Theoretical versus empirical secular change in zircon composition

Kirkland, Christopher L.; Yakymchuk, Chris; Olierook, Hugo K.H.; Hartnady, Michael I.H.; Gardiner, Nicholas J.; Moyen, Jean‐François; Smithies, R. Hugh; Szilas, Kristoffer; Johnson, Tim

doi:10.1016/j.epsl.2020.116660

Cited by 19 publications

(13 citation statements)

References 48 publications

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“…Further greenschist to amphibolite-facies metamorphic events occurred at ca. 2630 Ma, as recorded by metamorphic zircon overgrowths and neoblastic apatite 10 , and 2540 Ma, as evidenced from zircon 11 and titanite 12 . Both of these late-stage events may be related to protracted terrane assembly 13 , 14 .…”

Section: Background and Summarymentioning

confidence: 98%

Regional zircon U-Pb geochronology for the Maniitsoq region, southwest Greenland

et al. 2021

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Zircon U-Pb geochronology places high-temperature geological events into temporal context. Here, we present a comprehensive zircon U-Pb geochronology dataset for the Meso- to Neoarchean Maniitsoq region in southwest Greenland, which includes the Akia Terrane, Tuno Terrane, and the intervening Alanngua Complex. The magmatic and metamorphic processes recorded in these terranes straddle a key change-point in early Earth geodynamics. This dataset comprises zircon U-Pb ages for 121 samples, including 46 that are newly dated. A principal crystallization peak occurs across all three terranes at ca. 3000 Ma, with subordinate crystallization age peaks at 3200 Ma (Akia Terrane and Alanngua Complex only), 2720 Ma and 2540 Ma. Metamorphic age peaks occur at 2990 Ma, 2820–2700 Ma, 2670–2600 Ma and 2540 Ma. Except for one sample, all dated metamorphic zircon growth after the Neoarchean occurred in the Alanngua Complex or within 20 km of its boundaries. This U-Pb dataset provides an important resource for addressing Earth Science topics as diverse as crustal evolution, fluid–rock interaction and mineral deposit genesis.

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Section: Background and Summarymentioning

confidence: 98%

Regional zircon U-Pb geochronology for the Maniitsoq region, southwest Greenland

et al. 2021

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“…Whatever the Zr concentration in the Ditrău 1 melt was, the thermobarometric and geochemical modelling suggest that zircon grew early in the cooling history at temperatures above ca. 840 • C with at least 70% melt being present [54]. For the Ditrău 2 sample the maximum Zr whole-rock concentration is ca.…”

Section: Zircon U-pb Agesmentioning

confidence: 92%

“…840 • C, meaning that zircon growth will have started at sub-liquidus conditions with ca. 70% melt present [54]. In this scenario, zircon growth is completed at ca.…”

Section: Zircon U-pb Agesmentioning

confidence: 99%

“…There are currently no thermobarometric models for zircon available for syenitic and nepheline syenitic rock compositions. Nevertheless, the thermobarometric models of [54,55] can be used to estimate the temperature ranges for Zr saturation and zircon growth in the investigated rocks. The aim of these model calculations is to derive some indication of when zircons are crystallized during the melt solidification process, i.e., what time point of the intrusion history is actually dated by the zircon growth ages.…”

Section: Zircon U-pb Agesmentioning

confidence: 99%

“…900 µg/g (Figure 4). Applying thermobarometric models of zircon growth [54] shows the onset of zircon crystallization in Ditrău 1 to be at around 950 • C (at an estimated 0.6 GP and for an Si-poor A-type granite composition). This temperature is within the range of the liquidus of the Ditrău 1 melt and virtually identical to the estimated Zr saturation temperature of 953 ± 18 • C for the Ditrău 1 melt with 900 µg/g Zr (Table 1).…”

Section: Zircon U-pb Agesmentioning

confidence: 99%

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Petrochronological Evidence for a Three-Stage Magmatic Evolution of the Youngest Nepheline Syenites from the Ditrău Alkaline Massif, Romania

Klötzli

Burda

et al. 2022

Minerals

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The Ditrău Alkaline Massif (DAM) is an igneous massif in the Eastern Carpathian Mountains of Romania. Numerous geochronological and geochemical studies have proposed a long formation history (ca. 70 m.y.) of the DAM from Middle Triassic to Cretaceous times, which is hardly reconcilable with geochemical evolutionary models and the geotectonic environment during the Mesozoic in this part of the Eastern Carpathian Mountains. In order to put tighter age constraints on the igneous processes forming the DAM, two nepheline syenites from the so-called Ghiduţ and Lăzarea suites were investigated. Based on field and geochemical evidence, the two rock suites represent the younger part of the DAM intrusives. Detailed zircon characterization, in situ zircon SIMS U-Pb dating, and geochemical modelling were used to establish the timing of zircon crystallization and thus to set time constraints on the igneous formation of these parts of the DAM. The intrusion of the dated Ghiduţ suite sample took place at 232 ± 1 Ma in the Karnium, whereas the Lăzarea suite nepheline syenite sample was intruded at 225 ± 1 Ma in the Norium. Together with published geochemical and geochronological data, three different magmatic events can thus be identified: Ghiduţ suite at 231.1 ± 0.8 Ma, Ditrău suite at 230.7 ± 0.2 Ma, and Lăzarea suite at 224.9 ± 1.1 Ma. Although the ages of the events 1 and 2 are statistically indistinguishable, the combination of geochemical and petrochronological data certainly favor independent intrusion events. Thus, the igneous events forming the younger parts of the DAM encompassed a time span of ca. 13 m.y. Additionally, each igneous event can tentatively be divided in an older syenitic stage and a younger nepheline syenitic one, each with an age difference of some 100,000 years. No indication of any post 215 Ma igneous or hydrothermal activity was found. The new data and interpretation significantly improve our understanding of the temporal and geochemical evolution of the DAM and of alkaline complexes as such, demonstrating that the underlying igneous processes (melt generation, assimilation, fractionation, and the duration of plumbing systems) work on the same time scale for both sorts of magmatic rock suites.

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