PIMA in the SEG Newsletter

Alteration Mapping in Exploration: Application of Short-Wave Infrared (SWIR) Spectroscopy

October 1999, Number 39

Anne J.B. Thompson, Phoebe L. Hauff and Audrey J. Robitaille

ABSTRACT

Alteration mineral assemblages are important to the understanding of and exploration for hydrothermal ore deposits. Conventional mapping tools may not identify fine-grained minerals and define important compositional variations. Field portable short wave infrared (SWIR) spectrometers solve some of these problems and provide a valuable tool in evaluating the distribution of alteration assemblages. Spectrometers such as the PIMA-II allow rapid identification of minerals and mineral-specific variations at a field-base. Mineral assemblages, integrated with other exploration data, are then used to target drill holes and guide regional exploration programs. Data collection must be systematically organized and carried out by a trained operator. Analysis of data sets requires the use of spectral reference libraries from different geological environments and may be aided in some cases by computer data processing packages. Integration of results with field observations, petrography and X-ray diffraction analysis is necessary for complete evaluation. PIMA™ has been used successfully in the high-sulfidation epithermal, low-sulfidation epithermal, VMS and intrusion-related environments. Case studies from these systems demonstrate the ability to rapidly acquire and process SWIR data and produce drill logs and maps. The resulting information is critical for targeting.

The entire article is available from Spectral International (pusa@rmi.net) or PetraScience (anne@petrascience.com). Please contact us for a copy.