THE SOUTHERN AVOCA FAULT ZONE - SITE OF A NEWLY IDENTIFIED GREENSTONE-BELT IN WESTERN VICTORIA

A discontinuous belt of metabasite ('greenstone') occurs along the sou thern extension of the Avoca Fault Zone, southwest of Ballarat, Victor ia. This fault forms the boundary between the Stawell and Bendigo-Ball arat tectonic zones. In the Pitfield-Linton-Scarsdale area the 2 km-wi de fault zone separates simply deformed ?Ordovician turbidites on the east from polydeformed ?Cambro-Ordovician turbidites of similar charac ter to the west. Metabasites appear to be confined mainly to the easte rn edge of the fault zone, but ground magnetic traverses suggest that fault slivers may exist in the western part of the fault zone. Kinemat ic indicators suggest that the southern Avoca Fault Zone is a steep we sterly dipping thrust with west over east movement. Metamorphic grade in the area is greenschist facies, but the grade is slightly higher in the hangingwall, supporting a thrust sense of movement. The Pitfield metabasites are interpreted as an upthrust portion of a layer of ?Camb rian basic volcanics that underlies the Early Palaeozoic turbidite suc cession in the Stawell zone, similar to the Bendigo-Ballarat and Melbo urne zones. These similarities place the Stawell zone in the Lachlan F old Belt with the Bendigo-Ballarat and Melbourne zones. The boundary o f the Lachlan and Adelaide Fold Belts thus lies to the west of the Sta well zone.