Mineralogy of the pliocene trachyte and its carbonatitic minette inclusions in Ostrvica, FYR of Macedonia

Yanev, Yotzo and Boev, Blazo and Iliev, T. and Pecskay, Zoltan and Karadjov, M. and Boev, Ivan (2010) Mineralogy of the pliocene trachyte and its carbonatitic minette inclusions in Ostrvica, FYR of Macedonia. Eπιστημoνικ\acuteη Eπǎrepsilonτηρ\acuteιδα τoυ Tμ\acuteηματoς Γǎrepsilonωλoγ\acuteιας (A. Π. Θ.), 100. pp. 287-296.

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Abstract

The trachyte at Ostrvica hill (age 3.21±0.10 Ма) in Vardar zone is the most evolved volcan- ics of the ultrapotassic Pliocene-Quaternary series in F.Y.R. of Macedonia. It is aphyric, with clinopy- roxene and phlogopite microphenocrysts within a sanidine-anorthoclase groundmass. It contains inclu- sions of carbonatitic minette ranging in size from several mm to 6–7 cm. They are light coloured por- phyric rocks, rich in vacuoles, composed of phlogopite and completely altered olivine(?) phenocrysts amongst acicular clinopyroxenes within a feldspar–calcite groundmass with abundant Fe-oxides and acicular apatite microlites. The inclusions are rimmed by a mm thick mixing zone composed of the same minerals but with intermediate composition between that of minette and trachyte. The clinopyroxenes are mainly diopside-augite with low Ti and Al content (with 6Al only in the minette). Positive correla- tions are observed between Na and Fe3+, Al and Ti, and negative one – between Al and Si. In the inclu- sions phlogopites the negative correlation between Mg# and 4Al is found. The feldspars in the trachyte and minette inclusions are Ca-sanidine to Ca-anorthoclase, in the mixing zone – sanidine only. In the in- clusions two plagioclase generations (An41 and An25) exist. The estimated crystallization temperature of the minette clinopyroxenes is 1280–1180С, of plagioclase (An41) – 1130С and in the hosting trachyte – 1080С, at the pressures 6.9 and 7.7 kbar, respectively. The temperature of the feldspars crystalliza- tion (K-Na-feldspars and Pl24) in the minette groundmass is 809–878C. By analogy with other ultrapo- tassic volcanics from F.Y.R Macedonia it is suggested, that the discussed volcanics originated from phlogopite-bearing metasomatised mantle.

Item Type: Article
Uncontrolled Keywords: F.Y.R. of Macedonia, ultra-K series, trachyte, carbonatitic minette, magma mixing
Subjects: Natural sciences > Other natural sciences
Divisions: Faculty of Natural and Technical Sciences
Depositing User: Blazo Boev
Date Deposited: 20 Nov 2012 11:02
Last Modified: 07 Oct 2013 10:39
URI: http://eprints.ugd.edu.mk/id/eprint/1431

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