Low‐angle faults above and below a blueschist belt—Tinos Island, Cyclades, Greece

Abstract

A B S T R A C TNew observations from the Island of Tinos, Greece, allow a better definition of the structural position of the Alpine (Eocene) blueschist belt exposed in the islands of the Aegean Sea. These blueschists, over a significant part of the Aegean sea, are delimited from below by a lowangle thrust fault, while from above they are delimited by a low-angle, normal-type fault which omits a substantial crustal interval. Both underlying and overlying rocks were not affected by the high? metamorphism. The rapid uplift and exhumation of the high? rocks was therefore mainly the result of fault movements rather than erosion and whole-crust uplifting. The low-angle normal fault apparently had a major role in the uplift of the blueschists.TERRA Now (1989) 1, 182-187. tacts. These observations support pre-

Rifting and shallow-dipping detachments, clues from the Corinth Rift and the Aegean

“…Low-angle normal faults have been described in different geological situations including post-orogenic extension, exhumation of HP-LT metamorphic rocks and even intraoceanic rifting (Wernicke, 1981;1995;Lister et al, 1984;Avigad and Garfunkel, 1989;Abers et al, 1997;Axen et al, 1999;Hayman et al, 2003;Collettini and Holdsworth, 2004;Garcès and Gee, 2007). Such low-angle normal faults are often referred to as detachments.…”

The tectono-metamorphic evolution of a dismembered ophiolite (Tinos, Cyclades, Greece)

“…1) (Du'rr et al 1978a;Avigad & Garfunkel, 1989 The tectono-metamorphic evolution of a dismembered ophiolite 239 which underwent regional eclogite-and blueschist-facies metamorphism during the Eocene (Altherr et al 1979;Brocker et al 1993). In most localities, the rocks were fully overprinted by greenschist-facies assemblages at the Oligocene-Miocene boundary Schliestedt, Altherr & Matthews, 1987).…”

“…PhD. thesis), and were ascribed to an Upper tectonic Unit juxtaposed on top of the Alpine high pressure sequences by a low-angle normal fault (Avigad & Garfunkel, 1989. The main aim of this study is to gain a detailed knowledge of the origin and tectono-metamorphic evolution of this unique rock-unit and to interpret its place within the framework of the Alpine orogeny in the Cyclades.…”

“…2). The juxtaposition of the Upper tectonic Unit must have occurred in a relatively narrow time slot, limited on the one hand by the greenschistfacies metamorphic event dated at 23 to 21 Ma (Brocker et al 1993) and by the intrusion of the 18-Ma-old granite (Altherr et al , 1988) that cuts across the tectonic contact between the Lower and Upper units (Avigad & Garfunkel, 1989). The structure of Tinos as seen today was shaped by a Miocene or younger post-metamorphic phase of deformation that acted on all tectono-metamorphic units.…”

Kinematic reconstructions and magmatic evolution illuminating crustal and mantle dynamics of the eastern Mediterranean region since the late Cretaceous

“…Exhumation of these metamorphic units first occurred between 45 and 35-30 Ma in a syn-orogenic context, following a cold retrograde path (figure 5) [Altherr et al, 1979;Bonneau and Kienast, 1982;Avigad and Garfunkel, 1989;Trotet et al, 2001]. These Eocene HP-LT parageneses are particularly well preserved in the Syros and Sifnos islands where syn-orogenic extensional shear zones, such as the Vari detachment in Syros (figure 6), show top-to-the ENE and top-to-the N senses of shear, respectively (figure 3) [Trotet et al, 2001;Keiter et al, 2004;Ring et al, 2011;Roche et al, submitted].…”