Mineralogical characteristics of oxidized copper-porphyry ores at the Koktaszhal deposit

This paper presents the results of a comprehensive mineralogical study of oxidized copper-porphyry ore from the Koktashal deposit. Optical microscopy, silicate analysis, and quantitative phase analysis were used to characterize the mineral composition and forms of copper occurrence in the oxidation zone. The ore contains 0.735% total copper, of which 89.8% occurs in oxidized form, 6.39% in primary sulfides, 2.72% in secondary sulfides, and 1.09% in water-soluble form. The principal ore minerals are malachite (1.5–2.0%) and azurite (0.3–0.4%), accompanied by hematite with magnetite (0.5%), goethite (0.2%), and pyrite (0.2%), whereas copper sulfides and native copper occur only in trace amounts. The integration of classical mineralogical methods with quantitative phase analysis provides new insights into the distribution of copper occurrence forms and their relationship to oxidation processes. Malachite and azurite occur as well-crystallized vein and nest aggregates as well as colloform earthy masses developed along microcracks in association with iron hydroxides. Their close association with iron hydroxides and the near absence of copper sulfides represent a diagnostic feature of the oxidation zone in copper-porphyry systems. These findings improve the assessment of supergene alteration during exploration and support the classification of oxidation-zone ores as a distinct geological and industrial type for reserve estimation, ore body delineation, and processing scheme selection.