Kimberlite and kimberlitic intrusives of southeastern Australia

SUMMARY. Fifteen widely separated occurrences of kimberlite and kimberlitic rocks are now known in south-eastern Australia. Those that have been satisfactorily dated isotopically give ages ranging from Permian to Late Jurassic. One occurrence exhibits an intimate spatial association with carbonatite. The classification f these rocks as 'kimberlitic ' is partly based on their mode of emplacement, and particularly on the presence ofcrust/ mantle inclusions. Compared with African kimberlitic magmas, the southeastern Australian examples have lower incompatible-element co ents. These differences are interpreted asrepresenting slightly greater degrees of partial melting of a four-phase lherzolite assemblage at shallower depths ( ~ 65 kin) than typical African kim-berlite magma. FIFTEEN widely separated areas of kimberlite and kimberlitic rocks are now known in southeastern Australia, in the States of South Australia, Tas-mania, Victoria, and New South Wales (fig. t). Field relationships indicate that all these intrusives in southeastern Australia postdate the Proterozoic. Isotopic dating of whole rocks and phlogopite indi-cates a spread of ages. The Kayrunnera occurrence is the oldest that is isotopically dated, giving an Early Permian age of ~ 260 Ma (Stracke et al., i979), a date also confirmed by fission-track studie