On the origin of Tasmanian dolerites

Abstract

The Tasmanlan dolerites, part of the Ferrar Province of Australia and Antarctica, have some trace-element and isotopic compositions that suggest continental contamination of mantle-derived magmas. The debate has centred on whether the contamination occurred during intrusion into the crust, or if the mantle source itself was contaminated. The behaviour of Sr and O isotopes suggests that the mantle source had a δ18O composition of +6‰ and an initial 87Sr/86Sr ratio of 0.709, which supports the latter contention. Recently published Re-Os data likewise dismiss upper crustal contamination: Re-Os Isotopic compositions of magnetite-rich mineral separates from seven Tasmanian dolerites yield an isoc..