17:15 〜 19:15
[SGL22-P03] Constraining timing of brittle deformation in Sardinia Italy – implication for the site evaluation of the Einstein Telescope
キーワード：Einstein Telescope, Sardinia, brittle faults, illite, K-Ar dating
Deformation in the Earth's upper crust is often accommodated by brittle faulting with scales ranging from microscopic displacements to large regional tectonic structures. The geological history of Sardinia, Italy, has involved different geodynamic phases, including significant brittle deformation, and its history remains poorly understood, particularly in the crystalline basement where time constraints on brittle evolution are lacking. In order to evaluate the site suitability of the site candidate to host the Einstein Telescope (https://www.einstein-telescope.it/), this study focuses on a broader area which is virtually free of regional faults.
Brittle faults and clay gouges often contain authigenic illite, which can be dated by numerous isotopic tools [1]. In this study, we present the first K-Ar age data from nine clay gouges in Sardinia, which when integrated into the regional geological history, provide a clear Mesozoic brittle overprint of pre-existing Variscan crustal structure. Extensive mineral characterization, including detailed petrography (TS, SEM, TEM) and XRD clay analyses, was carried out prior to K-Ar age dating [e.g. 2]. The ages of the various clay gouges range from 241 to 127 Ma, with ages decreasing with grain size. The finest <0.1 μm fraction of a fault core gouge represents the youngest ages, ranging from 178.8 Ma to 126.5 Ma. The illite age data from both faults from both basement and the carbonate succession faults indicate that brittle faulting in the region might be associated with the Jurassic-Cretaceous post-break up tectonics of the southern European margin. The new age data also provide support a transition between Jurassic post-breakup tectonics and Pyrenean evolution, with implications for the regional tectonic history of Sardinia and its related fault gouge formation.
References
[1] Tsukamoto, et al., 2019. Direct Dating of Fault Movement. - In Tanner, D.C, Brandes, C. (Eds.) Understanding Faults: Detecting, Dating, and Modelling Faults. Elsevier, Chapter 7, 257-283.
[2] Zwingmann et al., 2010. Geology, 38, 6, 487-490; doi10.1130/G30785.1
Brittle faults and clay gouges often contain authigenic illite, which can be dated by numerous isotopic tools [1]. In this study, we present the first K-Ar age data from nine clay gouges in Sardinia, which when integrated into the regional geological history, provide a clear Mesozoic brittle overprint of pre-existing Variscan crustal structure. Extensive mineral characterization, including detailed petrography (TS, SEM, TEM) and XRD clay analyses, was carried out prior to K-Ar age dating [e.g. 2]. The ages of the various clay gouges range from 241 to 127 Ma, with ages decreasing with grain size. The finest <0.1 μm fraction of a fault core gouge represents the youngest ages, ranging from 178.8 Ma to 126.5 Ma. The illite age data from both faults from both basement and the carbonate succession faults indicate that brittle faulting in the region might be associated with the Jurassic-Cretaceous post-break up tectonics of the southern European margin. The new age data also provide support a transition between Jurassic post-breakup tectonics and Pyrenean evolution, with implications for the regional tectonic history of Sardinia and its related fault gouge formation.
References
[1] Tsukamoto, et al., 2019. Direct Dating of Fault Movement. - In Tanner, D.C, Brandes, C. (Eds.) Understanding Faults: Detecting, Dating, and Modelling Faults. Elsevier, Chapter 7, 257-283.
[2] Zwingmann et al., 2010. Geology, 38, 6, 487-490; doi10.1130/G30785.1