at relatively high temperatures (c...
Uploads
Papers by Angelo Minissale