ampling Density or sampling rate (the number of taken samples per unit area) is a significant sampling factor in exploration schemes. Determining the effect of sampling density variations by reducing the number of samples used to elemental anomalies detection and determining the effective sampling density in geochemical exploration has been done by several researchers. The results of these studies may lead to uncertainties, since only once data extraction methods have been used to reduce the sampling density, and this process has not been repeated. Investigation of the effect of variable sampling density and the effect of using different samples on the identification of geochemical indices associated with the deposit and on estimated values of mean copper element concentrations in lithological units are the purposes of this thesis. Simulation of low-density sampling was performed by the data reduction method and by repeated random sampling using the Monte Carlo method. A Dataset of stream sediment geochemical samples with a sampling density of about 0.4 per 1 sq. Km from the southern section 1: 100000 Varzaghan geological sheet with known copper deposit and events like Sungun porphyry copper deposit is employed and The True Sample Catchment Basin approach applied over them to determine the probability of copper detection. The results showed that using the True Sample Catchment basin method for analyzing the stream sediment geochemical data due to considering the factors of lithology, downstream dilution and the area of the true drainage basin performed well in recognition of Anomalous areas. Changing the density of the sampling causes changes in the estimated values of copper element concentration in the effective lithological units of the study area. A direct and close linear relationship between sample density and the probability of mineralization detection parameters is also shown in this study. Reducing the number of samples leads to misalignment of anomaly zones, errors in the identification of deposits and a decrease in mineral exploration risk. Considering the trend of changes in mean weighted values of copper concentration in lithology units and a 6.5 percent decline exploration chance in 0.33 sample per sq. Km sampling density, this sampling density as an effective sampling density and 397 samples as the minimum and a suitable number of sediment samples for geochemical exploration schemes have been suggested in this area.