SUNRISE-HILL UNCONFORMITY - A NEWLY DISCOVERED REGIONAL HIATUS BETWEEN ARCHEAN GRANITES AND GREENSTONES IN THE NORTHEASTERN PILBARA CRATON

Contacts between Archaean granites and greenstones in the northeastern part of the Pilbara Craton have been described as intrusive and tecto nic. New field observations in the Shay Gap region demonstrate that gr eenstones of the Gorge Creek Group unconformably overlie the Muccan an d Warrawagine batholiths. Regionally, the unconformity is marked by a persistent but relatively thin basal elastic sequence, locally with a granite boulder conglomerate, overlain by ore-bearing banded iron-form ation, fine-grained elastic rocks and chert. The granite basement is d ated at 3443 +/- 6 Ma. The precise age of the hiatus is unknown but it s maximum effect might have been the removal of a substantial thicknes s of Early to Middle Archaean strata.