Zircons from Syros, Cyclades, Greece--Recrystallization and Mobilization of Zircon During High-Pressure Metamorphism

Tomaschek, Frank; Kennedy, Allen; Villa, Igor M.; Lagos, M.; Ballhaus, Chris

doi:10.1093/petrology/egg067

Cited by 427 publications

(353 citation statements)

References 74 publications

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“…It is a disequilibrium texture, manifest by the replacement of U-Th-Y-rich zircon by U-Th-Y-poor zircon, as well as abundant pores, and Th-U-rich micro-inclusions in some cases. Such disequilibrium textures have been described in zircons from metamorphic rocks (Tomaschek et al 2003;Spandler et al 2004) as well as in pegmatites and granite (Xie et al 2005), and have been reproduced experimentally (Geisler et al 2003;Tomaschek 2004). In all these cases, the texture has been attributed to fluid interaction with zircon.…”

Section: Discussionmentioning

confidence: 75%

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Zircon texture and chemical composition as a guide to magmatic processes and mixing in a granitic environment and coeval volcanic system

Gagnevin

Daly

Kronz

2009

Contrib Mineral Petrol

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This study documents the chemical and textural responses of zircon in the Elba igneous complex, with particular reference to the 7-to 7.8-Ma-old Monte Capanne pluton in relation to its coeval volcanic counterpart (Capraia), using BSE imaging and quantitative electron microprobe analyses. The Monte Capanne pluton displays multiple field and geochemical evidence for magma mixing. The samples we have investigated (including monzogranitic, mafic enclave and dyke samples) display similar zircon textures and are associated with an extremely large range of trace and minor element (Hf, Y, HREE, Th, U) compositions, which contrast with relatively simple textures and zoning patterns in zircons from a Capraia dacite. We have used a relatively simple textural classification (patchy zoning, homogenous cores, oscillatory zoning and unzoned zircon) as the basis for discussing the chemical composition and chemical variation within zircons from the Monte Capanne pluton. Based on these data and other works in Lithos 78:101-118, 2004 , it is inferred that mixing between metaluminous and peraluminous melts occurred early in the evolution of the Monte Capanne magma chamber. In particular, mixing was responsible for the development of the patchy-zoning texture in the zircon cores, which was associated with reactions between other accessory phases (including monazite, apatite, allanite), which we infer to have significantly affected the Th distribution in zircon. Zircons from the MC pluton displaying ''homogeneous cores'' have chemical affinities with zircons in the coeval Capraia volcanic system, consistent with the participation of a Capraia-like mantle end-member during mixing. Further zircon growth in the MC pluton produced the oscillatory zoning texture, which records both long-term (crystal fractionation) and transient (recharge with both silicic and mafic magmas) events in a hybrid magma chamber. It is inferred that Hf and the Th/U ratio cannot be used alone to infer magmatic processes due to their dependency on temperature, nor are they a diagnostic feature of xenocrystic grains. This study shows that zircon chemistry coupled with detailed textural analysis can provide a powerful tool to elucidate the complex evolution of a magma system.

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Section: Discussionmentioning

confidence: 75%

“…Putnis 2002). Micrometer-sized pores, which may be a criterion for such a reaction (Tomaschek et al 2003), result from differences in the molar volume between the parent zircon and the reprecipitated zircon. Such pores enhance exchange of elements during dissolution by creating a pathway from the reaction front (Geisler et al 2007).…”

Section: Discussionmentioning

confidence: 99%

Zircon texture and chemical composition as a guide to magmatic processes and mixing in a granitic environment and coeval volcanic system

Gagnevin

Daly

Kronz

2009

Contrib Mineral Petrol

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“…~15-20 kbar, ~500 °C) whose metamorphic peak is dated at ~50 Ma, forming the Cycladic Blueschists unit and the Cycladic basement [Bonneau and Kienast, 1982;Bonneau, 1984;Wijbrans and McDougall, 1988;Tomaschek et al, 2003;Lagos et al, 2007]. 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].…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…The latter was partly accreted to the Pelagonian nappe contributing to the building of the Hellenides, while its buried part underwent early Eocene HP-LT metamorphism recorded in the Cycladic Blueschists unit and the Cycladic basement [Bonneau and Kienast, 1982;Bonneau, 1984;Wijbrans and McDougall, 1988;Tomaschek et al, 2003;Lagos et al, 2007]. These units were then progressively exhumed up to the end of the Eocene in the Cyclades and in the Olympos, Ossa and Pelion tectonic windows as a synorogenic extrusion wedge bounded by the Vari detachment on top (in Syros) and the SCSZ at the base (in Ios) (figure 9) Ring et al, , 2010Brun and Faccenna, 2008;Huet et al, 2009;Jolivet and Brun, 2010].…”

Section: A Continuous Subduction Migrating Southwardmentioning

confidence: 99%

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

2016

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“…For new metamorphic zircon to form in hightemperature (HT) metamorphic rocks, either the presence of a hydrous fluid or melt phase is required (e.g. Watson and Harrison 1983;Fraser et al 1997;Tomaschek et al 2003;Tichomirowa et al 2005). In the absence of fluids, metamorphic zircon may form via solid-state (partial) recrystallisation (e.g.…”

Section: Introductionmentioning

confidence: 99%

Zircon ages in granulite facies rocks: decoupling from geochemistry above 850 °C?

Kunz

Regis

Engi

2018

Contrib Mineral Petrol

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Granulite facies rocks frequently show a large spread in their zircon ages, the interpretation of which raises questions: Has the isotopic system been disturbed? By what process(es) and conditions did the alteration occur? Can the dates be regarded as real ages, reflecting several growth episodes? Furthermore, under some circumstances of (ultra-)high-temperature metamorphism, decoupling of zircon U-Pb dates from their trace element geochemistry has been reported. Understanding these processes is crucial to help interpret such dates in the context of the P-T history. Our study presents evidence for decoupling in zircon from the highest grade metapelites (> 850 °C) taken along a continuous high-temperature metamorphic field gradient in the Ivrea Zone (NW Italy). These rocks represent a well-characterised segment of Permian lower continental crust with a protracted high-temperature history. Cathodoluminescence images reveal that zircons in the mid-amphibolite facies preserve mainly detrital cores with narrow overgrowths. In the upper amphibolite and granulite facies, preserved detrital cores decrease and metamorphic zircon increases in quantity. Across all samples we document a sequence of four rim generations based on textures. U-Pb dates, Th/U ratios and Ti-in-zircon concentrations show an essentially continuous evolution with increasing metamorphic grade, except in the samples from the granulite facies, which display significant scatter in age and chemistry. We associate the observed decoupling of zircon systematics in high-grade non-metamict zircon with disturbance processes related to differences in behaviour of non-formula elements (i.e. Pb, Th, U, Ti) at high-temperature conditions, notably differences in compatibility within the crystal structure.

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Zircons from Syros, Cyclades, Greece--Recrystallization and Mobilization of Zircon During High-Pressure Metamorphism

Cited by 427 publications

References 74 publications

Zircon texture and chemical composition as a guide to magmatic processes and mixing in a granitic environment and coeval volcanic system

Zircon texture and chemical composition as a guide to magmatic processes and mixing in a granitic environment and coeval volcanic system

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

Zircon ages in granulite facies rocks: decoupling from geochemistry above 850 °C?

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