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Measurement of in-situ oxygen isotope ratios in monazite by SHRIMP ion microprobe: Standards, protocols and implications

Rubatto, Daniela; Putlitz, Benita; Gauthiez-Putallaz, Laure; Crepisson, Celine; Buick, Ian; Zheng, Y.-F.

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Monazite forms at sub-solidus conditions in a variety of metamorphic rocks and has been proven to be reactive to fluids, and thus is a potential monitor of fluid-rock interaction. As monazite can preserve multiple growth zones, in order to explore the potential of monazite as a fluid tracer in metamorphic conditions, microbeam analysis is required. We performed oxygen isotope analysis of monazite using the SHRIMP ion microprobe and newly characterized standards, for which we obtained laser...[Show more]

dc.contributor.authorRubatto, Daniela
dc.contributor.authorPutlitz, Benita
dc.contributor.authorGauthiez-Putallaz, Laure
dc.contributor.authorCrepisson, Celine
dc.contributor.authorBuick, Ian
dc.contributor.authorZheng, Y.-F.
dc.date.accessioned2015-12-13T22:16:07Z
dc.identifier.issn0009-2541
dc.identifier.urihttp://hdl.handle.net/1885/70710
dc.description.abstractMonazite forms at sub-solidus conditions in a variety of metamorphic rocks and has been proven to be reactive to fluids, and thus is a potential monitor of fluid-rock interaction. As monazite can preserve multiple growth zones, in order to explore the potential of monazite as a fluid tracer in metamorphic conditions, microbeam analysis is required. We performed oxygen isotope analysis of monazite using the SHRIMP ion microprobe and newly characterized standards, for which we obtained laser fluorination δ18O values (USGS-44069 monazite 7.67±0.26‰ and Itambé monazite 0.46±0.20‰). Reproducibility of δ18O ion microprobe analyses for USGS-44069 and Itambé monazites is in the order of 0.4-0.6‰, standard deviation at 95%c.l., similar to what is routinely obtained for silicates. This reproducibility is comparable to that of the analyses of experimental P-rich glasses, which are assumed to be homogeneous and free of geological imperfections. The variable composition of natural monazite has the potential to produce matrix effects during ion microprobe measurements. Monazite grains from the Malagasy syenite (Madagascar) and the Dora Maira whiteschists (Italy) display a scatter in δ18O values that show a negative correlation with Th content and is related to the huttonite [ThSiO4] and cheralite [CaTh(PO4)2] substitutions in monazite. The matrix effect on oxygen isotope measurements can be significant and is estimated to produce a shift in δ18O of circa -0.85 or -1.9‰ for every 10wt.% Th introduced by the huttonite and cheralite components, respectively. Corrections for this matrix effect are proposed on the basis of the natural samples investigated.Oxygen isotope fractionation factors for monazites of different compositions, cheralite and huttonite were calculated with the increment method. The results suggest that the substitution of trivalent LREE by tetravalent Ce and Th results in consistent enrichment of 18O in the monazites, whereas the substitution of tetravalent Th by divalent Ca results in the depletion of 18O in cheralite-rich monazite.Monazites from high-grade metasediments (Mount-Stafford, Central Australia) preserve inherited cores, but are homogeneous in oxygen composition. This suggests that diffusion may efficiently erase the oxygen isotope signature in monazite that experienced ~. 800. °C metamorphism.
dc.publisherElsevier
dc.sourceChemical Geology
dc.titleMeasurement of in-situ oxygen isotope ratios in monazite by SHRIMP ion microprobe: Standards, protocols and implications
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume380
dc.date.issued2014
local.identifier.absfor040203 - Isotope Geochemistry
local.identifier.ariespublicationU3488905xPUB2389
local.type.statusPublished Version
local.contributor.affiliationRubatto, Daniela, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationPutlitz, Benita, University of Lausanne
local.contributor.affiliationGauthiez-Putallaz, Laure, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationCrepisson, Celine, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationBuick, Ian, Stellenbosch University
local.contributor.affiliationZheng, Y.-F., University of Science and Technology of China
local.description.embargo2037-12-31
local.bibliographicCitation.startpage84
local.bibliographicCitation.lastpage96
local.identifier.doi10.1016/j.chemgeo.2014.04.029
local.identifier.absseo970104 - Expanding Knowledge in the Earth Sciences
dc.date.updated2015-12-11T07:22:49Z
local.identifier.scopusID2-s2.0-84901020582
CollectionsANU Research Publications

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