Extensional faulting on Tinos island, Aegean sea, Greece: How many detachments?
Résumé
Zircon and apatite fission track (ZFT and AFT) and (U-Th)/He, ;40;Ar/;39;Ar hornblende, and U-Pb zircon ages from the granites of Tinos Island in the Aegean Sea, Greece, suggest, together with published ZFT data, that there are three extensional detachments on Tinos. The Tinos granites crosscut the Tinos detachment. Cooling of the granites was controlled by the Livadi detachment, which occurs structurally above the Tinos detachment. Our U-Pb zircon age is 14.6 ± 0.2 Ma and two ;40;Ar/;39;Ar hornblende ages are 14.4 ± 0.4 and 13.7 ± 0.4 Ma. ZFT and AFT ages go from 14.4 ± 1.2 to 12.2 ± 1.0 Ma and 12.8 ± 2.4 to 11.9 ± 2.0 Ma. (U-Th)/He ages are from 10.4 ± 0.2 to 9.9 ± 0.2 Ma (zircon) and 11.9 ± 0.5 to 10.0 ± 0.3 Ma (apatite). All ages decrease northeastward in the direction of hanging wall transport on the Livadi detachment and age-distance relationships yield a slip rate of 2.6 (+3.3 / −1.0) km Ma;−1;. This rate is smaller than a published slip rate of 6.5 km Ma;−1; for the Vari detachment, which is another detachment structurally above the Tinos detachment. Because of the different rates and because published ZFT ages from the footwall of the Vari detachment are ∼10 Ma, we propose that the Vari detachment has to be distinguished from the older Livadi detachment. We discuss various models of how the extensional detachments may have evolved and prefer a scenario in which the Vari detachment cut down into the footwall of the Livadi detachment successively exhuming deeper structural units. The thermochronologic ages demonstrate the importance of quantitative data for constraining localization processes during extensional deformation.
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