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Variscan igneous activity at the Bohemicum/moldanubicum boundary
Kubínová, Šárka ; Holub, František (advisor) ; Pertoldová, Jaroslava (referee)
Variscan dike swarms associated with the Central Bohemian Plutonic Complex (CBPC) at the boundary between the Teplá-Barrandian and Moldanubian Units of the Bohemian Massif represent one of the most interesting geological phenomena. Frequency of dykes and their chemical variability do not have any comparable analogy in the whole European Variscides. This work is focused on the study of dyke rocks in the NE periphery of CBPC in geologically very complicated area with intrusions of predominantly deformed granitoids, contact metamorphosed sediments and magmatic rocks of "Islet Zone" with different protolith ages (forming remnants of the original roof of CBPC), deformed basic rocks of uncertain origin and age. The area extends up to the western boundary of the northernmost part of the Moldanubian high-grade metamorphic complex, the boundary itself being also tectonically problematic. Several localities with dyke rocks under study are situated in the area east of Senohraby (SE of Prague), on the northern side (right coast) of the Sázava river, and extend up to the area of Stříbrná Skalice. This area is rich in dykes of gabbro to diorite porphyry accompanied in some places with tonalite (rarely quartz diorite) porphyry and more rarely with amphibole lamprophyres (spessartite). Significantly younger dykes...
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Problems of definition and classification of lamprophyres
Kubínová, Šárka ; Holub, František (advisor) ; Štemprok, Miroslav (referee)
Lamprophyres are mafit to ultramafic porphyritic rocks containing phenocrysts of hydrated mafic minerals, namely dark mica (phlogopite, biotite) and amphibole that are present also in the matrix and commonly are euhedral or nearly euhedral. On the other side, felsic minerals as various feldspars and feldspathoids, are present only in the matrix sometimes containing also significant amounts of primary carbonates. Lamprophyres are commonly divided into three major groups - (1) calc-alkaline, (2) alkaline, and (3) ultramafic. Some of them are closely related to kimberlites, lamproites and carbonatites and gradual transitions to these rocks as well as to other non-lamprophyric types do exist. Lamprophyres are volumetricaly minor group of igneous rocks.. In some respects, however, they are very important, particularly for our understanding of complicated petrogenetic processes in the upper mantle and lower crust, and also diamond or gold prospecting. Significant role in proper lamprophyres classification is played by perception of processes of lamprophyres magmas forming and their possible interaction with crustal material or enrichment by some elements contained in mantle. Lamprophyres may be very similar to normal igneous rocks. These rocks can be distinguished only on the basis of some mineralogical...
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