Internal morphology, habit and U-Th-Pb microanalysis of amphibolite-to-granulite facies zircons: geochronology of the Ivrea Zone (Southern Alps)

Vavra, G.; Schmid, R.; Gebauer, D.

doi:10.1007/s004100050492

Cited by 836 publications

(466 citation statements)

References 35 publications

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“…분석된 U-Pb 겉보기 연령은 약 302±5 Ma 에서 2,536±15 Ma까지 넓은 범위의 연령 분포를 나 타내지만, 대부분 일치곡선상에 도시된다 (Fig. 4a) (Vavra et al, 1999;Hartman et al, 2000). Errors are 1-sigma; Pb c and Pb* indicate the common and radiogenic portions, respectively.…”

Section: 최성자·김동연·조등룡·김유봉unclassified

Detrital zircon U-Pb Ages of the Metapelite on the Southwestern Part of the Ogcheon Belt and Its Stratigraphical Implication

Choi¹,

Kim²,

Cho³

et al. 2015

The Journal of the Petrological Society of Korea

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Abstract:We investigated the zircon U-Pb ages of the metapelites from the Sungjeon-myeon Gangjin-gun, the southwestern Ogcheon belt, to provide geochronological constraints for the depositional age as well as the distribution of Late Paleozoic formation. Data from the detrital zircons are mostly concordant, yielding four major age groups: (1) Neoarchean (~2.5 Ga); (2) Paleoproterozoic (~1.86 Ga, Statherian); (3) Middle Devonian(~390 Ma); and (4) Late Paleozoic (~322 Ma, Serpukhobian). The youngest zircon age gives a weighted mean 206 Pb/ 238 U age of 322±4.8 Ma (n=16, MSWD=4.9), indicating deposition age of Early Carboniferous(Serpukhobian) or after. Therefore, the metapelites is considered to be the lowest Formation of the late Paleozoic Pyeongan Supergroup correlated with the Manhang Formation of the Samcheock coal fields and the Oeumri Formation(the Middle to Late Carboniferous) of the Hwasun coal field.

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Section: 최성자·김동연·조등룡·김유봉unclassified

Detrital zircon U-Pb Ages of the Metapelite on the Southwestern Part of the Ogcheon Belt and Its Stratigraphical Implication

Choi¹,

Kim²,

Cho³

et al. 2015

The Journal of the Petrological Society of Korea

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“…However, the range of HT metamorphic zircon dates (316-258 Ma; e.g. Vavra et al 1999;Ewing et al 2013) exceeds the range of magmatic zircon (315-280 Ma, e.g. Peressini et al 2007;Klötzli et al 2014) by about 20 Myr.…”

Section: Geological Settingmentioning

confidence: 99%

“…Roberts and Finger 1997;Vavra et al 1999;Schaltegger et al 1999;Hoskin and Black 2000;Rubatto et al 2001Rubatto et al , 2006Williams 2001;Rubatto 2002;Hermann and Rubatto 2003;Möller et al 2003;Tomaschek et al 2003;McFarlane et al 2005McFarlane et al , 2006Vonlanthen et al 2012;Vorhies et al 2013). Recent studies have improved our understanding of how to interpret metamorphic zircon in the context of the P-T evolution of rocks by modelling zircon growth during metamorphism (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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“…In fact, these kind of metamorphic zircons with higher Th/U ratios have been observed in many high-grade metamorphic rocks (e.g. granulites and eclogites) (Vavra et al, 1999;Zhai et al, 2011b;Rubatto and Hermann, 2003;Rubatto et al, 1999) and are generally interpreted as the result of the kinetically fast and chemically less selective continuous growth mechanism (Vavra et al, 1999) or the effect of fluid (Rubatto and Hermann, 2003;Rubatto et al, 1999).…”

Section: Metamorphic Evolution Of the Qiangtang Hp Basic Granulitementioning

confidence: 99%

Silurian high-pressure granulites from Central Qiangtang, Tibet: Constraints on early Paleozoic collision along the northeastern margin of Gondwana

Zhang

Dong

Cai

et al. 2014

Earth and Planetary Science Letters

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Internal morphology, habit and U-Th-Pb microanalysis of amphibolite-to-granulite facies zircons: geochronology of the Ivrea Zone (Southern Alps)

Cited by 836 publications

References 35 publications

Detrital zircon U-Pb Ages of the Metapelite on the Southwestern Part of the Ogcheon Belt and Its Stratigraphical Implication

Detrital zircon U-Pb Ages of the Metapelite on the Southwestern Part of the Ogcheon Belt and Its Stratigraphical Implication

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

Silurian high-pressure granulites from Central Qiangtang, Tibet: Constraints on early Paleozoic collision along the northeastern margin of Gondwana

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