The tectonic framework of the Alto Guaporé Belt, Amazonian Craton, Brazil, revealed by the integration of airborne geophysics, and geological and geochronological data

Abstract

The Alto Guaporé Belt represents a key component in the investigation of the geological history and reconstruction of the SW Amazonian Craton. Airborne geophysical, isotopic and geochronological data integrated with field data have provided new insight into the tectonic framework of this terrane. More than 90,000-line kilometers of airborne geophysical data, including magnetic and gamma-spectrometry data, acquired over of 43,018 square kilometers in the southeastern part of Rondônia and northwestern limit of Mato Grosso states between 2005 and 2006. Aeromagnetic data allowed the generation of geophysical maps, including the total magnetic intensity, the first order derivative, and the analytic signal amplitude, which enabled the identification of terrane limits, structural pattern and geometry of magnetic bodies. Integration of these products resulted in qualitative models of magnetic and structural domains highlighting and characterizing the three deformation events. The pseudo-gravity map enhanced the deep structures, it shows clear discrimination of deep sources between the Alto Guaporé Belt and the Jauru Terrane. This relation is not easily understood when a conventional analysis of magnetic data is performed. The airborne gamma-ray spectrometry data showed areas of concentration and dispersion of radioelements, improving the geologic mapping for the definition of geologic contacts, intrusive bodies and the overlap of areas with sedimentary covers and regolith material. The geological, geochronological U-Pb and isotopic Sm-Nd data helped constrain the geodynamic evolution for this portion of the Amazonian Craton. The geodynamic history and geologic architecture are important parameters for the definition of mineral systems and mineral exploration targeting models at regional and local scales.