First Evidence of the Post-Variscan Magmatic Pulse on the Western Edge of East European Craton: U-Pb Geochronology and Geochemistry of the Dolerite in the Lublin Podlasie Basin, Eastern Poland

The U–Pb measurements of youngest, coherent group of zircons from the Mielnik IG1 dolerite at the Teisseyre-Tornquist margin (TTZ) of East European Craton (EEC) in Poland yielded age of 300 ± 4 Ma. Zircon dated an evolved portion of magma at the late stage crystallization. It is shown that this isolated dyke from the northern margin of the Lublin Podlasie basin (Podlasie Depression) and regional dyke swarms of close ages from the Swedish Scania, Bornholm and Rügen islands, Oslo rift, Norway, and the Great Whine Sill in northeastern England, were coeval. They have been controlled by the same prominent tectonic event. The Mielnik IG1 dolerite is mafic rock with Mg-number between 52 and 50 composed of the clinopyroxene, olivine-pseudomorph, plagioclase, titanite, magnetite mineral assemblage, indicating relatively evolved melt. This hypabyssal rock has been affected by postmagmatic alteration. The subalkaline basalt composition, enrichment in incompatible trace elements, progressive crustal contamination, including abundance of zircon xenocrysts determines individual characteristics of the Mielnik IG1 dolerite. The revised age of dolerite, emplaced in vicinity of TTZ provides more evidences documenting the reach of the Permo-Carboniferous extension and rifting accompanied by magmatic pulses, that were widespread across Europe including the margin of the EEC incorporated that time into the broad foreland of the Variscan orogen.

Preservation and Destruction of Accumulations in Petroleum Systems of Western Margin of East European Craton

The offshore segments of the Pre-Dobrogea foredeep is absolutely unexplored, there is no a single well penetrated Paleozoic units within offshore areas. This study, a deep dive into petroleum system evolution of similar foredeep basin based on a 3D basin modeling was performed in order to get understanding of petroleum systems and geology of offshore segment of Pre-Dobrogea. Western edge of East European craton is about 1450 km takes from Western Black sea shore to Southern shore of Baltic sea. This area within Ukraine includes Pre-Dobrogea foredeep basin, Pre-Carpathian foredeep basin (Bylche-Volytsa foredeep), Lviv Paleozoic basin and extensive Paleozoic margin called Volyno-Podillia area (Figure 1). All mentioned basins have similar sedimentary history, similar dynamics of tectonic evolution, proven petroleum systems of almost the same age, discovered commercial and sub-commercial accumulations and are heavily underexplored and undervalued. 3D basin modeling as a primary exploration technique was applied to mentioned basins in order to identify common features in tectonic development, in sedimentation and evolution of petroleum systems. Identified basins’ similar features now could be extrapolated to underexplored formations and areas within the study area. Figure 1 Western margin of East European Craton with marked areas of study (edited after Mikołajczak, 2016)

Relative movements of the Bashkirian megazone blocks(the South Urals) according to paleomagnetic data.

<p>     The research object is magmatic bodies from the southern, central and northern parts of the Bashkirian megazone (the Southern Urals, meridian length of the Bashkirian megazone - 300 km). Most of the study intrusions have the Riphean age. In the Riphean the Bashkirian megazone was part of the East European craton. And in the Late Paleozoic rocks of the Bashkirian megazone were involved in the collision process. The formation of most studies bodies is associated with the Mashak magmatic event (the Riphean), which marks the collapse of the super-continent Nuna.</p><p>     The Middle Paleozoic component was isolated in 28 bodies. Probably it is the secondary component, that is widespread on the Southern Urals and has been repeatedly identified by other researchers. Directions comparison from different districts showed that there was a rotation of the southern, northern and central blocks of Bashkirian megazone relative to each other during the Late Paleozoic collision. At the same time, paleomagnetic directions from the northern regions (which are about 40-50 km apart from each other) statistically coincide or differ not so much. Which means that they were stable or relatively stable.</p><p>     Besides, the Riphean component was isolated and the paleomagnetic pole for the boundary of the Lower and Middle Riphean of the East European Craton (1349+/-11 Ma) is calculated from 8 thin sheet intrusions. Plat=8.4; Plong=162.4; A95=4.1.</p>