PROVENANCE OF PERMIAN-TRIASSIC AND ORDOVICIAN METAGRAYWACKE TERRANES IN NEW-ZEALAND - EVIDENCE FROM AR-40 AR-39 DATING OF DETRITAL MICAS/

Single-crystal Ar-40/Ar-39 ages of detrital micas from Greenland Group (Ordovician) low grade metagraywackes of the West Coast, South Island , New Zealand, indicate a source area having muscovite age patterns of 490-515 Ma. The detrital muscovite ages are characteristic of granito id and gneiss terranes of the Ross-Adelaide fold belt of Antarctica; t herefore, the source area far the Greenland Group sedimentary rocks wa s the immediately adjacent Pacific margin of Gondwana. Similar age det erminations for Rakaia terrane (Permian-Triassic) Torlesse Supergroup metagraywackes of the Wellington and Canterbury regions of New Zealand indicate that their source area included rocks having prominent musco vite cooling ages populations of 210-290 Ma (80%) and 410-460 Ma (15%) . The Torlesse detrital muscovite age data thus suggest that the sourc e area of the metagraywackes was not within the Lachlan fold belt of s outheast southeast Australia and analogues in Antarctica, nor in the a djacent Ross-Adelaide fold belt Rather, the Rakaia terrane of the Torl esse metagraywackes is a true suspect terrane derived from a source ar ea within the Hunter-Bowen fold belt of northeast Australia and the im mediately adjacent older orogens of eastern Queensland.