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Diamonds of multiple origins from New South Wales: further data and discussion



    Corresponding author
    1. Faculty of Science, Food & Horticulture, University of Western Sydney, NSW 1797, Australia.
    2. Australian Museum, 6 College Street, Sydney, NSW 2010, Australia.
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  • L. M. BARRON

    1. New South Wales Mineral Resources, 29–57 Christie Street, St Leonards, NSW 2065, Australia.
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Diamonds from Brickclay Creek, near Walcha, are associated with a Cenozoic nephelinitic intrusion and expand evidence for multiple origins for diamonds from New South Wales. Although the diamonds show similar morphology and C-isotope characteristics to the unusual subduction-related diamonds from the Bingara–Copeton fields, the greater topographic elevation of the associated rocks, and particularly the N aggregation relationships of the diamonds indicate a separate local source. Both yellow and white diamonds from Walcha show limited 1aB nitrogen aggregation (0–7%), similar to that of Ellendale 4 diamonds from Cenozoic pipes in Western Australia. A model is proposed for their local origin from a relatively young (Mesozoic?) subducted mantle slab below the eastern New England Orogen.