Two clinoptilolites from genetically different volcanoclastic formations have been studied. Both deposits are located in the Logudoro region (North-Western Sardinia, Italy) within epiclastic and pyroclastic formations related to calcalkaline volcanic activity. Chemical characterization performed by electron microprobe analysis on both samples showed a quite similar composition ([Si/(Si+Al)] = 0.81 divided by 0.82), with the exception of some extra-framework cations. In particular the epiclastic clinoptilolites turned out to be much higher in Mg content (0.72 vs. 0.26 a.f.u.) and considerably lower in K (1.10 vs. 2.37 a.f.u.) than the pyroclastic clinoptilolites. Previous investigations evidenced a different behaviour of the two clinoptilolite samples towards cation exchange processes and a substantial difference between the theoretical and experimental CEC. In this frame, Rietveld refinements based on synchrotron data allowed to define a different cationic population within the four exchangeable cation sites.

Crystal-chemistry and synchrotron-Rietveld refinement of two different clinoptilolites from volcanoclastites of north-western Sardinia

CRUCIANI, Giuseppe
1999

Abstract

Two clinoptilolites from genetically different volcanoclastic formations have been studied. Both deposits are located in the Logudoro region (North-Western Sardinia, Italy) within epiclastic and pyroclastic formations related to calcalkaline volcanic activity. Chemical characterization performed by electron microprobe analysis on both samples showed a quite similar composition ([Si/(Si+Al)] = 0.81 divided by 0.82), with the exception of some extra-framework cations. In particular the epiclastic clinoptilolites turned out to be much higher in Mg content (0.72 vs. 0.26 a.f.u.) and considerably lower in K (1.10 vs. 2.37 a.f.u.) than the pyroclastic clinoptilolites. Previous investigations evidenced a different behaviour of the two clinoptilolite samples towards cation exchange processes and a substantial difference between the theoretical and experimental CEC. In this frame, Rietveld refinements based on synchrotron data allowed to define a different cationic population within the four exchangeable cation sites.
1999
Cappelletti, P; Langella, A; Cruciani, Giuseppe
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/494283
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