Mesgaran Copper Field is located 29 km south of Sarbisheh City, east of Iran. Accessibility to the field is possible via Nehbandan-Sarbisheh Road. There is no rough topographic area in the field and nearly all of the field is accessible by usual cars. The geological structure of the area contains of mafic and ultramafic rocks. This field is a part of the Gold zone of Ahangaran-Bandan metallogenic province (Figure 1) [16].

In Mesgaran mining area Copper mineralization has occurred in pillow-lava and andesite-basalt sequences of eastern Iran (Figure 2). Two mineralization zones were identified as sulfide mineralization with silicified stockworks (primary mineralization) and supergene mineralization. The primary copper mineralization in this region is mostly in accordance to silicified or carbonate veins with epidote and chlorite in volcanic basalt [3].

These veins cross out the volcanic complex as stockworks which include Chalcopyrite, Bournite and Pyrite. In this region, we observed no evidence proving massive deposit or lens shape deposit creation. The main observed minerals

are sulfide and oxide forms of copper. Malachite, Azurite and lower amounts of Tenorite and native copper in oxide supergene zone and chalcopyrite and bournite as the primary sulfides have been detected. Oxidation and erosion caused geotite and hematite around sulfide minerals like Chalcopyrite and Pyrite (Figure 3). Alteration is observed almost everywhere on the surface but the degree of alteration varies. Generally alteration occurs when rocks react to hydrothermal and magmatic fluids and this reaction leads to chemical and mineralogic changes. Chlorite alteration has occurred in large scale which is a specific form of Propylitic alteration. Al, Fe and Mg rich fluids cased chlorite alteration in basic rocks [18].

In this region, argillic alteration (presence of Montmorillonite mineral) as a secondary alteration process is observed too. Most of the copper is in oxide form on the surface and because of high degree of oxidation and erosion, sulfide mineralization is rare in outcrops so deeper samples are needed to study the deposit. Drilling is the best choice in such situations. According to mineralization and the host rock (pillow lava and andesite-basalt), the mineralization type seems to be categorized as a massive sulfide and redbed type. Generally the mineralization manner (copper mineralization as stockworks), the host rock (pillow lava and andesite-basalt), the deposit development environment (a volcanic part of an

Ophiolite sequence) and the alterations (quartz-carbonate, epidote and chlorite) observed in this region and comparing them to the massive sulfide types leads to classify Mesgaran deposit as a Volcanic Massive Sulfide (VMS) type. But still more studies are needed to prove this claim with higher accuracy [18] [19] (see Figure 4).

200 kg of the sample is taken from Mesgaran Field after excavation. Then the sample is crushed by a jaw crusher and milled to obtain minus 120 microns size. After milling, XRF and XRD are applied to the sample to study phases and chemical composition. All tests and devices took place in laboratories of Amirkabir University of Technology. The main copper mineral phase in the sample is malachite and the main mineral phase of the sample is quartz that does not react with sulfuric acid. XRF device was X’Unique II Philips (Table 1).

For leaching tests, sulfuric acid of Merck Company is selected and distilled water is used for dilution. Moreover, a hotplate and 250 ml beaker are used for these tests. The hotplate has a digital temperature regulator and magnetic stirrer. First,

the solution is prepared for each test in a beaker together with specified pH and after reaching a defined temperature, a certain amount of copper ore with a size fraction of minus 120 micron is added to the solution for doing leaching tests in certain time periods. Four factors of acid concentrations, temperature, time and pulp density has been studied in three levels by the Taguchi method. As a consequence, L9 Taguchi orthogonal array has been selected for leaching tests. Tests are designed with the Taguchi method and Variance analysis (ANOVA) has been done in Design Expert for leaching tests and Microsoft Excel for cementation tests. The value of each parameter at every level has been presented in Table 2.

The cementation process of copper by iron powder is provided by following equation:

Cu 2 + + Fe ⇒ Cu + Fe 2 +

As a result of the differences in electrochemical potentials, a reaction will take place. The reaction potential of Iron and Copper is presented in Table 3.

(∆G˚)₂₉₈= −20.29 − 15.54 = −35.83 Kcal

According to the Gibbs free energy equation, the reaction will be obtained

spontaneously. In order to perform cementation tests, 100 ml of copper ore was dissolved in the solution and added up to a 250 ml beaker, and after regulating pH, the temperature will be adjusted by the hotplate. After these steps, iron powder will be added up to the solution in order to study the test.

In order to study the cementation of copper by iron powder, four parameters of pH, temperature, time and amount of iron powder were optimized in three levels by the Taguchi method. The value of each parameter at every level has been presented in Table 4.

The technique of defining and investigating all the possible conditions in an experiment involving multiple factors is known as the design of experiments. Basically, classical parameter design, developed by Fisher, is complicated and not easy to use. Especially, a large number of experiments must be conducted when the number of the process parameters increases. To solve this problem, Taguchi method uses a special design of orthogonal arrays to study the entire parameter space with a small number of experiments only [20] [21].

Experimental designs were first introduced by Fisher as an agricultural research tool in the 1920s [22]. His primary aim was to obtain the most information possible about a process with the least number of experiments. Experimental designs and optimization methods for chemists and other engineering branches were reviewed by Bayne and Rubin [23] , Debets [24] and Duckworth [25] , Taguchi [26] simplified the application of experimental design by using standardized library of basic designs called orthogonal arrays, along with some simple methods to modify these layout to fit individual situations. His methodology was also developed within an industrial environment and favoured productivity and cost effectiveness over the statistical rigor. Orthogonal arrays were used to assign factors to a series of experimental combinations which results could then be analyzed by using a common mathematical procedure. The main effect of these factors and preselected interactions between the factors were independently extracted. The identification of controlling factors and the quantitation of the magnitude of the effects was emphasized rather than just the identification of statistically significant effects. The number of trial chosen for an experimental design was based on the resolution desired. In a factorial design, one could study main effects as well as interactions between factors. This latter

characteristic was a major advantage of the technique but a major disadvantage of one-at-a-time variable testing. Main effects and interactions could be confounded, with one another if the experimental design of low resolution were chosen [27] [28].

The L9 array leaching tests which are modeled by the Taguchi method are inserted in Table 5.