Erosion of porphyry copper deposits estimated by quantitative elemental content analysis on the example of Aktogay and Sungun ore fields

Background. Porphyry copper deposits are attracting increased attention, which determines the relevance of studying their geochemical patterns to ensure a greater efficiency of geological fore casting. Aim. To establish distribution patterns of geochemical elemental associations in porphyry cop per deposits with respect to different levels of erosion by comparing the geochemical features of primary halos at the current level of the erosion section of the Aktogay porphyry copper ore field (Kazakhstan) and the results of geochemical testing of wells of the Sungun porphyry copper de posit (Iran). Materials and methods. A comprehensive geological and geochemical study of a large ore field — the Koldar massif — was carried out in the period from 1982 to 1991. Fieldwork was carried out by the specialists of the Department of Geology, Peoples Friendship University (UDN), in the southern marginal part of the Bakanas depression, considered as the northeastern segment of the Balkhash–Ili volcanic plutonic belt (Central Kazakhstan). A lithogeochemical sampling of bedrock of the Koldar granitoid massif, which includes three porphyry copper deposits (Aktogay, Aidarly, and Kyzylkiya), was carried out. The collected materials were subjected to computer processing. The geochemical data obtained on the Aktogay ore field were compared with the data of deep testing of the Sungun deposit. Lithogeochemical testing of the Aktogay ore field involved spectral, flame photometric (K, Na, Li, Rb, Cs), and atomic absorption analyses of about 1500 samples for the content of 17 elements (Pb, Cr, Ni, Co, V, Mo, Sn, Zn, Bi, Cu, Ag, Au, Li, Rb, Cs, Na, and K). Results. The above-ore, upper-ore, and under-ore levels of the erosion section of the Koldar porphyry copper deposits are clearly identified by quantitative elemental contents in primary lithochemical halos and the following trends in the ratios, typical of porphyry copper mineralization: Cu x Mo/Pb x Zn, Mo/Co, Cu/Mo, Cu x Mo/Cr, Ni/Co. The former two erosion levels of the Koldar deposit are comparable with similar deep levels of the Sungun deposit. Conclusion. The geochemical anomaly of the Kyzylkiya ore occurrence corresponds to the sub-ore level of ore mineralization.