Determinazione della dimensione temporale della deformazione e della denudazione/esumazione tramite la caratterizzazione e datazione K-Ar dell’illite, datazioni 40Ar/39Ar e tracce di fissione

La dimensione temporale è un parametro fondamentale da considerare in tutti gli studi di natura geologica. Per poter interpretare lunghe e complesse storie geologiche dal punto di vista della deformazione e per quantificare i processi strutturali è fondamentale “leggere” le variabili che controllano la deformazione dei materiali geologici (ad esempio la temperatura, la pressione, gli sforzi) solo dopo averle integrate correttamente sull’effettivo tempo geologico trascorso nell’intervallo temporale di interesse. A tal fine ci avvaliamo di numerose tecniche termocronologiche e geocronologiche che permettono di vincolare e chiarire i meccanismi esumativi della crosta terrestre e di datare con precisione la deformazione. Analisi K-Ar di illiti sincinematiche formatesi in rocce di faglia fragile sono la chiave per vincolare con estrema accuratezza l’età degli episodi di fagliazione che vengono archiviati all’interno delle faglie.

Pubblicazioni rilevanti:

- Viola G., Mancktelow N. and Seward D. (2001): Late Oligocene - Neogene evolution of Europe-Adria collision: New structural and geochronological evidence from the Giudicarie fault system (Italian eastern Alps). Tectonics, 20, 999-1020.

- Viola G., Mancktelow N., Seward D., Meier A. and Martin S. (2003): The Pejo fault system: an example of multiple tectonic activity in the Italian Eastern Alps, GSA Bulletin, 115, 5, 515-532.

- Viola G. and Anczkiewicz R. (2008): Exhumation history of the Red River shear zone in northern Vietnam: New insights from zircon and apatite fission-track analysis.  Journal of Asian Earth Sciences 33, 78-90.

- Kounov A., Viola G., de Wit M. And Andreoli M. (2008): A mid Cretaceous paleo-Karoo River valley across the Knersvlakte (NW coast of South Africa): Evidence from apatite fission-track analysis. South African Journal of Geology, 111, 407-418.

- B. Bingen, J. Jacobs, G. Viola, I.H.C. Henderson, Ø. Skår, R. Boyd, R.J. Thomas, A. Solli, R.M. Key and E. Daudi (2009): Geochronology of the Precambrian crust in the Mozambique Belt of NE Mozambique, and implications for Gondwana assembly. Precambrian Research, 170, 231-255.

- Kounov, A, Viola, G., de Wit, M. and Andreoli, M. (2009): Denudation along the Atlantic passive margin: New insights from apatite fission-track analysis on the Western coast of South Africa. In Lisker, F., Ventura, B. and Glasmacher, U.A. (eds.) "Thermochronological methods: from paleotemperature constraints to landscape evolution models", Geological Society of London, Special Publications, 324, 287-306.

- Viola, G., Mattila, J., Zwingmann, H. and Todd, A. (2011): Structural and K/Ar illite geochronological constraints on the brittle deformation history of the Olkiluoto region, southwest Finland. Posiva OY working report 2011-37.

- Viola, G., Henderson, I.H.C., Bingen B., and Hendriks B.W.H. (2011): The Grenvillian-Sveconorwegian orogeny in Fennoscandia: Back thrusting and extensional shearing along the “Mylonite Zone”. Precambrian Research, 189, 368-388.

- Viola, G., Zwingmann, H., Mattila, J. and Käpyaho, A. (2013): K/Ar illite age constraints on the Proterozoic formation and reactivation history of a brittle fault in Fennoscandia. Terra Nova, 25, 3, 236-244.

- Kounov, A., Viola, G., Dunkl, I. and Frimmel, H.E. (2013): Southern African perspectives on the long-term morpho-tectonic evolution of cratonic interiors. Tectonophysics, 601, 177-191.

- Torgersen, E., Viola, G., Zwingmann, H. and Harris, C.J. (2014): Structural and temporal evolution of a reactivated brittle-ductile fault: Part II. Timing of fault initiation and reactivation by K-Ar dating of synkinematic illite. EPSL, 407, 221-233.

- Torgersen, E., Viola, G., Zwingmann, H. and Henderson, I.C. (2015): Inclined K-Ar illite age spectra in brittle fault gouges: Effects of fault reactivation and wall-rock contamination. Terra Nova, 27, 106-113.

- Wang, Y., Zwingmann, H., Zhouh, L., Lo, C., Viola, G. and Hao, J. (2016): Direct dating of folding events by 40Ar/39Ar analysis of synkinematic muscovite from flexural-slip planes. Journal of Structural Geology, 83, 46-59.

- Bingen, B., Solli, A., Viola, G., Torgersen, E., Sandstad, JS., Whitehouse, M.J., Skår, Ø., Ganerød, M. and Nasuti, A. (2015): Geochronology of the Palaeoproterozoic Kautokeino Greenstone Belt, Finnmark, northern Norway: Tectonic implications in a Fennoscandia context. Norwegian Journal of Geology, 95, 3-4, 365-396.

- Scheiber, T., Viola, G., Wilkinson, C.M., Ganerød, M., Skår, Ø. and Gasser, D. (2016): Direct ⁴⁰Ar/³⁹Ar dating of Late-Ordovician and Silurian brittle faulting in the southwestern Norwegian Caledonides. Terra Nova, 28, 5, 374-382, DOI: 10.1111/ter.12230

- Viola, G., Scheiber, T., Fredin, O., Zwingmann, H., Margreth, A., Knies, J. (2016): Deconvoluting complex structural histories archived in brittle fault zones. Nature Communications, 7, 13448 doi: 10.1038/ncomms13448.

- Di Vincenzo, G., Grande, A., Prosser, G., Cavazza, W., DeCelles, P.G. (2016): 40Ar-39Ar laser dating of ductile shear zones from central Corsica (France): Evidence of Alpine (middle to late Eocene) syn-burial shearing in Variscan granitoids. Lithos, 262, 369-383.

- Fredin, O., Viola, G., Zwingmann, H., Sorlie, R., Bronner, M., Lie, J.-E., Grandal, E.M., Muller, A., Margreth, A., Vogt, C. and Knies, J. (2017): The inheritance of a Mesozoic landscape in western Scandinavia. Nature Communications, 8.

- Goodfellow, B.W., Viola, G., Bingen, B., Nuriel, P., Kylander-Clark, A.(2017): Palaeocene faulting in SE Sweden from U–Pb dating of slickenfibre calcite. Terra Nova, 29, 321-328.

- Scheiber, T. and Viola, G.(2018): Complex bedrock fracture patterns: A multipronged approach to resolve their evolution in space and time. Tectonics, doi: 10.1002/2017TC004763.

- Scheiber, T., Viola, G., van der Lelij, R., Margreth, A. and Schönenberger, J.(2019): Microstructurally-constrained versus bulk fault gouge K-Ar dating. Journal of Structural Geology, 127, 103868, doi:10.1016/j.jsg.2019.103868.

- Aldega, L., Viola, G., Casas-Sainz, A., Marcén, M, Román-Berdiel, T. and van der Lelij, R (2019): Unravelling multiple thermo-tectonic events accommodated by crustal-scale faults in northern Iberia, Spain: Insights from K-Ar dating of clay gouges. Tectonics, 38, doi: 10.1029/2019TC005585.

- Tartaglia G., Viola G., van der Lelij, R., Scheiber, T., Ceccato A. and Schonenberger J.(2020): “Brittle structural facies” analysis: A diagnostic method to unravel and date multiple slip events of long-lived faults. Earth and Planetary Science Letters, 545, 116420.

- Carboni, F., Viola, G., Aldega, L., van der Lelij, R.; Brozzetti, F.; Barchi, M. (2020): K-Ar fault gouge dating of Neogene thrusting: the case of the siliciclastic deposits of the Trasimeno Tectonic Wedge (Northern Apennines, Italy). Italian Journal of Geosciences, 139, 300 – 308.