Field Report. Field Trip to Poland May 2008
Leader : Padhraig Kennan
The trip centred on two areas in Southern Poland, the Variscan Karkonosze Granite in the western Sudetes on the northern margin of the Bohemian Massif and the Carpathian Tatra Mountains with their Variscan core and Alpine nappes. The two areas straddle the southern border of Poland with Czechia and Slovakia, respectively. On our first afternoon in Wroclaw, after having lunch Ð for which we paid according to the total weight of what we chose – Professor Michal Mierzjerewski led us on a short tour of the institute of Geological Sciences, in the old University of Wroclaw and the nearby Cathedral. The next three days were spent with Michal looking at the granite of the ~330Ma Karkonosze pluton (similar in age to, but younger than, the Leinster granite in Wicklow). We learned that granites are not all the same. Most of us had thought granite was simply quartz, feldspars and micas. We learned that the granite material rose through a conduit from below into the upper crust where it spread sideways as thin sheets before cooling and solidifying. Many granites have vertical sections that are mushroom- shaped.
We were shown that, by looking carefully, we could collect clues from the variations within the rock that would allow the sequence of the tectonic events that accompanied intrusion to be deduced. The positions and folding of veins (pale, fine-grained, biotite-free aplites and coarser pegmatites), the orientations of biotites and feldspars, the complex feldspar growth histories, rapakivi feldspars and the jointing patterns in the granite, all helped to build a picture of the plutonÕs history. Forensic geology, at itÕs best and most intricate! We visited two classic geological sites. The first was a riverbed associated with Hans Cloos who first described biotite schlieren (streaks). He carefully mapped these to define a regional dome Ð and the shape of the pluton. The second was an orbicular granite outcrop with grapefruit-sized orbicules of fibrous feldspar and quartz radiating outwards from a K- feldspar ÔseedÕ crystal. The fibrous minerals had grown as they did as a result of rapid volatile loss, mainly water, from the magma. This was the first orbicular granite ever described on outcrop, in 1797. There is a similar granite, if more complex, in Donegal. On our way east from Karkonosze towards the Tatra Mts, we stopped overnight at the ancient Zloty Stok Gold Mine, on the Polish-Czech border, which has a documented mining history dating from the 13th Century until 1962. It is now run as a tourist attraction by Elisabeth Szumska and her daughter Marta – with the help of the local community. We were given a very warm welcome by the family and had a great evening in the hostelry beside the mine eating a typical Polish meal (with, inter alia, snatches of operettas from the shy baritone amongst us.) Next morning, with the help of Professor Marek Lorenc from the Institute of Landscape Architecture, Wroclaw University of Environmental and Life Sciences, and guided by Marta, we had a fascinating visit to the mine.
There are over 300 kilometres of underground shafts, adits and galleries, in up to 21 levels. Only a few adits are open now, on a couple of different levels, but it was enough to give a real sense of the extent and history of the mining there. The gold occurs mainly in conjunction with arsenic minerals. It was only in the 18th Century that the arsenic itself was found to have a value and was also extracted. After lunch (thanks Elizebeth), we departed for a visit to a quarry in the Strzegom granite at the Gross Rosen concentration camp with its sad memories. There followed the drive across the Upper Silesian Coal Basin to our beds in Zakopane, in the foothills of the Tatra Mts. In dreadful weather, Dr. Jolanta Burda of the Institute of Geological Sciences, University of Silesia, walked us through some of the granite forming the core of the Tatra Mountain Massif, to reach a corrie lake fringed with snow and ice Ð Morskie Oko (OceanÕs Eye) lake. The surrounding peaks were invisible in the clouds. Later, we examined some outcrops belonging to the alpine nappes that cover the granite core, before everybody retired to a fire for sausages and a beer or two. Some (including the shy baritone) broke into song again. On our second last day, some had to depart for home. The remainder visited the salt mine at Wieliczka, near Krakow. Long before the bed-rock salt was discovered there in the Middle Ages, salt was extracted in
The walls have carvings of biblical scenes, in bas relief. No wonder this is a UNESCO ÔWorld Heritage SiteÕ. On our last Sunday in Krakow, some chose to take a tour to the Aushwitz Ð Birkenau concentration camp, while others chose to wander around looking at KrakowÕs fantastic Baroque architecture. It is a truly beautiful and unblemished city and we all want to go back. On this trip, our Irish and Polish colleagues completely changed our attitude from Ôseen one granite and youÕve seen them allÕ to Ôthere are granites and there are granitesÕ. Many thanks, from us all, for that! Angela Casey had a nightmare while booking flights with the airline cancelling our flights after bookings and payments were made, with all that that entailed, plus handling five different pockets for various payments throughout the trip she did a wonderful job. Also, to the instigator, the director of operations and the co-ordinator, Susan Pyne, our thanks are no les due. Finally, P‡dhraig Kennan, to whom we owe a huge debt of thanks for the enormous amount of background work that he put in so that the trip could run smoothly and without whose enthusiasm we would never have experienced the wonders of Polish geology. On behalf of all the ÔtrippersÕ, thanks to you all for a great trip, and by the way, where to next year?
Frank Clissman. & Peter.Lewis.