Experimental resetting of the U–Th–Pb systems in monazite

Seydoux‐Guillaume, Anne‐Magali; Paquette, Jean‐Louis; Wiedenbeck, Michael; Montel, Jean-Marc; Heinrich, Wilhelm

doi:10.1016/s0009-2541(02)00155-9

Cited by 282 publications

(142 citation statements)

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“…Ex per i ments at 900°C and 1000 MPa with monazite in the pres ence of an al kali-bear ing fluid Na 2 Si 2 O 5 + H 2 O re sulted in de ple tion of Pb or Th en richment . Seydoux-Guillaume et al (2002) in their 1000°C and 1 GPa ex per i ments uti liz ing a CaCl 2 -bear ing fluid doc u mented that monazite al ter ation results in Ca en rich ment and Pb re moval. The fluid-me di ated com plete re moval of Pb in al tered monazite do mains pro vides a pow er ful tool for dat ing metasomatic and hy dro ther mal processes, as was ex per i men tally dem on strated at 450°C and 450 MPa .…”

Section: Monazite In Metamorphic Rocksmentioning

confidence: 91%

“…Compositional al ter ations that may re sult in dis tur bance of the Th-U-Pb sys tem were pre vi ously doc u mented in na ture (Poitrasson et al, 1996(Poitrasson et al, , 2000Townsend et al, 2000;Petrík and Koneèný, 2009;TartÀse et al, 2011) and ex per i ments (Teufel and Hein rich, 1997;Seydoux-Guillaume et al, 2002;Harlov and Hether ing ton, 2010;Hether ing ton et al, 2010;Budzyñ et al, 2011Budzyñ et al, , 2015bHarlov et al, 2011;Wil liams et al, 2011). Ex per i ments at 900°C and 1000 MPa with monazite in the pres ence of an al kali-bear ing fluid Na 2 Si 2 O 5 + H 2 O re sulted in de ple tion of Pb or Th en richment .…”

Section: Monazite In Metamorphic Rocksmentioning

confidence: 99%

“…Such compositional al terations, which af fect monazite dur ing post-mag matic, hy dro thermal and metasomatic pro cesses, have been rec og nized in var ious gra nitic rocks (e.g., Poitrasson et al, 1996Poitrasson et al, , 2000Townsend et al, 2000;Petrík and Koneèný, 2009;TartÀse et al, 2011). Ex per i men tal rep li ca tions of nat u ral pro cesses in dicate that the re-equil i bra tion of monazite via cou pled dis so lution-reprecipitation may sig nif i cantly dis turb the Th-U-Pb system un der low-to high-grade con di tions (Teufel and Hein rich, 1997;Seydoux-Guillaume et al, 2002;Harlov and Hether ington, 2010;Hether ing ton et al, 2010;Budzyñ et al, 2011Budzyñ et al, , 2015bHarlov et al, 2011), which can re sult in the com plete reset ting of the Th-U-Pb sys tem even at 450°C . Our cur rent knowl edge pro vides a better un der stand ing of the al ter ation mech a nisms and im por tance of geo chron ol ogical data to avoid mean ing less dates in pet ro log i cal re con structions and to link the true ages with par tic u lar geo log i cal processes.…”

Section: Introductionmentioning

confidence: 99%

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Monazite stability and the maintenance of Th-U-total Pb ages during post-magmatic processes in granitoids and host metasedimentary rocks: A case study from the Sudetes (SW Poland)

Budzyń

Jastrzębski

2015

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1 Pol ish Acad emy of Sci ences, In sti tute of Geo log i cal Sci ences, Senacka 1, 31-002 Kraków, Po land 2 Pol ish Acad emy of Sci ences, In sti tute of Geo log i cal Sci ences, Podwale 75, 50-449 Wroc³aw, Po land Budzyñ, B., Jastrzêbski, M., 2016. Monazite sta bil ity and the main te nance of Th-U-to tal Pb ages dur ing post-mag matic processes in granitoids and host metasedimentary rocks: a case study from the Sudetes (SW Po land). Geo log i cal Quar terly, 60 (1): 106-123, doi: 10.7306/gq.1254The sta bil ity and main te nance of the age re cord of monazite dur ing post-mag matic pro cesses were stud ied in gra nitic and host metasedimentary rocks from the Sudetes (SW Po land). Un al tered monazite in the K³odzko-Z³oty Stok granitoid provided a Th-U-to tal Pb age of 329 ± 5 Ma, which con strains tim ing of the late stage of pluton em place ment. In con trast, monazite in the Jawornik granitoid re mained un al tered or was par tially re placed by sec ond ary phases, in clud ing (1) al la nite, epidote and, oc ca sion ally, ap a tite; (2) cheralite, al la nite and a mix ture of clays, Fe ox ides and pos si ble un known rare earth el e ment (REE) phases; and (3) K-feld spar and cheralite with sub se quent for ma tion of ti tan ite. Dif fer ent al ter ation prod ucts on the thin sec tion scale in di cate the lo cal char ac ter of the post-mag matic pro cesses af fect ing monazite in duced by alkali-rich flu ids. The al tered and un al tered monazite grains both yielded a Th-U-to tal Pb age of 343 ± 4 Ma. The Th-U-to tal Pb ages of the monazite in the ac com pa ny ing metasedimentary rocks ther mally af fected by in trud ing mag mas were also constrained. In the paragneiss in con tact with the Jawornik granitoid, the un al tered monazite and monazite par tially re placed by al la nite yielded an age of 344 ± 5 Ma. The monazite from the mica schist, far ther from the con tact with the granitoids, ex hibited an age of 336 ± 4.5 Ma. The 344-336 Ma ages dem on strated a re cord of monazite (re)growth dur ing pro longed Variscan meta mor phism. The pre dom i nant early Visean ages con strain the tim ing of the de vel op ment of the Z³oty Stok-Skrzynka Shear Zone and the em place ment of the Jawornik granitoid in tru sion. The age re sults, which are con sis tent with pre vi ous geo chron ol ogy, in di cate that the par tial al ter ation of the monazite did not af fect the in ter nal do mains or the main te nance of the monazite ages. Thus, this study re veals that monazite geo chron ol ogy can pro vide mean ing ful data in crys tal line rocks affected by fluid-in duced post-mag matic pro cesses.

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Section: Monazite In Metamorphic Rocksmentioning

confidence: 91%

Section: Monazite In Metamorphic Rocksmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Monazite stability and the maintenance of Th-U-total Pb ages during post-magmatic processes in granitoids and host metasedimentary rocks: A case study from the Sudetes (SW Poland)

Budzyń

Jastrzębski

2015

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“…1% of the radiogenic Pb accumulated in a few hundreds of Myr (Parrish, 1990;Kingsbury et al, 1993). Pb is stable in monazite structure (Podor and Cuney, 1997), and presents very low diffusion coeffi cients in most geological processes occurring in the continental crust (Seydoux-Guillaume et al, 2002;Cherniak et al, 2004;Gardés et al, 2007). The monazite structure is also very resistant to metamictization processes (Karioris, Gowda, Cartz, 1991).…”

Section: Theoretical Foundation and Premisesmentioning

confidence: 99%

Th-U-PbT dating by electron probe microanalysis, part I. monazite: analytical procedures and data treatment

Vlach

2010

Geol. USP, Sér. cient.

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Dating methodology by the electron probe microanalyser (EPMA) of (Th, U)-bearing minerals, highlighting monazite, acquired greater than ever importance in literature, particularly due to its superior spatial resolution, as well as versatility, which allow correlating petrological processes at times registered only in micro-scales in minerals and rocks with absolute ages. Although the accuracy is inferior to the one achieved with conventional isotopic methods in up to an order of magnitude, EPMA is the instrument that allows the best spatial resolution, reaching a few μm 3 in some conditions. Quantifi cation of minor and trace elements with suitable precision and accuracy involves the own instrumental and analytical set-ups and data treatment strategies, signifi cantly more rigorous when compared with those applied in conventional analyses. Th-U-Pb T dating is an example of these cases. Each EPMA is a unique machine as for its instrumental characteristics and respective automation system. In such a way, analytical procedures ought to be adjusted for laboratory specifi cities. The analytical strategies and data treatment adopted in the Electronic Microprobe Laboratory from Instituto de Geociências of Universidade de São Paulo, Brazil, with a JEOL JXA8600S EPMA, and a ThermoNoran-Voyager 4.3 automation system, are presented and compared with the ones used in other laboratories. The infl uence of instrumental factors and spectral overlaps on Th, U, and Pb quantifi cation is discussed. Applied procedures to interference correction, error propagation, data treatment, and fi nal chemical age presentation as well as to sampling and analyses are emphasized. Some typical applications are discussed, drawing attention to the most relevant aspects of electron microprobe dating.Keywords: Th-U-total Pb dating; Monazite; Microanalysis; Electron probe microanalyser (EPMA). RESUMOA metodologia de datação de minerais portadores de Th e/ou U com microssonda eletrônica (EPMA), com ênfase em monazita, adquiriu enorme importância em literatura, devido a sua alta resolução espacial e versatilidade, que permitem correlacionar processos petrológicos, por vezes registrados apenas em microescala em minerais e rocha, com idades absolutas. Embora a acurácia seja até uma ordem de grandeza inferior à alcançada com os métodos isotópicos convencionais, o EPMA é o equipamento que resulta na melhor resolução espacial, alcançando alguns poucos μm 3 sob algumas condições. A quantifi cação de elementos menores e em traços com precisão e acurácia adequadas envolve estratégias instrumentais, analíticas e de tratamento de dados específi cas e signifi cativamente mais rigorosas quando comparadas com as empregadas em análises convencionais. A datação Th-U-Pb T é um exemplo destes casos. Cada EPMA é um aparelho único em função de suas características instrumentais e sistema de automação e, desta forma, os procedimentos analíticos devem ser ajustados para as especifi cidades de cada laboratório. As estratégias analíticas e de tratamento de dados ado...

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“…% Pb) is typical for natural monazites. Multiple Isotope Dilution Thermal Ionisation Mass Spectrometer (IDTIMS) analyses yield concordant U-Pb ages of 474 ± 1 Ma [5] and document the isotopic homogeneity of the monazite. The precise knowledge of age and the low Pb and U content in this monazite allows us to estimate the main sources of uncertainties in age determination using EPMA.…”

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confidence: 94%

Evaluation of Uncertainties in Dating of Monazite by Electron Microprobe

Merlet

2005

MAM

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Over the last decades, determination of ages in monazite using Electron Probe Microanalysis (EPMA) has progressed to the point that it is now considered as a routine procedure within several laboratories worldwide [1,2]. Nevertheless, the typical age errors of individual electron probe spots reported in the literature are an order of magnitude larger than attainable by Secondary Ion Mass Spectrometry (SIMS) and two orders of magnitude larger than attainable by Thermal Ionization Mass Spectrometry (TIMS). The age errors frequently range from 40 Ma to 120 Ma, although after statistical treatment of a set of homogeneous ages, a precision of approximately 20 Ma can be obtained. Despite the low accuracy, the numerous studies have shown that the Th-U-totalPb method using the EPMA is a reliable method, easy to use, for detecting age variations on a very small scale. The effective limitation of the EPMA monazite ages determination concerns its relatively poor accuracy regarding mainly Pb determination. Similarly the relative uncertainties for U and Th are generally larger than 2%, which can lead to large errors. The error on the age for each analysed point depends on the U, Th and Pb concentration. As the Pb concentration is directly related to the age of the monazite and to the U and Th concentration, older is the monazite, better is the relative error. Since the first monazite dating study by EPMA [1] there has been improvements in data age processing, but only few evaluations of uncertainties in the Pb, U, Th determinations. As the error calculated on the age for each analysed point is the whole inaccuracies on Pb, U, Th determinations, this method requires high accuracies determinations of trace elements [3] as well as of major elements.The aim of the present experimental and theoretical study is firstly for evaluating precisely the uncertainties of EPMA dating of monazite and secondarily to give suggestions for minimizing them. Precise evaluation is not straightforward because sources of uncertainties include not only counting statistic but also many parameters like microprobe operating conditions (e.g., accelerating voltage, beam current, beam diameter, pulse height analyser), spectral background subtraction, quantification procedure, overlap, line shape, standards, sample preparation (polish, carbon coat, contamination), irradiation damage etc.. To estimate experimentally these sources, measurements were done on a large homogeneous monazite from the Itambe pegmatite district (Brazil [4]). The crystal homogeneous at the micrometer scale is free of fluid and solid inclusions. The composition (6.5 wt. % Th, 0.12 wt. % U and 0.15 wt. % Pb) is typical for natural monazites. Multiple Isotope Dilution Thermal Ionisation Mass Spectrometer (IDTIMS) analyses yield concordant U-Pb ages of 474 ± 1 Ma [5] and document the isotopic homogeneity of the monazite. The precise knowledge of age and the low Pb and U content in this monazite allows us to estimate the main sources of uncertainties in age determination using EPMA. As th...

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Experimental resetting of the U–Th–Pb systems in monazite

Cited by 282 publications

References 45 publications

Monazite stability and the maintenance of Th-U-total Pb ages during post-magmatic processes in granitoids and host metasedimentary rocks: A case study from the Sudetes (SW Poland)

Monazite stability and the maintenance of Th-U-total Pb ages during post-magmatic processes in granitoids and host metasedimentary rocks: A case study from the Sudetes (SW Poland)

Th-U-PbT dating by electron probe microanalysis, part I. monazite: analytical procedures and data treatment

Evaluation of Uncertainties in Dating of Monazite by Electron Microprobe

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