ORIGINAL ARTICLE The efficiency and accuracy of probability diagram, spatial statistic and fractal methods in the identification of shear zone gold mineralization: a case study of the Saqqez gold ore district, NW Iran Mirmahdi Seyedrahimi-Niaraq 1 • Amin Hekmatnejad 2 Received: 23 July 2019 / Revised: 29 February 2020 / Accepted: 20 March 2020 Ó Science Press and Institute of Geochemistry, CAS and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract In this study, geochemical anomaly separation was carried out with methods based on the distribution model, which includes probability diagram (MPD), fractal (concentration-area technique), and U-statistic methods. The main objective is to evaluate the efficiency and accuracy of the methods in separation of anomalies on the shear zone gold mineralization. For this purpose, samples were taken from the secondary lithogeochemical environ- ment (stream sediment samples) on the gold mineralization in Saqqez, NW of Iran. Interpretation of the histograms and diagrams showed that the MPD is capable of identifying two phases of mineralization. The fractal method could separate only one phase of change based on the fractal dimension with high concentration areas of the Au element. The spatial analysis showed two mixed subpopulations after U = 0 and another subpopulation with very high U values. The MPD analysis followed spatial analysis, which shows the detail of the variations. Six mineralized zones detected from local geochemical exploration results were used for validating the methods mentioned above. The MPD method was able to identify the anomalous areas higher than 90%, whereas the two other methods identified 60% (maximum) of the anomalous areas. The raw data without any estimation for the concentration was used by the MPD method using aminimum of calculations to determine the threshold values. Therefore, the MPD method is more robust than the other methods. The spatial analysis identified the detail soft hegeological and miner- alization events that were affected in the study area. MPD is recommended as the best, and the spatial U-analysis is the next reliable method to be used. The fractal method could show more detail of the events and variations in the area with asymmetrical grid net and a higher density of sampling or at the detailed exploration stage. Keywords Shear zone gold deposit  Modeling of probability diagram method  Concentration-area fractal method  U-spatial statistics method  Phases of efficiency and accuracy mineralization 1 Introduction Varieties of different anomaly separation methods were proposed in calculating threshold values during last two decades (Sinclair 1974, 1991; Govett et al. 1975; Cheng et al. 1994, 2000; Yusta et al. 1998; Cheng 1999; Gon- c ¸alves et al. 2001; Li et al. 2003; Lima et al. 2003; Zuo et al. 2009; Ghavami-Riabi et al. 2010; Ghannadpour and Hezarkhani 2016; Ghezelbash and Maghsoudi 2018; Liu et al. 2019; Yousefi et al. 2019). These methods were used for different case studies but not often compared to each other at the same time. Modeling of probability diagram (MPD), spatial analysis techniques such as moving aver- age, Kriging, U-statistic, and fractal (concentration-dis- tance and concentration-area diagrams) are some of the geochemical anomaly separation methods. In some of these methods, the statistical distribution is considered for & Mirmahdi Seyedrahimi-Niaraq m.seyedrahimi@uma.ac.ir Amin Hekmatnejad amin.hekmatnejad@utalca.cl 1 Floor No. 2, Faculty of Engineering, University of Mohaghegh Ardabili, Daneshgah Street, Ardabil City, Ardabil Province 5619911367, Iran 2 School of Mining Engineering, University of Talca, Camino a Los Niches Km 1, 8370456 Curico ´, Chile 123 Acta Geochim https://doi.org/10.1007/s11631-020-00413-7