Zircon U–Pb emplacement ages of intrusions in the Mary Kathleen Domain, Mount Isa Inlier, Australia

The Mary Kathleen Domain (MKD), within the Mount Isa Inlier, Queensland, hosts numerous occurrences of Cu ± Au mineralisation, which are spatially associated with igneous intrusions. However, the temporal relationships between the emplacement (crystallisation) ages of these intrusions and important mineralisation events remain ambiguous in most cases. This is further complicated by secondary overprinting of primary magmatic rocks (and mineralisation) during later metamorphic or hydrothermal events, which can potentially reset datable mineral archives. Here we present 29 new U–Pb zircon ages for magmatic intrusions from across the MKD, which are all interpreted as emplacement ages. Our results, combined with previous data, show that most intrusions in the MKD were emplaced during at least four discrete periods of magmatic activity between ca 1880 Ma and ca 1500 Ma; these are the Kalkadoon–Leichhardt Igneous Province (ca 1860 Ma), Argylla Igneous Province (ca 1780 Ma), Wonga–Burstall Igneous Province (ca 1760–1710 Ma) and Williams Igneous Province (ca 1550–1500 Ma). Available geochronology data on ore mineralisation associated with intrusions within the MKD suggest that most mineralisation formed coeval with the emplacement of the Williams Igneous Province; however, intrusions of this province are only exposed in the northern portion of the MKD. Therefore, in other areas where reported ore mineralisation ages (i.e. ca 1500 Ma) are much younger than the spatially related magmatic emplacement ages of intrusions, mineralisation is probably the result of remobilisation of older mineralisation temporally linked to the surrounding intrusions. These results also highlight the need for detailed mapping of the field relationships between different magmatic phases and the surrounding country rock to resolve ambiguities in the geological history and stratigraphic succession observed within some areas of the MKD.

Australian Journal of Earth Sciences

Australian Journal of Earth Sciences

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1440-0952

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N/A

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