Rio Tinto Mining & Exploration Ltd., Santiago, Chile

The Los Menucos District, Rio Negro, Argentina, provides an excellent case history of a complex epithermal gold system mapped and explored using a combination of field mapping and multispectral/hyperspectral remote sensing. The district offers a host of argillic and advanced argillic alteration minerals at the surface, many of which are difficult to identify visually. A strategy utilizing regional targeting with Landsat TM to optimize field mapping followed by district-level survey with hyperspectral imaging (HSI) data demonstrates the value added by high-spectral resolution aircraft data. Standardized analysis methods consisting of spatial and spectral data reduction to a few key endmember spectra provides a consistent way to map spectrally active minerals. Minerals identified in the Los Menucos district using the JPL Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) include hematite, goethite, kaolinite, dickite, alunite, pyrophyllite, muscovite/sericite, montmorillonite, calcite, and zeolites. Hyperspectral maps show good correspondence with the results of field reconnaissance verification and spectral measurements acquired using an ASD field spectrometer. Further analysis of Hyperion (satellite-based) hyperspectral data indicates that similar mapping results can be achieved from satellite altitudes. These examples illustrate the high potential of hyperspectral remote sensing for geologic mapping and mineral exploration.