Geophysical Surveying

Airborne geophysical surveys have the ability to cover large areas of land in short periods of time and in a cost-effective manner. The methods chosen for the Cordillera del Condor Belt are Magnetics, Electromagnetic and Radiometric surveying, all of which have the ability to image prospective gold, copper-gold and base-metal targets. The deliverables or products from each of the survey types are described below, together with images.

Magnetic Survey


Magnetic Map
[Click to Enlarge] The magnetic survey passively measures relative proportions of magnetic minerals in the rocks. The contrast within and between rock formations can define significant geological contacts and structures and provide focus for geological teams, which are mobilized on the ground. Perhaps more importantly, major structural contacts (faults) can often be identified - faults provide a potential conduit for the mineralizing fluids. Interpretation of favourable structural setting for potential mineral resources is critical in identifying important areas for investigation.

In the Cordillera del Condor Belt, the intersections between broad fault domains is an important control on mineralization, as noted at deposits like Fruta Del Norte and in the Chinapintza District.

Electromagnetic Survey


Geophysical Equipment Prior to Take-off
[Click to Enlarge] Electromagnetic surveys are more complex than magnetic surveys, though no less effective. A transmitter on the helicopter emits a primary electromagnetic field, which penetrates the rocks below to depth. If the primary field encounters a conductive body, such as a mineralized zone, a secondary field is generated and measured by the receiver (also being carried by the aircraft).

The secondary field generated will vary in intensity according to the size, shape and conductivity of the mineralization in the subsurface. The magnitude of the secondary field is measured over several 'channels' which equate to snapshots over time. Anomalies in "early" channels may not be particularly significant, whereas anomalies which persist into "late" channels are generally significant effects generated by increased conductivity in rocks in the subsurface that maintain the secondary field over a greater period of time.


Electromagnetic Map
[Click to Enlarge] The data is often examined in the form of a map, showing anomalies on a particular channel, the higher the channel, the longer the conductivity was maintained. This is a useful way to review the overall responses in the survey area.

Detailed examination of data as profiles is a more complex but more effective way to identify and rank anomalies.



[Click Images to Enlarge]


Radiometric Survey

Radiometrics of Gamma-Ray Spectrometry, is a measure of the natural radiation in the earth's surface. This can provide information about the distribution of certain soils and rocks. Geologists and geophysicists routinely use this geophysical method as a geological mapping tool to identify domains on the earth's surface where rock types change. A radiometric survey measures the spatial distribution of three radioactive elements (potassium-K, thorium-Th and uranium-U) in the top 30-45 cm of the earth's crust. The abundances of K, Th and U are measured by detecting the gamma-rays produced during the natural radioactive decay of these elements.

Radioactive elements occur naturally in the crystals of particular minerals. The abundance of minerals changes across the earth's surface according to variations in rock and soil type. The energy of gamma rays is related to the source radioactive element and is used to measure the abundance of those elements in an area. By measuring the energy of gamma rays emitted in an area, it is possible to infer the presence of particular minerals in the earth's surface. In the Cordillera del Condor, radiometrics can identify areas of potassic alteration, which often defines the centre of gold-copper porphyry systems.