Partial resetting of the U-Th-Pb systems in experimentally altered monazite: Nanoscale evidence of incomplete replacement

Grand'Homme, Alexis; Janots, Émilie; Seydoux‐Guillaume, Anne‐Magali; Guillaume, Damien; Bosse, Valérie; Magnin, Valérie

doi:10.1130/g37770.1

Cited by 97 publications

(46 citation statements)

References 22 publications

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“…Let y be I UMβ (obs)/I ThMα (net), and let x be I UMβ (obs). Then, the regression line for Cooma Granodiorite monazites is given by: When DL UMβ = 0.0807 is substituted for x, we have f ThMγ = 0.00626, similar to values obtained in previous studies (e.g., Suzuki and Kato, 2008;Grand'Homme et al, 2016;Jercinovic and Williams, 2005). The error margin of the inclination is ±0.0049 and that of the intercept is ±0.0049.…”

Section: Introductionsupporting

confidence: 60%

CHIME monazite dating: Pb analysis on an R<sub>R</sub> = 100 mm spectrometer and correction of interferences between Th, U, and Pb with natural monazite

Shimizu

Shibata

Suzuki

et al. 2017

Journal of Mineralogical and Petrological Sciences

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This paper outlines an advanced procedure involving the chemical Th-U-total Pb isochron method (CHIME) dating of monazite using a field-emission electron probe microanalyzer (FE-EPMA) equipped with spectrometers of 100 mm Rowland circle (R R ) radius. The higher count rate of R R = 100 mm wavelength dispersive spectrometer (WDS) compared to R R = 140 mm WDS enables measurements to be taken in a shorter time. CHIME dating using R R = 100 mm WDS had previously been difficult because of lower resolution compared to that of R R = 140 mm WDS. This problem has been overcome by a new interference correction method using natural monazites.

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Section: Introductionsupporting

confidence: 60%

CHIME monazite dating: Pb analysis on an R<sub>R</sub> = 100 mm spectrometer and correction of interferences between Th, U, and Pb with natural monazite

Shimizu

Shibata

Suzuki

et al. 2017

Journal of Mineralogical and Petrological Sciences

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“…2.5 Ga (cf. Grand'Homme et al, 2016Kelly et al, 2012). Investigations are underway to resolve this issue, and to test the association of accessory minerals produced by fluid infiltration processes with metamorphic events in the Nain Province.…”

Section: Petrographic Considerations In Accessory Mineral Datingmentioning

confidence: 99%

Peak to post-peak thermal history of the Saglek Block of Labrador: A multiphase and multi-instrumental approach to geochronology

et al. 2018

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A B S T R A C TThe Saglek Block of coastal Labrador forms the western margin of the North Atlantic Craton, where Archean gneisses and granulites have been reworked during the Paleoproterozoic. Previous work has established that the block is a composite of Eoarchean to Mesoarchean protoliths metamorphosed to upper amphibolite and granulite facies at around 2.8-2.7 Ga. New in-situ microbeam dating of accessory minerals in granoblastic gneisses reveals a complex peak to post-peak thermal history. Zircon growth at ca. 3.7-3.6 Ga provides the age of formation of the tonalitic protoliths to the gneisses. Further zircon growth in syn-tectonic granitic gneiss and monazite growth in a variety of orthogneisses confirm peak metamorphic conditions at ca. 2.7 Ga, but also reveal high-temperature conditions at ca. 2.6 Ga and 2.5 Ga. The former is interpreted as the waning stages of the 2.7 Ga granulite event, whereas the latter is associated with a younger phase of granitic magmatism. In addition, apatite ages of ca. 2.2 Ga may represent either cooling associated with the 2.5 Ga event or a previously unrecognized greenschist-facies metamorphism event that predates the Torngat Orogeny.

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“…, Grand'Homme et al . ). The latter cannot be considered as no patchy textures were observed in BSE images (Figure a) or systematic increases in the Th/U ratios with decrease in U contents due to dissolution–precipitation reactions (Table ) (e.g., Seydoux‐Guillaume et al .…”

Section: Discussionmentioning

confidence: 97%

“…, Grand'Homme et al . ), making it a potential monitor for the timing of fluid transport (Williams et al . , Gauthiez‐Putallaz et al .…”

mentioning

confidence: 99%

“…Volume diffusion of Pb in monazite is negligible, even under high-grade metamorphic conditions, resulting in a closure temperature above 900°C (e.g., Cherniak et al 2004, Gard es et al 2006). However, the monazite U-Pb system can be reset by fluid-mediated coupled dissolutionprecipitation processes (e.g., Seydoux-Guillaume et al 2002, Grand'Homme et al 2016, making it a potential monitor for the timing of fluid transport (Williams et al 2011, Gauthiez-Putallaz et al 2016. Additionally, detrital monazites have been shown to provide a more accurate record of the sources from which recent sediments were derived (e.g., Hietpas et al 2011), because they are less refractory than zircons and their ages should representmore faithfullylow-to medium-grade orogenic activity in the source region.…”

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confidence: 99%

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The Diamantina Monazite: A New Low‐Th Reference Material for Microanalysis

Gonçalves

Lana

Scholz

et al. 2017

Geostandard Geoanalytic Res

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Most monazite reference materials (RMs) for in situ U‐Pb geochronology are rich in Th; however, many hydrothermal ore deposits contain monazite that is low in trace element contents, including Th, U and Pb. Because of potential problems with matrix effects and the lack of appropriate matrix‐matched RMs, such variations can bias dating of hydrothermal deposits. In this paper, we describe a polycrystalline low‐U and low‐Th Diamantina monazite from the Espinhaço Range, SE Brazil. It has a U‐Pb ID‐TIMS weighted mean 207Pb*/235U ratio of 0.62913 ± 0.00079, 206Pb*/238U of 0.079861 ± 0.000088 and 207Pb*/206Pb* of 0.057130 ± 0.000031, yielding a weighted mean 206Pb*/238U date of 495.26 ± 0.54 Ma (95% c.l.). In situ dates acquired with different methods (LA‐(Q, SF, MC)‐ICP‐MS and SIMS) are within uncertainty of the ID‐TIMS data. U‐Pb LA‐(Q, MC)‐ICP‐MS runs, using Diamantina as a primary RM, reproduced the ages of other established RMs within < 1% deviation. The LA‐MC‐ICP‐MS analyses yielded homogeneous Sm‐Nd isotopic compositions (143Nd/144Nd = 0.511427 ± 23, 2s; 147Sm/144Nd = 0.1177 ± 13, 2s) and εNd(495 Ma) of −18.7 ± 0.5 (2s). SIMS oxygen isotope determinations showed measurement reproducibility better than ± 0.3‰ (2s), confirming Diamantina's relative homogeneity at test portion masses below 1 ng.

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Partial resetting of the U-Th-Pb systems in experimentally altered monazite: Nanoscale evidence of incomplete replacement

Abstract: International audienc

Cited by 97 publications

References 22 publications

CHIME monazite dating: Pb analysis on an R<sub>R</sub> = 100 mm spectrometer and correction of interferences between Th, U, and Pb with natural monazite

CHIME monazite dating: Pb analysis on an R<sub>R</sub> = 100 mm spectrometer and correction of interferences between Th, U, and Pb with natural monazite

Peak to post-peak thermal history of the Saglek Block of Labrador: A multiphase and multi-instrumental approach to geochronology

The Diamantina Monazite: A New Low‐Th Reference Material for Microanalysis

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