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Importance of Gypsum Purity in Electric Imaging
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, Near Surface 2009 - 15th EAGE European Meeting of Environmental and Engineering Geophysics, Sep 2009, cp-134-00092
- ISBN: 978-90-73781-72-6
Abstract
Gypsum deposits are the currently exploited sulphate rocks with industrial purposes. In addition to the expensive drilling projects, geophysical techniques can be considered to estimate the economical potential of these deposits. The scope of this study is to characterize the geoelectrical response of gypsum rocks to accurately define their range of resistivity and evaluate the influence of accompaining minerals in gypsum formations. Electric imaging has been successfully applied to identify the gypsum deposits interlayered in lutite units. Nevertheless, the gypsum-lutite boundaries can be shown diffuse and uncertain in the tomographyc lines. A meaningful correlation between electric resistivity and purity of gypsum has been determined. It is clear that resistivity for the investigated gypsum facies varies in a rather wide range, from 50 to 1500 Ωm; the highest values are attributed to sulphate layers with >90% of gypsum mineral. Lutite units display higher values than expected, given that lutites related to evaporite deposits are commonly marly, silty, evaporite minerals-rich and clay-poor. The results show that electric resistivity lines could be useful in prospection of gypsum deposits. However, imaging prospection should be supported by an accurate petrological study of the deposits, in order to properly interpret the resistivity profiles.