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  • Author: Stanislav Jeleň x
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The first evidence of Acidithiobacillus albertensis in weathered ore samples from active gold mine Hodruša-Hámre (Slovakia)

Abstract

Sulphur-oxidising autotrophic bacterial communities in deep biosphere from weathered ore samples from active gold mine Hodruša-Hámre, Slovakia were analysed using cultivation approach followed by DNA extraction, PCR amplification and 16S rRNA gene analyses. Indirect measurement of pH changes in cultivation media evidenced the presence of acidophilic bacteria with active production of acids. The decrease of pH was observed at the beginning of isolation and later pH in range of 1.5 – 2 was maintained in both, sulphuric acid and thiosulphate, media. The presence of homogenous population of gram-negative rods was proved by Gram staining. Molecular analyses have revealed that the population of sulphur-oxidising bacteria in gold mine is dominated by a single species of Aciditiobacillus genus, identified as A. albertensis, suggesting the low level of autotrophic bacteria diversity in deep deposits. For the first time this species was isolated from weathered rocks of a gold mine subsurface environment.

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K-Ar and Rb-Sr geochronology and evolution of the Štiavnica Stratovolcano (Central Slovakia)

Abstract

The Štiavnica Stratovolcano in Central Slovakia is the largest volcano in the Neogene to Quaternary Carpathian volcanic arc. A large caldera, an extensive subvolcanic intrusive complex and a resurgent horst with late stage rhyolite volcanites are the most characteristic features. The results of new K-Ar and Rb-Sr isotope dating using more sophisticated methodical approaches have changed our view on the timing of volcanic and intrusive activity. K-Ar dating of groundmass fractions combined with Rb-Sr isochron dating in the cases of possible rejuvenation has provided highly reliable results. The lifespan of the stratovolcano is apparently shorter than assumed earlier. Evolution of the stratovolcano took place in five stages during the Early Badenian to beginning of Early Pannonian time: (1) construction of the extensive andesite stratovolcano during the interval 15.0-13.5 Ma; (2) denudation of the volcano concluded with the initial subsidence of a caldera and the contemporaneous emplacement of a subvolcanic intrusive complex of diorite, granodiorite, granodiorite porphyries and quartz-diorite porphyries during the interval 13.5-12.9 Ma; (3) subsidence of the caldera and its filling by differentiated andesites during the interval 13.1-12.7 Ma - volcanic activity overlapping with the emplacement of the youngest intrusions; (4) renewed explosive and effusive activity of less differentiated andesites during the interval 12.7-12.2 Ma; (5) uplift of the resurgent horst in the central part of the caldera accompanied by rhyolite volcanic/intrusive activity during the interval 12.2-11.4 Ma. Extensive epithermal mineralization was contemporaneous with the uplift of the resurgent horst and rhyolite volcanic activity and continued till 10.7 Ma

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