Banská Štiavnica Mining District, Štiavnica Mts, Banská Bystrica Region, Slovakia

The Banská Štiavnica ore district is in the central zone of the largest stratovolcano in the Central Slovakia Neogene Volcanic Field.

The following types of ore deposits (mineralizations) have been identified in the Banská Štiavnica ore district (Lexa et al., 1999):

1. Quartz-pyrophyllite-pyrite high-sulphidation system at Šobov, related to the diorite intrusion.

2. Magnetite skarn deposits and occurrences at contacts of the granodiorite pluton with Mesozoic carbonate rocks. Magnetite ores occur as lenses in the calcic skarns.

3. Stockwork/disseminated base metal deposit along an irregular network of fractures in apical parts of the granodiorite pluton and in remnants of basement rocks: sphalerite and galena and minor chalcopyrite and pyrite. In overlying andesites the mineralization is accompanied by metasomatic quartzites and argillites with pyrophyllite, kaolinite, illite and pyrite.

4. Porphyry/skarn copper deposits and occurrences related to granodiorite/quartz-diorite porphyry dyke clusters and stocks around the granodiorite intrusion. The mineralized zone is represented by accumulations of chalcopyrite in exo- and endo-skarns, usually of the magnesian type affected by serpentinization. Besides chalcopyrite, pyrhotite, minor bornite, chalcocite, tennantite and magnetite, rare molybdenite and gold are present. The alteration pattern around productive intrusions includes an external zone of propylitization, a zone of argillitic alteration (kaolinite – illite – pyrite) and an internal zone of phyllic alteration (quartz – sericite – pyrite). Biotitization is rare and limited to porphyry intrusions.

5. Intrusion related “mesothermal” gold deposit in an andesitic environment just above the granodiorite intrusion. Gold of high fineness with base metal mineralization is contained in brecciated and/or banded quartz veins of subhorizontal orientation, parallel to the surface of granodiorite pluton. At least the first phase of mineralization is older than quartz-diorite porphyry sills, which separate granodiorite and blocks of mineralized andesite.

6. Hot spring type advanced argillic systems in the caldera filling. Silicites and opalites accompanied by kaolinite, alunite and pyrite grade downward into smectite dominated argillites.

7. Vein type epithermal precious/base metal deposits and occurrences as a result of the long lasting interaction among structural evolution of the resurgent horst and evolving hydrothermal system, extensive intrusive complex and deep seated siliceous magma chamber serving as heat and magmatic fluid source. Three types of epithermal veins occur in a zonal arrangement:
(a) base metal veins ± Au with transition to Cu ± Bi mineralization at depth in the east/central part of the horst,
(b) Ag – Au veins with minor base metal mineralization and
(c) Au – Ag veins located at marginal faults of the horst. Isotopic composition of oxygen and hydrogen in hydrothermal fluids indicate mixing of magmatic and meteoric component (with generally increasing proportion of meteoric component towards younger mineralization periods?). Veins are accompanied by zones of silicification, adularization and sericitization, indicating a low sulphidation environment.

8.  Replacement base metal mineralization of a limited extent in the Mesozoic carbonate rocks next to sulphide rich epithermal base metal veins.

References:
- Lexa, J., Štohl, J., and Konečný, V. (1999): The Banská Štiavnica ore district: relationship between metallogenetic processes and the geological evolution of a stratovolcano. Mineralium Deposita 34, 639-654.

- http://www.mujweb.cz/www/stiavnica/