Stability of accessory minerals and the mobility of rare lithophile elements and C in the rocks of collisional orogenic zones: prograde and retrograde transformations
Investigators from institution:
Igor Broska, Marian Janák, Stanislava Milovská
Pavel Uher, Martin Ondrejka, Vladimír Bilohuščin
Project will deal with stabilities and transformations of accessory minerals (with emphasis to REE, Nb, Ta, C) from granitic and metamorphic rock in the process of subduction and exhumation. By the identification of primary and secondary phases and by quantification of the transformations (reactions among the phases) it is possible to derive P-T-X parameters of metamorphism and suggest a tectonic interpretation. Complex transformations of the accessories involve also rock-forming minerals which enables the calculation of reactions. In detail there will be studied REE minerals (allanite, monazite, and products of their alterations) along with apatite, Nb-Ta phases, tourmaline, Fe-Ti oxides according to the rock type. The study of monazite (non)stability has direct consequences for the age interpretation of complex grains. A special attention is given to transformation graphite-diamond in ultrahigh-pressure rocks. For successful solving the project goals proper terrains are suggested where, besides polymetamorphic rocks of the Western Carpathians, ultrahigh-pressure rocks of the Pohorje, Caledonides, and Rhodope Mts. are well developed. The project has a character of basic research but some of expected results are applicable to “nuclear ceramics” suggested for as materials for deposits of radioactive waste because knowledge of geochemical mobility during alteration is important for post-depositional risk estimates.