عنوان مقاله [English]
The Early to Middle Proterozoic Willyama Inliers in western New South Wales extend to the Curnamona section of the Olary Block in eastern South Australia. In
succession, these rocks consist of the Composite gneiss and migmatite Suite, the Quartzofeldespathic Suite, the Calcsilicate Suite, the Bimba Suite, and the Psammo
pelite Suite. The middle parts of the succession correlate stratigraphically to the units within the Broken Hill Block in New South Wales which host the well known Broken
Hill orebody. The Willyama Inliers in the Curnamona 1:250,000 sheet contain a magnetic marker horizon which consists of (i) The Quartzofeldespathic Suite, (ii) The
Calcsilicate Suite and (iii) The calcalbitite rocks (the gradation between the two Suites). This allows mapping these stratiform stratabound anomalous base metal horizons under
cover from latitude 32°S to 31°30'S and longitude 140_ to 141_ on the Kalabity and Mulyongari 1:100,000 sheets (7200 km2) using the magnetic data. The position of the non-magnetic, sulphidic and economic target, the Bimba Suite, can be deduced from the
location of the Quartzofeldespathic magnetic marker and the dip as determined from the magnetic modelling.
The magnetic marker, a distinctive feature on the magnetic maps, allows mapping of folds whose axes trend Northeast-Southwest and major shears which strike NW-SE and
NNE-SSW. The magnetic information indicates that the WilIyama rocks extend further north of the limited outcrop (latitude 32° OO'S) to latitude 31° 30'S; and to the Frome area (latitude 31 ° 00' S); and probably to the central area of the Curnamona Craton along the eastern part of the Benageri ridge. On the Curnamona 1 :250,000 sheet half
the magnetic anomalies arise from the Willyama rocks outcropping, near surface or covered. The magnetic maps indicate various types of granitic intrusions under cover.
The depth to the magnetic sources on the eastern three quarters of the Benageri 1:100,000 sheet in the Curnamona area is less than 350 metres and almost half of them are less than 200 metres deep. Such depths would not rule out exploitation of any orebodies which may be located in this prospective region. Magnetic interpretation shows that no willyama rocks are present at such relatively shallow depths in the western half of the benageti 1:100,000 sheet. This is cinsistent with the occasional drill hole data.