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The “Tufo Giallo della Via Tiberina” (Sabatini Volcanic District, Central Italy): a complex system of lithification in a pyroclastic current deposit

 

P. Cappelletti1, P. Petrosino1, M. de Gennaro1, A. Colella1, S. F. Graziano1, M. D’Amore1, M. Mercurio2, G. Cerri3, R. de Gennaro4, G. Rapisardo1, A. Langella2

 
1 Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, Università degli Studi di Napoli Federico II, Largo San Marcellino 10, 80138 Napoli, Italy
2 Dipartimento di Scienze e Tecnologie, Università degli Studi del Sannio, Via dei Mulini 59/A, 82100 Benevento, Italy
3 Dipartimento di Scienze della Natura e del Territorio, Università degli Studi di Sassari, Via Piandanna 4, 07100 Sassari, Italy
4 CISAG, Università Federico II di Napoli, Via Mezzocannone 8, 80134 Napoli, Italy
 
 
Mineralogy and  Petrology, 109, 85–101, (2015)
 
Abstract
The Sabatini Volcanic District belongs to the Roman magmatic province of Central Italy, and the Tufo Giallo della Via Tiberina was one of the most voluminous pyroclastic flow-forming eruptions in this district. Post-depositional processes strongly affected this pyroclastic flow deposit leading to the crystallization of different authigenic phases (chabazite, phillipsite, feldspar).A field volcanological survey, along with a careful mineralogical characterization of a large amount of samples of the lithified facies, allowed us to reconstruct a type section primarily based on the amounts of the main authigenic phases. Chabazite always prevailed over phillipsite throughout the entire section, although in the innermost portions of the deposit, where temperatures remained high, chabazite mostly converted into a more stable phase such as an adularia-like phase. In addition to the zeolitization process, the fairly strong mechanical properties of this tuff can be also ascribed to the diffuse occurrence of microcrystalline calcite, which reprecipitated as a secondary phase after the dissolution of carbonaceous clasts.
 
Key-words: Sabatini district, zeolites, pyroclastic flow, lithification