Geology, mineralogy and origin of Zhyrychi native copper deposit (North-Western Ukraine)
Abstract
Geologia, mineralogia i geneza złoża miedzi rodzimej Zhyrychi (NW Ukraina)
The paper presents geological settings, resources and mineral composition of the ore 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 intraflow pyroclastics in central part of the Volhyn trappean province, originated in the Late Vendian during Tornquist rifting. The majority of copper is concentrated in native form and occurs as disseminated grains, veinlets and nuggets. Locally native silver, copper-sulphides (chalcosite, digenite, bornite and covellite) and cuprite replace native copper. The ore bodies are controlled by faulting and occur as strata- bound, but are locally enriched in nuggets in tuffs and fissured zones in basalts. Ag, Pd, Rh and Au can also be economically important. The major copper ores were deposited together with prehnite-pumpellyite paragenesis, originated in the succession: pumpellyite prehnite (ąnative copper) laumontite (or wairakite) (ąnative copper). The ore bodies were formed during cooling of the mineral-forming hydrothermal system at the end of the Vendian volcanic activity. The syngenetic intergrowths of native copper with prehnite, precipitated after pumpellyite, and homogenization temperature of fluid inclusions in later wairakite (210335°C) indicate that the major deposition of native copper took place at 200400°C. The following propylitization, smectitization and analcimization of the country rocks probably occurred during attenuation 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.
The paper presents geological settings, resources and mineral composition of the ore 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 intraflow pyroclastics in central part of the Volhyn trappean province, originated in the Late Vendian during Tornquist rifting. The majority of copper is concentrated in native form and occurs as disseminated grains, veinlets and nuggets. Locally native silver, copper-sulphides (chalcosite, digenite, bornite and covellite) and cuprite replace native copper. The ore bodies are controlled by faulting and occur as strata- bound, but are locally enriched in nuggets in tuffs and fissured zones in basalts. Ag, Pd, Rh and Au can also be economically important. The major copper ores were deposited together with prehnite-pumpellyite paragenesis, originated in the succession: pumpellyite prehnite (ąnative copper) laumontite (or wairakite) (ąnative copper). The ore bodies were formed during cooling of the mineral-forming hydrothermal system at the end of the Vendian volcanic activity. The syngenetic intergrowths of native copper with prehnite, precipitated after pumpellyite, and homogenization temperature of fluid inclusions in later wairakite (210335°C) indicate that the major deposition of native copper took place at 200400°C. The following propylitization, smectitization and analcimization of the country rocks probably occurred during attenuation 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.