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The STUDIA UNIVERSITATIS BABEÅ-BOLYAI issue article summary
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Abstract: The pegmatites from Răzoare are located in gneisses from Răzoare Formation, one of the four metamorphic formations which were distinguished in the Preluca Mountains by Rusu et al. (1981) and Balintoni (1997). The Preluca Mountains represent one of the seven crystalline islands located in NW Transilvania. The metamorphic rocks, which build up these mountains, belong to Baia de Aries group (Rusu et al., 1981; Balintoni, 1997).
Along the massif, the metamorphic grade decreases from SE towards NW and varies from sillimanite to biotite zones of the amphibolite facies. The first metamorphic event (M1) generated staurolite and kyanite as index minerals, and the second one yielded sillimanite. The second metamorphic event (M2) acted only upon the Răzoare Formation. The P-T calculations (Radu, 1997) show that the metamorphic peak corresponds to 5300-6000C temperature and 6-8 kbar pressure. The presence of kyanite in some micaschists indicates that P-T conditions were above the kyanite-sillimanite invariant curve and they fit the initial granitic migmatitic melting (Radu, 1997).
The pegmatite emplacement is connected to M2 event (Balintoni, 1997; Radu, 1997). Generally, the pegmatites have a granite composition and consist of quartz, feldspars and muscovite as rock-forming minerals and of biotite, tourmaline, garnet, apatite and zircon as accessory minerals. At Răzoare, the pegmatites are enriched in accessory minerals comparative with the pegmatites found in the other three formations.
The apatite is found as large green prismatic crystals (up to about 3 cm in length) or rounded grains associated with feldspars (albite prevailing over K-feldspar), garnet and quartz or, as disseminated crystals among albite, perthite, quartz, tourmaline and garnet, when it can be observed only in thin sections.
This paper deals with the geochemical features of apatite from the Răzoare. Previous researches carried out by Macovei & Pomārleanu (1980) and Mārza et al. (1986) using IR and XR spectra stated that fluorine-apatite is the main component of apatite from the Răzoare pegmatites. So far, a comprehensive geochemical study regarding major and trace components of the apatite from the Răzoare pegmatite has not been performed. The available data are qualitative and show that this mineral concentrates same trace elements such as Mn, Fe, Mg, Al, Cu, La, Sm, Eu, Dy (Mārza et al., 1986) or (UO2)2- (Macovei & Pomārleanu, 1980). |
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