Delineating mineralized phases based on lithogeochemical data using multifractal model in Touzlar epithermal Au–Ag (Cu) deposit, NW Iran Seyed Mehran Heidari a , Majid Ghaderi a,⇑ , Peyman Afzal b a Department of Economic Geology, Tarbiat Modares University, Tehran, Iran b Department of Mining Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran article info Article history: Received 2 July 2011 Accepted 20 December 2012 Available online 31 January 2013 Editorial handling by A. Danielsson abstract The aim of this study is to delineate and separate mineralization phases based on surface lithogeochem- ical Au, Ag, As and Cu data, using the Concentration–Area (C–A) fractal method in the Touzlar epithermal Au–Ag (Cu) deposit, NW Iran. Four mineralization phases delineated by multifractal modeling for these elements are correlated with the findings of mineralization phases from geological studies. The extreme phase of Au mineralization is higher than 3.38 ppm, which is correlated with the main sulfidation phase, whereas Ag extreme phase (higher than 52.48 ppm) is associated with silicic veins and veinlets. The resulting multifractal modeling illustrates that Au and Ag have two different mineralization trends in this area. Extreme (higher than 398.1 ppm) and high mineralization phases of Cu from the C–A method cor- relate with hydrothermal breccias and main sulfidation stage in the deposit, respectively. Different stages of Au mineralization have relationships with As enrichment, especially in high and extreme (higher than 7.9%) phases. The obtained results were compared with fault distribution patterns, showing a positive correlation between mineralization phases and the faults present in the deposit. Moreover, mineraliza- tion phases of these elements demonstrate a good correlation with silicification and silicic veins and veinlets. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Study of mineralogy and paragenetic sequence provides useful data on ore-forming processes in deposits in a way that character- istics of different types of deposits exist in their mineral assem- blages (Craig and Vaughan, 1994). Therefore, delineation and separation of mineralization phases are two important tasks in economic geology studies as well as mineral exploration. Among different types of deposits, separation of mineralization is difficult in epithermal precious-metal deposits due to close relation be- tween alteration and mineralization. These deposits are very important, because they produce a great proportion of gold and sil- ver throughout the world (Hedenquist et al., 2000). Mineralogical and geochemical characteristics are the basis for separation of min- eralization phases in epithermal deposits (e.g., Pirajno, 1992; Rich- ards, 1995; White and Hedenquist, 1995; Sillitoe, 1997; Hedenquist et al., 2000; Jensen and Barton, 2000; Pirajno and Ba- gas, 2002; Chouinard et al., 2005; Hoefs, 2009). Classical methods are based on mineralographical and petrographical studies includ- ing alteration assemblage and ore mineral identification using X- ray Diffraction (XRD), Electron Probe Micro Analyzer (EPMA), Scan- ning Electron Microscopy (SEM) and Portable Infrared Mineral Analyzer (PIMA) (Hudson, 2003; San Shen and Yang, 2004; Choui- nard et al., 2005; Hoefs, 2009). Fluid inclusion and stable isotope studies are other methods for delineating different mineralization phases based on thermometric and isotope element parameters within other geological characteristics (e.g., Faure et al., 2002; Boy- ce et al., 2007). Fractal geometry established by Mandelbrot (1983) is a non-lin- ear geometry based on the Latin word ‘‘fractus’’ and has been widely applied in geosciences (e.g., Turcotte, 1986; Meng and Zhao, 1991; Agterberg et al., 1993, 1996; Cheng et al., 1994; Goncalves et al., 1998; Cheng, 1999; Sim et al., 1999; Davis, 2002; Shen and Zhao, 2002; Li et al., 2003; Ali et al., 2007; Carranza, 2009; Zuo et al., 2009a,b,c,d; Afzal et al., 2010; Carranza and Sadeghi, 2010; Zuo, 2011a,b). Cheng et al. (1994) proposed the Concentration– Area (C–A) fractal method for separating different geochemical populations especially for hydrothermal deposits. This method has been an evolution in geochemical studies for recognition of dif- ferent grade anomalies and related mineralization from back- ground. Fractal dimensions in geological and geochemical processes correspond to variations in physical attributes such as rock type, vein density or orientation, fluid phase, alteration phe- nomena, structural feature or dominant mineralogy, and so on (Sim et al., 1999). It has been revealed that hydrothermal mineral deposits, such as epithermal Au–Ag (Cu) deposits, present non-Euclidean variations in ore element concentrations in rocks 0883-2927/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.apgeochem.2012.12.014 ⇑ Corresponding author. Tel./fax: +98 21 82884406. E-mail address: mghaderi@modares.ac.ir (M. Ghaderi). Applied Geochemistry 31 (2013) 119–132 Contents lists available at SciVerse ScienceDirect Applied Geochemistry journal homepage: www.elsevier.com/locate/apgeochem