The Forrestania EM Test Range is situated approximately 85km by road/track east of Hyden and ~155km by road/track SSE of Southern Cross. The test range is well positioned and provides easy access if traveling from Perth or Kalgoorlie (~4-5hrs).
The Forrestania EM Test Range has been designed to allow testing/trialling of various electromagnetic methods (surface, airborne and downhole techniques) over two, discrete and varying bedrock conductors defined during previous geophysical exploration completed on behalf of Image Resources NL. The two bedrock conductors defined and drilled by Image Resources successfully tested these targets, intersecting barren, semi-massive to massive sulphides (po-rich).
The western conductor (IR2) is of limited areal size (<75x75m), shallow depth <100m, high conductance >7000S and dips northward ~30-40 degrees. This conductor is strongly defined by surface and downhole TEM and makes for an interesting airborne TEM target.
The eastern conductor (IR4) is extensive in strike/plunge extent (~500-600m+) and reasonably well constrained in depth extent (~100-150m). The conductive source is situated at considerable depth ~300-325m (western side) to ~400m+ (eastern side), is highly conductive ~5000-10000S and dips northward ~30-40 degrees. IR4 is a more challenging conductive target for surface TEM methods with smaller transmitter loops.
The local electrical environment is characterised by the presence of a conductive overburden (~10-20S), highly resistive bedrock units and lack of any other bedrock conductors in the immediate area other than the IR2 and IR4.
Work Completed at the EM Test Range
- FLTEM dB/dt and B-Field HT-SQUID coverage over the IR4 bedrock conductor with large and small transmitter loops. FLTEM dB/dt coverage over the IR2 bedrock conductor with large and small transmitter loops. Figure 1 highlights some of these results. Completed as a standard survey by Outer Rim Exploration Services.
- MLTEM dB/dt and B-Field fluxgate coverage over the IR4 bedrock conductor (200m transmitter loops, Figure 2 – Courtesy of GEM Geophysical Surveys.
- DHTEM dB/dt – Crone PEM surveys, holes FRC1 and FRCD3 Figure 3. Completed as a standard survey by Outer Rim Exploration Services.
- Fixed Loop Total Field (SAMSON) surveying – Figure 4 – courtesy of Khumsup Ltd
- Helicopter EM surveys – HELITEM (Fugro Airborne Surveys, 2011), VTEM-max (Geotech Airborne Ltd, 2011). An example of the HELITEM and VTEM-max is shown in Figures 5 & Figures 6 respectively. Both datasets are available through the contractors only.
- ZTEM survey by Geotech Airborne Ltd
- 200m modern aeromagnetic/radiometric data coverage.
Proposed Work to be Completed at the EM Test Range
- MLTEM using SQUID
- DHTEM B-Field surveying of holes FRC1 and FRCD3 (FRCD3 is now blocked).