ABSTRACT SOBOCKÝ, Tomáš: Minerals of rare lithophile elements: Indicators of granitoid evolution under magmatic to supergene conditions from Velence area in Hungary and Ditrău massif in Romania [Dissertation work]. Comenius University in Bratislava. Faculty of Natural Sciences. Department of Mineralogy and Petrology. Supervisor: doc. Mgr. Martin Ondrejka, PhD. Bratislava: Faculty of Natural Science, CU, 2020, 149 p. Accessory monazite-(Ce), -(La), -(Nd), cheralite, xenotime-(Y), fluorapatite and allanite-(Ce) represent primary REE-bearing minerals in subsolvus A-type granite, and its differentiates in Velence Hills, Transdanubian Unit, (Hungary). The chemical EPMA analyses showed monazite-(Ce) with dominant cheralite and subordinate huttonite substitution mechanism while xenotime-(Y) suggested thorite substitution trend. The presence of allanite-(Ce) and cheralite indicate higher activity of Ca. Monazite-(Ce) in-situ electron-microprobe Th-U-total Pb dating of the Velence granite massif determined 289 ± 2,9 Ma age, which confirmed the post-Hercynian, Permian, (Cisuralian) magmatic crystallization. In contrast, xenotime-(Y) gave age of 266 ± 5,2 Ma which corresponds to Permian (Guadalupian) post-magmatic (subsolidus) recrystallization of xenotime-(Y) due to younger event connected with subsequent overprint of the parental granitic rocks. Although monazite-(Ce) remains relatively unaffected, fluid-induced breakdown of xenotime-(Y) produced numerous tiny thorite and cheralite inclusions in the altered xenotime-(Y) domains which can be formed by coupled dissolution-reprecipitation reactions between magmatic xenotime-(Y) and younger late to post-magmatic granitic fluids. Secondary assemblage of accessory sulphates, phosphates and carbonates include jarosite, Pb-rich jarosite and alunite, corkite, hinsdalite, rhabdophane-(Ce), -(La) and -(Nd), brockite and bastnäsite and represents rich low-temperature to supergene association. Detailed study reveals a wide miscibility among rhabdophane-tristramite-brockite solid solution and complex substitution mechanisms within the alunite, beudantite and plumbogummite groups. The formation of this rare secondary minerals reveals extensive remobilization of rare-earth elements (REE), Th, U, P, S, Fe and Pb under supergene conditions originated from total leaching of the primary magmatic minerals by acid sulphate solutions connected with an adjacent Palaeogene intrusion of diorite-andesite and the accompanying hydrothermal sulfide mineralization. In contrast, REE carbonates were precipitated by CO2-rich alkali solutions. Studied granitoid rocks in Ditrău alkaline massif (Romania) are represented by diorite, syenite, granite and pegmatitic differentiates. The primary magmatic minerals titanite, ilmenite, rutile, pyrochlore, fluorapatite, allanite-(La), zirconolite, zircon and baddeleyite, which are the main carriers of HFSE and REE. The presence of such extensive variable accessory assemblage of rare lithophile elements indicates high level of differentiation and fractionation of melt rich in HFSE, REE and this suggest also Nb/Ta, Zr/Hf, Y/Ho ratios in minerals. The post-magmatic and hydrothermal stage is represented by secondary assemblage of accessory pyrochlores, REE carbonates and rare thorutite. The higher activity of lanthanides and actinides during hydrothermal stage is caused by a presence of F and Cl ligands, which allowed the complexation of these elements, fractionation and mobility in alkali aqueous fluids rich in CO2. Rare lithophile elements, such as REE, Zr, Hf, U, Th, Nb, Ta, Ti can be significantly remobilised and fractionated in fluid regime and under low-temperature if the hydrothermal fluid is rich in halogens, particularly F. Key words: A-type granitoids, Velence, Ditrău, lithophile elements, accessory minerals, dissolution-reprecipitation processes