1,721,218 research outputs found
Lacalamita, M., Mesto, E., Mongelli, G., Mameli, P., Cerri, G., Pinto, D., Buccione, R., Schingaro, E. 2023. Characterization of Red Muds as valuable resource for sustainability. Convegno Nazionale Italiano sui Geopolimeri. Bari February, 16-17 2023.
No full textCaratterizzazione critallochimica di granati titaniferi del M. Vulture(Basilicata): stati di ossidazione e distribuzione degli elementi nei siti cristallografici
No full textCrystal chemical characterization of titaniferous garnets from Mt. Vulture(Italy): oxidation states and distribution of elements among the crystallographic sites
No full textAn in situ HT-HP single crystal X-ray diffraction study of armstrongite, a microporous zirconium silicate
No full textArmstrongite, CaZr[Si6O15]·2H2O, is a natural “zeolite-like” Zr-silicate with a heteropolyhedral framework consisting of SiO4 tetrahedra and ZrO6 octahedra that form cavities occupied by Ca-exchangeable cations (Mesto et al., 2014). The behavior at non ambient conditions of armstrongite from Khan Bogdo deposit (Gobi, Mongolia) was studied by in-situ High Temperature Single Crystal X-ray Diffraction (HT SCXRD), both in air and under dry conditions up to 500°C and 375 °C respectively, and by in-situ High Pressure Single Crystal X-ray Diffraction (HP SCXRD) using synchrotron X-ray diffraction data (collected up to 8.01 GPa), a diamond anvil cell and the mix methanol:ethanol:water as hydrostatic pressure-transmitting fluid.
On heating an abrupt discontinuity in the trend of the cell parameters and unit-cell volume occurs at T = 275°C in dry condition and at T = 450°C in air. The cell volume decreased by ~7.5%, compared to that measured at RT, and is compatible with the loss of the two water molecules. The dehydrated phase (solved and refined at 275°C only under dry conditions) exhibits the same space group (C2/m) as RT armstrongite, significantly shortened a and b cell dimensions, increased β angle, and smaller unit-cell volume (a = 13.406(3), b = 13.752(3), c = 7.811(2) Å, β = 110.22(3)°, V = 1351.3(5) Å3) with respect to the hydrated phase (a = 14.0135(7), b = 14.1234(6), c = 7.8388(4) Å, β = 109.401(4)°, V = 1463.4(1) Å3) at RT. The process is also accompanied by the distortion of the cavities as a consequence of Ca splitting and positional disorder of tetrahedral framework oxygens. The dehydration/rehydration process of armstrongite is completely reversible as also found from previous HT XRPD investigation (Schingaro et al., 2018).
HP SCXRD data show a first-order phase transition between 4.01(5) and 5.07(5) GPa. In the high-pressure polymorph, the unit-cell volume triplicates. The bulk compression of armstrongite is mainly accommodated through the tilting of both SiO4 tetrahedra and ZrO6 octahedra around the shared oxygen hinges. The high-P polymorph of armstrongite is found to be stiffer (KV0 increase of ~ 66%), and a remarkable change of the elastic anisotropic scheme occurs. No evidence of crystal-fluid interaction, with a selective sorption of molecules of the pressure-transmitting fluid through the cavities, was observed.
Mesto, E., Kaneva, E., Schingaro, E., Vladykin, N., Lacalamita, M. & Scordari, F. (2014): Armstrongite from Khan
Bogdo (Mongolia): crystal structure determination and implications for zeolite-like cation exchange properties. Am.
Mineral., 99, 2424-2432.
Schingaro, E., Lacalamita, M., Mesto, E. & Della Ventura, G. (2018): Thermal stability and dehydration of armstrongite,
a microporous zirconium silicate. Micropor. Mesopor. Mat., in press
Doronzo MD, Schingaro E, Armstrong-Altrin J S, Zoheir B (Editors) 2019 Petrogenesis and Exploration of the Earth's Interior . Proceedings of the 1st Springer Conference of the Arabian Journal of Geosciences (CAJG-1), Tunisia 2018. Springer 2019 ISSN 2522-8714 ISSN 2522-8722 (electronic) Advances in Science, Technology & Innovation IEREK Interdisciplinary Series for Sustainable Development ISBN 978-3-030-01574-9 ISBN 978-3-030-01575-6 (eBook) https://doi.org/10.1007/978-3-030-01575-6
No full textThe Earth’s interior is a source of heat, which attributes our planet a uniquely distinctive feature. It is actually the heat source that helps regulate the formation and evolution of rocks toward larger scales, while trending minerals and sediments toward minutely smaller scales. In this respect, the exploration of georesources (by-products) has to be closely related to pet- rogenesis (processes). Indeed, one of the major challenges encountered in quantitative geo- sciences lies in the eager attempt to retrieve the unknown causes of well-known effects, or inversely, predicting the unknown effects of well-known causes. It is actually in this junction that the beauty of science generally resides. More particularly, our planet is an ever-lasting stronghold of surprises worth of exhaustive studies, ranging from the inner thermodynamic processes affecting rocks evolution to the outer by-products characterizing exploration. Noteworthy, also, is that any geodynamic context proves to display peculiar geological, mineralogical, and petrological aspects, which help characterize the wide range of geographic areas lying on the surface.
These proceedings’ volume is an outcome of the best-selected papers, accepted for pre- sentation at the first Springer Conference of the Arabian Journal of Geosciences (CAJG-1), Tunisia 2018. The book exhibits a selection of the most recently conducted studies dealing with the area of rocks’ petrogenesis and exploration of georesources, elaborated by experi- enced researchers from, but not limited to, well-established research institutes based in the Mediterranean and Mid-Eastern regions. The major raised themes and issues include, mainly, the composition and thermodynamics of rocks, mineralogy and mineral resources, geology and exploration of ore deposits, geochemistry, and provenance of sediments. This volume should provide new insights into the processes and products associated with the Earth’s interior and the relating georesources. More specifically, the most recently drawn observations and proxy datasets, as figured in the book, should help fill some important gaps persisting in the existing mineralogical, geochemical, petrological, and volcano-logical records across, but not restricted to, the Mediterranean and Mid-Eastern regions.
Barcelona, Spain Domenico M. Doronzo
Bari, Italy Emanuela Schingaro
Mexico City, Mexico John S. Armstrong-Altrin Benha, Egypt/Kiel, Germany Basem Zoheir
July 201
Armstrongite at non ambient conditions: An in-situ high temperature single crystal X-ray diffraction study
Full text linkThe dehydration process of armstrongite, CaZr[Si6O15]·2H2O, from Khan Bogdo deposit (Gobi, Mongolia) was studied by in-situ High Temperature Single Crystal X-ray Diffraction (HT SCXRD) in air from 25 to 500 °C and in N2atmosphere from 25 to 375 °C. An abrupt discontinuity in the trend of the a and b parameters and of the unit-cell volume was observed at T = 275 °C in dry conditions and at T = 450 °C in air. This discontinuity is associated to dehydration and to a first-order transition. When compared to RT armstrongite, the dehydrated phase structure (obtained at 275 °C only under dry conditions) is characterized by the same space group (C2/m), cell volume decrease of ∼7.5%, compatible with the loss of the two water molecules, positional disorder of Ca over three sites, splitting of some of the heteropolyhedral framework oxygen atoms, tilting of Zr octahedra and Si tetrahedra and, distortion of four-, six- and eight-membered channels. Differently from other Zr-silicate structures, the channels dimension of the dehydrated structure (defined as the ratio between the longest and shortest diagonals of the channels) allowed the armstrongite structure to completely recover the structural water after 21 days exposure to humid conditions
Meccanismi di sostituzione nelle Ti-flogopiti del Monte Vulture e implicazioni petrologiche
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