SHRIMP U-Pb geochronology of authigenic xenotime and its potential for dating sedimentary basins

I.R. Fletcher, Birger Rasmussen, Neal Mcnaughton

    Research output: Contribution to journalArticle

    80 Citations (Scopus)

    Abstract

    SHRIMP (Sensitive High-Resolution Ion MicroProbe) analytical procedures have been developed to enable dating of the small, early diagenetic xenotime overgrowths that commonly occur on zircons in siliciclastic sedimentary rocks. The method will be particularly useful in Precambrian terranes, where diagenetic xenotime dating could play a role equivalent to biostratigraphic dating in the Phanerozoic. Reliable Pb-207/Pb-206 data are more readily obtained than Pb-206/U-238, which also favours application to the Precambrian. However, it is demonstrated that Pb-206/U-238 dating of larger overgrowths (> 10 mu m) is also viable and applicable to Phanerozoic samples. SHRIMP Pb/Pb geochronology of authigenic xenotime in an unmetamorphosed Palaeoproterozoic sandstone in the Kimberley Basin has constrained diagenesis to a precision of +/- 7 Ma. In contrast, greenschist-facies metasediments of the Archaean Witwatersrand Basin, South Africa, contain both authigenic and alteration xenotime that record a complex history of growth from early diagenesis to the last major thermal event to affect the basin.
    Original languageEnglish
    Pages (from-to)845-859
    JournalAustralian Journal of Earth Sciences
    Volume47
    Issue number5
    DOIs
    Publication statusPublished - 2000

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