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dc.contributor.authorTomlinson, Emma
dc.date.accessioned2023-08-30T17:32:14Z
dc.date.available2023-08-30T17:32:14Z
dc.date.issued2023
dc.date.submitted2023en
dc.identifier.citationO'Sullivan, Gary J, Hoare, Brendan C, Mark, Chris, Drakou, Foteini, Tomlinson, Emma L, Uranium-lead geochronology applied to pyrope garnet with very low concentrations of uranium, Geological Magazine, 2023en
dc.identifier.otherY
dc.identifier.urihttp://hdl.handle.net/2262/103806
dc.descriptionPUBLISHEDen
dc.description.abstractWe present U–Pb dates from peridotitic pyrope-rich garnet from four mantle xenoliths entrained in a kimberlite from Bultfontein, South Africa. Garnet dates magmatic emplacement due to the high mantle residence temperatures of the source material prior to eruption, which were most likely above the closure temperature for the pyrope U–Pb system. We determine a U–Pb date of 84.0 ± 8.1 Ma for the emplacement of the Bultfontein kimberlite from garnet in our four xenolith samples. The date reproduces previous dates obtained from other mineralisotope systems (chiefly Rb–Sr in phlogopite). Garnet can be dated despite extremely low concentrations of U (median ~0.05 μg/g), because concentrations of common Pb are often low or non-detectable. This means that sub-concordant garnets can be dated with moderate precision using very large laser-ablation spots (130 μm) measured by quadrupole inductively coupled plasma – mass spectrometry (LA-Q-ICP-MS). Our strategy demonstrates successful U–Pb dating of a U-poor mineral due to high initial ratios of U to common Pb in some grains, and the wide spread of isotopic compositions of grains on a concordia diagram. In addition, the analytical protocol is not complex and uses widely available analytical methods and strategies. This new methodology has some advantages and disadvantages for dating kimberlite emplacement versus established methods (U-based decay systems in perovskite and zircon, or Rb- or K-based systems in phlogopite). However, this method has unique promise for its potential application to detrital diamond prospecting and, more speculatively, to the dating of pyrope inclusions in diamond.en
dc.language.isoenen
dc.relation.ispartofseriesGeological Magazine;
dc.rightsYen
dc.subjectpyropeen
dc.subjectgarneten
dc.subjectgeochronologyen
dc.subjectmantleen
dc.subjectkimberliteen
dc.subjectdiamonden
dc.subjectgeochemistryen
dc.titleUranium-lead geochronology applied to pyrope garnet with very low concentrations of uraniumen
dc.typeJournal Articleen
dc.type.supercollectionscholarly_publicationsen
dc.type.supercollectionrefereed_publicationsen
dc.identifier.peoplefinderurlhttp://people.tcd.ie/tomlinse
dc.identifier.rssinternalid252700
dc.identifier.doihttp://dx.doi.org/10.1017/S0016756823000122
dc.rights.ecaccessrightsopenAccess
dc.identifier.orcid_id0000-0002-0646-6640


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