FOG Freiberg Online Geoscience FOG is an electronic journal registered under ISSN 1434-7512 2016, VOL 46 Christoph Breitkreuz and Uwe Kroner (conveners) Workshop on “Late Paleozoic magmatism in the Erzgebirge / Krušné hory: Magma genesis, tectonics, geophysics, and mineral deposits” - Abstracts - 42 pages, 23 contributions Content Preface .......................................................................................................................................................... 3 Vertical evolution of the Cínovec granite cupola – chemical and mineralogical record (Breiter) ............... 4 The Late Paleozoic volcanic centres in Central Europe – What do we know and what we need to know! (Breitkreuz) ................................................................................................................................................... 7 The initial phase of the Late Carboniferous Altenberg-Teplice Volcanic Complex: Volcanosedimentary evolution of the Schönfeld–Altenberg Depression Complex (Breitkreuz et al.) .......................................... 9 Reprocessing of deep seismic reflection profiles from the Erzgebirge / Krušné hory area (Buske et al.) .. 11 Correlating the lithofacies schemes of the Late Paleozoic Teplice Rhyolite, Central-European Variscides (German-Czech border) (Casas-García et al.) ........................................................................................... 13 The exhumation channel of the Erzgebirge: From heat advection to the emplacement of Sn-W enriched granites (Hallas et al.) ................................................................................................................................. 15 The Late Paleozoic crystal-poor vitrophyric Planitz-ignimbrite of the Chemnitz Basin, eastern Germany: Indications for crustal contamination and magma mixing (Heuer et al.) ................................................... 17 The Lower Permian Rochlitz Supervolcano, Northern Saxony Volcanic Complex, Germany: Characterization of large crystal-rich ignimbrites (Hübner et al.) .............................................................. 19 Cassiterite of the hydrothermal polymetallic “Felsitzone” mineralization of Großschirma (Saxony, Germany): New insights into mineralogy and geochemistry (Járóka & Seifert) ....................................... 21 Re-evaluation of the mineral resource potential of the German Ore Mountains (Erzgebirge) using artificial neural networks (Kallmeier et al.) .............................................................................................................. 22 The tectonic framework of the Erzgebirge /Krušné hory (Kroner) ............................................................ 23 Chemical and isotopic characterization of the Hämmerlein tin-skarn deposit, western Erzgebirge, Germany (Lefebvre et al.) ........................................................................................................................... 25 Trace-element chemistry of quartz during magmatic-hydrothermal transition in the evolved granitic system of the eastern Krušné hory/Erzgebirge (Peterková & Dolejš) ........................................................ 26 The Early Permian Wurzen Caldera System of northern Saxony, Germany: Mineral chemistry and texture disclose insights into an intra-continental magma reservoir (Repstock et al.) ............................................ 27 Tin, tungsten, and tantalum mineralization – more than just the result of magmatic fractionation (Romer) .................................................................................................................................................................... 29 New 3D model of the Cinovec deposit (Sesulka) ....................................................................................... 30 Altenberg-Teplice Caldera revealed by the airborne and ground gamma-ray spectrometry (Skácelová et al.) ............................................................................................................................................................... 31 Tectonic framework of Sn-W enriched magmatism: Examples from NW Iberia and SW England (Stephan et al.) ........................................................................................................................................................... 32 Fold/cleavage relationships as indicator for late Variscan sinistral transpression: the Rheno-Hercynian– Saxo-Thuringian boundary zone, Central European Variscides (Stephan et al.) ........................................ 34 1 The “Older” and “Younger” granites from the Western Erzgebirge – comparison of different zircon dating methods (Tichomirowa et al.) ..................................................................................................................... 36 Geochronology and magnetic fabrics of the Altenberg-Teplice granite porphyry: implications for emplacement style of a caldera ring dike (Tomek et al.) ............................................................................. 39 Tin distribution between melt and restite during partial melting of metasedimentary rocks Wolf et al.) ... 41 Tectonic setting of late-orogenic plutonism in the Bohemian Massif (Žák) ............................................... 42 2 Preface The Erzgebirge / Krušné hory at the northern margin of the Bohemian Massif is one of the centre pieces of the Late Paleozoic Variscan orogen. It stands out for medium to high-grade metamorphic nappes, large plutonic and volcanic complexes, and, of course, for diverse mineralisations, mined for over 800 years. The Erzgebirge / Krušné hory has been in the focus of geoscientific research for more than two centuries. In recent years, a large number of studies were carried out or are under way, including tectonics, magmatic and metamorphic petrology, physical volcanology, economic geology, petrophysics, paleomagnetics, and geochronology. The Erzgebirge / Krušné hory comprise a large and diverse set of existing data gained from outcrop, mine edifice and drilling. Current activity, such as high-accuracy geochronology, mineral chemistry and isotopes, reprocessing of seismic lines, remote sensing and geometric modelling, adds to the understanding of this unique structural unit. Among others, the magma genesis, the plutonic-volcanic connection, and the related mineralisation are important topics. The Erzgebirge / Krušné hory is not just “Local Geology – Heimatkunde”: It’s a prime example of a well exposed and well-documented block evolved in a late- to post-continent-continent collisional setting – associated with complex mineralisations: The community should know about it! We are very pleased about the strong response to the call of this field workshop – More than 40 participants from Armenia, Chile, Czech Republic, Germany and Poland registered! Our thanks go to the organisation team of the Institute of Geology of the TU Bergakademie Freiberg! Welcome to Freiberg, with kind regards, Christoph Breitkreuz and Uwe Kroner 3 Vertical evolution of the Cínovec granite cupola – chemical and mineralogical record Breiter, K. Institute of Geology of the Czech Academy of Science, Rozvojová 269, CZ-165 00 Praha 6, Czech Republic; [email protected] The 1597 m deep borehole CS-1 located in the centre of the Cínovec pluton represents an ideal object for evaluation of vertical structure of rare-metal bearing magmatic systems. A combination of textural and chemical methods was applied to whole-rock and mineral samples to define chemical and mineral composition of all granite facies and to identify the extent of magmatic and metasomatic processes during differentiation of the pluton and formation of the deposit. New evolutionary model of the deposit was proposed. The Cínovec rare-metal granite in the eastern part of the Krušné Hory/Erzgebirge (Czech Republic/Germany) was formed in the final stage of magmatic evolution of the late Variscan volcano- plutonic system of the Teplice caldera. The granite is slightly peraluminous; enriched in F, Li, Rb, Cs, Nb, Ta, Sn, W, Sc and U; and poor in P, Mg, Ti, Sr and Ba. The uppermost part of the granite cupola hosts a greisen-type Sn-W-Li deposit. The fully cored borehole CS-1 permits study of the vertical evolution of the pluton to a depth of 1597 m. Based on the macroscopic inspection, automated mineralogy (TIMA) measurements, detail study of rock- forming and accessory minerals and whole-rock chemical data, the following lithological units were distinguished within the CS-1 borehole: 1. The uppermost part of the cupola from the current surface to a depth of 260 m (the "canopy" of the pluton) is composed of mostly leucocratic equigranular fine-grained albite-zinnwaldite granite (ZiGC). The granite consists of subhedral albite, anhedral quartz and zinnwaldite and sericitized K-feldspar. Typical accessory minerals are fluorite, topaz, zircon, cassiterite and columbite; in lesser amounts xenotime, thorite, and monazite. 2. Quartz- and quartz-zinnwaldite greisens (GR) were encountered in the 34–213 m interval; the largest greisen body was found at a depth of 147–167 m. Greisens are mostly medium grained, composed of anhedral mica flakes and aggregates of quartz grains, anhedral fluorite and euhedral topaz crystals. Along with ore minerals (cassiterite, columbite, scheelite>wolframite), zircon, xenotime, thorite and different REE-fluorocarbonates appear in accessory amounts. The contacts between granite and greisen are sometimes relatively sharp, with only a mm-sized transition