Abstract not available. This series is produced to expedite the release of information by making unedited manuscript material available to the public in advance of formal publication, and to act as a repository for relevant supporting data that are referred to in published reports. Open Files can be maps; reports; voluminous data sets resulting from multiparameter geophysical and geochemical surveys; consultants' reports; preliminary, unvetted field and laboratory results. They are all critically reviewed by one specialist. The series is geared towards specialists (mining industry, land-use planning, geoscience students) rather than the general public.