engleski

Ar/Ar dating and fluid inclusion study of muscovite from the pegmatite of Srednja Rijeka, within granitoids of Moslavačka gora Mt., North Croatia

Pegmatite quartz containes numerous fluid inclusions (FIs). So far three types of FIs have been recognized, high density - low salinity and high density - high salinity aqueous - carbonic FIs and aqueous FIs. In the former degree of fill (water) varies between 0.45 and 0.60. TfmCO2 occurs in the temperature range between -74.0 and -76.0 C and TmCO2 is observed between-56.9 and 65.5 C, what is assigned to the presence of other volatiles (CH4, N2). Tmice is in the interval between -2.0 and -9.0 C. Tm clathrate is between 6.5 and 7.0 C, what corresponds to 5.8 and 6.2 wt% equ.NaCl, assuming negligible clathrates of N2 and CH4 has been formed. Homogenization of the carbonic phase proceeds into liquid phase in the temperature range between 19.2 and 20.0 C. The temperature of total homogenization into liquid phase ThTOT, occurs between 340 and 360 C. FIs study is still in progress. The muscovite from Srednja Rijeka pegmatite gave a plateau age of 73.2+-0.8 Ma. No overprint or excess Ar is indicated by the age spectrum and thus the plateau age can be considered as the time of muscovite crystallization and/or cooling.

Ar/Ar dating; pegmatite; fluid inclusion study; granitoids; Moslavačka gora; Croatia

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