A gravity survey was performed to study a 3D geometry<br>and physical characteristics of the Pariquera-<br>Açu alkaline, a rock emplaced in the Ribeira Valley<br>(SE – Brazil). As result, the gravity pattern, density<br>distribution, 3D geometry and consequent volume,<br>mass and uniaxial stress of the alkaline, were determined.<br>The obtained results will consent to refine the<br>present geological interpretation and, in particular, to<br>establish the nature of the alkaline body tectonic<br>emplacement.<br>To approach the problem, geophysical and numerical<br>methods for determining the Bouguer residual field<br>are reported. Mathematical tools as Butterworth filter,<br>least squares and robust polynomial were selected,<br>taking into account the available data, including those<br>from magnetic and radiometric surveys. Qualitative<br>and quantitative analyses were used to establish the<br>polynomial degree for which the gravity regional<br>field would be better represented. The best fit worth a<br>6th degree robust polynomial, being any discrepancy<br>with the observed gravity field within a mGal.<br>Compared to other models, the obtained geophysical<br>parameters together with the boundary conditions<br>inferred from geological information, select the presented<br>3D irregular shape gravity model as preferred.


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