Geology, mineralogy and origin of Zhyrychi native copper deposit (North-Western Ukraine)

The paper presents geological settings, resources and mineral composition of theore bodies of the Zhyrychi copper deposit found in the North- Western Ukraine at the end of the last century. The deposit is located in the Vendian basaltic flows and in traflow pyroclastics in central part of the Volhyn trappean province, originated in the Late Vendian during Torn quistrifting. The majority of copper is concentrated in native form and occurs as disseminated grains, veinlets and nuggets. Locally native siver, copper- sulphides (chalcosite, digenite, bornite and covellite) and cuprite replace native copper. The ore bodies are controlled by faulting and occur as stratabound, but are locally enriched in nuggets in tuffs and fissured zones in ba alts. Ag, Pd, Rh and Aucan also beeco nomically important. The major copperores were deposited to gether with prehnite- pumpellyite para genesis, originated in the succession: pumpellyite – prehnite (šnative copper) – laumontite (or wairakite) (šnative copper). The ore bodies were formed during cooling of the mineralforming hydrothermal system at the end of the Vendian volcanic activity. The syngenetic inter growths of native copper with prehnite, precipitated after pumpellyite, and homogenization temperature of fluid inclusions in later wairakite (210–335gradeC) indicate that the major deposi tion of native copper took place at 200–400gradeC. The following propylitization, smectitization and analcilization of thecountry rocks probably occurred during at tenuation of the hydrothermal activity after magmatism ceased. All these processes were accompanied by dissolution of copper ore and its redistribution with local enrichment in copper nuggets.