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[Article in Italian] Geotermia profonda ed energia: elettricità, litio geotermico, materie prime critiche

ABSTRACTWe present the geological map (1:10.000) of the Montecastelli Pisano area, where (i) the relationships between Neogene-Quaternary transfer and normal faults have been carefully mapped (Sheet 1), and (ii) the mantle sequence of the Ligurian Ocean has been analysed (Sheet 2). Fault analyses allowed to define: (i) NE-trending fault system (left-lateral strike- to oblique-slip faults) belonging to a transfer shear zone; and (ii) NW-trending normal to oblique-slip faults. Their evolution is framed in the extensional tectonics affecting the Northern Apennines since Early-Middle Miocene. The ophiolite complex is constituted by serpentinized spinelharzburgite with minor serpentinized dunite channels cut by gabbro dykes. A km-scale cataclastic zone cut the mantle section, locally hosting Cu-Fe mineralization. The goal of this work is to present the distribution of the main fractures affecting an area where the occurrence of ophiolite can favor the success of the CO2 reinjection project.

Several Jurassic, ophiolite-hosted Cu-Zn VMS deposits occur in Tuscany. They are hosted by tectonic units of oceanic affinity (Ligurian Units), such as the well-known deposits of nearby Liguria. Industrial production was small and definitively ceased in the 1960s. Locally, massive ore (chalcopyrite-bornite-chalcocite) with an exceptionally high grade was found. The Montecatini Val di Cecina mine exploited the largest “bonanza” and, for few decades in the 19th century, became one of the most profitable copper mines in Europe. This study provides an updated review of these deposits. Tuscan Cu-Zn VMSs mostly occur in proximity of the contact between the serpentinite-gabbro basement and the overlying basalts. Chalcopyrite-pyrite stockworks occur in serpentinite-gabbro cut by dolerite dykes, while the largest massive sulphide bodies are hosted by polymictic-monomictic breccias at the base of pillow basalts. Early chalcopyrite ores were mechanically–chemically reworked and upgraded to bornite-rich nodular ore embedded in a chlorite, calcic amphibole, Fe-rich serpentine, quartz, andradite, ilvaite, and xonotlite assemblage. This bornite-rich ore contains substantial amount of sphalerite and pyrite and ubiquitous grains of clausthalite, hessite, tellurium, and gold. They represent a prime example of the sub-seafloor portion of a hybrid mafic-ultramafic oceanic hydrothermal system formed in an OCC along the slow spreading ridge of the Jurassic Piedmont-Ligurian Ocean. The peculiar mineralogical–textural character of the bornite-rich ore was driven by an interface coupled dissolution–precipitation process mediated by fluids.

Abstract Muon radiography (muography) is an imaging technique based on atmospheric muon absorption in matter that allows to obtain two and three-dimensional images of internal details of hidden objects or structures. The technique relies on atmospheric muon flux measurements performed around and underneath the object under examination. It is a non-invasive and passive technique and thus can be thought of as a valid alternative to common prospecting techniques used in archaeological, geological and civil security fields. This paper describes muon radiography measurements, in the context of archaeological and geological studies carried out at the Temperino mine (LI, Tuscany, Italy), for the search and three-dimensional visualisation of cavities. This mine has been exploited since Etruscan times until recently (1973), and is now an active tourist attraction with public access to the tunnels. Apart from the archaeological interest, the importance of mapping the cavities within this mine lies in identifying the areas where the extraction ores were found and also in the safety issues arising from the tourist presence inside the mine. The three-dimensional imaging is achieved with two different algorithms: one involving a triangulation of two or more measurements at different locations; the other, an innovative technique used here for the first time, is based on the back-projections of reconstructed muon tracks. The latter requires only a single muographic data tacking and is to be preferred in applications where more than one site location can be difficult to access. Finally the quality of the three-dimensional muographic imaging was evaluated by comparing the results with the laser scan profiles obtained for some known cavities within the Temperino mine.

Abstract Petrology and timing of magmatic-hydrothermal systems and the linkage between plutonic and volcanic domains are central topics in geosciences, because of broad implications for natural hazards and exploitation of natural resources. We investigated by the 40Ar–39Ar method the timescale of a well-characterized natural example, the Mio-Pliocene Campiglia Marittima magmatic-hydrothermal system (Tuscany, Italy). 40Ar–39Ar data from pristine and homogeneous trioctahedral micas and sanidine from the plutonic-hydrothermal-subvolcanic-volcanic sequence (from the Botro ai Marmi Granite to the San Vincenzo Rhyolite) record crystallization ages and define a temporal sequence lasting 973 ± 43 ka, starting from 5.409 ± 0.043 Ma. K-feldspar from mafic and felsic porphyries, unlike micas, are affected by submillimetre, micropore laden, alteration domains consisting of secondary K-feldspar and albite, and yielded staircase-shaped age spectra, compatible with a ternary mixing. Results document that the San Vincenzo Rhyolite consists of two diachronous batches, the first emplaced at 5.0024 ± 0.0062 Ma, closely following emplacement of mafic porphyries, the second at 4.4359 ± 0.0045 Ma. Bulk of hydrothermal deposits, consisting of skarns and associated Zn–Pb(-Ag) mineralization predating Fe–Cu ore, formed within the first ~ 400-ka lifetime of the whole sequence and was closely followed by the first eruption which should have run out most of the ore-forming potential of the system.

Campiglia Marittima (hereafter Campiglia) has a long record of attracting interest on its ore deposits that have been intermittently exploited from the Copper Age to the late XX century. Since the XIX century, Campiglia has been a key locality for the debate on skarn-forming processes due to the presence of mining activities ensuring access to ever new rock exposures. The pioneering study of vom Rath and the comparison with attractive chemical model (e.g., Korzhinskii’s theory) in the XX century made Campiglia a “classic” example of skarn ore deposit, from the causative intrusion to the marble host rock. In recent years, detailed field investigations integrated by petrographic, geochemical, and isotopic analyses revealed a more complex and stimulating geological history. The Campiglia skarn was later intruded by mafic magma causing textural reworking and chemical redistribution as well as the reverse telescoping process with Fe-Cu sulfides overprinting previously formed Pb-Zn ore. This work aims to trace the evolution of the scientific thinking on the Campiglia ore deposit by comparison with existing skarn-forming models and, ultimately, shows that the current skarn-forming model(s) cannot fully explain the textural and geochemical features of the Campiglia skarn.

Italy has no record of Li production, even though it is well known for its outstanding Li mineral specimens from the Elba Island pegmatites. Because of the current geopolitical situation, the opportunity for a systematic appraisal of resources is evident. Most European Li production comes from deposits associated with Late Paleozoic magmatic rocks. In Italy, such rocks occur extensively in Sardinia and Calabria, but their potential for Li is unknown, and deserves a more systematic exploration. Also of potential interest are the Permo–Triassic spodumene pegmatites in the Austroalpine units of the Central Alps. The Tertiary pegmatites (Elba Island and Central Alps) contain Li minerals, but do not appear large enough to warrant bulk mining. However, we notice that Tertiary–Quaternary magmatic rocks of the Tuscan and Roman magmatic provinces have systematically higher Li contents than those recorded in normal arc igneous rocks worldwide. Specifically, Tuscan granites contain up to 350 μg/g Li, mostly hosted by biotite (up to 4000 μg/g Li); the Capo Bianco aplite (Elba Island) contains up to 1000 μg/g. There are other small Li occurrences associated with Mn deposits and metabauxites, and there is a hypothetical potential for sediment-hosted deposits in the post-orogenic Lower Permian Alpine basins. However, the most promising potential seems to be associated with subsurface fluids. High-enthalpy fluids in geothermal fields may contain up to 480 mg/L Li. Lower-temperature thermal waters may also contain significant Li (>10 mg/L). Moreover, a visionary, but not impossible, perspective may consider a deep injection of water to interact with, and extract Li from, magmatic rocks.

The magmatic-hydrothermal transition in granite-related, rare-metal metallogenic systems has received great attention as economic rare metal (including rare earth) minerals reach saturation and trigger mineralization at this stage. However, deciphering the details of the melt-fluid evolution process and the distribution behavior of rare metals remains difficult. Here, we applied tourmaline chemistry and B isotopes to unravel processes at the magmatic-hydrothermal transition that are responsible for rare-metal partitioning in the Huoshibulake (HS) and Tamu (TM) REE-Nb-mineralized intrusions in Southern Tianshan, SW Central Asian Orogenic Belt. Three types of tourmaline are identified in the plutons: (1) disseminated tourmaline in the granite, with a brown-yellow core (HS-DB) and blue-green rim (HS-DG); (2) orbicular tourmaline, with a brown-yellow core (HS-OB and TM-OB) and blue-green rim (HS-OG and TM-OG); and (3) vein tourmaline (HS-V and TM-V). Compositionally, all these tourmalines exhibit extremely low Ca and Mg contents and are classified as schorl. The substitution processes of major-element variations are dominantly caused by (Al,□)(Fe,Na)−1 exchange vectors. Four generations of tourmaline crystallization are established based on the petrographic, compositional, and B isotopes evolution of the tourmaline. First, the HS-DB crystals crystallized from the highly evolved residual melt, and then HS-OB and TM-OB precipitated from immiscible B-rich aqueous melts during the magmatic-hydrothermal transition. Subsequently, the blue-green overgrowths (HS-DG, HS-OG, and TM-OG) crystallized from exsolved hydrothermal fluids. Finally, the formation of HS-V and TM-V resulted from another melt pulse from a deeper magma chamber. The magmatic tourmaline exhibits a narrow range of δ11B values between −12.6 to −10.0‰, while the hydrothermal tourmaline shows significantly heavier and variable δ11B values ranging from −10.2 to −4.9‰. The fractionation of B isotopes is reproduced by Rayleigh fractionation modeling. Lower Nb and Sn contents in the orbicular tourmaline relative to those precipitated from the residual melt, along with the lack of rare-metal minerals in the orbicules, indicate that B-rich melt/fluid exsolution does not necessarily contribute to the rare-metal mineralization. In comparison, the veins contain abundant rare-metal and REE minerals in close paragenesis with fluorite, and the vein tourmaline shows high-Nb and -Sn contents. These observations suggest that saturation of fluorite triggered the precipitation of rare metals, and fluorine played a critical role in rare metal concentration and mineralization. This study highlights the potential of tourmaline to trace the magmatic-hydrothermal transition and provide insights into rare-metal mineralization in the granitic systems. [ABSTRACT FROM AUTHOR]

Several Jurassic, ophiolite-hosted Cu-Zn VMS deposits occur in Tuscany. They are hosted by tectonic units of oceanic affinity (Ligurian Units), such as the well-known deposits of nearby Liguria. Industrial production was small and definitively ceased in the 1960s. Locally, massive ore (chalcopyrite-bornite-chalcocite) with an exceptionally high grade was found. The Montecatini Val di Cecina mine exploited the largest "bonanza" and, for few decades in the 19th century, became one of the most profitable copper mines in Europe. This study provides an updated review of these deposits. Tuscan Cu-Zn VMSs mostly occur in proximity of the contact between the serpentinite-gabbro basement and the overlying basalts. Chalcopyrite-pyrite stockworks occur in serpentinite-gabbro cut by dolerite dykes, while the largest massive sulphide bodies are hosted by polymictic-monomictic breccias at the base of pillow basalts. Early chalcopyrite ores were mechanically–chemically reworked and upgraded to bornite-rich nodular ore embedded in a chlorite, calcic amphibole, Fe-rich serpentine, quartz, andradite, ilvaite, and xonotlite assemblage. This bornite-rich ore contains substantial amount of sphalerite and pyrite and ubiquitous grains of clausthalite, hessite, tellurium, and gold. They represent a prime example of the sub-seafloor portion of a hybrid mafic-ultramafic oceanic hydrothermal system formed in an OCC along the slow spreading ridge of the Jurassic Piedmont-Ligurian Ocean. The peculiar mineralogical–textural character of the bornite-rich ore was driven by an interface coupled dissolution–precipitation process mediated by fluids. [ABSTRACT FROM AUTHOR]

[Article in Italian] Geotermia profonda ed energia: elettricità, litio geotermico, materie prime critiche [ABSTRACT FROM AUTHOR]

Transmission-based muography (TM) is an innovative imaging technique based on the measurement and analysis of the cosmic ray muons flux attenuation within the target under investigation. This technique allows imaging inner-body density differences and has successfully been applied in a wide range of research fields: geology, archaeology, engineering geology and civil engineering. The aim of this study is to show the reliability of TM as an innovative, noninvasive geophysical method for ore body prospecting and other mining related studies. The measurements were carried out at the Temperino mine in the San Silvestro Archaeological and Mining Park (Campiglia Marittima, Italy), where several magmatic and metasomatic geological units are embodied. Among them, a Cu–Fe–Zn–Pb(–Ag) sulfide skarn complex primarily composed by hedenbergite and ilvaite minerals. Using the acquired muon imaging data obtained with the MIMA (Muon Imaging for Mining and Archaeology) detector prototype (cubic detector of 0.5 × 0.5 × 0.5 m3), the presence of a high-density vein inside the skarn body within the rock volume above the muon detector was identified, localized and interpreted. Applying a back-projection algorithm to the obtained 2D transmission map made it possible to estimate and visualize as point cloud data, in a 2D or 3D environment, the identified high-density body and its relative distance from the detector. The results of this study highlight the potential of muography as a support tool to other geophysical methods in the field of mining exploration. [ABSTRACT FROM AUTHOR]

Italo Calvino travelled to Japan in 1976 and, throughout his career, became increasingly acquainted with Japanese literature and Buddhist philosophy. This encounter is evidenced by the 'Japanese shelves' of his Roman library and by several authorial reflections, which this article scrutinises in order to highlight the material-ecocritical relevance of Calvino's contact with Japanese nature and culture. In particular, this analysis interprets Japanese gardens as spaces where Calvino rethinks his sense of the human and more-than-human by establishing their mutually constitutive relations. Augustin Berque's concept of 'trajectivity', according to which dualisms are constantly transcended in Japanese milieux, guides this exploration of how Calvino's Japanese reflections in Collezione di sabbia articulate his dialectical challenge to logocentrism in 'The Written World and the Unwritten World', to gendered dichotomies in the Japanese chapter of Se una notte d'inverno un viaggiatore, and to traditional humanism in Palomar. [ABSTRACT FROM AUTHOR]

Campiglia Marittima (hereafter Campiglia) has a long record of attracting interest on its ore deposits that have been intermittently exploited from the Copper Age to the late XX century. Since the XIX century, Campiglia has been a key locality for the debate on skarn-forming processes due to the presence of mining activities ensuring access to ever new rock exposures. The pioneering study of vom Rath and the comparison with attractive chemical model (e.g., Korzhinskii's theory) in the XX century made Campiglia a "classic" example of skarn ore deposit, from the causative intrusion to the marble host rock. In recent years, detailed field investigations integrated by petrographic, geochemical, and isotopic analyses revealed a more complex and stimulating geological history. The Campiglia skarn was later intruded by mafic magma causing textural reworking and chemical redistribution as well as the reverse telescoping process with Fe-Cu sulfides overprinting previously formed Pb-Zn ore. This work aims to trace the evolution of the scientific thinking on the Campiglia ore deposit by comparison with existing skarn-forming models and, ultimately, shows that the current skarn-forming model(s) cannot fully explain the textural and geochemical features of the Campiglia skarn. [ABSTRACT FROM AUTHOR]

We present the geological map (1:10.000) of the Montecastelli Pisano area, where (i) the relationships between Neogene-Quaternary transfer and normal faults have been carefully mapped (Sheet 1), and (ii) the mantle sequence of the Ligurian Ocean has been analysed (Sheet 2). Fault analyses allowed to define: (i) NE-trending fault system (left-lateral strike- to oblique-slip faults) belonging to a transfer shear zone; and (ii) NW-trending normal to oblique-slip faults. Their evolution is framed in the extensional tectonics affecting the Northern Apennines since Early-Middle Miocene. The ophiolite complex is constituted by serpentinized spinelharzburgite with minor serpentinized dunite channels cut by gabbro dykes. A km-scale cataclastic zone cut the mantle section, locally hosting Cu-Fe mineralization. The goal of this work is to present the distribution of the main fractures affecting an area where the occurrence of ophiolite can favor the success of the CO2 reinjection project. [ABSTRACT FROM AUTHOR]

The new tourmaline supergroup mineral dutrowite, Na(Fe 2.52+ Ti 0.5)Al 6 (Si 6 O 18)(BO 3) 3 (OH) 3 O, has been discovered in an outcrop of a Permian metarhyolite near the hamlet of Fornovolasco, Apuan Alps, Tuscany, Italy. It occurs as chemically homogeneous domains, up to 0.5 mm, brown in colour, with a light-brown streak and a vitreous lustre, within anhedral to subhedral prismatic crystals, up to 1 mm in size, closely associated with Fe-rich oxy-dravite. Dutrowite is trigonal, space group R 3 m , with a=15.9864(8) , c=7.2187(4) Å, V=1597.68(18) Å 3 , and Z=3. The crystal structure was refined to R1=0.0257 for 1095 unique reflections with Fo>4σ (Fo) and 94 refined parameters. Electron microprobe analysis, coupled with Mössbauer spectroscopy, resulted in the empirical structural formula X (Na 0.81 Ca 0.20 K 0.01) Σ1.02 Y (Fe 1.252+ Mg 0.76 Ti 0.56 Al 0.42) Σ3.00 Z (Al 4.71 Fe 0.273+ V 0.023+ Mg 0.82 Fe 0.182+) Σ6.00 T [(Si 5.82 Al 0.18) Σ6.00 O 18 ] (BO 3)3O(3) (OH) 3O(1) [O 0.59 (OH) 0.41 ] Σ1.00 , which was recast in the empirical ordered formula, required for classification purposes: X (Na 0.81 Ca 0.20 K 0.01) Σ1.02 Y (Fe 1.432+ Mg 1.00 Ti 0.56) Σ3.00 Z (Al 5.13 Fe 0.273+ V 0.023+ Mg 0.58) Σ6.00 T [(Si 5.82 Al 0.18) Σ6.00 O 18 ] (BO 3) 3V (OH) 3 W [O 0.59 (OH) 0.41 ] Σ1.00. Dutrowite is an oxy-species belonging to the alkali group of the tourmaline supergroup. Titanium is hosted in octahedral coordination, and its incorporation is probably due to the substitution 2Al 3+ = Ti 4+ + (Fe,Mg) 2+. Its occurrence seems to be related to late-stage high-T/low-P replacement of "biotite" during the late-magmatic/hydrothermal evolution of the Permian metarhyolite. [ABSTRACT FROM AUTHOR]

Muon radiography (muography) is an imaging technique based on atmospheric muon absorption in matter that allows to obtain two and three-dimensional images of internal details of hidden objects or structures. The technique relies on atmospheric muon flux measurements performed around and underneath the object under examination. It is a non-invasive and passive technique and thus can be thought of as a valid alternative to common prospecting techniques used in archaeological, geological and civil security fields. This paper describes muon radiography measurements, in the context of archaeological and geological studies carried out at the Temperino mine (LI, Tuscany, Italy), for the search and three-dimensional visualisation of cavities. This mine has been exploited since Etruscan times until recently (1973), and is now an active tourist attraction with public access to the tunnels. Apart from the archaeological interest, the importance of mapping the cavities within this mine lies in identifying the areas where the extraction ores were found and also in the safety issues arising from the tourist presence inside the mine. The three-dimensional imaging is achieved with two different algorithms: one involving a triangulation of two or more measurements at different locations; the other, an innovative technique used here for the first time, is based on the back-projections of reconstructed muon tracks. The latter requires only a single muographic data tacking and is to be preferred in applications where more than one site location can be difficult to access. Finally the quality of the three-dimensional muographic imaging was evaluated by comparing the results with the laser scan profiles obtained for some known cavities within the Temperino mine. [ABSTRACT FROM AUTHOR]

Geothermal systems in terrains affected by polyphase deformation have reservoirs with a 3D geometry that is always difficult to predict. In this paper we describe a fossil exhumed geothermal system exposed in eastern Elba Island that developed in a polyphase folded and faulted setting, which can help us to understand how geothermal fluids circulate in geological bodies with inherited structures. Geothermal circulation at Elba allowed the deposition of Fe-ore deposits (haematite/magnetite and pyrite) and altered rock volumes, which represent tracers of the palaeo-fluid flow. Normal and oblique-slip faults dissected a polyphase folded metasiliciclastic succession and produced a secondary permeability in the range of 5 × 10−13 to 5 × 10−16 m2. From the permeable fault zones acting as feeder conduits, geothermal fluids permeated the hydraulically connected metasiliciclastic rock bodies previously deformed by two generations of folds. Geothermal fluids followed the already defined geometry, thus giving rise to apparent folded mineralized levels. Fluid migration into the metasiliciclastic rocks was possible due to their chemical aggression, which favoured the dissolution and reprecipitation of quartz, and Fe-oxide and sulphide deposition. Renewed fluids maintained their chemical properties (pH value and temperature, mostly). This conclusion provides inputs for reconstructing geothermal conceptual models and evaluating the geothermal potentiality of exploitable areas developing in similar geological settings. [ABSTRACT FROM AUTHOR]

Italy has no record of Li production, even though it is well known for its outstanding Li mineral specimens from the Elba Island pegmatites. Because of the current geopolitical situation, the opportunity for a systematic appraisal of resources is evident. Most European Li production comes from deposits associated with Late Paleozoic magmatic rocks. In Italy, such rocks occur extensively in Sardinia and Calabria, but their potential for Li is unknown, and deserves a more systematic exploration. Also of potential interest are the Permo–Triassic spodumene pegmatites in the Austroalpine units of the Central Alps. The Tertiary pegmatites (Elba Island and Central Alps) contain Li minerals, but do not appear large enough to warrant bulk mining. However, we notice that Tertiary–Quaternary magmatic rocks of the Tuscan and Roman magmatic provinces have systematically higher Li contents than those recorded in normal arc igneous rocks worldwide. Specifically, Tuscan granites contain up to 350 μg/g Li, mostly hosted by biotite (up to 4000 μg/g Li); the Capo Bianco aplite (Elba Island) contains up to 1000 μg/g. There are other small Li occurrences associated with Mn deposits and metabauxites, and there is a hypothetical potential for sediment-hosted deposits in the post-orogenic Lower Permian Alpine basins. However, the most promising potential seems to be associated with subsurface fluids. High-enthalpy fluids in geothermal fields may contain up to 480 mg/L Li. Lower-temperature thermal waters may also contain significant Li (>10 mg/L). Moreover, a visionary, but not impossible, perspective may consider a deep injection of water to interact with, and extract Li from, magmatic rocks. [ABSTRACT FROM AUTHOR]

Petrology and timing of magmatic-hydrothermal systems and the linkage between plutonic and volcanic domains are central topics in geosciences, because of broad implications for natural hazards and exploitation of natural resources. We investigated by the 40Ar–39Ar method the timescale of a well-characterized natural example, the Mio-Pliocene Campiglia Marittima magmatic-hydrothermal system (Tuscany, Italy). 40Ar–39Ar data from pristine and homogeneous trioctahedral micas and sanidine from the plutonic-hydrothermal-subvolcanic-volcanic sequence (from the Botro ai Marmi Granite to the San Vincenzo Rhyolite) record crystallization ages and define a temporal sequence lasting 973 ± 43 ka, starting from 5.409 ± 0.043 Ma. K-feldspar from mafic and felsic porphyries, unlike micas, are affected by submillimetre, micropore laden, alteration domains consisting of secondary K-feldspar and albite, and yielded staircase-shaped age spectra, compatible with a ternary mixing. Results document that the San Vincenzo Rhyolite consists of two diachronous batches, the first emplaced at 5.0024 ± 0.0062 Ma, closely following emplacement of mafic porphyries, the second at 4.4359 ± 0.0045 Ma. Bulk of hydrothermal deposits, consisting of skarns and associated Zn–Pb(-Ag) mineralization predating Fe–Cu ore, formed within the first ~ 400-ka lifetime of the whole sequence and was closely followed by the first eruption which should have run out most of the ore-forming potential of the system. [ABSTRACT FROM AUTHOR]

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