Application of Fractal Technique for Analysis of Geophysical - Geochemical Databases in Tekieh Pb-Zn Ore Deposit (SE of Arak)

Tekieh Lead-Zinc ore deposit that is located in the Sanandaj-Sirjan structural zone has been recognized as one of the most important mineralized regions in Malayer-Isfahan metallogenic sub-state, south east of Arak (Momenzadeh and Ziseman, 1981). Carbonate host units have been developed along (or across) the Vishan-Tekieh anticline as the main structure extended in NW-SE trends (Annells et al, 1985). According to geochemical investigations (Salehi, 2004), the element content of the mineralized regions has originated from Alpine post-volcanisms and subsequently it has migrated toward early Cretaceous formations (dolomitic limestones) among several hypogenic stages (Torkashvand et al., 2009). Also echelon type structures consisting of folded systems and inversed faulting of structures are the most common features in western and eastern parts of ore deposit regions (Annells et al, 1985). Syngenetic enrichments beside limited (rarely developed) epigenetic mineralization have been known as two main phases which are closely relevant to ore forming processes in the massive lenses and vein type occurrences, respectively (Momenzadeh and Ziseman, 1981).
Material and In this research, two statistical techniques that consist of classical and fractal equations (Mandelbrot, 2005) were applied in geochemical (Torkashvand et al., 2009) and geophysical (Jafari, 2007) databases for obtaining the linear and nonlinear distributions of geochemical elements (Tekieh Pb-Zn content) in association with resistivity variations and induction polarization measurements (Calagari, 2010). According to linear statistical techniques (Torkashvand et al., 2009), the main central parameters such as mean, median and mode in addition to variances and standard deviations as distribution tendencies could be used for obtaining the regression coefficients of the databases. However, in fractal statistics, a reliable regression between geoelectrical - geochemical anomalies should be calculated based on measuring the fractal dimensional variations in the recursive patterns (Mehrnia, 2013). In practice, the Area-Concentration equations (Mandelbrot, 2005) were applied in resistivity, induction polarization, Pb and Zn datasets for achieving the nonlinear relationships in anomalous regions which were characterized by increasing in regression coefficients with more spatial correlation of the variable than linear statistics (Mehrnia, 2013).
This research showed that both linear and nonlinear statistics are able to estimate the spatial association of geochemical anomalies with geophysical variables. A meaningful increase in the regression coefficient was also revealed after measuring the self-similar peculiarities of concentration values on gridded plots (Salehi, 2004; Torkashvand et al., 2009). From the fractal point of view, Pb ore-minerals have been deposited in the western sub-region, while Zn mineralization seems to be extended in the depth of eastern alterations. Also a predictable geochemical zonation can be considered in the western target (meaningful Pb anomalies) that is more patterned than the eastern halos according to geological observations (Momenzadeh and Ziseman, 1981) and mineralogical evidences (Salehi, 2004). An increase in Supra ore/Sub ore proportional content was measured in the western sub-region which indicated more reliable potential of Pb mineralization (Galena as a particular indication of sulfide-rich minerals) than the same phases of ore forming processes in the eastern sub-region, although the content of Pb-ores rapidly decreases in the eastern target and is replaced by Zn minerals (Sphalerite as particular indication of sulfide-rich mineralization). Because power law relationships are significant in both geochemical and geophysical anomalies (Mehrnia, 2013) a detailed program including borehole geophysics and litho-geochemical land-surveys should be considered in the prospected regions. Therefore, upcoming phases should emphasize on self-organized distribution of Pb-Zn anomalies to introduce a new set of nonlinear distributions in order to find the confidence regression coefficients between the variables. As the final results, fractal analysis of available databases represented new target areas with better mineralization aggregations than linear analysis of the anomalous regions according to micrographs. It means that surficial mineralization processes could be extended in depth and enriched next to altered host units because of a nonlinear but self-organized distribution of geochemical- geophysical anomalies in Tekieh ore deposit region.