Characterization of hydrothermally altered materials in the Central Volcanic Range, Costa Rica, using TM data

摘要

In this study, Crosta technique is used to delineate the associated zones of hydrothermal alteration in the Central Volcanic Range, Costa Rica. This technique consists on a selective principal components analysis applied for mapping iron oxide and clay minerals. These materials are directly related with several types of hydrothermal alteration (potassic, phyllic, propylitic and argillic alteration). Multispectral imagery from Landsat 5 and 7 is used in order to make a multitemporal approach. Image processing includes fusion technique and calibration to reflectance. Fusion technique is applied to enhanced spatial resolution. For calibration to reflectance, a radiative transfer code is used. Analysis of TM and ETM+ data resulted in the identification of a large variety of minerals and materials. Results from multispectral images is merged with aerial photography from an area of special interest, Izaru Volcano, and contrasted with field radiometry data. Preliminary results are presented.