ABSTRACT
The vermiculite deposits of the Queimada Nova locality of the Paulistana region of Piaui State in northeast Brazil is associated with the ultrabasic intrusives. In this work an attempt has been made to define the nature of the deposit using the three dimensional modeling and geostatistics. The thickness was determined through a total of 89 drill holes that were distributed in a grid pattern, covering an area of 300 m × 250 m. The thickness of vermiculite beds varies from a minimum of 0.85 m to a maximum of 19.39 m with a mean of 10.8 m and a variance of 15.58. The modeling included the thickness of the vermiculite bed and the soil cover above the bed. The model shows highly irregular nature of the surface of the deposit. Variographic analysis showed an average variogram with a reasonably good structure without anisotropy. The variogram reflect the apparent pinch and swell nature of the deposit resulting from dykes and sills in the study area and modified my structural deformation.
