Aleksandra Gawęda

Plate Tectonic Evolution of the Southern Margin of Laurussia in the Paleozoic

The role of an active margin of Eurasia during Mesozoic and Cenozoic times was well defined (Golonka, 2004). The trench-pulling effect of the north dipping subduction, which developed along the new continental margin caused rifting, creating the back-arc basin as well as transfer of plates from Gondwana to Laurasia. The present authors applied this model to the southern margin of Laurussia during Paleozoic times. The preliminary results of their work were presented during the Central European Tectonic Group (CETEG) in 2011 in Czech Republic. The supercontinent of Laurussia, defined by Ziegler (1989), included large parts of Europe and North America. The southern margin of this supercontinent stretched out between Mexico and the Caspian Sea area. The present authors attempted to characterize the entire margin, paying the special attention to Central and Eastern Europe.

The origin of magmatic layering in the High Tatra granite, Central Western Carpathians – implications for the formation of granitoid plutons

The High Tatra granite intrusion is an example of a Variscan syn-tectonic, tongue-shaped intrusion. In some portions of the intrusion, structures occur which appear to be of sedimentary origin. These include structures similar to graded bedding, cross-bedding, troughs and flame structures, K-feldspar-rich cumulates and magmatic breccias. Formation of these structures might be related to changing magma properties, including crystal fraction, development of a crystal mush and a decrease in magma viscosity, stimulated by influx of mafic magma and high volatile content. The suggested processes in operation are: gravity-controlled separation, magma flow segregation, deposition on the magma-chamber floor, filter pressing and density currents stimulated by tectonic activity.%The formation of the sedimentary structures was also aided by the presence of large numbers of xenoliths that acted as a heat sink and influenced the thermal field in the intrusion, stimulating rapid cooling and crystal nucleation. Sinking xenoliths deformed the layering and, to some extent, protected the unconsolidated crystal mush from erosion by magma flowing past.%Areas with well-developed sedimentary magmatic structures can be viewed as having involved magma rich in crystals locally forming closely-packed networks from which residual melt was extracted by filter pressing, and preserved in leucocratic pods and dykes. Interleaved, non-layered granite may be interpreted to have formed from the magma with initially low crystal fractions.%It is suggested that the intrusion was formed from numerous magma injections representing different stages in the mixing and mingling of felsic and mafic sources. It solidified by gravitation-driven crystal accumulation and flow sorting on the magma chamber floor and on the surfaces of large numbers of xenoliths. Shear stress acting during intrusion might have influenced the formation of magmatic structures.

U-Pb zircon age of the youngest magmatic activity in the High Tatra granites (Central Western Carpathians)

Detailed cathodoluminescence (CL) imaging of zircon crystals, coupled with Laser Ablation Multi-Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS) U-Pb zircon dating was used to develop new insights into the evolution of granitoids from the High Tatra Mountains. The zircon U-Pb results show two distinct age groups (350±5 Ma and 337±6 Ma) recorded from cores and rims domains, respectively. Obtained results point that the last magmatic activity in the Tatra granitoid intrusion occurred at ca. 330 Ma. The previously suggested age of 314 Ma reflects rather the hydrothermal activity and Pb-loss, coupled with post-magmatic shearing.

Tourmalines from the Western Tatra Mountains (W-Carpathians, S-Poland) Their characteristics and petrogenetic importance

Tourmalines are the most important Fe-Mg minerals in the pegmatites and leucogranites intruding the crystalline core of the Western Tatra Mountains (South Poland). They also occur in the folded host rocks inside the contact zone. The chemical composition and the weak zonation of the investigated tourmalines are both consistent with the field observations which suggest their magmatic/late magmatic origin and a close association with the Li-poor leucogranites and Al-rich, Ca-poor metasediments. The irregular distribution of the tourmaline-bearing rocks can be interpreted as reflecting three factors, i.e. , limited boron and water availability in the metasedimentary rocks during anatexis, variable oxygen fugacity (controlled partly by the presence of graphite) and restricted mobility of the mafic cations, necessary for tourmaline formation. The exsolution of a boron-rich fluid phase, incompatible with silicate melt, and its escape along a shear zone is also considered. The differences in Fe 3+ /Fe 2+ characterising the Western Tatra tourmalines could result both from f O 2 variations in the source metasediments during anatexis and from the interaction of magmatic/postmagmatic fluids with the metamorphic host rocks.

Geochemistry and palaeotectonic setting of amphibolites from the Western Tatra Mountains, southern Poland

Amphibolites from the crystalline basement of the Western Tatra Mountains, which are found as small lenses within migmatitic gneisses and mica schists, were formed during pre- or early Variscan amphibolite-facies metamorphic events, and subsequently intruded by the post-metamorphic Variscan Tatra Granite. The amphibolites occur in both the upper and lower metamorphic complexes, which are separated by a major subhorizontal shear zone in the Western Tatra Mountains. The amphibolites can be divided into three types: massive, striped and garnetiferous. The striped and massive amphibolites, concordant with a dominant S1 foliation, and the garnet amphibolites, which cross-cut the S1 banding in the gneisses, were all originally intrusive dolerites. The striped amphibolites (consisting primarily of hornblende, andesine and quartz), and later, cross-cutting garnet-hornblende-andesine-quartz-bearing amphibolites, predominate in the lower part of the dominantly migmatitic upper complex, and are exposed mainly on the ridges. The massive amphibolites, which contain a similar mineral assemblage, mainly occur in the usual unmigmatized lower structural unit. Chemical studies indicate that three amphibolite suites are present, which probably originated as a series of enriched tholeiites, similar to more recent plume-influenced magmas, which were derived by partial melting of a spinel lherzolite with primitive mantle composition and compositionally slightly modified by crustal contamination. The amphibolites were intruded as dolerites into clastic sediments which had accumulated in an extensional basin floored by attenuated continental crust, a situation similar to that of amphibolites found in metamorphic complexes within the Variscan belt, e.g. in the Orlica–Snieznik area of the Sudetes, where amphibolites chemically similar to those in the Western Tatra also occur. Copyright

Geochronology and petrogenesis of granitoid rocks from the Goryczkowa Unit, Tatra Mountains (Central Western Carpathians)

Abstract The geochemical characteristics as well as the LA-MC-ICP-MS U-Pb zircon age relationship between two granitoid suites found in the Goryczkowa crystalline core in the Western Tatra Mountains were studied. The petrological investigations indicate that both granitoid suites were emplaced at medium crustal level, in a VAG (volcanic arc granites) tectonic setting. However, these suites differ in source material melted and represent two different magmatic stages: suite 1 represents a high temperature, oxidized, pre-plate collision intrusion, emplaced at ca. 371 Ma while suite 2 is late orogenic/anatectic magma, which intruded at ca. 350 Ma. These data are consistent with a period of intensive magmatic activity in the Tatra Mountain crystalline basement. The emplacement of granitoids postdates the LP-HT regional metamorphism/ partial melting at ca. 387 Ma and at 433-410 Ma, imprinted in the inherited zircon cores.

Petrogenesis of kyanite-quartz segregations in mica schists of the Western Tatra Mountains (Slovakia)

Abstract In the Tatra Mountains (Slovakia) metamorphic complex, kyanite-quartz segregations with biotite-rich selvage occur in mylonitized mica schists. In this paper, the problem of fluid flow and aluminium mobility during the uplift of the crystalline massif, and the position of the segregations in the history of Western Tatra metamorphic complex, is adressed. The reaction Alm + Rt ➔ Ilm + Ky + Qtz is considered to be the result of a pressure drop from above to below 9 kbar. Ti-in-biotite geothermometry shows the temperature range to be 579-639°C that is related to heating and decompression associated with granite intrusion. Major-element mass-balance calculations show that Al remained stable in the selvage + segregation system whereas other elements (e.g. Cr, HFSE) were mobilized. The kyanite-quartz segregations formed from local fluids generated during dehydration of the metapelitic rocks during uplift. The main mechanism was likely diffusion-driven mass-transfer into extension-related cracks.

Megacrysts of kyanite from Baranec Mt., Western Tatra Mountains, Slovakia

Abstract Large crystals of kyanite (<15 cm in size) occur in quartz segregations in Paleozoic gneissses on Baranec Mt., Western Tatra Mountains, northern Slovakia. Blue kyanite crystals coexist with quartz and plagioclase. The kyanite contains inclusions of apatite, monazite. gamet, rutile and biotite and overgrowths of retrograde sillimanite. muscovite and biotite. The kyanite crystals are the largest found up to now in the Tatra crystalline massif or in the other Western Carpathians crystalline cores. Kyanite. with the co-existing mineral assemblage, is indicative of a HP stage duiing Hercynian metamorphism of the Western Tatra Mountains.

Paralava from Coal-Dump Combustion in Upper Silesia, Poland: Melt Separation Leaving a Cordierite-Rich Restite.

In this article, we present the results of the investigations into peculiar cordierite (indialite)-rich concentrations found in paralava from two coal dumps from the Upper Silesia Coal Basin, Poland. The temperature of the fusion process was in the range of 900–1100 °C and the main product is a ryolitic, peraluminous paralava. The crystallization and separation of cordierite (indialite)-rich restite from glassy paralava was probably controlled by changing oxygen fugacity and high viscosity of the fused rocks. The resorption of monazite and associated mobilization of phosphorus to form Fe–Mg–Ca phosphates and P-enrichment of the glassy paralava, pose questions about the behavior of REE and Th released from monazite during the fusion caused by coal combustion.