Identification of clays and Fe oxide minerals rich alteration zones using a Landsat 8 image of Pu Sam Cap area, Lai Chau

Abstract

The hydrothermal alteration zones are the important sign for mineral exploration and can be identified by remote sensing images completely, but this is limited due to the effect of vegetable. We address this problem by a method called “Directed Principal Component Analysis” (DPCA) that involves calculating principal components on two input band ratio images. One ratio is a geological discriminant, confused by the presence of vegetation; the second ratio is chosen for its suitability as a vegetation index. DPCA applied on Landsat 8 image in Pu Sam Cap area, Lai Châu characteristied by argilic alteration, sericite alteration, etc., with the typical minerals like kaolinite, illite, etc., and pyrite, chalcopyrite, magnetite; specularite, etc., The results have identified Fe - rich zones in Bai Bang and Nam Tra areas; clay minerals are concentrated mainly in Nam Tra area and along the main faults. The results are also compared with previous research data and fieldtrip data that shows similarity and feasibility. This paper indicated limitation of Landsat image such as spatial resolution, spectral resolution, etc., when applied in the tropical area.