Exploration and Economic Significance of the Gossan Around Chahar Gonbad Copper-Gold Mine, Sirjan

Gossan occurs considerably around the Chahar Gonbad copper-gold mine. The mineralogy of gossan includes: hematite (Fe2O3), goethite (FeO(OH)), and limonite (Fe2O3.H2O) with colloform texture, as wewll as quartz, calcite and clay minerals. Enrichment factors include: Ag=1.08, As=1.19, Bi=70.12, Mn=4.11, Mo=2.37, Pb=1.51, Sb=1.7 and Fe=1.71 in comparison to the mineralized rocks. However, Cu=0.03, S=0.03 and Se=0.04 are strongly depleted; Zn= 0.94 is slightly depleted. Based on correlation coefficients, four droups can be distinguished. The first group includes Bi, Cu and Sb which have a good correlation with Fe and Mn. The reason for this correlation is probably the adsorption of Bi, Cu and Sb by iron and manganese hydroxides - oxides in gossans. The second group comprises of Pb and Ag which have a good correlation with Bi, Cu, and Sb, without any relationship with Fe and Mn. The third group elements are As, Mo and Zn which have no correlation with Fe and Mn, as they form insoluble complexes. The fourth group includes sulfur and selenium which formed by sulfide weathering, gossan formation and sulfate minerals. The correlation of Bi with Cu is caused by weathering of sulfide minerals and formation of gossan. Bi, Cu and Au enrichments in the gossan are 3123.94, 12.62 and 400 times the clarck values. All the elements in the gossans, in particular Bi could be considered as the possible exploration guides around Chahar Gonbad area.