The age of Cu-Au mineralisation, Cloncurry district, Mount Isa Inlier, as determined by 40Ar/39Ar dating

Abstract

40Ar/39Ar dating of alteration biotite, muscovite, and amphibole from a number of post-peak metamorphic deposits and from hydrothermal alteration systems associated with granitic intrusions in the Williams Batholith, Cloncurry district, Mount Isa Inlier, has revealed the timing of hydrothermal activity and mineralisation. Alteration biotite from the Ernest Henry Cu-Au, Starra Au-Cu, and Mount Elliott Cu-Au deposits; sericite associated with hematite breccias in the Wimberu Granite; muscovite from an albitite pipe which intrudes the Gilded Rose Breccia; and a sericite from a granite near Osborne - all give ages which are inferred to be broadly contemporaneous with the late ~1520-1490 Ma phases of the Williams and Naraku Batholiths. At the Osborne Cu-Au deposit, hornblende and biotite alteration products which predate Cu-Au mineralisation give a maximum age of ~1540 Ma for the deposit. Show more