Nanoscale evidence for uranium mobility in zircon and the discordance of U–Pb chronometers

Seydoux‐Guillaume, Anne‐Magali; Bingen, Bernard; Paquette, Jean‐Louis; Bosse, Valérie

doi:10.1016/j.epsl.2014.10.044

Cited by 37 publications

(15 citation statements)

References 36 publications

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“…The cryptocrystalline-microporous nature of metamict and recrystallized zircon grain #1 in Charlevoix melt rock sample SI-1 (Fig. 3) may have facilitated preferential diffusive Pb loss and U-Th-Pb chronometric resetting (Seydoux-Guillaume et al 2015) during the Charlevoix impact (i.e., a high-temperature and high-shock pressure but short-duration thermal event) while being largely unaffected by the later (Acadian?) tectonometamorphic episode revealed by 40 Ar/ 39 Ar ages of~370-400 Ma obtained from the same melt rock sample (Buchner et al 2010.…”

Section: Discussionmentioning

confidence: 99%

In situ U–Pb analysis of shocked zircon from the Charlevoix impact structure, Québec, Canada

Schmieder

Shaulis

Lapen

et al. 2019

Meteorit & Planetary Scien

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Laser ablation inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) U–Pb geochronology of shocked zircon grains in a vesicular‐fluidal impact melt rock from the ≥54 km Charlevoix impact structure, Québec, Canada, suggests an Ordovician to Silurian age of 450 ± 20 Ma for the impact. This age is anchored by concordant U–Pb results of ~450 Ma for a U‐rich, cryptocrystalline zircon grain in the melt rock, interpreted as a recrystallized metamict zircon crystal; the U–Th–Pb system of the metamict grain was seemingly chronometrically reset by the Charlevoix impact, but withstood later tectonometamorphic events. The new zircon age for Charlevoix is in agreement with a stratigraphically constrained Late Ordovician maximum age of ~453 Ma and corroborates earlier suggestions that the impact occurred most likely in the Ordovician, and not ~100 Myr later, as indicated by previous K/Ar and 40Ar/39Ar geochronologic results. The latter may reflect postimpact thermal overprint of impactites during the Salinian (Late Silurian to Early Devonian) and/or Acadian (Late Devonian) orogenies. U–Pb geochronology of zircon crystals in anorthosite exposed in the central uplift of the impact structure yielded a Grenvillian crystallization age of 1062 ± 11 Ma. The preferred Ordovician age for the Charlevoix impact structure, which is partially overthrusted by the Appalachian front, suggests the impact occurred during a phase of Taconian tectonism and an episode of enhanced asteroid bombardment of the Earth. Our results, moreover, demonstrate that (recrystallized) metamict zircon grains may be of particular interest in impact geochronology.

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Section: Discussionmentioning

confidence: 99%

In situ U–Pb analysis of shocked zircon from the Charlevoix impact structure, Québec, Canada

Schmieder

Shaulis

Lapen

et al. 2019

Meteorit & Planetary Scien

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“…These zircons were not significantly affected by the eclogite-facies metamorphism. On the contrary, metamict zircons display a highly damaged crystal lattice and thereby do not behave any longer as a closed system, allowing fluids to strongly interact with the grains (Seydoux-Guillaume et al, 2015). In favourable cases, temperature and maybe pressure may also trigger such complex behaviour, but temperature alone cannot reset the U-Pb system even in very high temperature metamorphic facies (Paquette et al, 2004).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

From opening to subduction of an oceanic domain constrained by LA-ICP-MS U-Pb zircon dating (Variscan belt, Southern Armorican Massif, France)

Paquette

Ballèvre

Peucat

et al. 2017

Lithos

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International audienceIn the Variscan belt of Western Europe, the lifetime and evolution of the oceanic domain is poorly constrained by sparse, outdated and unreliable multigrain ID-TIMS U-Pb zircon dating. In this article, we present a complete in situ LA-ICP-MS dataset of about 300 U-Pb zircon analyses obtained on most of the ophiolitic and eclogitic outcrops of Southern Brittany, comprising new dating of previously published zircon populations and newly discovered rock samples. In situ dating and cathodo-luminescence imaging of each zircon grain yields new absolute time-constraints on the evolution of the Galicia-Moldanubian Ocean. The new results confirm that the opening of this oceanic domain is well defined at about 490 Ma. In contrast, the generally-quoted 400-410 Ma-age for the high-pressure event related to the subduction of the oceanic crust is definitely not recorded in the zircons of the eclogites. In light of these new data, we propose that the obduction of oceanic rocks occurred at about 370-380 Ma while the high-pressure event is recorded at 355 Ma in only a few zircon grains of some eclogite samples.Additionally, this large scale dating project demonstrates that the zircons from eclogites do not systematically recrystallise during the high pressure event and consequently their U-Pb systems do not record that metamorphism systematically. These zircons rather preserve the isotopic memory of the magmatic crystallization of their igneous protolith. Another example of an eclogite sample from the French Massif Central illustrates the frequent mistake in the interpretation of the ages of the early hydrothermal alteration of zircons in the oceanic crust versus partial or complete recrystallization during eclogite facies metamorphism

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“…The effect of metamictisation on the U-Pb systematics of zircon is well known (Mezger & Krogstad, 1997). It includes components of radiogenic Pb loss, incorporation of non formula elements like Ca and common Pb, and mobility of U at low temperature (Nasdala et al, 2010;Seydoux-Guillaume et al, 2015). The lower intercept ages in Finnmarksvidda are thus interpreted as a result of radiogenic Pb loss in zircon that did accummulate radiation damage between the Palaeoproterozoic and Phanerozoic.…”

Section: Caledonian U-pb Lower Intercept Agesmentioning

confidence: 99%

Geochronology of the Palaeoproterozoic Kautokeino Greenstone Belt, Finnmark, Norway: Tectonic implications in a Fennoscandia context

Bingen¹,

Solli²,

Viola³

et al. 2016

NJG

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Nanoscale evidence for uranium mobility in zircon and the discordance of U–Pb chronometers

Cited by 37 publications

References 36 publications

In situ U–Pb analysis of shocked zircon from the Charlevoix impact structure, Québec, Canada

In situ U–Pb analysis of shocked zircon from the Charlevoix impact structure, Québec, Canada

From opening to subduction of an oceanic domain constrained by LA-ICP-MS U-Pb zircon dating (Variscan belt, Southern Armorican Massif, France)

Geochronology of the Palaeoproterozoic Kautokeino Greenstone Belt, Finnmark, Norway: Tectonic implications in a Fennoscandia context

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