Mizera, Marcel and Behrmann, Jan H. (2016) Strain and flow in the metamorphic core complex of Ios Island (Cyclades, Greece). International Journal of Earth Sciences, 105 (7). pp. 2097-2110. DOI 10.1007/s00531-015-1259-y.

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Abstract

We have analysed strain and flow kinematics in the footwall of the South Cyclades Shear Zone (SCSZ), an important tectonic boundary within the Attic-Cycladic Crystalline Complex exposed on Ios Island, Cyclades, Aegean Sea. Coarse-grained augen gneisses in the basement unit flooring the SCSZ and forming a metamorphic core complex are excellently suited to measure finite strain using the Fry method and estimate the vorticity number (Wk) of flow with the “blocked-object” method. The results show that Oligo-Miocene exhumation of the basement unit during extension brought approximately 70 % N–S crustal stretching and up to 40 % subvertical shortening in a plane strain environment (k = 0.99). Linear down-section strain decrease constrains a zone of contact deformation of the SCSZ of about 1.5 km thick. Kinematic vorticity number estimates suggest little deviation from pure shear (Wk = 0.26). Finite strain and Wk are not correlated, indicating that the Ios basement and the overlying cover units were stretched compatibly. While the SCSZ is a localized zone of high strain, net displacement, however, may be restricted to about ten kilometres. This has important repercussions on large-scale tectonic models for extension in the Aegean.

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