Detrital zircon and micropalaeontological ages as new constraints for the lowermost tectonic unit (Talea Ori unit) of Crete, Greece

Kock, Stéphane; Martini, Rossana; Reischmann, T.; Stampfli, Gérard M.

doi:10.1016/j.palaeo.2006.08.006

Cited by 21 publications

(58 citation statements)

References 36 publications

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“…The first scenario is also inconsistent with a lack of Ordovician‐Devonian magmatic rocks or coeval detrital zircon population over the northern margin of modern Africa, in the External Hellenides (Chatzaras et al, ; Dörr et al, ; Kock et al, ; Kydonakis et al, ; Zulauf et al, ) and the Pelagonian terrane (Zlatkin et al, ), which represent the Gondwanan margin fringed by terranes of the External domain (Figures , a, and b).…”

Section: Phases Of Accretion Of Peri‐gondwanan Terranes To Laurussiamentioning

confidence: 99%

New Detrital Zircon Geochronology From the Cycladic Basement (Greece): Implications for the Paleozoic Accretion of Peri‐Gondwanan Terranes to Laurussia

2018

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Between the eastern Mediterranean basin in the South and the East European (Baltica) Craton to the north, we distinguish two fundamental pre‐Variscan geological domains: an Internal domain, which hosts Ordovician‐Devonian (450–400 Ma) igneous rocks and detrital zircon populations, and an External domain, which contains no 450‐ to 400‐Ma zircon ages. From the Balkan Peninsula to the Turkish plate, the aforementioned Internal domain includes the Serbo‐Macedonian Massif, the Istanbul and Sakarya terranes, whereas the External domain, holding a more distal position relative to Baltica, includes the Pelagonian terrane and the External Hellenides. The two domains are interpreted as two consecutive (i.e., Caledonian and Variscan) Paleozoic accretionary belts, attached to the southern margin of Baltica. The Cycladic and Pelagonian terranes are currently juxtaposed along strike of the central Hellenides in Northern Greece. The Cycladic Massif is a Cadomian‐type terrane, while the Pelagonian displays an Avalonian‐type affinity. Despite its Avalonian affinity, the Pelagonian lacks Ordovician‐Devonian (450–400‐Ma) zircon ages. In contrast, detrital zircon grains of such ages are abundant in the Cycladic Massif. In this study, the Ordovician‐Devonian detrital zircon population is recognized also in pre‐Variscan (>310‐Ma) Cycladic Basement from Ios and Naxos Islands, affiliating the Cycladic Massif with the Internal (Caledonian) domain. This indicates that the Caledonian accretion incorporated some Cadomian‐type terranes. It also suggests that the protolith of the Cycladic blueschists was deposited within the Internal domain, that is, northeast of the Pelagonian terrane. This recognition helps to reconstruct the Paleozoic and Mesozoic paleogeography of the peri‐Gondwanan terranes.

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Section: Phases Of Accretion Of Peri‐gondwanan Terranes To Laurussiamentioning

confidence: 99%

New Detrital Zircon Geochronology From the Cycladic Basement (Greece): Implications for the Paleozoic Accretion of Peri‐Gondwanan Terranes to Laurussia

2018

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“…1). There, the Late Carboniferous/ Early Permian to Oligocene metasediments of the Talea Ori group, are tectonically overlain by the Phyllite-quartzite unit (e.g., Epting et al 1972;Kuss and Thorbecke 1974;Creutzburg and Seidel 1975;Jacobshagen et al 1978;König and Kuss 1980;Bonneau 1984;Jacobshagen et al 1986;Kock et al 2007;Robertson 2012;Zulauf et al 2016). The Talea Ori group comprises characteristic platy marbles with cherts (Plattenkalk sensu stricto) at the top, which are correlated to other outcrops of similar Plattenkalk-chert associations on Crete and the Peloponnesus (Kuss and Thorbecke 1974;Jacobshagen et al 1978;Soujon et al 1998).…”

Section: Regional Geologymentioning

confidence: 99%

A ductile extensional shear zone at the contact area between HP-LT metamorphic units in the Talea Ori, central Crete, Greece: deformation during early stages of exhumation from peak metamorphic conditions

Seybold

Trepmann

Janots

2018

Int J Earth Sci (Geol Rundsch)

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We report on an extensional ductile shear zone in central Crete at the contact area between the high-pressure low-temperature (HP-LT) metamorphic Phyllite-Quartzite unit sensu stricto (PQ s.str.) and the Talea Ori group (Plattenkalk unit). Mapping and microscopic analysis along the 20 km long contact reveal extensional shear bands, shear band cleavages (C′-type) and associated quartz veins in both units, occurring over a width of up to a kilometer. The shear offset along the shear bands is systematically perpendicular to the contact with the hanging block (PQ s.str.) being downfaulted. Abundant discordant quartz veins are associated to shear band boundaries, asymmetric boudinage and foliation boudinage, forming m-wide vein networks. These mesoscopic deformation structures together with related microstructures such as strain shadows, growth rims of albite porphyroblasts and stylolites indicate dissolution-precipitation creep as main deformation mechanism accompanied by vein formation. Temperatures during deformation are indicated to be close to peak metamorphic temperatures (≥ 300-350 °C) by the growth rims of albite porphyroblasts and micas present in the shear band cleavages, which are consistent with quartz vein microstructures showing subgrains and sutured high angle grain boundaries. Peak metamorphic temperatures inferred by the degree of graphitization of carbonaceous material are similar in the hanging wall and the footwall of the shear zone, which is consistent with fast and nearly adiabatic exhumation. Our study demonstrates the importance of ductile shear zones with high strain rate dissolution-precipitation creep and vein formation in HP-LT metamorphic rocks for the early exhumation history.

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“…In grain-size data from image analysis of dated zircons presented by Sircombe et al (2001), there is a weak but statistically signifi cant correlation between age and grain-size parameters (younger grains tend to be longer or have greater values for width × length). In Kock et al (2007), Proterozoic grains are all <200 µm long, whereas Phanerozoic grains range up to 380 µm. Clearly, zircon age populations commonly have different characteristic size ranges.…”

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confidence: 99%

Hydrodynamic fractionation of zircon age populations

Lawrence

Cox

Mapes

et al. 2010

Geological Society of America Bulletin

124

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Zircons in transport in the modern Amazon River range from coarse silt to medium sand. Older grains are smaller on average: Mesozoic and Cenozoic grains have average equivalent spherical diameter (ESD) 122 ± 42 µm (lower fi ne sand), whereas grains >2000 Ma have average ESD 67 ± 14 µm (upper coarse silt). As a full Wentworth size class separates the two values, zircons in these age populations are hydraulically distinct.Host sand size is correlated with average size of co-transported zircons, implying hydrodynamic fractionation. Zircon size is positively correlated with percent medium sand, and inversely correlated with percent very fi ne sand (p <0.0001 in both cases). In samples with >50% medium sand, average zircon size is 100 µm, compared with 80 µm in samples with >50% very fi ne sand. We infer from these data that zircon deposition is not size-blind, and that zircons track with hydraulically comparable sand grains. As different aged grains tend to have different characteristic sizes, this indicates the possibility of hydrodynamic fractionation of age populations.Five samples representing different hydrodynamic microenvironments of a single dune present signifi cantly different detrital zircon age spectra, apparently the result of hydraulic processes. Peak mismatch (age peaks failing to overlap at 2σ level) is the most common disparity; but age populations present in some samples are missing from other samples. The lack of correspondence among the samples appears to exceed that attributable to random sampling. We conclude that hydrodynamic fractionation of zircons and zircon-age populations does occur. Zircon size should therefore be taken into consideration in detrital zircon provenance analysis.

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Detrital zircon and micropalaeontological ages as new constraints for the lowermost tectonic unit (Talea Ori unit) of Crete, Greece

Cited by 21 publications

References 36 publications

New Detrital Zircon Geochronology From the Cycladic Basement (Greece): Implications for the Paleozoic Accretion of Peri‐Gondwanan Terranes to Laurussia

New Detrital Zircon Geochronology From the Cycladic Basement (Greece): Implications for the Paleozoic Accretion of Peri‐Gondwanan Terranes to Laurussia

A ductile extensional shear zone at the contact area between HP-LT metamorphic units in the Talea Ori, central Crete, Greece: deformation during early stages of exhumation from peak metamorphic conditions

Hydrodynamic fractionation of zircon age populations

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