ASTER IMAGES APPLIED TO RECOGNITION OF IGNEOUS-METAMORPHIC UNITS AND ASSOCIATED STRUCTURES IN THE "RODEO VIEJO PLUTON", SAN LUIS, ARGENTINA

The aim of this work is to apply ASTER data processing to recognition, differentiation and mapping of igneous-metamorphic units and associated structures in the area of Rodeo Viejo, in San Luis, Argentina. This region is part of the Sierras Pampeanas Orientales System aged to the Superior Precambrian - Inferior Paleozoic. The outcrops found in the district are biotitic quartz schists with intruding syn-kinematic granitoids with the major phase of metamorphism and deformation M2 and F2. Furthermore, the site presents a series of post-kinematic intrusions that constitute the so-called Rodeo Viejo complex composed by the plutons of Rodeo Viejo and El Salado. These are elongated dioritic-tonalitic bodies that stand in variable orientations from N-S to NW-SE. The group has intruding acid granitoids and is represented in this sector by the Paso del Tigre pluton and associated pegmatites. This contribution describes an evaluation of an ASTER L1B scene dated on January 10, 2003. The combinations and operations performed with the bands of the three subsystems (VNIR, SWIR and TIR) allowed a more accurate geological mapping than the one previously carried out in this zone using Landsat 5 System and interpretations of air-photographs (approximate scale 1:20,000). This was achieved due that geological units and their color and texture differences within were identified and thus information on possible hydrothermal alterations, contact types, structures, etc., was obtained. The digital terrain model allowed three-dimensional views from the desired perspective as well as products such as a slope map and shadow images, which were used to construct the structures and drain map. The different products allowed the construction of a geological map with an error <15 m in X and Y, which is acceptable for a (1:100,000) cartography. Furthermore, the metamorphic rock (biotitic quartz schists) intruded by the Rodeo Viejo pluton was discriminated. In addition, the small sized Paso del Tigre granitic body and the associated pegmatitic veins are related to a bright toned aureole that corresponds to a possible hydrothermal alteration. Sometimes, it is difficult to map this aureole due to the working scale. Finally, these products also satisfactorily differentiate the quaternary filling that partially covers the basement.