MAPPING ALTERATION IN THE HILLSBORO MINING DISTRICT, NEW MEXICO, USING AVIRIS DATA

The Hillsboro mining district is located in the Animas Mountains in Sierra County, New Mexico, approximately 180 miles south of Albuquerque. The Copper Flat porphyry is a Laramide copper deposit located near the center of the district. The porphyry has been exposed by limited mining, revealing local and distal zonation of minerals related to the emplacement of the porphyry and mineralization. In addition to the copper porphyry, skarns, jasperoids and precious metal veins are present at the site. Alteration assemblages within the district are prevalent, varied, and have been well studied and documented.

High altitude Airborne Visible Infra-Red Imaging Spectrometer (AVIRIS) data was acquired over the area during the summer of 1998 from an altitude of approximately 65,000 feet. This remotely sensed data has a spatial resolution of approximately 20 meters and measures spectral radiance in 224 bands of the electromagnetic spectrum between 0.38 and 2.5 micrometers. AVIRIS data can be used to create maps of certain minerals by comparing the reflectance spectra of materials on the ground to reference spectra of known minerals. AVIRIS data has been used with success many times in the past to map minerals occurring on the surface. This project is being conducted to evaluate the effectiveness of using AVIRIS data to map different types of alteration associated with each deposit type present within the Hillsboro district. The results of the project may lead to a better understanding of the distribution of alteration minerals within the district. Limonite minerals and many clay minerals have been mapped and preliminarily field checked using a portable spectrometer. X-ray diffraction analysis is being performed on samples from the site to further confirm the results of mineral mapping. This research is being conducted in collaboration with the New Mexico Bureau of Mines and Mineral Resources.