Fission track geochronology of King Island, Bass Strait, Australia: Relationship to continental rifting

Abstract

Fission track ages have been determined on sphene and apatite from the granitic rocks of King Island in Bass Strait, southeastern Australia. In all cases sphene and apatite ages are markedly discordant. Sphene ages compare very closely to earlier KAr measurements and indicate an emplacement age of about 350 m.y. for the east coast group of granites and their important scheelite mineralization. Apatite ages are all younger by about 80-200 m.y. suggesting that fission tracks were not fully retained in this mineral until the Cretaceous. During the Cretaceous King Island was at the edge of the developing Otway Rift Valley which resulted in the breakup of Australia and Antarctica. Uplift of the b..