1,721,223 research outputs found
Strategies for enhancement and promotion of SiLiBA, the lithotheque of the University of Bari (Italy)
No full textGeological collections assume an undisputed importance since they gather materials for their relevance asspecific geological events or for mineral and rock group representativeness, or for historical and educationalsignificance.
SiLiBA, the lithotheque of geological cherts at the Earth and Geoenvironmental Department of the Universityof Bari Aldo Moro is an example of the scientific and educational value of Universities’ geological collections.It is composed of about 900 samples of primary and secondary geological cherts coming mainly from minesand deposits in Apulia and Basilicata (Italy) and from some regions of Croatia. The lithotheque is connected toa laboratory for the characterisation of chert samples. SiLiBA cherts have been studied by means of a non-invasive protocol (Delluniversità et al. 2019) thanks to which, through macroscopic and mesoscopicobservations, colourimetric measurements and chemical and micropaleontological analyses, a very largeamount of original data, as well as images at different scale, has been produced and collected in a database.
Naturally, for the collection dissemination a fundamental role is played by the most widespread and innovativetools, especially in the historical period we are experiencing, in which the global virtual connection of people,things and ideas is essential for continuing to interact with each other, exchange information and improvethemself, both in life and work.
With a view of economic sustainability and resource optimization and in order to create a global connectionbetween archaeologists and geologists, the collection promotion has been improved by means of a dedicatedwebsite.
It is articulated into submenus and includes sections containing archaeological information on procurementand manufacturing of cherts in the Prehistory, history of the lithotheque, publications and events and activities,including experimental archaeology laboratories and tutorials. The website focus is the section concerning the database reports, thanks to which the visitor can consult allthe data sheets, setting geographic or geological or by name criteria searching. The SiLiBA site is enriched bya section reporting the interactive 3D reconstruction of the most representative samples.
Even if the input of some data is not yet complete, the site is online and explorable. The future goal is tocreate a social profile in order to reach as many users as possible, especially in school and universitycommunities, and to publish interesting and original contents that can move people closer to geologicalcollections and to the Earth sciences and to the archaeology field
Relationships between sinkholes areal distribution, tectonic alignments and recent Seismicity in Abruzzo (Central Italy)
No full text
Archaeometric study of the Roman marbles reused in the late Antiquity St. Saturnino Basilica (Cagliari, Italy)
No full textThe St. Saturnino Basilica (Cagliari, Sardinia, Italy) rises over a sacred site since the origins of the town of Cagliari.
The original sepulchral function of the area were consolidated and implemented during the Roman Empire and it
became a Christian cemetery after the martyrium of St. Saturnino (beginning of the IV Century A.D.). In this period the
original chapel of the church was built starting a long evolution of the building across half a millennium, until its
Romanesque evolution. The basilica was abandoned and partially destroyed at the beginning of the XIV Century. The
formal technical reading of its architectural structure and elements is complicated by the frequent reuse of Roman
artifacts during the Byzantine and Romanesque phases as well as the presence of diachronic source materials. The
naked-eye analysis of geomaterials present in the monumental highlights a significant number of lithologies (i.e.,
various kinds of limestones and sandstones, marbles, volcanic rocks, etc.), some of which are in an advanced state of
alteration. We present the results of a multi-method archaeometric study (mineralogical-petrographic observations on
thin sections, XRF trace elements analysis and 18O vs. 13C stable isotope ratio investigation) concerning the architectural
stone elements reused in the basilica between the late Antiquity and Romanesque periods. The majority of lithologies
belongs to the local outcrops of Cagliari Miocenic geological formation (e.g., limestone and sanstones). The provenance
study has focused on classical marbles used for manufacturing Roman architectural elements (column shafts, bases,
capitals, pilasters, slabs, etc.), which are thought to come from extra-regional sources. All the different macrofacies of
marbles were sampled taking precise reference to the various construction phases and structural changes of the
monument occurred in the centuries. The preliminary results show that the marbles come mainly from Apuan Alps
(Italy) and subordinately from Greek quarrying areas
Rocks’ Rheology and Seismic Attenuation: What do we know?
No full textRheological properties of the rocks, depending on various parameters (grain size,
composition, hydrous conditions), determine their deformation mode in response to the tectonic
stress. At shallow depths, the rocks show a pressure-dependent frictional (brittle) behavior, which
turns in a viscous (ductile creep) behavior, as temperature increases (e.g., Jacquey and Cacace 2021).
The brittle-ductile transition (BDT) occurs at depths where the shear stress, driving the two
deformation modes, are equal for some given strain rate, composition, stress regime, and thermal
gradient. Such a transition marks the maximum depth of the intraplate earthquakes and of fluids
circulation in porous media.
Seismological datasets accounts for real media properties, providing wave propagational
attributes (e.g., seismic wave velocities and attenuation) that can be exploited to add constraints to
the BDT depth. Seismic wave attenuation can be used as a potential attribute for subsurface
characterization. Indeed, its inverse, the seismic quality factor (Q), depends on the seismic frequency,
as well as on temperature, water content, and grain size of the rocks (e.g., Karato & Spetzler, 1990;
Jackson & Faul, 2010). Therefore, it is likely that seismic attenuation and the viscous modes of
deformations of rocks can be correlated, based on their dependency on the aforementioned conditions,
as expressed by an Arrhenius-type equation (Farina et al., 2019).
In this study, we investigate the quantitative relationships between seismic attenuation and
viscous rocks' rheology, especially across the domain where rocks transition from a dominant brittle
to a more ductile deformation mode. We rely on a Burgers mechanical model to derive shear wave
attenuation (1/Qs
), for several dry and wet crustal rheology, thermal conditions, and different strain
rates values. This allows us to establish geothermal and mechanical conditions at which the BDT
occurs and to cross-correlate this transition to computed shear seismic wave attenuation values. In
particular, we observe a relatively significant Qs
reduction for strain rates of 10-13 s
-1
, despite the
assumed rock‘s rheology and thermal conditions. These first results confirm our hypothesis that
variations in the Qs
factor can be effectively used to identify the BDT’s depths in tectonically active
areas. Ongoing and future works will focus on a further validation of the modelling implications by
systematic analyses of observations derived from rocks’ laboratory experiments
U-Th-Pb dating of hydrothermal ore deposits from electron probe micro-analysis of uraninite: the cases of Cogne, Val Vedello and Novazza (Italian Alps)
Get PDFUraninite (UO2) is an uncommon accessory mineral in some magmatic, metamorphic and sedimentary rocks. Chemical analyses of uraninite performed by electron probe micro-analyzer (EPMA) can be profitably used for U-Th-Pb dating. We employed this technique to constrain the age of formation of two types of hydrothermal deposits from the Italian Alps, namely an ophiolite-hosted magnetite deposit (Cogne, western Alps) and two uranium deposits (Novazza and Val Vedello, Orobic Alps). In the first case, we aimed to establish whether the Cogne magnetite deposit, a relatively uncommon type of ophiolite-hosted deposit, was Alpine or pre-Alpine. In the second case, we used uraninite to date the hydrothermal events responsible for widespread siderite occurrences in the Southalpine domain. At Cogne uraninite occurs as rare inclusions in magnetite and forms anhedral to euhedral crystals, ranging in size from 1 to 40 μm. Textural evidence suggests that uraninite formed contemporaneously with magnetite, thus uraninite was used to date the magnetite mineralization. Based on all the radiometric age determinations (n = 53), we calculated a weighted average age of 152.8 ± 1.3 Ma (mean square weighted deviation, MSWD = 1.3), which is consistent with a pre-Alpine genesis of the ore, related to an oceanic seafloor hydrothermal system. At the two uranium deposits of Novazza and Val Vedello (Orobic Alps), abundant carbonate minerals (mainly siderite and Fe-rich dolomite) are associated with sulfides (dominant sphalerite, pyrite and galena) and uraninite, and form disseminations, veins and impregnations in the volcanoclastic facies of the Early Permian Collio Formation. At both sites, uraninite shows textural equilibrium with siderite and Fe-rich dolomite, but widespread alteration and recrystallization complicate the scenario. Therefore, we only analyzed apparently unaltered uraninite grains, which are a few-micron large at Novazza and submicron- to micron-sized at Val Vedello. Radiometric ages for the Novazza deposit range from ~ 290 to ~ 130 Ma (n = 20). The uraninite ages for the Val Vedello deposit (n = 62) are scattered between ~270 and ~ 50 Ma, but one large (20 μm) uraninite grain has a plateau age of 169 ± 3 Ma (MSWD = 1.4; n =13). By
averaging the oldest ages obtained for Novazza and Val Vedello, we obtained a best-estimate formation age for siderite-uraninite mineralization of 275 ± 13 Ma (MSWD = 3.2; n = 6). Younger ages are interpreted to reflect protracted interaction with hydrothermal fluids and/or deformation/recrystallization during Jurassic rifting and successive Alpine orogenesis. Our examples confirm that uraninite EPMA chemical U-Th-Pb dating can be a valuable tool in solving some geological issues, having also the advantage of being more affordable and rapid, compared to other analytical techniques. Moreover, the improvement of EPMA resolution (spot size << 1 μm) in modern instruments may enlarge the range of potentially analyzable samples
The formation of coesite in impact rocks
Get PDFCoesite, a high-pressure silica polymorph, is a diagnostic indicator of impact cratering in quartz-bearing target rocks. The mechanism formation of coesite is still debate since its discovery in 1960s therefore it remains the subject of numerous studies aiming to better understand how silica polymorphs react under sudden and extreme P-T increases. Here, I show evidence documenting the coesite formation through direct quartz-tocoesite transformation in subsolidus conditions studying two different impact events: Kamil crater (Egypt), a small-scale simple crater of 45 m in diameter, and the large-scale Australasian tektite/microtektite strewn field
Toluene and n-hexane competitive adsorption on high-silica ZSM-5 zeolite
No full textFuel-based compounds, such as toluene and n-hexane, are common pollutants present in water and wastewater. Due
to their tendency to persist in air, water and soil and to bioaccumulate through the food chain, they are included among
the most hazardous compounds for human health and environment. Acquatic ecosystems are especially vulnerable
because of the frequent use of water bodies as recipients of potentially toxic liquids and solids from domestic,
agricultural and industrial wastes. Hence, the removal of fuel-based compounds, through adsorption onto inorganic
sorbents is of considerable interest. Due to their selectivity towards organic contaminant and fast adsorption kinetics, it
has been recently highlighted that High Silica Zeolites are hydrophobic sorbent materials suitable for adsorption
processes (Martucci et al., 2015; Pasti et al., 2016). The aim of this work is to determine the ZSM-5 zeolite degree of
selectivity and its structural changes when a competitive adsorption of toluene and n-hexane occurs. A sample of ZSM-
5 zeolite (MFI topology, SiO2/Al2O3 ratio=280), was provided by Tosoh Corporation and loaded with a binary mixture
of toluene and n-hexane. Kinetics and adsorption isotherm data were obtained via Headspace Solid Phase
Microextraction-GC. Powders patterns were collected before and after adsorption on a Bruker D8 Advance
diffractometer equipped with SOL-X detector. Thermal (TG and DTA) analysis were performed in air up to 900°C at
10°C/min. This multidisciplinary approach allowed us to: 1) measure the sorption capacity of zeolite materials weighed
against organic pollutants dissolved in water; 2) characterise the sorbent structure after pollutant adsorption; 3) localise
the organic species in the zeolite channel systems; 4) probe the interaction between the adsorbate and zeolite framework.
Rietveld refinements provide information about the relative position of molecules inside the structure after toluene, nhexane
and their mixture adsorption. Data reveal that 1) n-hexane and toluene are preferentially adsorbed whether as
single components than as binary mixture; 2) zeolite selectivity is higher towards the n-hexane than toluene. Differences
Fourier maps analysis shows that n-hexane, water, and toluene have been adsorbed at about 8.95%, 2.2%, and 1.59%,
respectively, in good agreement with both adsorption data and thermal analysis. As a matter of fact, ZSM-5 zeolite
preferably adsorbs n-hexane, even in presence of a competitor, such as toluene.
Martucci, A., Braschi, I., Bisio, C., Sarti, E., Rodeghero, E., Bagatin, R., Pasti, L. (2015): Influence of water on the retention of
methyl tertiary-butyl ether by high silica ZSM-5 and Y zeolites: a multidisciplinary study on the adsorption from liquid and gas
phase. RSC Adv., 5, 86997-87006.
Pasti, L., Rodeghero, E., Sarti, E., Bosi, V., Cavazzini, A., Bagatin, R., Martucci, A. (2016): Competitive adsorption of VOCs from
binary aqueous mixtures on zeolite ZSM-5. RSC Adv., 6, 54544-54552
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