Case Studies - Mineral Exploration

Phelps Dodge Deposit

The Phelps Dodge volcanic massive sulphide deposit is located in the northern Abitibi, Québec, Canada, approximately 38 km to the west of the Matagami mining camp. The deposit was discovered in the early 1970s as a result of ground follow up and drilling of an AEM anomaly. The original AEM survey was flown with a single-frequency, fixed-wing system (Rio Mullard Otter). Subsequent work along the strike of the favourable geology has led to the discovery of the deeper Caber (1994) and Caber North (1995) deposits, 2 to 2.5 km along strike to the southeast. Many GEOTEM surveys have been flown in this area.

The Phelps Dodge massive sulphide zone shown in red (1.6 Mt of 1.1% Cu and 4.9% Zn) dips at 65 degrees, has a strike length of 120 metres, average thickness of 10 metres and a depth extent of 450 metres. The deposit subcrops beneath 15 to 20 metres of overburden. The mineralisation is associated with a geological equivalent of the Matagami camp Key Tuffite, which marks the contact between the hanging-wall andesite and the foot- wall rhyolite.

            
   dB/dt Profile Data                                    B-Field Response

Cross Section 1E- Flight Direction is South.

The GEOTEM dataset shown was acquired with a 90 Hz waveform frequency and a 2 ms pulse width.

The X-axis and Z-axis dB/dt responses indicate a distinct conductor dipping steeply to the north, with a coincident positive magnetic response. The effect of the overburden is seen on the early-channel data particularly for the Z axis.

The X-axis and Z-axis B-field responses also indicate a distinct conductor. The response shape is sharper and the overburden response is suppressed compared to the dB/dt data.

Data presented with the permission of Noranda Mining and Exploration Inc. Deposit information from Rod Woolham, Geophysical Consultant.