Preliminary geochemical characterization of the Mts. Simbruini karst aquifer (Central Italy)

Mts. Simbruini karst aquifer feeds important springs whose capture contributes to the water supply of Rome City. To improve the geochemical characterization of this aquifer, we analyzed 36 groundwater samples, 29 from springs and 7 from shallow wells, collected in 1996 and 2019. Atomic adsorption spectroscopy, tritration, ionic chromatography and mass spectrometry were the used analytical methods. Ground waters are bicarbonate alkaline-earth type and HCO3 dominance confirms that the aquifer is hosted in carbonate rocks. Total alkalinity vs. cations plot indicates that CO2 driven weathering controls the water chemistry. The probability plots of HCO3, cations and Ca2+ +Mg2+ indicate four groundwater populations with the less represented one (9 samples) characterized by the highest PCO2 values (>0.3 atm). Most anomalous values of the dissolved PCO2 are from springs located near the center of the studied area. Four samples have negative values of d13CCO2 (about -22‰ vs. PDB), indicating its organic origin, but two other samples have positive values (1.6 and 2.6 ‰ vs. PDB), similar to those observed in the CO2 of deep origin discharged at the close Colli Albani volcano. Therefore, geochemical evidence indicates that the Mts. Simbruini aquifer is locally affected by the input of deep originated CO2, likely rising up along fractures, interacting with a recharge of meteoric origin, as evidenced by its d2H and d18O isotopic signatures.

A myriad of melt inclusions: a synchrotron microtomography study of melt inclusions and vapour bubbles from Colli Albani (Italy)

<p>Melt inclusions provide a window into the inner workings of magmatic systems. Both mineral chemistry and volatile distributions within melt inclusions can provide valuable information about the processes modulating magma ascent and preceding volcanic eruptions. Many melt inclusions host vapour bubbles which can be rich in CO<sub>2</sub> and H<sub>2</sub>O and must be taken into consideration when assessing the volatile budget of magmatic reservoirs. These vapour bubbles can be the product of differential volumetric contraction between the melt inclusion and host phase during an eruption or indicate an excess fluid phase in the magma reservoir. Thus, determining the distribution of volatiles between melt and vapour bubbles is integral to our fundamental understanding of melt inclusions, and by extension the evolution of volatiles within magmatic systems.</p><p>A large dataset of 79 high-resolution tomographic scans of clinopyroxene and leucite phenocrysts from the Colli Albani Caldera Complex (Italy) was recently acquired at the German Electron Synchrotron (DESY). These tomograms allow us to quantify the volume of melt inclusions and associated vapour bubble both glassy and microcrystalline melt inclusions. Notably, in the glassy melt inclusions the vapour bubbles exist either as a single large vapour bubble in the middle of the melt inclusion or as several smaller vapour bubbles distributed around the edge of the melt inclusion. These two types of melt inclusions can coexist within a single crystal. We suggest that the occurrence of these rim- bubbles is caused by one of two exsolution pathways, either pre-entrapment and bubble migration or post entrapment with preferential exsolution at the rims. By combining the analysis of hundreds of melt inclusions with the chemistry of the host phase we aim to unveil magma ascent rates and distribution of excess fluids within the magmatic system of Colli Albani, which produced several mafic-alkaline large volume ignimbrites.</p>

The transitions from mildly explosive to caldera-forming eruptions at Colli Albani volcano (Italy)

<p>The Colli Albani volcano is an ultrapotassic caldera complex located 30 km to the SE of Rome and has displayed a wide range of eruptive behaviors, ranging from effusive activity to highly explosive and large volume eruptions (up to 63 km<sup>3</sup> dense rock equivalent per eruption) despite its mafic nature.</p><p>We combine physical volcanology, petrology, and geochemistry to focus on the mildly explosive to effusive products of two sections (Tuscolo and Artemisio) which are located on opposite sides of the main caldera and stratigraphically between the last large ignimbrite, Villa Senni. The target of this study is to identify the processes responsible for the transition from the smaller explosions to the larger caldera-forming ignimbrite eruptions, and eventually trace how the magmatic system rebuilds in the interim.</p><p>Whole rock analyses, mineral chemistry, and petrography of fall deposits from both field localities are compared with an existing dataset for the Villa Senni ignimbrites. We will use unsupervised and supervised machine learning approaches to identify similarities and differences between large caldera-forming eruptions and mild-explosive to effusive activity and identify the processes modulating the transition between these two behaviours.</p>

The Rome gas blowout zone (Central Italy)

<p>Colli Albani is an alkali-potassic quiescent volcano of Central Italy that last erupted 36 ka ago. Several lahar generating water overflows have occurred from Albano crater lake, the most recent in Roman times (IV Century B.P.) and the resulting deposits form a surficial impermeable cover on its north-western flank. An important NW-SE trending volcano-tectonic fracture extends from the volcano to the periphery of Rome city. This is a leaky fracture allowing deep magmatic gas to rise toward the surface. In zones where the impervious cover has been removed by excavations, as Cava dei Selci, the gas is freely discharged into the atmosphere creating local hazardous conditions. Elsewhere, the gas dissolves and pressurizes the shallow aquifer confined underneath the impervious cover. Any time this aquifer is reached by a drilling, a dangerous gas blowout may be generated, i.e. a sudden emission of a jet of gas, nebulized water and fine loose fragments of volcanic rocks. Since 2003 four gas blowouts, from ~ 45–50 m deep drillings, have occurred at the boundary between Rome and Ciampino municipalities, a site designed as the Rome gas blowout zone. Dangerous atmospheric CO<sub>2</sub> and H<sub>2</sub>S concentrations killed some animals and several families had to be evacuated because of hazardous gas concentration inside their houses. The emitted gas consists mostly of CO<sub>2</sub> (>90 vol.%) and contains a low but significant quantity of H<sub>2</sub>S (0.3–0.5 vol.%); it has the highest helium isotopic R/Ra value (up to 1.90) of all Colli Albani natural gas discharges. This He isotopic value is similar or even slightly higher than in the fluid inclusions of phenocrysts of the Colli Albani volcanic rocks, suggesting a likely magmatic origin of the gas. Colli Albani volcano is characterized by anomalous uplift, release of magmatic gas and episodic seismic crises. The Rome gas blowouts represent a geochemical window to investigate deep volcanic processes. Should a volcanic unrest occur, gas hazard would increase in this densely inhabited zone, as the input of magmatic gas into the confined aquifer might create overpressure conditions leading to a harmful phreatic explosion, or increase the emission of hazardous gas through newly created fractures.</p>

Twenty years of CO2-emission monitoring at Cava dei Selci, Colli Albani volcano (Central Italy)

<p>Carbon dioxide flux from the soil has been monitored for 20 years at Cava dei Selci, the main degassing site of Colli Albani quiescent volcano. Cava dei Selci gas discharge occurs at the north-western periphery of the volcano, within an old stone quarry crossed by a NW-SE volcano-tectonic lineament. The area around the manifestation has been densely urbanized and lethal accidents by gas inhalation have occurred to a man and to dozens of animals including cows and sheep. Some houses had to be permanently evacuated because of hazardous indoor gas concentrations. Emitted gas is dominated by CO<sub>2</sub> (>90 vol.%) with <1 vol.% of H<sub>2</sub>S. Isotopic composition (δ<sup>13</sup>C and <sup>3</sup>He/<sup>4</sup>He) suggests a deep magmatic origin. No significant compositional variations have been recorded during the observation period.</p><p>Surveyed area includes a fixed grid of 130 points, regularly distributed over an area of about 5500 m<sup>2</sup>, where soil CO<sub>2</sub> flux surveys have been carried out 55 times from May 2000 to August 2020 by accumulation chamber. Collected data have been reprocessed by sequential Gaussian simulation. The total diffuse CO<sub>2</sub> output is highly fluctuating, with a maximum rate of 24.8 t*d<sup>−1</sup> in January 2006 and a minimum value of 5.6 t*d<sup>−1</sup> in December 2003; the estimated mean±1σ is 12.1±4.5 t*d<sup>−1</sup>. All the flux maps show typically a highly emissive area in the internal sector of the investigated grid, with NW-SE elongation. Another anomalous zone, with the same elongation, is found in the SW of the survey area. Diffuse degassing rate (total flux normalized by survey area) is similar to that of active volcanic zones.</p><p>In the same zone an automatic permanent station continuously measured the soil CO<sub>2</sub> flux and environmental parameters (which may influence the soil gas flux) from 2004 to 2008 and from 2019 to present. Results of timeseries processing by Multiple Linear regression and Principal Component analysis, commonly used to filtrate and clear data from atmospheric inferences (for example at Stromboli and Campi Flegrei), were unsatisfying for Cava dei Selci. Therefore, we reprocessed the timeseries by the stochastic Gradient Boosting Trees regression technique. This allowed to explain up to 55 % of the CO<sub>2</sub> variance by environmental variations; 45 % of the variance therefore reflects deep-seated processes. This technique looks promising for the regression of soil CO<sub>2</sub> flux timeseries. The results of 20 years monitoring confirm that Cava dei Selci is a convenient site for both monitoring a potential unrest of the volcano and assessing the gas hazard in the nearby inhabited zone.</p>

Scipione Borghese: Actor protagonist pe pământurile tuscolane

"Scipione Borghese: Leading Actor on Tuscan Lands. The contribution focuses on the figure of Cardinal Scipione Borghese (1577-1633) and on the role he playedas patron of the arts in the Colli Albani area, in particular in the city of Frascati (located 20 kilometers east of Rome). The cardinal, nephew of Pope Paul V Borghese and very important personality of the Roman curia, is investigated hereas a promoter of the arts and in particular as the patron of many architectural and landscape arrangements made on the hills of Frascati. The villas purchased by the Borghese family under went enlargement, reconstruction and decoration (such as Villa Taverna, Villa Torlonia, Villa Mondragone and Villa Grazioli). The cardinal and the Villas moved a lot of money and many artistic workers (architects, painters, sculptors, plasterers, masons, etc.) that made Frascati the Petrified testimony of the economic, political and cultural ideas of the Borghese himself. Keywords: Scipione Caffarelli Borghese; Paolo V Borghese; Flaminio Ponzio; Girolamo Rainaldi; Giovanni Vasanzio; Matthäus Greuter; Rome; Frascati; Alban Hills; Monte Porzio Catone; Burghesianum, patronage; Villa "