The Maricunga Belt (chilean Precordillera) and its hydrothermal alteration zones as revealed by multispectral remote sensing and field studies
Remote sensing techniques offer a unique chance to analyse and map wide or nearly inaccessable areas under certain geoscientific aspects in relatively short time and at low cost. Therefore geological field campaigns together with multispectral image analysis were carried out for the Maricunga Belt i...
|Division/Institute:||FB 14: Geowissenschaften|
|Date of publication on miami:||13.09.2004|
|Edition statement:||[Electronic ed.]|
|Subjects:||Geology; Chile; Mineral Alteration; Remote Sensing; Landsat TM; ASTER; Mineralogy; Exploration Fernerkundung; Geologie; Chile; Mineralogie|
|DDC Subject:||550: Geowissenschaften, Geologie|
|Legal notice:||Copyright (2004) by T. Prinz and L. Bischoff|
Remote sensing techniques offer a unique chance to analyse and map wide or nearly inaccessable areas under certain geoscientific aspects in relatively short time and at low cost. Therefore geological field campaigns together with multispectral image analysis were carried out for the Maricunga Belt in the chilenean Precordillera, south of the regional mining settlements San Salvador and Potrerillos (Atacama). On the basis of Landsat-TM 5, ASTER, radar-based DGM-data and field mapping/sampling the lithological/structural characteristics of several OH-bearing hydrothermal alteration zones of mostly Neogene age have been investigated because of their high value for future exploration. The often unknown regional tectonic framework which seems to have controlled the alteration dimensions are also discussed. In order to obtain reasonable lithological classification criteria for the remote sensing data fundamental statistical selection rules like the optimum index factor (OIF) were applied to the combination of single TM bands. Furthermore specific band ratios (5/7; 5/4, 5/1) and principal components were utilized to enhance the spectral properties of the argillized, bleached clay- and/or silica-rich alteration surfaces. Additional spectral measurements were carried out for each representative lithological unit of the alteration zones to estimate the quality of the calculated classifications/ratios for geological mapping. In some cases complementary geochemical data has been studied in order to obtain direct clues for understanding the type of some detected hydrothermal alterations. Finally the achieved data was compiled in a geological map which shows more than 20 hydrothermally altered surfaces in relation to the regional geology and the specific tectonic framework. The influence of three major fault systems (the N-S orientated West Fissure System, the NE-SW orientated Inca De Oro System and a poorly described NW-SE System) for the setting of the alterations seems to be obvious.