The age of the diamond-bearing pipes and associated leucite lamproites of the West Kimberley region, Western Australia.

New K/Ar and Rb/Sr ages obtained for 14 separate lamproite intrusions in the Fitzroy area of this region confirm the early Miocene ages previously obtained for the Fitzroy lamproites. Similar (early Miocene) ages were obtained for the leucite lamproite intrusions and one of the newly discovered diamondiferous pipes of olivine lamproite resembling kimberlite. This is consistent with their close spatial association in the field and their petrological and geochemical similarities. There is a small difference in age between the northernmost intrusions of the Ellendale area (20-22 m.y.) and those further south in the Noonkanbah area (18-20 m.y.). The early Miocene ages of the West Kimberley diamond pipes make these the youngest primary source of diamond yet found. (Authors' abstract)-R.A.H.