A nature of bimodal magmatism associated with Cambro-Ordovician rifting in Gondwana: the NE Bohemian Massif perspective in view of the integrated field data and multiisotopic studies on whole rocks and minerals, specifically zircons
Bimodal magmatism related to Early Palaeozoic thermal event in the northern part of Gondwana has been widely documented in rock successions extending from Spain to Poland. Geochemical studies of acid and mafic rocks, albeit their close occurrence, commonly lead to different conclusions. This bimodal magmatism is either correlated with an intracontinental rifting, oceanic rifting or collisional events in Early Palaeozoic times. This project offers a new, integrated approach for understanding the deep-seated processes related to the Cambrian/Ordovician rifting in the Northern Gondwana from the perspective of the Sudetes (Poland and Czech Republic). Bimodal associations in the Sudetes are the objects of the multimethodological study (whole rock and Sm-Nd geochemistry, U-Pb dating and Hf and O isotopes in zircons, immobile trace element distribution in zircon). PhD student in the project: Marek Śliwiński (MSc).
Bimodal - felsic (light) and mafic (dark) metavolcanics association of the Staré Město Belt, the Sudetes.
The conducted research is part of a broad discussion on the origin, igneous succession and early evolution of the Variscan tectonic microplates of Central Europe, which constituted the northern edge of the Gondwana continent in the Early Paleozoic. At that time, Gondwana, composed of Precambrian rocks, occupied a large part of the southern hemisphere, while along its northern edge, volcano-sedimentary were formed and extensive granitoid intrusions took place. Intensive igneous and sedimentary processes resulted in a significant formation of the continental crust, which now covers the area of southwestern and central Europe, including the Sudetes in Poland. Early Paleozoic magmatism led to the formation of often chemically contrasting igneous rocks (basic and acid), which from Spain to Poland are exposed in the form of characteristic bimodal associations. The Variscan microplates were gradually separated from northern Gondwana during the Paleozoic and then collided during the Variscan orogeny. In the Bohemian Massif, the Variscan terranes of Moldanubia, Saxothuringia and Tepla-Barrandia occur, and the latter two, according to most researchers, also extend to the Sudetes. The mechanism that caused bimodal back-arc volcanism is not fully understood. An oceanic volcanism enforced the drift of these microplates. Our integrated geological, geochemical, geochronological and isotopic studies conducted in the Sudetes (Poland, Czech Republic) have shown that in the Saxothuringian and Tepla-Barrandian microplates, acid and basic rocks are of the same age – they crystallized approximately 495 million years ago and were most likely formed by the same geotectonic process. Magmas probably formed in a geochemical environment of a continental arc, where the oceanic crust subducted beneath the continental crust (in this case Gondwana), promoting a crustal, back-arc extension. At this time and setting, the rocks at the mantle-crust boundary were melted and then intruded into the higher levels. They give rise to rhyolite and basaltic lavas flows onto the earth's surface. The provenance studies on metasedimentary rocks indicate that the described phenomena from the Sudetes took place in the western and/or northern African periphery of Gondwana. Paleozoic microplate drift led to the collision of the Saxothuringian microplate with microcontinent of Avalonia and the continent of Laurussia. Our study indicated that the two main stages of this collision occurred ~370 and ~340 million years ago.
Articles:
Jastrzębski, M., Żelaźniewicz, A., Stawikowski, W., Budzyń, B., Krzemińska E., Machowiak. K., Madej, S., Białek, D., Sláma, J., Czupyt., Z., Jaźwa, A, 2023. The eastern part of the Saxothuringian Terrane characterized by zircon and monazite data from the Doboszowice Metamorphic Complex in the Sudetes (Poland). Annales Societatis Geologrum Poloniae, 93: 229–249. https://doi.org/10.14241/asgp.2023.11
Śliwiński M, Jastrzębski, M. Sláma, J. 2022. Detrital zircon analysis of metasedimentary rocks of the Staré Město Belt, the Sudetes: implications for the provenance and evolution of the eastern margin of the Saxothuringian terrane, NE Bohemian Massif. Geological Quarterly. 66: 21. DOI: http://dx.doi.org/10.7306/gq.1653
Abstracts:
Śliwiński M., Jastrzębski M., Sláma J., Machowiak K., Kozub-Budzyń G A., Krzemińska E., Míková J. 2023. Pre-Variscan and Variscan evolution of the eastern Saxothuringian margin: petrological, geochemical and geochronological study of the Stáre Město Belt, the Sudetes. Goldschmidt conference 2023, conf.goldschmidt.info/goldschmidt/2023/meetingapp.cgi/Paper/15363
Jastrzębski M., Śliwiński M., Machowiak K., Sláma J., 2023. Zircon geochemistry and geochronology of the volcano-sedimentary rocks of the Kaczawa Complex, the Sudetes (SW Poland): new data for early Palaeozoic development of the Saxothuringian basin. Goldschmidt conference 2023, conf.goldschmidt.info/goldschmidt/2023/meetingapp.cgi/Paper/15849
Jastrzębski M., Machowiak K., Śliwiński M., Sláma J. 2023. Zircon isotopic and geochemical record of early Palaeozoic volcanism and sedimentation of the Kaczawa Complex, the Sudetes (SW Poland). 19th meeting of the Central European Tectonic Studies Group (CETeG) Abstract Book, 34
Śliwiński M., Jastrzębski M., Sláma J., Machowiak K., Fuenlabrada J. M., Kozub-Budzyń G. A., Krzemińska E., Míková J., 2023. Age, petrogenesis, and metamorphic evolution of the metavolcano-sedimentary complex of the Staré Město Belt, the Sudetes. 19th meeting of the Central European Tectonic Studies Group (CETeG) Abstract Book, 90-91
Jastrzębski M., Machowiak. K., Śliwiński, M. Sláma J., 2022. New age constraints for Early Palaeozoic volcanism and sedimentation of the Kaczawa Complex, the Sudetes (SW Poland), Abstract EGU22-8478
Śliwiński, M., Jastrzębski, M., Machowiak K., Sláma J. 2022. Age and geotectonic setting of metavolcanic rocks in the eastern Saxothuringian margin: whole rock geochemistry, zircon trace element geochemistry and U-Pb geochronology of the Staré Město Belt (Czech Republic, Poland). Abstract EGU22-8363
Jastrzębski, M., Żelaźniewicz, A., Sláma J., Krzemińska, E. 2021. Zircon geochronology of the Sudetic portion of Teplá-Barrandia: protolith ages, provenance and significance as source rocks for Devonian and Carboniferous sedimentary basins. 18th Meeting of the Central European Tectonic Studies Group, Book of Abstracts. 53-54
Śliwiński, M., Jastrzębski, M., Machowiak, K., Sláma, J., 2021. Whole rock geochemistry and zircon geochronology of meta-volcanic rocks from the Staré Město Belt, the Sudetes, 18th Meeting of the Central European Tectonic Studies Group, Book of Abstracts. 126.
Śliwiński, M., Jastrzębski, M., 2021. Pressure-Temperature evolution of amphibolites in the Staré Město Belt in the Sudetes. Book of Abstracts, 3rd European Mineralogical Conference EMC 2020, 360
Jastrzębski, J., Sláma, J., Krzemińska, E., 2021. Diversity of Late Cambrian felsic magmas in the SW Poland: an insight from U-Pb and O zircon study. Book of Abstracts, 3rd European Mineralogical Conference EMC 2020, 193.
