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This study reports the complex textural and chemical features of K-feldspar megacrysts (up to 5 cm long) hosted in trachydacitic lava flows, lava domes, and coulees from Mt. Amiata volcano (Tuscan Magmatic Province, Central Italy). Backscattering and cathodoluminescence imaging, coupled with core to rim major and trace elements patterns, reveal complex zoning, and resorption surfaces associated with sharp chemical variations (e.g., Sr and Ba). These zoning patterns originated by disequilibrium and re-equilibration events, related to the repeated influx of mafic magmas or convective motions in the trachydacitic magma reservoir. Multiple mafic magma refilling occurences are also supported by the field record of abundant microgranular magmatic enclaves in the studied products. Our results highlight that the abnormal dimension of the studied K-feldspars originates by the interplay between petrological and kinetic processes involving: (i) extensive dissolution; (ii) heterogeneous nucleation; (iii) alternation of spasmodic growth events in disequilibrium and near-equilibrium crystallization. The repeated influx of hotter magmas and reheating can determine the thermal condition to the growth of few, large K-feldspar megacrysts. Also, the strong textural and chemical similarities observed in the K-feldspar megacrysts from Mt. Amiata volcanic rocks and Mt. Capanne monzogranite (Elba Island, Central Italy) support the hypothesis of a phenocrystic origin of intrusive K-feldspar megacrysts.

This work is aimed at reconstructing the morphology of the volcanic ed-ifice o Vesuvius before the most famous eruption that occurred in 79 AD, destroyed the cities of Pompeii, Herculaneum, and Stabiae, and was described by Pliny the Younger. This result has been achieved by using both volcanological data and historical documents. The previous history of the volcano and the distribution of the deposits of the 79 AD eruption has been used as a guide for the reconstruction of the pre-eruptive morphology. This is consistent with the few indications given by the ancient writings and the frescoes found during archaeological excavations in Pompeii and Herculaneum.

The carbonate rocks outcropping in the area south of Florence can be useful for the production of binding materials. The aim of this paper is to characterize the rocks to be used for the production of cement and limes in the area south of Florence by means of chemical, mineralogical and petrographic studies and by defining their main physical properties. In particular, this study analyses rock samples from different outcroppings around the south of the province of Florence in the Greve in Chianti - Passo dei Pecorai area. Based on the collected data the rock samples coming from the Greve in Chianti area can be used for producing mainly eminently hydraulic lime.

Information related to the evolution of geomagnetic field in space and time are recorded in the rocks and are the subject of archaeomagnetic studies. These studies allowed us to better understanding the geomagnetic field evolution as well as to improve our comprehension of several geological aspects of the historic evolution of the Earth and human history. Here, based on the description of the functioning principia and models of past and presently used magnetometers we provide, based on our past experience, some suggestions to improve accuracy of archaeomagnetic measurements on fired archaeological materials and volcanic products.

We report on some recent experiences of scientific dissemination activities on geomaterials carried out by a network of scientific organizations in Tuscany (Italy). The primary message we want to disseminate is that even the most "insignificant" rock (e.g., those constituting the bar or kitchen counter-tops) stores in their interior very useful information beyond the beautiful colors and their aesthetic appearance. These rocks can tell stories of very old geological periods on how they were formed. Their structures, texture and shape, as well as their chemistry and mineralogy provide clues to the reconstruction of geological events. Moreover, the rocks used in urban architecture and monuments are an inexhaustible archive containing a lot of historical and economic information on the development of a city and its surrounding area. The role of geologists, in this context, is to provide to the public, in clear and engaging language, the tools necessary to solve the puzzle (i.e., identify the most important types of rocks and rock-forming minerals, know their physico-chemical properties, their textures and structures and discover the environments in which they formed). A specific objective of this work is to stimulate an exchange between various research organizations (universities, public research institutions, museums, associations, etc.) and the civil society.

In this Chapter, we present the results of the stratigraphic review on a data-set of 66 boreholes drilled into the Monte Amiata volcanic edifice, including 5 recently drilled deep-wells. The purpose of this review was to obtain a reliable database for the reconstruction of the morpho-structural surface of the Monte Amiata substratum. The map elaborated confirms the presence of a 15 km2 depression in the south-western portion, and a morphological high in the north-eastern portion of the volcanic edifice. The same morphological features, with less detail and some dimension differences, were have been identified by all previous studies and variously interpreted. The morpho-structural analysis carried out in this Chapter leads to the exclusion of this depression because of purely erosive phenomena or pre-volcanics, as claimed by the previous authors. Our results are: (i) a better definition of the morphology of the substratum depression in the south-western part of the volcano, and (ii) the interpretation of the origin of this depression as possibly linked both to the transtensive tectonic system that has been active over the last 300 ka and to Monte Amiata volcanism.

Exploratory wells drilled by the Tuscan regional authority in order to gather data for defining a better hydrogeological model of the area provided also new data on the state of fracturing of the volcanic units. In this contribution, we present the study of core samples and in-hole data of 4 wells drilled in Monte Amiata volcano. The Monte Amiata volcanic rocks are characterized by very low matrix permeability; in spite of this they host an important aquifer. We can therefore deduce that within these rocks groundwater flow and storage take place mainly through fractures. As typical in this kind of rocks, generally groundwater flows through single faults and related damage zones. These discontinuities and, in particular, the fracture intersections are thus potential high permeability zones and sites for groundwater circulation and storage. In order to verify the role played by fractures and better characterize the hydrological features of the reservoir, the fractures have been identified and their strike and dip directions measured using oriented log image probe. The (not oriented) core samples have been studied for fracture dip measurements and fracture density evaluation (number of fracture/meter). In the cores, it was possible to observe the morphology of fracture surfaces, the occurrence of secondary minerals, and rare slickenside kinematic indicators. The fracture density observed in core samples and in hole image logs is generally comparable. Usually, core samples show a higher density fracture than in-hole images due to the presence of both natural and mechanically induced fractures. The discrimination between natural and induced fractures was based on characteristic fracture surface morphology, fracture geometry and occurrence of secondary minerals, and by comparing the in-hole image log and the core samples. Coring induced fractures were normally characterized by torsional and core-plug or unloading related fractures. Typically, the natural fractures show secondary minerals coatings on the fracture surface and are characterized by high dip angles (60-80°), whereas the mechanical fractures are not mineralized and characterized by a lower dip angle (20-40°). The measured fracture frequency per meter in the image log does not show a random distribution. The fracture distribution with depth is indeed well clustered, with high fracture densities alternating with less fractured portions. Taking into account both cores and image log data, where available, we observed intense fracturing located at defined depth intervals. The structural data measured by oriented hole image log have been used to get insights into the fracture orientations throughout the wells. The pole fracture distribution shows two main clusters quite orthogonally oriented and representative of two main sets of fractures. Set I consist of ENE-WSW oriented fractures, and Set II, more dispersed, is characterized by fractures oriented NNW-SSE. Moreover, considering the distribution of fracture orientations with depth, we note that ENE-WSW striking fractures become more frequent with increasing depth. Kinematic evidence is very rare and was found in the core samples rarely, indicating a mostly dip-slip movement, probably related to major normal faults. We suggest that the high fracture density zones, locally characterized also by the presence of cavities detected in the image log, could correspond to zones of localized deformation as main faults. Fracture dip and orientations collected within the wells are comparable with those measured at surface in the SW sectors of the Monte Amiata volcanic edifice. This confirms that the data collected at depth in the analyzed wells could be taken as representative of the deformation style characterizing this area. No evidence of a similar fracture pattern occurs in the core interval interesting the flysch substratum, which is instead characterized by a ductile pervasive cleavage and folding typical of Alpine regional deformation as observed in the Argille a Palombini outcrops. The study of the core-samples within the basal volcanic units provided also new insights on the modalities of magma emplacement, by the recognition of peculiar structures supposed to be genetically related to the magma emplacement phases, during the Monte Amiata volcanic edifice construction.

Earth pigments from Monte Amiata comprise the famous "terra di Siena" (raw sienna) and "terra di Siena bruciata" (burnt sienna) that have been ones of the yellow-brown and red pigments most widely used by Italian and European painters from the Renaissance to 19th century. These Earth pigments are lacustrine sediments composed mainly of hydrated iron oxide (limonite/goethite) produced by biochemical precipitation of iron-rich waters. The quarrying localities were at Castel del Piano, Arcidosso, Piancastagnaio, and Abbadia San Salvatore. Diatomaceous earths from Monte Amiata are soft, friable, earthy, very fine-grained, siliceous lacustrine sediments usually light in color (white if pure) composed of diatom's fossilized skeletons. The main quarrying localities were at Castel del Piano and Santa Fiora. Two new coring were performed in the lacustrine deposits of the Bagnolo Diatomaceous earth quarry (Santa Fiora). The age of the lacustrine basins comprising the Earth pigments and Diatomaceous earth ore deposits is following the volcanic activity of the volcano of Monte Amiata. The evolution of these lake basins has been reconstructed in four phases. The first phase is represented by the sedimentation of clay and iron hydroxides in well-developed lacustrine basins, during cold climate conditions that are suggested by the pollen predominance of Pinus, Picea, and Betula. During the second phase, the lake conditions continue, but the sedimentation of iron hydroxides basins become different from those where sedimentation of the Diatomaceous earth begins. In the latter, there are abundant plant, ictiological, and entomological fossils that indicate a warm continental climate with great development of Fagus, Abies, and Castanea. The lithological and paleontological characteristics of the Diatomaceous earth suggest a gradual drying of the lake and the transition to a humid fresh climate. The third phase is characterized by the simultaneous end of the lacustrine deposition in all the basins, and by the alluvial sedimentation of volcaniclastic sands and gravel. This sharp environmental change is interpreted as the effect of a climate change that established cold and rainy conditions. The last stage shows a low colluvial and alluvial sedimentation with a substantial stability of the topographic surface that has favored the development of intense pedogenesis.

Monte Amiata is a volcano characterized by acidic effusive products, emitted between 304 - 230 ka. The peculiar textural and petrographic features together with the uncommon length of the lava flows erupted at Monte Amiata have stimulated our interest and raised the following questions: "What were the temperatures and viscosities which brought to the eruption of those extraordinarily crystal-rich magmas and to the emplacement of those up to 8 km long and on average 30 m thick lava flows and exogenous lava domes at Monte Amiata?" In order to answer these questions, we, firstly, estimated, by the use of the most recent geo-thermometric tools, the temperatures representative of the storage, ascent, and emplacement of the magmatic and volcanic mixtures. Later, we used the obtained temperature values to estimate the crystalbearing viscosity of the volcanic mixtures governing the emplacement of lava flows at Monte Amiata. Our results revealed that responsible of the emplacement of the above-mentioned lavas was, likely, a combination of the anomalously high eruptive temperature and the large volume of the erupted products. These conditions favoured the maintaining of the emplacement temperature well above the limit temperature for viscous flow, i.e. the glass transition, for a time long enough (e.g. years) to allow, also at their relatively high viscosities, to flow the observed lengths.Monte Amiata is a volcano characterized by acidic effusive products, emitted between 304 - 230 ka. The peculiar textural and petrographic features together with the uncommon length of the lava flows erupted at Monte Amiata have stimulated our interest and raised the following questions: "What were the temperatures and viscosities which brought to the eruption of those extraordinarily crystal-rich magmas and to the emplacement of those up to 8 km long and on average 30 m thick lava flows and exogenous lava domes at Monte Amiata?" In order to answer these questions, we, firstly, estimated, by the use of the most recent geo-thermometric tools, the temperatures representative of the storage, ascent, and emplacement of the magmatic and volcanic mixtures. Later, we used the obtained temperature values to estimate the crystalbearing viscosity of the volcanic mixtures governing the emplacement of lava flows at Monte Amiata. Our results revealed that responsible of the emplacement of the above-mentioned lavas was, likely, a combination of the anomalously high eruptive temperature and the large volume of the erupted products. These conditions favoured the maintaining of the emplacement temperature well above the limit temperature for viscous flow, i.e. the glass transition, for a time long enough (e.g. years) to allow, also at their relatively high viscosities, to flow the observed lengths.

The volcanic rocks of Monte Amiata host a major shallow regional aquifer exploited for the domestic water supply of a wide area of Southern Tuscany. The volcanic aquifer lies over a thick sequence of flysch units (approx. 300 - 600 m), consisting of shale and limestone to the south, and shale and sandstone to the north of the volcanic edifice. An exploration well was drilled in 2010 by the Tuscan regional authority to monitor the water table level and improve the hydrogeological model of the Monte Amiata volcanic aquifer. The well is located close to Poggio Truzzolo at 1086 m a.s.l. It crossed the whole volcanic sequence, found the water table of the volcanic aquifer at 783 m a.s.l. and reached the flysch substratum at 556 m a.s.l. In this chapter, we describe evidences of water-rock interaction in the volcanic rocks, both above and below the present-day water table, in order to study its variations with time. Therefore, we studied the mineralogy and petrology of the rock samples, the location, type and mineralization of the in-hole fractures. The results are interpreted considering the existing geological, geochemical and hydrogeological data. The main outcomes of this well are: 1) the location of the water table level at a depth of 302 m b.g.l. (783 m a.s.l.), in agreement with the results of recent magneto-telluric surveys, and in contrast with previous hydrogeological models; 2) the absence of present or past interaction between volcanic rocks and hydrothermal fluids, the alteration minerals being present only in fractures and indicating fluids of low temperature and low pH due to gas inflow in the volcanic reservoir; 3) the volcanic reservoir is characterized by fracture permeability, as shown by the fracture system found along the well.

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David Lazzaretti Well (DLW) was drilled in the southern part of Monte Amiata, close to the Poggio Trauzzolo lava dome at an altitude of 1086 m a.s.l.; it reached a depth of 545 m below ground level (b.g.l.) and was almost entirely continuous cored. DLW crossed the volcanic complex and, at 530 m b.g.l., reached the sedimentary substratum. In the DLW rocks correlated to the oldest outcropping units (BTC Auct.) were observed from top of the core until 317 m b.g.l. (about 250 m thick). From 317 m b.g.l. further volcanic units were found almost continuously until 530 m b.g.l., where they rest directly on top of the sedimentary substratum without any palaeosoil interposition. These "oldest" units are composed mainly of porphyritic trachydacite with distinctive presence of mega K-feldspars (up to 5 cm), set in a highly vesicular and microcrystalline groundmass; they show a typical abundance of magmatic enclaves and xenoliths. These characteristics are interpreted as lava dome lithofacies by the close similarity with typical lava dome lithofacies at Monte Amiata. The core sample TRZ 51 (326-327 m b.g.l.) is sited stratigraphically below the oldest outcropping units. 40Ar-39Ar dating on this sample of the pair sanidine megacryst-ground mass displays a slight difference in the ages, 301.6 ± 3.3 and 291.1 ± 3.5 ka, respectively. The average and standard deviation of the four 40Ar-39Ar ages in literatures on sanidines of the oldest outcropping units is 299.8 ± 6.2 ka, a value that overlaps within error with both new ages.

Here we present a new volcanological map of the Southwestern portion of the Vesuvius volcano at a scale of 1:10,000. Mapped units were subdivided into Unconformity-Bounded Stratigraphic Units. This work constitutes a significant development with respect to previous maps, particularly for the medieval lavas. It also includes a series of volcanic–tectonic lineaments, which have never been reported in any of the previous cartographic works. Archeological and historical data were used for mapping the lava emitted during the last 2000 years. All the historical lava flow paths and tephra deposits of the last 4000 years that were reported on the map and evidence the intimate relationship between volcanological and morphological features, and the development of human activity on this very densely populated sector of the volcano.

Borgia et al. (2014) illustrated an active volcanic spreading model for the Amiata volcanic area (southern Tuscany, Italy). Although, at first glance, the model may appear appealing, this is not fully supported by the available data and the paper does not take into account their discussion. Accordingly, the supposed negative consequences of the Borgia et al. (2014) model on both contamination of shallow water and geothermal exploitation can likely be regarded as speculative.

Peralkaline silicic magmas were erupted at Pantelleria in a variety of eruptive typologies and magnitudes: pyroclastic flows, Plinian to strombolian pumice fallout and lava flows. The initial cycle (330- 180 ka) was characterized mainly by effusive activity, and was followed by an intermediate cycle (181 - 85 ka), characterized by a clear drift to explosive activity. This period, onto we focus, is bracketed by six ignimbrite-forming eruptions (older and intermediate of the two caldera collapses at 140 and 50 ka that characterize the volcanological history of the island, which drained silicic and variably peralkaline magma for a cumulative volume close to 6 km3 DRE. These ignimbrites lack of continuity among the few outcrops (commonly in vertical scars) and also suffer from strong welding and rheomorphism. First reconstructions and correlations [Mahood and Hildreth, 1986], although still valid for many aspects, suffer from the poor precision of K/Ar ages, especially when Ar excess and xenocrystic contamination are common, as is the case for Pantelleria lavas and pyroclastic rocks. Recently, new correlations based on paleomagnetic methods [Speranza et al., 2012] succesfully identified and correlated two welded pyroclastic breccias outcropping in the NE and SW sectors of the island with the old caldera collapse, and also demonstrated the equivalence of two other ignimbrite units previously considered as separate eruptions. Based on 14 new 40Ar/39Ar ages (laser heating on anorthoclase feldspar separates) ages and petrographic data, we propose an updated stratigraphy for the intermediate period and to provide accurate age brackets to the correlations. Recently, the application of 40Ar/39Ar methods on much younger (age < 20 ka) silicic lavas and tephra at Pantelleria [Scaillet et al., 2011], demonstrated highly precise and contributed to unravel the complex post-Green Tuff stratigraphy. Our results can be summarized as follows: - The pre-La Vecchia caldera eruptive history ended with the emplacement of two trachytic ignimbrites (at 181 ± 1.2 ka and 171 ± 1.7 ka), which were emplaced only in the south sector of the island. Both were truncated by the old (La Vecchia) caldera collapse. - The age of the old caldera collapse is now tightly constrained between 139-146 ka , i.e. the new age of the welded pyroclastic breccia (previously undated). that represents the caldera-forming eruption [Speranza et al., 2012]. - After the La Vecchia caldera collapse, the first ignimbrite eruption occurred at 123 ka with a trachy-comenditic and crystal-rich unit emplaced in the NE to NW sectors of the island. - At 107 ka a crystal-rich trachytic ignimbrite was erupted, together with some fines-rich lobes that (K/Ar ages) were previously considered as two different units, but with similar 40Ar/39Ar ages. - Higher up in the stratigraphic sequence, two previously considered different ignimbrites (for an inferred volume of erupted magma close to 1.5 km3 DRE) demonstrated coeval by 40Ar/39Ar dating, and together are part of an eruptive paroxysm at 85 ka comparable in magnitude to the Plinian eruption of the Green Tuff (age 50 ka), - The the recurrence time of the above mentioned eruptions, for a cumulative erupted magma volume close to 6 km3 DRE, suggest that at the end of the inter-eruptive period 85-50 ka the production and evolution rates of pantellerite magma peaked to reach a maximum peralkalinity.

The study of core samples and in-hole data of a 545 m deep well drilled in Mt. Amiata extinct volcano allowed a better characterization of the shallow volcanic reservoir, which is exploited for domestic utilization. The new discovery is that: 1) the water table level is at a depth of 302 m b.g.l. (783 m a.s.1.), in agreement with recent magnetotelluric surveys, and in disagreement with previous hydrogeological models; 2) there is no evidence of present or past interaction with geothermal fluids, the alteration minerals being present only in fractures within the volcanic rocks and indicating fluids of low temperature and relatively low pH due to gas inlets in the volcanic reservoir: and 3) the volcanic reservoir is characterized by fracture permeability, as shown by the fracture system along the well. On the base of these new data the previous geological and hydrogeological models of Mt. Amiata should be revised. In particular, the hypothesis of a catastrophic lowering of the water table in a short time span is unlikely. (C) 2014 Elsevier B.V. All rights reserved.

International audience; At Pantelleria, peralkaline silicic magmas were erupted across a range of eruptive typologies and magnitudes: pyroclastic flows, Plinian to strombolian pumice fallout and lava flows. In this paper we focus on the intermediate cycle of eruptive activity which is bracketed by ignimbrite units slightly older than the two caldera collapses which marked the volcanological activity of the island. This age interval (180-85 ka) was punctuated by six ignimbrite-forming eruptions (silicic and variably peralkaline) for a cumulative erupted magma volume of approximately 6 km3 dense rock equivalent. Based on new 40Ar/39Ar (Na,K)-feldspar ages and petrographic data, we propose an updated volcanostratigraphic scheme for these welded and rheomorphic ignimbrites that can be summarised as follows: (i) the age of the old ('La Vecchia') caldera collapse is now tightly constrained between 140 and 146 ka and the caldera-forming eruption can be traced to a lithic-rich welded tuff breccia that outcrops in two opposite sectors of the island (south-west and north-east); (ii) four ignimbrite units previously considered unrelated are now merged in two distinct eruptive paroxysmal events at 107 and 85 ka. In particular, the 85 ka eruptive event is comparable in magnitude to the younger (caldera forming) Green Tuff Plinian eruption; (iii) the recurrence patterns of the 107 and 85 ka eruptions, compared to the Green Tuff, allow us to qualitatively assess that the climax in production of low-temperature silicic and peralkaline melt was focused in the age interval 85-45 ka.

The island of Pantelleria (Sicily Strait), the type locality for pantellerite, has been the locus of major caldera-forming eruptions that culminated, ca. 50 ka ago, in the formation of the Cinque Denti caldera produced by the Green Tuff eruption. The post-caldera silicic activity since that time has been mostly confined inside the caldera and consists of smaller-energy eruptions represented by more than twenty coalescing pantelleritic centers structurally controlled by resurgence and trapdoor faulting of the caldera floor. A high-resolution 40Ar/39Ar study was conducted on key units spanning the recent (post-20 ka) intracaldera activity to better characterize the present-day status (and forecast the short-term behavior of) the system based on the temporal evolution of the latest eruptions. The new 40Ar/39Ar data capture a long-term (> 15 ka) decline in eruption frequency with a shift in eruptive pace from 3.5 ka−1 to 0.8 ka−1 associated with a prominent paleosol horizon marking the only recognizable volcanic stasis around 12–14 ka. This shift in extraction frequency occurs without major changes in eruptive style, and is paralleled by a subtle trend of decreasing melt differentiation index. We speculate that this decline probably occurred (i) without short-term variations in melt production/differentiation rate in a steady-state compositionally-zoned silicic reservoir progressively tapped deeper through the sequence, and (ii) that it was possibly modulated by outboard eustatic forcing due to the 140 m sea level rise over the past 21 ka. The intracaldera system is experiencing a protracted stasis since 7 ka. Coupled with recent geodetic evidence of deflation and subsidence of the caldera floor, the system appears today to be on a wane with no temporal evidence for a short-term silicic eruption.

built a complex sequence of interfingered deposits emitted by closely spaced eruptive vents which are frequently associated with dome-building phases and pantelleritic lavas flows. Field relationships allowed us to recognize eight eruptive units, all lying above the Montagna Grande trachytes. As a whole, petrochemical characteristics of the erupted products indicate an evolutionary trend in which Na-clinopyroxene was the liquidus phase, followed by alkali feldspar. Amphibole and quartz are late-crystallizing, whereas aenigmatite is both early- and late-crystallizing as well. Aenigmatite and Na-clinopyroxene crystallization buffers efficiently the increase of agpaicity, induced by feldspar crystallization, to values of agpaitic index