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Excursion to Slanské a Zemplinské vrchy 2024

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The excursion took place from 24.4.-28.4.2024 in the locality of the neovolcanic Slanské vrchy mountain range, which extends in the eastern part of Slovakia east of the city of Prešov and with its length of 100 km extends to the territory of neighboring Hungary. The Slovak part of the mountain range consists dominantly of andesite stratovolcanoes reaching heights from 800 m.a.s.l. up to 1092 m.a.s.l., which stretch in a crescent-shaped chain from north to south. They were formed at the fault interface between the tectonic units of the Západní Karpaty (gemerikum, fatrikum) in the west and hard-to-classify units in the east – zemplinikum, Pozdišovsko-Inačovská unit. The first magmatic activity is dated to the Lower Miocene as a result of the Alpine orogeny. The well-recognizable stratovolcanoes include, from north to south: Šťavnica, Zlatobáňský, Makovica, Strechovy vrch, Bogota, Hradisko, Bradlo and Velký Milič. During their formation, parts of them also underwent significant hydrothermal transformation, during which ore and opal mineralization were established.

some visited localities:

Zlatá Baňa
– Zlatobansky stratovolcano
– 140 types of minerals described
-polymetallic (Mo-Cu-Pb-Zn-Ag) and antimony mineralization
– antimonite, amethyst, bournonite, boulangerite, metastibnite, cinnabarite, galena, pyrite

Fig. 1 – Zlatá Baňa locality

Dubnik
– the southern part of the Zlatá Baňa stratovolcano
– the formation of mineralization in andesite lava flows by post-magmatic hydrothermal activity
– significant deposit of opals (precious, milky,  hyalit)
-historical mining of cinnabarite as an ore of mercury

Fig. 2 – Dubnik precious opal

Herlany
-Strechový vrch stratovolcano
– the famous mäsovy opal of a brown-red color

The next part of the excursion took place in an elevation formed by Permocarbon continental sediments with anthracite and thick layers of tuffs – the Zemplinské vrchy. It is a synclinal structure of a complex structure consisting mainly of highly metamorphosed rocks (mainly gneisses, amphibolites).

Byšta – Brezina
-near the Velký Milič stratovolcano
– agates, chalcedony

Velká Trňa
– the western slope of the Zemplinské Vrchy
-Anthracite

Fig. 3 – Excursion checking the geological map in the field

SGA Student Chapter Prague – The 20th Anniversary

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Since 2022 is the year of celebrations for the SGA Student Chapter Prague, we have decided to organize the annual SGA Prague Christmas meeting and the 20th Anniversary celebration on 7th December. The event took place at the Faculty of Science, Charles University. On the same day we organized an excursion to the gold mine near Jílové u Prahy took place for those interested.

SGA

The Society for Geology Applied to Mineral Deposits (SGA) is an international scientific society that promotes the science of mineral deposits. The society consists of over 1300 members among researchers, professionals and students from universities, industry and governments interested in economic geology, mineral resources, industrial minerals and environmental aspects related to mineral deposits. SGA regularly organizes conferences, international courses and workshops. The next SGA Biennial Meeting will be held in Zürich, Switzerland between 28th August and 1st September 2023. An integral part of the organization is the long-term support of geoscience students through the SGA Educational Fund.

History of the SGA Student Chapter Prague

This year marks exactly 20 years since several students from Charles and Freiberg Universities founded the first-ever SGA Student Chapter. In 2002, a joint Prague-Freiberg Chapter was established by Dr. Anna Vymazalová and Dr. Alex Otto, both master students at the time. This newly formed Chapter’s first event was an excursion to the Svornost mine in Jáchymov, Czech Republic in April 2003. Subsequently, a division occurred and the independent SGA Student Chapter Prague was established. Despite the difficulties during the years 2020 and 2021 caused by the COVID-19 pandemic, the SGA Student Chapter Prague has around 70 members.

This year, we celebrate two significant anniversaries simultaneously—the 20th anniversary of the existence of the SGA Student Chapter and the 10th president in office.

SGA Student Chapter Prague Christmas meeting

We are pleased that 83 SGA supporters from the Czech Republic, Germany, Portugal, Spain, Switzerland and Slovakia gathered for the anniversary celebrations. Eleven of them took part in the international field trip. The official program in the Mineralogical lecture room started at 4:30 p.m. with an opening speech by President Jan Kamenský. This was followed by a lecture by Ivan Mateo Espinel Pachon from the University of Geneva on the topic: “Controlling the redox evolution of arc magmas on continental margins: an approach to melt inclusion”. This lecture has followed a presentation by Dr. Anna Vymazalová, one of the founders of the SGA Student Chapter Prague, with her talk on the history of the SGA Student Chapter Prague. Afterwards, representatives of the student associations SEG-SGA Barcelona and SGA Colombia-Bogóta gave a short presentation of their activities and encouraged students to cooperate internationally. After the presentations, we visited the Mineralogical Museum of the Faculty of Science and the Chlupáč Museum. The entire program ended with a meeting in the Malé sbírky lecture room, where we had a unique opportunity to discuss plans for upcoming years.

Fig. 1 – Excursion to the Pepř mine near Jílové u Prahy, author of the photo: Jan Mráček
Fig. 2 – Tour of the Mineralogical Museum at the Faculty of Science, author of the photo: Jan Mráček

We would like to thank our sponsors, without whose help the organization and provision of the program would be very complicated. In particular, we would like to thank the Faculty of Science of Charles University, Řeznictví Jiří Görgl (Butchery Jiří Görgl), Pekařství Kabát (Bakery Kabát) and the Vinařství Cenek (Winery Cenek).

A field-trip to the gold mining district in Jílové, Czech Republic

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Václav Santolík

“Everything is functional here,” says Vladimír Pravda showing us his “office” 300 meters below ground, where we got by a minecart. He is a member of a group of enthusiasts that bought the dilapidated Jílové mines a few years ago. With his coworkers, he spends weekends on restoring the clogged stoles and abandoned machinery.

Fig. 1 – Observation of gold-bearing quartz veins in the Jílové Mine.

Gold mining has a long tradition in the Czech Republic. There are several historically famous mining districts like Jílové, Mokrsko, Kašperské Hory and Zlaté Hory. Unfortunately, all have been shut down during or shortly after the communist era. Currently exploration is proceeding at Zlaté Hory, however, the local socio-political situation does not favor any reopening of old mines.

The Jílové gold-bearing district was one of the most important areas of historical gold mining in Bohemia. The tradition of panning dates back to the period of Celtic settlement. In the 13th and 14th centuries, when gold was obtained mainly by deep mining with a total production of approximately 10 tons of gold, the Jílové district was probably the most profitable gold-bearing district in the Kingdom of Bohemia. Unfortunately, the mines with all documentation have been burnt during the husite wars in the 15th century. The profit from reopening in the 16th to 19th century and in the years 1938 – 1968 was not even close to that of the medieval times. Finally, the geological studies from the 1960s concluded that the mining would no longer be profitable.

The fame of the Jílové district may have been based on the fact that gold was often found here in the form of coarse-grained aggregates and irregular sheets weighing up to several kilograms. The gold is present in quartz and quartz-carbonate veins, often accompanied by sulfides (pyrite, arsenopyrite, etc.), tellurium and bismuth minerals, scheelite, etc. Gold-bearing deposits usually have simple mineral composition, however, 51 minerals have been described from the Jílové district – many of them are rare, often detectable only during microscopic research.

Fig. 2 – Happy visiters of Jílové Mine at the end of excursion.

After several hours under ground, Vladimír wanted to provide us with some hands-on experience. “The country rock is very hard here, therefore, dynamite was used for digging the stoles. Here is a trigger that they used: you just need to spin the arm several times and push this button when it starts to blink,” he passes a small box to my friend. After my friend pushed the button, a staggering bang froze us. “I told you everything was functional here,” claimed Vladimír calmly. “This way, please. Before the smoke and dust reaches us.”

Fieldtrip report: Zlaté Hory deposits and history of mining

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Fig. 1: Participants of the fieldtrip. Photo by V. Santolík.

At the end of October 2021, the SGA student chapter in Prague held a three-day autumn excursion focused on a mining district Zlaté Hory in Jeseníky mountains and its surroundings. The area is composed of Variscan metamorphic rocks like phyllite, micaschist, paragneiss, orthogneiss, amphibolite and limestone, which were formed from Cadomian (~570 Ma) to Variscan (~300 Ma) times. The polymetallic VHMS deposit occurs in metamorphosed Devonian formations and is currently a matter of exploration for possible gold mining.

1st day. History of Au, Fe and Mo mining in the Zlaté Hory region.

The first day was focused on surface signs of previous mining and was lead by Dr. Josef Večeřa. These are dominated by placer mining marks like pits, hollows and canals as well as underground mining marks like pits and adits. The researchers were able to define three stages of mining based on different mining techniques – medieval, modern and 19th century. Interestingly, the different stages are commonly seen at a single locality. For example, in Hláska forest near Ludvíkov village, there are several pits following a single ore bearing structure and depending on the distance between particular pits, it can be inferred, whether they correspond to the medieval or modern period. Consequently, we visited a locality near Vidly village where we found several minerals related to iron ore which was mined until 18th century, including magnetite, hematite, specularite and jasper.

2nd day. Minerals collecting in mine Zlaté Hory – west; “Blue drift”.

On the second day, we went down into the Zlaté Hory – west mine, where the current exploration takes place. The walk to the end of the drift was nearly 4 km long, unfortunately the oxygen level detector did not allow us to stay there for a longer time and search for minerals. However, during the 4-kilometer walk we still managed to find several appealing minerals, for instance pyrite, galena, sphalerite, cerussite and copper. On the way back, we entered the “Blue Drift”, which is called blue for the intriguing blue colored allophane covering the walls. After a few hours in the mine, we visited local museum with a nice exposition of minerals and rocks found in the area.

Fig. 2: Azure blue allophane covering walls in the “Blue Drift”. Photo by V. Santolík.

3rd day. History of mining – open-air museum.

On the third day morning, we visited an outdoor museum dedicated to old miners and old mining techniques. We learned about their lifestyle and tools they used for daily life as well as the methods and equipment applied for gold obtainment. At the end, we were encouraged to find some gold with a gold washing pan in the arranged containers with sand and water. The most adventurous of us could not resist despite the freezing water and managed to find a few gold grains. Finally, with minds full of new experience and bags full of new minerals, we returned back home.

Fig. 3: Gold mining open-air museum in Zlaté Hory. Photo by V. Santolík.
Fig. 4: Collected quartz sample with a native gold. The biggest gold has a size of 200 µm. Photo by M. Tuhý.

Děkujeme IGCP 682 – MINE TAILING REVALORIZATION (Duration: 2019-2021) za finanční podporu, která přispěla k organizaci této exkurze / We thank IGCP 682 – MINE TAILING REVALORIZATION (Duration: 2019-2021) for its financial support, which helped to organise this excursion.