Combined Electric, Electromagnetic and Gamma Spectrometric Methods Applied to the Pariquera-Açu Alkaline Complex

Abstract

The Pariquera-Açu Alkaline Complex, located in the city of Pariquera-Açu (State of São Paulo), is one of the Brazilianalkaline complexes which has considerable mining potential. The combined use of several methods helped to determinepossible areas for exploration. Geophysical prospecting methods were used to assess the exploration potential of theseareas. The methods used in this study were gamma-spectrometry, induced polarization and electrical survey. Previousgeophysical studies were carried out to better understand the structural evolution of the complex and were not limited tothe study of the lithological variation. Gravimetric studies showed a zone of intense fenitization, which is consistent withalkaline complexes with carbonatites. A dipole-dipole survey conducted in the central part of the complex indicated thepresence in the subsurface of a resistive lithology with high chargeability. These factors, together with other studies onthe alkaline complex, suggest the presence of carbonatite in the area, which is corroborated by gamma spectrometry data,given the concentrations of Th (8 ppm) and U (3.5 ppm) and considering that the measurements were performed over a nonradioactivesedimentary cover.

Keywords

• Gamma Spectrometry
• Electric methods
• Electromagnetic methods