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Metodo Ufficiale n°IV.2 - Diffrattometria a raggi X. Analisi mineralogica semiquantitativa
No full textL’analisi mineralogica semiquantitativa di campioni di suolo ricchi in componente argillosa consente di ricavare stime dell’abbondanza percentuale dei minerali argillosi presenti. Non deve essere considerata come un mezzo per determinare le quantità assolute di minerali in un determinato campione, quanto piuttosto, un “ottimo” metodo per monitorare le variazioni quantitative degli stessi minerali in sequenze di campioni.E’ opportuno evitare che il campione venga sottoposto a trattamenti invasivi come attacco acido, macinazione spinta, sonicazione e uso di disperdenti che potrebbero modificare la composizione e/o la struttura dei minerali e quindi alterare il tracciato diffrattometrico. L’analisi semiquantitativa viene generalmente eseguita sul tracciato diffrattometrico della frazione granulometrica <2μm (diametro di una sfera equivalente) del preparato orientato dopo solvatazione con glicole etilenico
High-frequency cyclicity, palaeoclimate and palaeoenvironments in the upper Messinian Lago-Mare deposits of the Fonte dei Pulcini section (Majella Mts., central Italy).
No full textLate Messinian Lago-Mare deposits show high-frequency cyclicity in the whole Mediterranean Basin. Both mm- and cm-scale cyclicities have been observed in several ODP sites as well as in stratigraphic sections from the Mediterranean borderland. We have analyzed a well-exposed late Messinian Lago-Mare section from the Adriatic side of the central Apennines (Italy). At the Fonte dei Pulcini section (SE Majella Mts.), mm- and cm-scale white-and-dark couplets have been observed in the field. A 50cm regular-spaced sampling has been performed in the uppermost 53m of the late Messinian Lago-Mare clays. On the 107 collected samples, geochemical (CaCO3 content), mineralogical (XRD analyses) and micropalaeontological investigations have been performed. In addition, SEM and Microprobe investigations as well as mineralogical and micropalaeontological analyses have been carried out on single lamina from a 34cm-thick interval of mm-scale laminites.The uppermost Messinian Lago-Mare facies of the Fonte dei Pulcini section (southeastern Majella), which developed in the pre-orogenic Adriatic foreland basin, shows high-frequency cyclicities that consist of mm- and cm-scale white-and-dark couplets (fig. 1). Similar cyclicities characterize the uppermost Messinian Lago-Mare deposits recovered in several western Mediterranean ODP sites (Iaccarino and Bossio, 1999) as well as on the Mediterranean borderlands (Vismara-Schilling et al., 1976; Fortuin et al., 1995; Bassetti et al., 1994; 1998; Roveri et al., 2001). Since these high-frequency sedimentary signatures are widespread in the whole Mediterranean Basin, allocyclic mechanisms (e.g. climatic changes) have to be considered as a primary cause for generating these rhythmic deposits.Besides the mm- and cm-scale rhythmites found in the field, spectral analyses performed on the CaCO3 data set from the Fonte dei Pulcini A section evidenced higher periodicities of about 2.1 m (f = 0.47 cycles/m), 2.8 m (f = 0.35 cycles/m) and 5.6 m (f = 0.17 cycles/m). Using the estimated sedimentation rate (about 1 m/ky) for the late Messinian Lago-Mare episode of the Majella area, the computed depth periodicities have been time converted into 2.1 ky, 2.8 ky and 5.6 ky. These periodicities are tentatively related to hypercycles of the sunspot activity since similar cyclicity values have been found by cosmogenic isotope data (Vitinsky et al., 1986; Usoskin and Mursula, 2003) or recognized in Carboniferous varves (Milana and Lopez, 1998).Taking into account the estimated sedimentation rate, the lowest periodicity observed in the analyzed section as mm-scale laminites should represent an annual cyclicity. Then, each individual white-and-dark couplet can be considered as a “varve” since it represents a sedimentary cycle produced during the course of a year.The varved sediments in the upper Messinian deposits of the Majella area show a marked seasonality with the alternation of humid and more arid conditions. This marked seasonality could be explained with the climate conditions related to the monsoon system developed in the Mediterranean region during the late Miocene (Griffin, 2002).Relevant climatic oscillations from drier to moister and colder conditions in the late Messinian of the Mediterranean realm are revealed by both palynological (Bertolani Marchetti and Marzi, 1988; Bertini, 1992; 1994; Bertini, in press) and mineralogical investigations (Chamley, 1975; Chamley and Robert, 1980; Martìnez-Ruìz et al., 1999). In t
Estudio petrológico del volcanismo cuaternario de los Monti Cimini y el volcán de Vico, Lazio, Italia
No full textThis paper provides new geochemical, petrographic, and isotopic data over a set of 39 samples representative of all different units present in the quaternary volcanism of Monti Cimini region (Provincia Magmatica Toscana) and Vico volcano (Provincia Magmatica Romana). Monte Cimini volcanics are older in age (around 0.94 Ma) includes trachytic and latitic rocks with isotopic ratios 87Sr/86Sr 0.713413„b14 a 0.715685„b5, and 143Nd/144Nd 0.512053„b3 to 0.5121339„b3. Vico volcano (0.4 Ma) products range between phonolitic and trachyandesitic compositions and shows 87Sr/86Sr values of 0.710923„b5 a 0.711264„b6 and 143Nd/144Nd 0.512092„b3 to 0.512122„b3. All these new data are in good agreement with their former attribution to the aforementioned magmatic provinces
Latest Messinian climatic changes and sedimentary response in the Adriatic foreland basin
No full textLa successione tardo messiniana di Fonte dei Pulcini (FPA) (Maiella sud-orientale), deposta in un bacino di avampaese, ha registrato numerose variazioni paleoambientali in termini di paleoprofondità, paleosalinità, apporto detritico, evaporazione/precipitazione e aridità/umidità. Queste variazioni paleoambientali sono state messe in evidenza attraverso l’analisi integrata di dati paleontologici, geochimici e mineralogici. L’analisi della suscettività magnetica nella successione di FPA ha permesso di effettuare una calibrazione astrocronologica delle variazioni paleoambientali e paleoclimatiche, vincolando la sezione tra 5,394 e 5,335 Ma. Confrontando la curva dell’insolazione con le variazioni paleoambientali registrate dalla sezione FPA è stato messo in evidenza un ritardo di 5-8 ka tra la causa astronomica della variazione climatica e la risposta del bacino sedimentario
Estudio petrológico del volcanismo cuaternario de los Monti Cimini y el volcán de Vico, Lazio, Italia
No full textThis paper provides new geochemical, petrographic, and isotopic data over a set of 39 samples representative of all different units present in the quaternary volcanism of Monti Cimini region (Provincia Magmatica Toscana) and Vico volcano (Provincia Magmatica Romana). Monte Cimini volcanics are older in age (around 0.94 Ma) includes trachytic and latitic rocks with isotopic ratios 87Sr/86Sr 0.713413+-14 a 0.715685+-5, and 143Nd/144Nd 0.512053+-3 to 0.5121339+-3. Vico volcano (0.4 Ma) products range between phonolitic and trachyandesitic compositions and shows 87Sr/86Sr values of 0.710923+-5 a 0.711264+-6 and 143Nd/144Nd 0.512092+-3 to 0.512122+-3. All these new data are in good agreement with their former attribution to the aforementioned magmatic province
Ni/CeO2-Al2O3 catalysts for the dry reforming of methane: the effect of CeAlO3 content and nickel crystallite size on catalytic activity and coke resistance
Full text linkThe catalytic performances of Ni/CeO2–Al2O3 catalysts for the dry reforming of CH4 (DRM) were investigated. Catalysts with different Ni dispersion and different amounts of CeAlO3 species were prepared by
different methods and characterized by BET, XRD, XPS, Raman, TPR, and TPO techniques. Catalytic activity
was studied during the time on stream in the range 873–1073K with a mixture of CH4:CO2:Ar = 40:40:20 vol.%
and GHSV 90,000 cm3 g−1 h−1. The intrinsic catalytic activity increased with the increase of Ni crystallite
size. Carbon was deposited as nano-fibers and graphite when catalysts worked at lower temperatures, and
the largest amount was found on the catalyst with the largest Ni crystallite size. The formation of graphitic
deposits is limited by the presence of CeAlO3 species formed during catalyst activation. CA preparation
method results particularly attractive because it allows obtaining catalysts with small Ni crystallite size
and high content of CeAlO3 species, which both have a role in suppressing the carbon deposition and
therefore in obtaining stable catalytic performances
Raman, SEM-EDS and XRPD investigations on pre-Columbian Central America "estucado" pottery
No full textSeventeen different colored fragments from six selected pre-Columbian estucado ceramics from El Salvador have been investigated by Raman spectroscopy, scanning electron microscope coupled to an energy dispersive spectrometer (SEM/EDS) and X-ray powder diffraction (XRPD). The peculiarity of this kind of ceramics consist of the unusual presence of a white engobe, traditionally termed stucco, between the ceramic body and the decoration elements, hence the name estucado ceramics. The aim of this work was to study the unusual manufacturing technique and to identify the chemical composition of the engobe and of the pigment palette. The results showed that the stucco layer is made of clay (kaolinite) with traces of titanium oxide (anatase). Remarkably, this is the same composition of the white pigments used for the decoration layer, thus excluding an early use of natural titanium oxide as a white pigment in the estucado productions as suggested in previous investigations. Moreover, the presence of kaolinite and anatase both in the stucco and in the decoration layer suggests a cold-working or low temperature technique. The red, yellow and green decorations were realized by the use of natural ochre, while in all the blue and gray decorations Maya blue pigment was identified. Finally, an amorphous carbon pigment of vegetal origin and manganese oxide were used to obtain black pigments
High-resolution stratigraphy of the pre-evaporitic/evaporitic transition in the late Messinian Adriatic foreland domain
No full textOne of the most spectacular evaporative event in the Earth history occurred in the Mediterranean Basin, during the late Messinian (Messinian Salinity Crisis, MSC), as a consequence of the restriction in the Atlantic-Mediterranean connection. Enclosed marine environments could record evaporative deposition undergo restriction in circulation coupled with climate forcing.
The aim of this paper is to investigate what happened in the sedimentary basin of the Adriatic foreland domain approaching the MSC by using an interdisciplinary study, which includes stratigraphy, paleontology, mineralogy, and magnetostratigraphy. The study area is the NW flank of the Maiella Mountains, where the MSC is well recorded by both the deposition of the Lower Evaporites and the post-evaporitic deposits of the Lago-Mare event. For getting a complete record of the pre-evaporitic/evaporitic transition in the study area, a 23m depth borehole was drilled starting from the 20cm-thick carbonate horizon (Calcare di Base) just at the base of the first gypsum cycle of the Lower Evaporites. Beneath the Calcare di Base, the sedimentary core recovered 3.8 m of dark clays rich in organic matter, punctuated by 5 carbonate-rich layers.
The rest of the recovered sedimentary core is characterized by limestones and marly limestones rich in small lithotamnium, bryozoa, and benthic foraminifera, pertaining to the uppermost part of the Bolognano Formation. All the sedimentary core was analysed, collecting 5-10 cm thick samples.
The occurrence of the carbonate-rich layers within the dark clays allows us to recognize 5 sedimentary cyles, possibly forced by precessional cyclicity. Calcareous nannofossils show two peaks of Sphenolithus abies within the 2nd and 4th cycle from the top. Small Reticulofenestra and Helicosphaera carteri show one peak within the 1st cycle, as well as in the 3rd and 4th cycles. Among the planktonic foraminifera, Turborotalita multiloba shows a peak within the 4th cycle whereas Orbulina universa has two peaks, within the 3rd and 4th cycles. The uppermost 50cm of the sedimentary core are completely barren.
Although no major changes in lithology can be recognized in the fine-grained deposits, magnetic susceptibility decreases to extremely low values in the 1st and 2nd cycles, in the upper part of the sedimentary core. The depletion of magnetic minerals in this interval seems higher than can be attributed solely to dilution by magnetite-poor sediments, which implies that magnetite dissolution could have occurred.
Our analyses on the paleontological record of the pre-evaporitic deposits in the Maiella foreland basin show results very similar to other pre-evaporitic Messinian successions from the Mediterranean Basin.
Finally, the calibration of the sedimentary core with the insolation curve allow us to confirm the precessional forcing of the sedimentary record in the Messinian Adriatic foreland basin during the pre-evaporitic stage
Characterisation of artificial patinas on bronze sculptures of the Carlo Bilotti Museum (Rome)
No full textTwo bronze sculptures, Ettore e Andromaca, a reproduction of a plaster model by Giorgio de Chirico, and Cardinale, a cast made from an original by Giacomo Manzù, stand outside the Carlo Bilotti contemporary art museum in Villa Borghese park (Rome). The composition of the artificial brown patina present on the statues’ surface, which was applied for aesthetic purposes, is unknown. This paper reports analysis carried out to identify the composition of the artificial patina and describe the corrosion products formed in outdoor conditions. Raman spectroscopy and scanning electron microscopy equipped with X-ray microanalysis were performed on sample fragments and powder scrapings taken from the bronze statues. X-ray powder diffraction was used whenever possible and subject to conservation priorities. Our data revealed, in the artificial brown patina, the formation of copper oxides (cuprite and tenorite) on the surface of both sculptures as possible result of oxidisation treatments performed with a blowtorch before the artificial patination process began. Furthermore, a copper nitrate (gerhardtite) was identified as an ingredient in the preparation applied to the bronze surfaces. The green areas revealed the presence of corrosion products as copper sulphate hydroxide (brochantite) and copper sulphate-chloride (connellite), which form under acid rains conditions
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