A suite of sulphide-bearing diamonds recovered from the Ellendale 4 and 9 pipes in the Ellendale diamond province of lamproite intrusions in north-western Australia have been investigated for their nitrogen aggregation state and the Re-Os isotope geochemistry of the sulphide inclusions. The Ellendale lamproites, dated at ca. 20 Ma (Allsopp et at., 1985) intrude the King Leopold Mobile Belt just south of the Kimberley craton and are thus an atypical, off-craton diamondiferous locality. The diamonds contain roughly equal proportions of peridotitic and eclogitic inclusions (Hall & Smith, 1984; Griffin et at., 1988; Jaques et at., 1989). The diamonds in this study range in size from 0.26 to 0.92 carats and are dominated, with the exception of one octahedron, by highly resorbed tetrahexahedroida.

Includes bibliographical references (leaves 97-115).