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De Benedetti, Arnaldo A.
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De Benedetti, Arnaldo A.
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- PublicationOpen AccessGeological Map of the Tocomar Basin (Puna Plateau, NW Argentina). Implication for the Geothermal System Investigation(2020)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; This paper presents a detailed geological map at the 1:20,000 scale of the Tocomar basin in the Central Puna (north-western Argentina), which extends over an area of about 80 km2 and displays the spatial distribution of the Quaternary deposits and the structures that cover the Ordovician basement and the Tertiary sedimentary and volcanic units. The new dataset includes litho-facies descriptions, stratigraphic and structural data and new 234U/230Th ages for travertine rocks. The new reconstructed stratigraphic framework, along with the structural analysis, has revealed the complex evolution of a small extensional basin including a period of prolonged volcanic activity with different eruptive centres and styles. The geological map improves the knowledge of the geology of the Tocomar basin and the local interplay between orogen-parallel thrusts and orogen-oblique fault systems. This contribution represents a fundamental support for in depth research and also for encouraging geothermal exploration and exploitation in the Puna Plateau region.259 40 - PublicationRestrictedPreliminary Data on the Structure and Potential of the Tocomar Geothermal Field (Puna Plateau, Argentina)(2016)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ; ; ; ; ; ; ;This study presents new stratigraphic, structural and hydrogeological data on the Tocomar geothermal volcanic area (Puna plateau, Central Andes, NW Argentina), together with preliminary geochemical and magnetotelluric data. The main geothermal reservoir is located within the fractured Pre-Palaeozoic–Ordovician units. The reservoir is recharged by meteoric waters. Geothermal fluids upwell where main regional structures intersect secondary structures associated with the development of the Tocomar basin. Preliminary data indicate a reservoir temperature of ~ 200 °C and a local geothermal gradient of ~ 130°C/km associated with the Quaternary volcanic activity in the Tocomar area.322 5 - PublicationOpen AccessThermal interactions of the AD79 Vesuvius pyroclastic density currents and their deposits at Villa dei Papiri (Herculaneum archaeological site, Italy)(2018-03-12)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ;Pyroclastic density currents (PDCs) can have devastating impacts on urban settlements, due to their dynamic pressure and high temperatures. Our degree of understanding of the interplay between these hot currents and the affected infrastructures is thus fundamental not only to implement our strategies for risk reduction, but also to better understand PDC dynamics. We studied the temperature of emplacement of PDC deposits that destroyed and buried the Villa dei Papiri, an aristocratic Roman edifice located just outside the Herculaneum city, during the AD79 plinian eruption of Mt Vesuvius (Italy) by using the thermal remanent magnetization of embedded lithic clasts. The PDC deposits around and inside the Villa show substantial internal thermal disequilibrium. In areas affected by convective mixing with surface water or with collapsed walls, temperatures average at around 270◦C (min 190◦C, max 300◦C). Where the deposits show no evidence of mixing with external material, the temperature is much higher, averaging at 350◦C (min 300◦C; max 440◦C). Numerical simulations and comparison with temperatures retrieved at the very same sites from the reflectance of charcoal fragments indicate that such thermal disequilibrium can be maintained inside the PDC deposit for time-scales well over 24 hours, i.e. the acquisition time of deposit temperatures for common proxies. We reconstructed in detail the history of the progressive destruction and burial of Villa dei Papiri and infer that the rather homogeneous highest deposit temperatures (average 350◦C) were carried by the ash-sized fraction in thermal equilibrium with the fluid phase of the incoming PDCs. These temperatures can be lowered on short time-(less than hours) and length-scales (meters to tens of meters) only where convective mixing with external materials or fluids occurs. By contrast, where the Villa walls remained standing the thermal exchange was only conductive and very slow, i.e. negligible at 50 cm distance from contact after 24 hours. We then argue that the state of conservation of materials buried by PDC deposits largely depends on the style of the thermal interactions. Here we also suggest that PDC deposit temperatures are excellent proxies for the temperatures of basal parts of PDCs close to their depositional boundary layer. This general conclusion stresses the importance of mapping of deposit temperatures for the understanding of thermal processes associated with PDC flow dynamics and during their interaction with the affected environment.348 113 - PublicationRestrictedConditions for long-lasting gas eruptions: The 2013 event at Fiumicino International Airport (Rome, Italy)(2016)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ;; ; ; ;; ; ;; ; ; ; ; ; ; ;A hazardous gas eruption from two very close shallow boreholes occurred near the Fiumicino International Air- port of Roma (Italy) from August to December 2013. The erupted gas was mostly CO2 of deep origin and gas out- put was high and sustained over time reaching values of nearly 20 t day− 1. After 3 months, the gas flux was still above 5 t day− 1 and was only stopped in December 2013 by long and expensive works of closure of the bore- holes. The gas eruption was uncommon as being associated with the building of two mud volcanoes. This style of sustained deep CO2 eruptions contrasts with the more common short-lived eruptions of shallow biogenic methane-dominated gas pockets. In this work, we present the chronology of the event, the results of geological, geochemical, and geophysical monitoring and a numerical modeling. We propose that the August–December 2013 sustained and prolonged event does not relate to the simple degassing of a shallow, isolated pocket of gas. On the contrary, it reflects very specific conditions in a shallow reservoir (hosted in a 10 m thick gravel layer at −40 m within the Tiber river delta deposits), related to the interplay between the total pressure and the fraction of free CO2 initially present, across very narrow value ranges around 0.59 MPa and 0.18, respectively. The coexistence of short-lived and long-lived eruptions from the same reservoir suggest that these conditions are not achieved everywhere in the gas reservoir, despite its homogeneous properties. This consideration implies ei- ther a pressure compartmentalization of the reservoir, or the occurrence of a transient, possibly associated with an impulsive release of gas from greater depths. The involvement of deeper and larger gas reservoirs connected along faults is evidenced by geophysical investigations. This conceptual model bears significant implications for gas hazard studies554 6