Temporal and genetic relationships between the Kidston gold-bearing Breccia Pipe and the Lochaber Ring Dyke Complex, North Queensland, Australia

insights from in situ U-Pb and Hf-isotope analysis of zircon

Valeria Murgulov*, William L. Griffin, Suzanne Y. O'Reilly

*Corresponding author for this work

    Research output: Contribution to journalArticle

    6 Citations (Scopus)

    Abstract

    An existing model for the temporal and genetic relationships between the Kidston gold-bearing Breccia Pipe and the nearby Lochaber Ring Dyke Complex has been evaluated using in situ U-Pb and Hf-isotope analyses of zircon grains. The Oak River Granodiorite, the host rock to the Kidston Breccia Pipe, has 1,551 ± 6 Ma old zircon cores overgrown by 417.7 ± 2.2 Ma rims. The Black Cap Diorite and Lochaber Granite within the Lochaber Ring Dyke Complex have crystallisation ages of 350.7 ± 1.3 and 337.9 ± 2.6 Ma respectively. The gold-rich Median Dyke within the Kidston Breccia Pipe has a crystallisation age of 335.7 ± 4.2 Ma, and thus is temporally related to the Lochaber Granite. However, zircon grains from the Median Dyke have less radiogenic Hf-isotope compositions (εHf from -7.8 to -15.8) than those from the Black Cap Diorite εHf = 0.4 to -7.2) and the Lochaber Granite (εHf = -1.0 to -7.5), but within the range defined by zircons from the Oak River Granodiorite εHf = -8.0 to -29.2). The Hf-isotope data thus rule out the proposed fractional crystallisation relationship between the Kidston gold-bearing rocks and the Lochaber Ring Dyke Complex. The Kidston Median Dyke may have been produced by mixing between Lochaber Granite magmas and magmas derived by remelting of the Oak River Granodiorite, which was itself derived from Proterozoic crust. There is no evidence for a juvenile component in the Lochaber Ring Dyke Complex or the Median Dyke. The gold enrichment in the Kidston rocks thus may reflect the multi-stage reworking of the Proterozoic crust, which ultimately produced the Carboniferous felsic magmas.

    Original languageEnglish
    Pages (from-to)17-45
    Number of pages29
    JournalMineralogy and Petrology
    Volume95
    Issue number1-2
    DOIs
    Publication statusPublished - 2009

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