Avaliacao dos produtos integrados TM-Landsat, Radarsat e gamaespectrometricos na caracterizacao tectonica e mapeamento geologico de area mineralizada em ouro na regiao de Alta Floresta - MT / Landsat TM, Radarsat and airborne gamma ray digital data integrated products evaluation for tectonic characterization and geological mapping of a gold mineralized area,

Vanessa Madrucci

The Alta Floresta region, located in the northern part of the Mato Grosso State, is characterized by an almost flat terrain, with intense anthropogenic activities, a high potential in terms of gold mineralization, and a poor geological knowledge. This research has focussed on the application of digital remote sensing integrated products (TM-Landsat/Standard RADARSAT, TM-Landsat/airborne gamma ray and RADARSAT/airborne gamma ray)aiming geological mapping and mineral exploration in this kind of complex environment. Ascending (S3)and descending (S1)RADARSAT and TM-Landsat images were geometrically corrected (orthoretified)and digitally merged through decorrelation and IHS transformation. The integration of optical and SAR with airborne gamma (Total Count, Uranium, Thorium, Potassium and ratios)were based on pseudo-color tables and IHS transform. A performance evaluation was also carried out taking into consideration the contribution of each integrated product for the geological mapping. The results of investigation have shown that the integrated products presented an excellent performance in the discrimination of the main lithoestructural domains. General variations of patterns in the remote sensing/gamma products, given by colors and related textural attributes, were well correlated with changes in the geology. On other hand, the integration of RADARSAT with TM-Landsat was important in highlighting the major structural patterns due to the complementary geometry of the SAR (ascending and descending passes, distinct look azimuths)and the sun (elevation and azimuth angles)illuminations. Seven lithoestructural domains were characterized: basement, volcano-sedimentary sequence, basic rocks, granitoids, acid extrusives, anorogenic granites, and a metasedimentary cover, with ages ranging from the Archaen to Meso Proterozoic. In addition, remarkable N60-70W trend strike-slip systems (ductil, ductil-brittle shear zones)were detected and characterized through visual interpretation of the integrated products and field verification. The investigation has shown the importance of the usage of digital integration based on orbital remote sensing and airborne geophysical data for geological mapping. It has provided also new insights regarding the controls for the primary gold mineralization in the area.

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