Calcite pseudomorphs after aragonite: A tool to unravel the structural history of high-pressure marbles (Evia Island, Greece)

Gerogiannis, Nikolaos; Aravadinou, E.; Chatzaras, Vasileios; Xypolias, P.

doi:10.1016/j.jsg.2021.104373

Cited by 15 publications

(26 citation statements)

References 67 publications

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“…Even though imbrication has interesting implications for the CBU's structural history, the present tectonic model of progressive subduction, underplating, and return flow is supported by our data (particularly by the compiled metamorphic geochronology) whether or not the central section is imbricated. Evidence for syn‐subduction imbrication has been documented elsewhere in the Cyclades, for example on Evia where lower marbles were thrust over the upper marble sequence during prograde, top‐to‐the‐SE shearing (Gerogiannis et al., 2021); on NE Sikinos and Ios islands where several old‐on‐young inversions occur throughout the meta‐sedimentary strata near the CBU‐Cycladic Basement contact (Poulaki et al., 2019); and on Milos (Grasemann et al., 2018). Therefore, if syn‐subduction tectonostratigraphic repetition is confirmed on Syros, imbrication may be a common and/or recurring process during Eo‐Oligocene subduction across the Cyclades.…”

Section: A Revised Tectonic Model For the Cbu On Syrosmentioning

confidence: 97%

Subduction, Underplating, and Return Flow Recorded in the Cycladic Blueschist Unit Exposed on Syros, Greece

et al. 2022

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Exhumed high‐pressure/low‐temperature (HP/LT) metamorphic rocks provide insights into deep (∼20–70 km) subduction interface dynamics. On Syros Island (Cyclades, Greece), the Cycladic Blueschist Unit preserves blueschist‐to‐eclogite facies oceanic‐ and continental‐affinity rocks that record the structural and thermal evolution linked to Eocene subduction. Despite decades of research, the metamorphic and deformation history (P‐T‐D) and timing of subduction and exhumation are matters of ongoing discussion. We suggest that Syros comprises three coherent tectonic slices and that each slice underwent subduction, underplating, and syn‐subduction return flow along similar P‐T trajectories, but at progressively younger times. Subduction and exhumation are distinguished by lineations and ductile fold axis orientations, and are kinematically consistent with previous studies that document top‐to‐the‐S‐SW shear (prograde‐to‐peak subduction), top‐to‐the‐NE shear (blueschist facies exhumation), and then E‐W coaxial stretching (greenschist facies exhumation). Amphibole zonations record cooling during decompression, indicating return flow above a cold slab. Multi‐mineral Rb‐Sr isochrons and compiled metamorphic geochronology show that the three slices record distinct stages of peak subduction (53–52, ∼50, and 45 Ma) that young with structural depth. Retrograde blueschist and greenschist facies fabrics span ∼50–40 and ∼43–20 Ma, respectively, and also young with structural depth. Synthesized data sets support a revised tectonic framework for Syros, involving subduction of structurally distinct coherent slices and simultaneous return flow of previously accreted tectonic slices in the subduction channel shear zone. Distributed, ductile, dominantly coaxial return flow in an Eocene‐Oligocene subduction channel proceeded at rates of ∼1.5–5 mm/yr and accommodated ∼80% of the total exhumation of this HP/LT complex.

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Section: A Revised Tectonic Model For the Cbu On Syrosmentioning

confidence: 97%

Subduction, Underplating, and Return Flow Recorded in the Cycladic Blueschist Unit Exposed on Syros, Greece

et al. 2022

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“…Subsequent extensional reactivation of the Basal Thrust was reported by Ring, Glodny, et al. (2007), but data presented thus far seemingly indicate that this event contributed only marginally to the tectonic evolution of the island (Gerogiannis et al., 2021; Ring, Glodny, et al., 2007).…”

Section: Tectonic Settingmentioning

confidence: 93%

“…At least three distinct phases of ductile deformation may therefore be discriminated within the CBU, relating respectively to subduction, syn‐orogenic exhumation, and post‐orogenic extension. The first two are represented largely by distributed ductile strain yielding complex isoclinal folds and mylonites, as well as subduction‐related structures like the intra‐CBU Trans‐Cycladic Thrust (Figure 1; Grasemann et al., 2018; Wind et al., 2020) or the Basal Thrust/Cyclades‐Menderes Thrust dividing the CBU and Basal Unit (Gerogiannis et al., 2021; Gessner et al., 2001). Although some central segments of the detachment systems record distributed deformation in the footwall (Grasemann et al., 2012; Jolivet, Lecomte, et al., 2010), deformation associated with post‐orogenic extension was comparatively localized, controlled by low‐angle detachments exposed on many Cycladic islands (e.g., Gautier & Brun, 1994; Jolivet et al., 2004).…”

Section: Tectonic Settingmentioning

confidence: 99%

“…Olympos, Evia, and Samos, and contains evidence for overprinted HP‐LT metamorphic assemblages of alleged Oligocene to early Miocene age (Gerogiannis et al., 2021; Ring et al., 2001, Ring, Glodny, et al., 2007; Schermer, 1989; Shaked et al., 2000). Thrusting of the CBU atop the Basal Unit is inferred from paleogeographic correlations and the consistent tectonostratigraphic relationship between the units (e.g., Gerogiannis et al., 2021; Xypolias et al., 2003). Little is known directly of the conditions and timing of underthrusting and subsequent exhumation of the Basal Unit.…”

Section: Tectonic Settingmentioning

confidence: 99%

“…Along with Ios and Sikinos, southern Evia is one of a select few localities where structural levels below the CBU are exposed (e.g., Avigad et al., 1997). Accordingly, Evia has frequently been targeted to understand the convergent phases of orogenesis related to nappe stacking (e.g., Gerogiannis et al., 2021; Ring, Glodny, et al., 2007). The record of Oligo‐Miocene exhumation on Evia has received comparatively little attention, despite the island occupying the footwall to the North Cycladic Detachment System (NCDS; Jolivet, Lecomte, et al., 2010; Figure 1).…”

Section: Introductionmentioning

confidence: 99%

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Stretched Thin: Oligocene Extrusion and Ductile Thinning of the Basal Unit Along the Evia Shear Zone, NW Cyclades, Greece

et al. 2022

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Subduction–exhumation cycle recorded by calcite deformation microstructures: blueschist-facies metacarbonates and kinematic implications for deformation of the Meliata Unit (Western Carpathians)

Potočný,

Jeřábek,

Plašienka

2023

Int J Earth Sci (Geol Rundsch)

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The Meliata Unit (Meliaticum) is a tectonic superunit of the Western Carpathians that incorporates the blueschists-facies Bôrka Nappe and the low-grade metasediments and polygenetic mélange, Meliata Unit s.s., both occurring as scattered tectonic slices overlying the Gemeric Superunit. Calcitic marbles were sampled in a wide area within the Bôrka Nappe and blocks embedded in Jurassic oceanic sediments (Meliata Unit s.s.). Based on the microstructural evaluation and electron backscatter diffraction analysis (EBSD), the carbonates of the Bôrka Nappe experienced differential post-subduction P–T–D paths related to a collisional/exhumation setting following closure of the Neotethys-related “Meliata Ocean”. Variations in the calcite deformation microstructures were used to distinguish three principal microstructural groups. The first group (G1) contains large columnar and lobate calcite grains (≥ 1 mm) reflecting peak P–T conditions during subduction of the Meliata oceanic lithosphere. The second group (G2) exhibits dynamic recrystallization of the original G1 grains resulting in grain size reduction (< 0.5 mm) and shape-preferred orientation related to exhumation and formation of the accretionary complex. The third group (G3) shows a ‘foam’ microstructure with a uniform grain size (0.4–1 mm), sharp grain boundaries and triple junctions. The G3 microstructure may have been caused by a static recrystallization at elevated temperatures postdating the main deformation, and it is restricted to peripheries of the underlying Veporic metamorphic dome and probably is not associated with the Meliata sequences nor its tectono-metamorphic evolution. The corrected kinematic sections indicate dominantly ESE–WNW-trending lineations suggesting top-to-WNW kinematics of the Meliata subduction–exhumation process for G1 and G2 microstructures, and Gemeric–Veporic E–W orogen-parallel stretching for G3.

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Calcite pseudomorphs after aragonite: A tool to unravel the structural history of high-pressure marbles (Evia Island, Greece)

Cited by 15 publications

References 67 publications

Subduction, Underplating, and Return Flow Recorded in the Cycladic Blueschist Unit Exposed on Syros, Greece

Subduction, Underplating, and Return Flow Recorded in the Cycladic Blueschist Unit Exposed on Syros, Greece

Stretched Thin: Oligocene Extrusion and Ductile Thinning of the Basal Unit Along the Evia Shear Zone, NW Cyclades, Greece

Subduction–exhumation cycle recorded by calcite deformation microstructures: blueschist-facies metacarbonates and kinematic implications for deformation of the Meliata Unit (Western Carpathians)

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