oa Geophysical–Geological Interpretation of the Cobham Lake and Milparinka 1:250 000 Map Sheet Areas, Northwest NSW

As part of the New Frontiers exploration initiative, a new series of geophysical–geological interpretation of 1:250 000 map sheet areas is being completed. Interpretation of the Cobham Lake and Milparinka map sheets in the far northwest of NSW has been completed and highlights and extends the following major domains:

• Proterozoic units of the eastern Curnamona Province are present in the west of Cobham Lake sheet where rock types exposed in the Broken Hill area extend northward under relatively thin cover.

• The Bancannia Trough (thick sequences of Cambrian to Devonian age) and Quinyambie Trough (Cretaceous sediments) share a northwesterly trend.

• The Koonenberry Belt comprises a complex structural zone where Neoproterozoic to Cambro-Ordovician units have been affected by a series of orogenic events.

• Intrusions of Silurian age (such as the Tibooburra Granodiorite), possible Cambro- Ordovician age, and Permian diatremes are interpreted.

• The contact zone is drawn between the Koonenberry Belt and the western extent of the Thomson Orogen.

Aeromagnetic data (1VD and TMI imagery) were used to create a framework plot of anomaly sources, assisting recognition of discontinuities, fractures, and textural domains. Previous interpretations, gravity data, mapping, drilling, seismic, and regional studies were integrated to allocate appropriate stratigraphy. Accompanying reports document aspects such as unit characteristics, major structures, magnetic susceptibility data, anomalous features, mineralisation, and depth to basement information. The Cobham Lake and Milparinka map sheets both have extensive cover of Cretaceous, Tertiary and Quaternary sediments and sedimentary rocks but offer exploration targets at shallow depths.

Technical Area: Geophysics in Government Surveys