New knowledge about U-Cu mineralization in the Kozie Chrbty Mts. and its relationship to the late (Neotectonic) structures (Hronic Unit, Western Carpathians, Slovakia)

Stratiform U-Cu mineralization (0.02-1.13 % U) in the eastern part of the Kozie Chrbty Mts. is bound to the Permian volcano-sedimentary complex of the Ipoltica Group, Hronic Unit (Western Carpathians). The wide surroundings of the deposits are formed by other, Triassic sediments of Hronic Unit (limestones, dolomites, quartzites, shales) also by Paleogene sedimentary complexes of the Podtatranská Group (sandstones, conglomerates, claystones). The ore deposits (Vikartovce, Kravany, Švábovce, Spišský Štiavnik) are situated in the arcosic sandstones of the Upper Permian part of the Kravany Beds with carbonized fragments of higher plants. The deposits were exploited during the survey (60s – 70s of the 20th century).

Relatively late tectonic events affected the volume and the quality (and also minig-technical conditions) of considered ore deposits. This tectonics resulted in iregular distribution of mineral ore in this region. In the western part of the Dúbrava Mts. (Vikartovce, Kravany deposits), the distribution of the ore is relatively regular, limited to 1 – 2 ore bearing horizons. In this case the structure of the deposits is limited mainly by Vikartovce Fault with subvertical sence of movement.

Concerning the tectonic condition, Kravany and Vikartovce deposits are situated to the north (in the bedrock block) and in close proximity (200 – 300 m) of Vikartovce Fault of east-to-west direction. On the contrary, the Švábovce and Spišský Štiavnik deposits are located on a neotectonic structure that limits Dúbrava Mts. from the north (W-E direction). The Kravany and Vikartovce deposits are disrupted by disjunctive tectonics in two directions: faults east-to-west causing 5 – 10 m declines of southern blocks faults, and faults with northeast-to-southwest direction causing 10 m declines of southwestern blocks. The deposit conditions on the eastern part of the Dúbrava Mts. are limited by the combination of the neotectonic fault systems: Vikartovce, Gánovce and Muráň-Divín.

At the Kravany deposit, local tectonic caused the formation of so-called „zone ore mineralization“, when U-Cu mineralization occurs in the tectonic zone (reprocessed carbonized plant residues, uraninite, pyrite, chalcopyrite and carbonates).

Stratiform, infiltration U-Cu-Pb mineralization in the eastern part of the Kozie Chrbty Mts. is bound to the Upper Permian clastic sediments (Kravany Beds, member of Malužiná Formation, Hronic Unit). Their lithological composition is represented  by green  to dark gray fine to medium-grain arcosic sandstones, arcoses, gray-black sandstones and siltstones with a significant content of carbonized plant debris. Uranium mineralization together with Cu and Pb mineralization are concentrated mainly in the cracks and pores of corbonized organic matter. Stratiform U-Cu-Pb mineralization is represented by minerals: uraninite, coffinite, U-Ti oxides accompanied by arsenopyrite, chalcopyrite, pyrite, marcasite, tetrahedrite, tennantite, galena, sphalerite, quartz, calcite and dolomite. The age of stratiform mineralization was set at 263 – 274 Ma, based on U-Pb dating.

Secondary minerals described in the supergene zone of U ore deposits are uranophane, autunite, torbernite, metatorbernite, azurite, malachite, arsenopyrite, goethite, limonite, covellite, chrysocolla, gypsum and zálesíite.

 

Acknowledgements: This work was supported by the Slovak Research and Development Agency under the contract APVV-19-0065, VEGA 1/0563/22, KEGA 033UMB-4/2021.