Publication details
MINERÁLNÍ ASOCIACE FOSFÁTOVÝCH NODULÍ Z GRANITICKÉHO PEGMATITU OD CYRILOVA U VELKÉHO MEZIŘÍČÍ, MOLDANUBIKUM; ČÁST I PRIMÁRNÍ A EXSOLUČNÍ FÁZE
| Title in English | Mineral assemblages of the phosphate nodules from the granitic pegmatite at Cyrilov near Velké Meziříčí, Moldanubicum; part I primary and exsolution phases. |
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| Authors | |
| Year of publication | 2007 |
| Type | Article in Periodical |
| Magazine / Source | Acta Mus. Moraviae, Sci. geol. |
| MU Faculty or unit | |
| Citation | |
| Field | Geology and mineralogy |
| Keywords | zwieselite; graftonite; sarcopside; wolfeite; triphylite; harrisonite; ixiolite; Nb-rich ferberite; Nd and Sm-rich monazite-(Ce); granitic pegmatite; Moldanubicum |
| Description | Granitic pegmatite near Cyrilov, the type locality of cyrilovite, belongs to the beryl columbite phosphate subtype of the REL Li type, despite the absence of the beryl. The primary phosphates and associate minerals occur in two assemblages: i) zwieselite nodule minerals zwieselite, uraninite, ilmenite, ixiolite and Nb rich ferberite and ii) graftonite nodule minerals graftonite, sarcopside, wolfeite, triphylite, harrisonite, monazite (Ce) and xenotime (Y). The triphylite is completely altered to ferrisicklerite and heterosite. The solidification of the phosphate assemblages began with crystallization of zwieselite, which decreased the content of F in the melt; this allowed consequent graftonite crystallization. Graftonite crystallized as Li,OH rich precursor. In the graftonite nodule assemblage, exsolution proceeds in (at least) two stages: i) a Li,OH rich precursor unmixed to wolfeite, sarcopside I, graftonite II and to the precursor of triphylite and sarcopside II, ii) a further decrease of temperature induces an exsolution of triphylite and sarcopside II from their precursor. The genetic position of harrisonite is not clear. Subhedral monazite (Ce) associated with wolfeite, graftonite II and sarcopside I and worm like monazite(Ce) from triphylite sarcopside II intergrowths is rich in Nd (up to 20,35 wt.% Nd2O3) and Sm (uo to 10,47 wt.% Sm2O3). Based on the chemical composition of primary phosphates and Nb Ta Ti W oxides examined, the assemblage crystallize from Li poor melt with moderate content of F and low degree of Fe/Mn and Nb/Ta fractionation. |
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