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Della Ventura, Giancarlo
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Della Ventura, Giancarlo
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Della Ventura, G.
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ORCID
17 results
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- PublicationRestrictedTH, U, REE MINERALS IN THE GARA ADJEMAMAYE PERALKALINE GRANITE (CENTRAL HOGGAR, ALGERIA)(2011)
; ; ; ; ; ; ;KAHOUI, Mohammed; USTHB, FSTGAT, Dept of Geology, Bab Ezzouar-El Alia, ALGIERS ;DELLA VENTURA, Giancarlo; Dipartimento Scienze Geologiche,Università di Roma Tre, ROMA ;MAHDJOUB, Yamina; USTHB, FSTGAT, Dept of Geology, Bab Ezzouar-El Alia, ALGIERS ;BELLATRECCIA, Fabio; Dipartimento Scienze Geologiche,Università di Roma Tre, ROMA ;Cavallo, Andrea; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;LOUNI, Chahira; USTHB, FSTGAT, Dept of Geology, Bab Ezzouar-El Alia, ALGIERS; ; ; ; ; The Gara Adjemamaye peralkaline granite outcrops in the Egere-Aleksod terrane (central Hoggar). The main facies is a grey to cream heterogranular rock composed of quartz, mesoperthite, sodi-calcic amphibole, sodic pyroxene, annitic biotite, opaques, Fe-Ti oxides, zircon and abundant (Th, U, REE) bearing minerals. The latter are often finely dispersed in veins crossing the rock, suggesting crystallization due to extensive late-stage remobilization. This work represents a contribution to the crystal-chemistry of these rare minerals and the metasomatic mobility of incompatible elements such as Ti, Zr and REE in igneous environments.171 8 - PublicationRestrictedA 3D imaging textural characterization of pyroclastic products from the 1538 AD Monte Nuovo eruption (Campi Flegrei, Italy)(2019)
; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ;The explosive volcanic event of the 1538 AD Monte Nuovo eruption (Volcanic Explosivity Index, VEI = 2) in the Campi Flegrei high-risk caldera (Italy) has a strategic significance in the framework of volcanology and volcanic hazard of caldera-forming magmatic systems. In fact, it represents the last and unique historical eruption of the highly populated Phlegraean restless-caldera, and its precursory and eruptive phenomena are well-known because they were described in detail by contemporaneous eyewitnesses. In this study, a set of samples representative of the complete stratigraphic sequence of the Monte Nuovo eruption was characterized using phase-contrast synchrotron radiation computed microtomography and quantitatively investigated through the development of a new protocol for 3D textural analysis of highly-vesiculated volcanic rocks. Previous studies of products from this eruption are available in the literature, mostly based on 2D imaging techniques, and thus provide a useful data set for comparison. The 3D textural measurements allow us to investigate the subvolcanic processes (mechanisms and timing of magma degassing) that occurred during magma ascent in the conduit for each stage of the eruption and their relationship with the variations in the eruptive style described in the contemporaneous accounts of the eruption. This information is fundamental for the definition of a volcanic eruption scenario for such low-VEI events, often recurrent in the history of the caldera, and is useful both for hazard assessment and emergency planning.587 8 - PublicationOpen AccessNeutron and XRD Single-Crystal Diffraction Study and Vibrational Properties of Whitlockite, the Natural Counterpart of Synthetic Tricalcium PhosphateA crystal chemical investigation of a natural specimen of whitlockite, ideally Ca9Mg(PO4)6[PO3(OH)], from Palermo Mine (USA), was achieved by means of a combination of electron microprobe analysis (EMPA) in WDS mode, single‐crystal neutron diffraction probe (NDP) and single‐crystal X‐ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. The crystal‐chemical characterization resulted in the empirical formula (Ca8.682Na0.274Sr0.045)Σ9.000(Ca0.034□0.996)Σ1.000(Mg0.533Fe2+0.342Mn2+0.062Al0.046)Σ0.983(P1.006O4)6[PO3(OH0.968F0.032)Σ1.000]. Crystal‐structure refinement, in the space group R3c, converged to R1 = 7.12% using 3273 unique reflections from NDP data and to R1 = 2.43% using 2687 unique reflections from XRD data. Unit cell parameters from NDP are a = 10.357(3) Å, c = 37.095(15) Å and V = 3446(2) Å3, and from XRD, the parameters are a = 10.3685(4) Å, c = 37.1444(13) Å and V = 3458.2(3) Å3. NDP results allowed a deeper definition of the hydrogen‐bond system and its relation with the structural unit [PO3(OH)]. The FTIR spectrum is very similar to that of synthetic tricalcium phosphate Ca3(PO4)2 and displays minor band shifts due to slightly different P‐O bond lengths and to the presence of additional elements in the structure. A comparison between whitlockite, isotypic phases from the largest merrillite group, and its synthetic counterpart Ca3(PO4)2 is provided, based on the XRD/NDP and FTIR results.
30 12 - PublicationOpen AccessHydrothermal genesis and growth of the banded agates from the Allumiere-Tolfa volcanic district (Latium, Italy)In this work, we studied the hydrothermal agates from the Neogene–Quaternary volcanic district of Allumiere-Tolfa, northwest of Rome (Latium, Italy) using a combination of micro-textural, spectroscopic, and geochemical data. The examined sample consists of (1) an outer cristobalite layer deposited during the early stages of growth, (2) a sequence of chalcedonic bands (including i.e., length-fast, zebraic, and minor length-slow chalcedony) with variable moganite content (up to ca. 48 wt%), (3) an inner layer of terminated hyaline quartz crystals. The textures of the various SiO2 phases and their trace element content (Al, Li, B, Ti, Ga, Ge, As), as well as the presence of mineral inclusions (i.e., Fe-oxides and sulfates), is the result of physicochemical fuctuations of SiO2-bearing fuids. Positive correlation between Al and Li, low Al/Li ratio, and low Ti in hyaline quartz points to low-temperature hydrothermal environment. Local enrichment of B and As in chalcedony-rich layers are attributed to pH fuctuations. Analysis of the FT-IR spectra in the principal OH-stretching region (2750–3750 cm−1) shows that the silanol and molecular water signals are directly proportional. Strikingly, combined Raman and FT-IR spectroscopy on the chalcedonic bands reveals an anticorrelation between the moganite content and total water (SiOH+ molH2O) signal. The moganite content is compatible with magmatic-hydrothermal sulfate/alkaline fuids at a temperature of 100–200 °C, whereas the boron-rich chalcedony can be favored by neutral/acidic conditions. The fnal Bambauer quartz growth lamellae testifes diluted SiO 2-bearing solutions at lower temperature. These fndings suggest a genetic scenario dominated by pH fuctuations in the circulating hydrothermal fuid
45 8 - PublicationRestrictedSynthesis and solid solution in “rubidium richterite”, Rb(NaCa)Mg5 Si8 O22 (OH,F)2The OH–F substitution in “synthetic Rb-richterite” has been investigated along the join Rb(NaCa)Mg5Si8O22(OH)2–Rb(NaCa) Mg5Si8O22(F)2. Syntheses were done by conventional hydrothermal techniques (Tuttle-type vessels) at 800 °C, 1 kbar P( H2O). SEM microscopy showed very high yields of acicular to prismatic amphibole crystals up to XF = F/(F + OH) = 0.6. Beyond this value, a micaceous phase and a very fine-grained granular phase were present. Powder X-ray diffraction patterns show a single amphibole phase below XF = 0.6; above XF = 0.6, a distinct peak at d = 12.18 Å indicates the presence of a mica and there is a broad hump starting at ~ 20o 2θ and ~ 15o wide, both features increasing in intensity with increasing XF. Cell dimensions at XF = 0 are compatible with an ideal amphibole composition Rb(NaCa)Mg5Si8O22(OH)2 and evolve with increasing XF up to XF = 0.6, where there is a sharp discontinuity in a, β and V. The infrared OH-stretching spectrum of the OH end-member shows a main band at 3732 cm−1 which is assigned to the local MgMgMg–OH→ Rb arrangement, and a minor band at 3670 cm−1 assigned to the local MgMgMg–OH→ □ arrangement. This latter band indicates a slight departure toward tremolite. Intermediate OH–F compositions show the appearance of a second band at 3718 cm−1, whose intensity is proportional to the F content in the system, in accord with OH−OH and OH–F arrangements across the filled A-site. For XF > 0.6, the OH-stretching spectra are complicated by the appearance of two more peaks at 3705 and 3685 cm−1. Additional bands at lower wavenumbers, centered around 3595, 3540 and 3475 cm−1, respectively, are better resolved by collecting the spectra on disks heated at 250 °C to remove the adsorbed moisture in the pellet. Combining the behavior of unit-cell dimensions and the infrared spectra with mass-balance arguments indicates that at high XF values, Na replaces part of the Rb at the A-site in the amphibole and the tremolite component of the amphibole increases, while “Rb tetrasilicic magnesium mica” crystallizes, along with semi-amorphous nanophases. The variation in band intensities as a function of XF indicates that OH and F randomly occupy local pairs of O(3) sites across a (filled) A-site, and that there is no short-range order of OH and F.
35 2 - PublicationOpen AccessIn situ high-temperature XRPD and FTIR study of melanterite(2021)
; ; ; ; ; ; ; ; ; ; ; The thermal behavior of melanterite from the Fornovolasco mine (Tuscany, Italy) has been investigated via differential thermal analysis (DTA), thermogravimetry (TG), in situ high-temperature X-ray powder diffraction (XRPD) and Fourier-transform infrared spectroscopy (FTIR). The DTA curve showed endothermic peaks at 70, 100, 260, 500–560 and 660 °C whereas the TG curve evidenced a total mass decrease of ~68%, in keeping with the loss of all H2O and SO4 groups. Rietveld refinements were performed for all the collected patterns in the 25–775 °C range and converged at 1.57 ≤ R (%) ≤ 2.75 and 1.98 ≤ Rwp (%) ≤ 3.74. The decomposition steps FeSO4·7H2O → FeSO4·4H2O (25 ≤ T ≤ 50 °C) → FeSO4·H2O (50 < T ≤ 100 °C) → FeOHSO4 (75 < T ≤ 200 °C) → Fe2(SO4)3 (400 < T ≤ 500 °C) → Fe2O3 (500 < T ≤ 775 °C) were obtained. The high-temperature infrared analysis confirmed that melanterite undergoes a three-step dehydration in the 25–300 °C temperature range. The FeOHSO4 phase is stable over a wide range of temperature and transforms partially to Fe2(SO4)3 without the formation of Fe2O(SO4)2. The findings highlight a different behavior of the studied sample with respect to the synthetic salt.76 34 - PublicationRestrictedPhase transition induced by solid solution: The Ca-Mg substitution in richteritic amphiboles(2010)
; ; ; ; ; ; ; ; ;Iezzi, G.; Dipartimento DIGAT, Università G.d'Annunzio, Chieti, Italy ;Della Ventura, G.; Dipartimento di Scienze Geologiche, Università di Roma Tre, Roma,Italy ;Tribaudino, M.; Dipartimento di Scienze della Terra, Università di Parma, Parma, Italy ;Nemeth, P.; Department of Surface Modifications and Nanostructures, Chemical Research Center of the Hungarian Academy of Sciences,Budapest, Hungary ;Margiolaki, I.; European Synchrotron Radiation Facility (ESRF),Grenoble, France ;Cavallo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Gaillard, F.; ISTO, Université d’Orleans Campus Geosciences,Orléans, France ;Beherns, H.; Institut of Mineralogy, University of Hannover,Hannover, Germany; ; ; ; ; ; ; Eleven compositions along the join Na(NaMg)Mg5Si8O22(OH)2-Na(NaCa)Mg5Si8O22(OH)2 (“magnesiorichterite”-richterite) have been synthesized at T = 800–850 °C and PH2O = 0.35–0.5 GPa. The run products have been characterized by electron probe microanalysis (EPMA), synchrotron and conventional X-ray powder diffraction (XRPD), Fourier transformed infrared (FTIR) spectroscopy, and selected area electron diffraction (SAED-TEM). Nominally, the chemical variation along the join can be expressed as BMgxBCa1–x with 0 ≤ x ≤ 1. A combination of EPMA and FTIR data in the OH-stretching region show that a complete solid solution is obtained under the conditions used. Nevertheless, a slight deviation from the nominal compositions involving a limited loss of Na at A and B sites, balanced by an increase of Ca at the B site, is present. Several indications of a displacive and coelastic P21/m → C2/m transformation induced by the Ca-Mg chemical substitution are observed. The phase transition occurs at B-site composition (Xc) close to B(Na1Mg0.7Ca0.3). C2/m samples with a Ca content of 0.34, 0.45, and 0.54 apfu show a significant strain tail related to local compositional inhomogeneities. This residual strain disappears as the amount of BCa significantly increases with respect to that of BMg. The transformation behavior observed here mirrors that of pyroxenes along the join diopside (CaMgSi2O6)-enstatite (Mg2Si2O6). The cell parameters of amphiboles with CMg5, TSi8, and W(OH)2 and variable A- and B-site populations follow almost linear and continuous trends, indicative of small amounts of spontaneous strain accompanying these monoclinic phase transitions and the absence of significant miscibility gaps among different amphibole groups when quenched from higher temperatures of crystallization.149 21 - PublicationRestrictedSynthetic ANaB(NaxLi1 ¡ xMg1)CMg5Si8O22(OH)2 (with x = 0.6, 0.2 and 0) P21/m amphiboles at high pressure: a synchrotron infrared study(2009)
; ; ; ;Iezzi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Liu, Z. ;Della Ventura, G.; ;high-pressure behavior of three synthetic amphiboles crystallized with space group P21/m at room conditions in the system Li2O–Na2O–MgO–SiO2–H2O has been studied by in situ synchrotron infrared absorption spectroscopy. The amphiboles have compositions ANa B(NaxLi1 ¡ xMg1) CMg5 Si8 O22(OH)2 with x = 0.6, 0.2 and 0.0, respectively. The high-P experiments up to 32 GPa were carried out on the U2A beamline at Brookhaven National Laboratory (NY, USA) using a diamond anvil cell under non-hydrostatic or quasi-hydrostatic conditions. The two most intense absorption bands in the OH-stretching infrared spectra can be assigned to two non-equivalent O–H dipoles in the P21/m structure, bonded to the same local environment M1M3Mg3–OH–ANa, and pointing toward two diVerently kinked tetrahedral rings. In all samples these bands progressively merge to give a unique symmetrical absorption with increasing pressure, suggesting a change in symmetry from P21/m to C2/m. The pressure at which the transition occurs appears to be linearly correlated to the aggregate B-site dimension. The infrared spectra collected for amphibole B(Na0.2Li0.8Mg1) in the frequency range 50 to 1,400 cm¡1 also show a series of changes with increasing pressure. The data reported here support the inference of Iezzi et al. (Am Miner 91:479–482, 2006a) regarding a new high-pressure C2/m amphibole polymorph characterized by two equivalent and kinked double-chains, stable at very high-pressure.140 21 - PublicationOpen AccessTerahertz continuous wave spectroscopy: a portable advanced method for atmospheric gas sensing(2022-05-23)
; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ;Motivated by the increasing demand to monitor the air-quality, our study proved the feasibility of a new compact and portable experimental approach based on Terahertz (THz) continuous wave high resolution spectroscopy, to detect the presence of the air's contaminants as greenhouse gases (GHG) and volatile organic compounds (VOCs). In this specific work, we first characterized, determining their molar absorption coefficient in the spectral region (0.06-1.2) THz, the pure optical response of the vapor of five VOCs: methanol, ethanol, isopropanol, 1-butanol and 2-butanol. In particular, 1-butanol and 2-butanol are characterized for the first time in literature at THz frequencies. Then we studied the optical response of their mixtures achieved with ambient air and ethanol. The results show that it is possible for a differentiation of single components by describing their spectral absorption in terms of the linear combination of pure compounds absorption. This proof of concept for this apparatus study and set-up paves the way to the use of THz Continuous wave high resolution spectroscopy for the environmental tracking of air pollutants.37 41 - PublicationOpen AccessNuove specie minerali al Somma-Vesuvio: fluoro-edenite(2009)
; ; ; ; ;Russo, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Della Ventura, G.; Dipartimento di Scienze Geologiche Università Roma Tre ;Campostrini, I.; Dipartimento di Chimica Strutturale e Stereochimica Inorganica Università di Milano ;Preite, D.; via Piave, 16 I-20024 Garbagnate (Milano); ; ; Despite the impossibility to make mineralogical researches on the field, the volcanic complex of Monte Somma-Vesuvius keeps surprising with new findings of mineral species for that locality. In an “old” sample belonging to Domenico Preite, picked up at Le Novelle quarry, Ercolano, Napoli, thanks to EDX and micro- FTIR analysis the fluoro-edenite was identified. This is the second Italian finding for the species after the one of the Etnean type locality of Monte Calvario, Biancavilla, Catania (Gianfagna & Oberti, 2001).260 231