PRECAMBRIAN OROGENESIS - WAS IT REALLY DIFFERENT

Identification of macro-tectonic regimes responsible for development o f orogenic or mobile belts becomes increasingly difficult with age. Es pecially Precambrian mobile belts are difficult to interpret because o f a lack of 'far-field data' such as palaeogeographic reconstructions and palaeomagnetic data from contemporaneous oceanic crust. Neverthele ss, most Precambrian mobile belts can be fitted into actualistic macro -tectonic models of orogenesis involving destructive plate margins. Ar chaean granite-greenstone areas are an exception in that they are diff icult to fit to such actualistic models. One possible explanation is t hat they partly developed in a setting which is different from modern macro-tectonic regimes. A granite-greenstone area in the Yilgarn Crato n, Western Australia, is presented as an example of unusual geometries in such a setting.