NEW CONCEPTS IN GEOPHYSICAL DATA ANALYSIS FOR CONCEALED MINERAL DEPOSITS

Cenozoic basins of the Basin and Range Geologic Province contain a large potential for undiscovered mineral deposits in bedrock concealed by basin fill. We have developed several technologies aimed at best using geophysical and geologic data to help assess and define these concealed deposits. These include identification of concealed lithology, detailed modeling of mineralized regions, and using potential penetrative fractures to help identify mineralization at depth.

Both aeromagnetic and ground-based magnetic surveys have been found to be useful for identifying concealed lithology in the Basin and Range of Arizona and Nevada. Upward continued Earth’s magnetic field data from exposed lithologies are compared to data from magnetic bedrock concealed by basin fill using measures that summarize the physical appearance (texture) of the magnetic data. These textural measures include statistics, fractal and multifractal measures, and power spectra. Using ground-based magnetic profile data, lithologies concealed by up to 100 m of basin fill can be discriminated in some cases. Using aeromagnetic data, textural measures combined with possibility theory have also identified concealed lithology in deeper parts of basins (1 km and more) in some cases.

The complex succession of intrusions in the Patagonia Mountains, Arizona has been well defined. This area hosts two known porphyry copper systems as well as a large number of other types of mineral deposits. Using aeromagnetic and other data, including estimated reversed rock remanence, detailed modeling defines a favorable terrane for a wide variety of concealed mineral deposits associated with a late phase of the Patagonia batholith.

Potential penetrative fractures are estimated by spatially correlating curvilinear surface features with deep seated curvilinear geophysical anomalies. These throughgoing fractures may be related to mineralization at depth near locations where they are spatially correlated with mineralization at the surface. Preliminary results from Arizona and Nevada show promise.

As mineral terranes mature, resource development will need to utilize mineralized systems that are not exposed at the surface; technologies such as ours will contribute to meeting resource demands of the future.