Skip to content

Research at St Andrews

Apatite: a U-Pb thermochronometer or geochronometer?

Research output: Contribution to journalArticle


C. L. Kirkland, C. Yakymchuk, K. Szilas, N. Evans, J. Hollis, B. McDonald, N. J. Gardiner

School/Research organisations


Apatite is an accessory mineral that is frequently found in both igneous and clastic sedimentary rocks. It is conventionally considered to be characterized by a closure temperature range between 375 and 600 °C and hence has been employed to address mid-temperature thermochronology questions relevant to the reconstruction of thermal events in the middle to lower crust. However, questions remain as to whether apatite faithfully records thermally-activated volume diffusion profiles, or rather is influenced by recrystallization and new growth processes. We present a case study of two apatite samples from the Akia Terrane in Greenland that help chart some of the post magmatic history of this region. Apatite in a tonalitic gneiss has distinct U-enriched rims and its U-Pb apparent ages correlate with Mn chemistry, with a high Mn group yielding an age of c. 2813 Ma. The U-Pb and trace element chemistry and morphology support an interpretation in which these apatite crystals are originally igneous and record cooling after metamorphism, with subsequent generation of discrete new rims. Epidote observed in the sample implies a <600 °C fluid infiltration event associated with apatite rims. The second sample, from a granitic leucosome, contains apparently homogeneous apatite, however U-Pb analyses define two distinct discordia arrays with different common Pb components. An older, c. 2490 Ma, component is associated with elevated Sr, whereas a younger, c. 1800 Ma, component has lower Sr concentration. A depth profile reveals an older core with progressively younger ages towards a compositionally discrete late Paleoproterozoic rim. The chemical and age profiles do not directly correspond, implying different diffusion rates between trace elements and U and Pb. The variation in core ages is interpreted to reflect radiogenic-Pb loss from a metamorphic population during new rim growth. The younger, c. 1800 Ma U-Pb age is interpreted to date new apatite growth from a compositionally distinct reservoir driven by tectonothermal and fluid activity, consistent with regional mica Ar-Ar ages. Results from these two samples show that recrystallization, dissolution and regrowth processes likely formed the younger rim overgrowths, and at temperatures below those often considered to be closure temperatures for Pb diffusion in apatite. The results from these samples imply many apatite grains may not record simple thermally activated Pb diffusion profiles and cautions against inversion of apatite U-Pb data to thermal histories without detailed knowledge of the grain growth/alteration processes.



Original languageEnglish
Pages (from-to)143-157
Number of pages15
Early online date7 Aug 2018
Publication statusPublished - Oct 2018

    Research areas

  • Apatite, Geochronology, Greenland, Metamorphism, Pseudosection, Themochronology, U-Pb

Discover related content
Find related publications, people, projects and more using interactive charts.

View graph of relations

Related by author

  1. A window into an ancient backarc? The magmatic and metamorphic history of the Fraser Zone, Western Australia

    Glasson, K. J., Johnson, T. E., Kirkland, C. L., Gardiner, N. J., Clark, C., Blereau, E., Hartnady, M. I. H., Spaggiari, C. & Smithies, H., Apr 2019, In : Precambrian Research. 323, p. 55-69 15 p.

    Research output: Contribution to journalArticle

  2. Building Mesoarchaean crust upon Eoarchaean roots: the Akia Terrane, West Greenland

    Gardiner, N. J., Kirkland, C. L., Hollis, J., Szilas, K., Steenfelt, A., Yakymchuk, C. & Heide-Jørgensen, H., Mar 2019, In : Contributions to Mineralogy and Petrology. 174, 20.

    Research output: Contribution to journalArticle

  3. Zircon U–Pb, Lu–Hf and O isotopes from the 3414 Ma Strelley Pool Formation, East Pilbara Terrane, and the Palaeoarchaean emergence of a cryptic cratonic core

    Gardiner, N. J., Wacey, D., Kirkland, C. L., Johnson, T. E. & Jeon, H., Feb 2019, In : Precambrian Research. 321, p. 64-84 21 p.

    Research output: Contribution to journalArticle

  4. Secular change in TTG compositions: implications for the evolution of Archaean geodynamics

    Johnson, T. E., Kirkland, C. L., Gardiner, N. J., Brown, M., Smithies, R. H. & Santosh, M., 1 Jan 2019, In : Earth and Planetary Science Letters. 505, p. 65-75 11 p.

    Research output: Contribution to journalArticle

  5. Modelling the hafnium-neodymium evolution of early Earth: a study from West Greenland

    Gardiner, N. J., Johnson, T. E., Kirkland, C. L. & Szilas, K., Jan 2019, In : Journal of Petrology. 60, 1, p. 177-197 21 p.

    Research output: Contribution to journalArticle

Related by journal

  1. Lithos (Journal)

    Anouk Margaretha Borst (Reviewer)
    27 Oct 2017

    Activity: Publication peer-review and editorial work typesPeer review of manuscripts

Related by journal

  1. Can we extract ultrahigh-temperature conditions from Fe-rich metapelites? An example from the Khondalite Belt, North China Craton

    Li, X., White, R. W. & Wei, C., Mar 2019, In : Lithos. 328-329, p. 228-243

    Research output: Contribution to journalArticle

  2. Dating agpaitic rocks: a multi-system (U/Pb, Sm/Nd, Rb/Sr and 40Ar/39Ar) isotopic study of layered nepheline syenites from the Ilímaussaq complex, Greenland

    Borst, A. M., Waight, T., Finch, A. A., Storey, M. & Le Roux, P., Jan 2019, In : Lithos. 324-325, p. 74-88 15 p.

    Research output: Contribution to journalArticle

  3. Implications of 770 Ma Rhyolitic Tuffs, eastern South China Craton in constraining the tectonic setting of the Nanhua Basin

    Qi, L., Xu, Y., Cawood, P. A., Wang, W. & Du, Y., Jan 2019, In : Lithos. 324-325, p. 842-858

    Research output: Contribution to journalArticle

  4. Neoarchean magmatic arc in the Western Liaoning Province, northern North China Craton: geochemical and isotopic constraints from sanukitoids and associated granitoids

    Fu, J., Liu, S., Cawood, P. A., Wang, M., Hu, F., Sun, G., Gao, L. & Hu, Y., 26 Oct 2018, In : Lithos. In press

    Research output: Contribution to journalArticle

ID: 261213902