Studie zirkonu z alkalického syenitu od Naloučan, moldanubikum

Varování

Publikace nespadá pod Filozofickou fakultu, ale pod Přírodovědeckou fakultu. Oficiální stránka publikace je na webu muni.cz.
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ŠKODA Radek KLEMENTOVÁ Mariana ČOPJAKOVÁ Renata

Rok publikování 2009
Druh Článek v odborném periodiku
Časopis / Zdroj Acta Mus. Moraviae, Sci.geol.
Fakulta / Pracoviště MU

Přírodovědecká fakulta

Citace
Obor Geologie a mineralogie
Klíčová slova zircon; typology; radiation damage; metamictization; fluid interaction
Popis The fine-grained part of alkali-feldspar syenite near Naloučany is extremely enriched in Zr, Th and U. In these parts the zircon content reach 5 percent. The zircon forms euhedral crystals 100 do 350 micrometers in size with uniform typology. Among crystal faces dominate prism (100) and pyramid (101). The prism (110) and pyramids (301), (211), and (121) are less evolved. According Pupins classification studied zircons fall into S24-S25 indicated crystallization temperature about 850 oC and confirmed high alkalinity. In the BSE four different parts of zircon were observed: i) central part with inclusions of thorite, ii) dark parts propagating along fractures, iii) homogeneous rim, and iv) bright zones between central part and rim. The dark parts contain higher concentrations of Ca, Fe, Al and Ti. Based on the U and Th content the radiation damage was calculated. The highest degree of radiation damage shows bright parts (0.38-0.66 dpa) and the lowest was recorded in the rim (0.07-0.31 dpa). The dark parts exhibit lower damage (0.11-0.38 dpa) than central parts (0.17-0.46 dpa). Metamict state was confirmed by HRTEM. The first percolation point was reached about 0.11 dpa. Low calculated radiation damage in the most altered dark parts suggest loss of U > Th during mineral-fluid interaction.
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