Structures, flow stresses, and estimated strain rates in metamorphic rocks of the Small Cyclades Islands Iraklia and Schinoussa (Aegean Sea, Greece).

Behrmann, Jan Hinrich and Seckel, Claudia (2007) Structures, flow stresses, and estimated strain rates in metamorphic rocks of the Small Cyclades Islands Iraklia and Schinoussa (Aegean Sea, Greece). Geotectonic Research, 95 (1). pp. 1-11. DOI 10.1127/1864-5658/07/0095-0001 .

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Like the larger Cyclades Islands (e.g. Naxos, Paros, Ios) the Small Cyclades Islands form part of the Attic-Cycladic crystalline basement belt. Subduction in the Paleogene was associated with high-pressure metamorphism, followed by a Barroviantype overprint, local partial melting and granitic plutonism in the Neogene. On the islands of Iraklia and Schinoussa Neogene metamorphism did not exceed mid-greenschist grade, and there are some well preserved older high-pressure/low temperature metamorphic assemblages. The rocks and structural geology of both islands had previously not been analysed in detail. Rocks present are calcite and dolomite marbles, in part with preserved paleosoils (metabauxites and metalaterites), and a suite of metapelitic schists with associated glaucophane schists and piemontite quartzites. There is a ductile deformation history comprising four events. The two older ones (D1, D2) are associated with high strains, and have resulted in a subhorizontal foliation, a N-S trending stretching lineation, and recumbent isoclinal folds with variable axial orientations. At least D1 is bracketed by the growth of glaucophane, with uncertain kinematics. D2, syn-blueschist grade on Iraklia, however, has a clear top-to-north sense of shear. D3 and D4 caused upright folds with N-S and E-W trending fold axes, respectively. This is evidence for late, two-phase horizontal shortening. As the deformed rocks show only a slight static metamorphic overprint, we have estimated flow stresses from dynamically recrystallized grain sizes of quartz and calcite. Coincident flow stress estimates are 28-62 MPa in quartzites, and 31-56 MPa in the marbles. Together with syntectonic temperature extimates, and applying published flow laws, this leads to estimated deformation rates on the order of 10−12 to 10−14 sec−1. Even though deformation history and kinematics is very similar to that on Naxos Island, the clear relation of the earlier part to high-pressure metamorphism on Iraklia and Schinoussa speaks in favour of a subduction-related setting here. This is in contrast to the later formation of metamorphic core complexes in the north (Naxos) and south (Ios).

Document Type: Article
Keywords: Metamorphic rocks, Iraklia Island, Schinoussa Island, Small Cyclades Islands, Aegean Sea, Greece
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1127/1864-5658/07/0095-0001
ISSN: 1864-5658
Date Deposited: 16 Feb 2010 11:53
Last Modified: 24 Jul 2017 09:42

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