International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

PETROLOGY OF THE MALA FATRA GRANITOID ROCKS (WESTERN CARPATHIANS, SLOVAKIA)

Pages: 27 - 37

Authors: IGOR BROSKA, IGOR PETRIK, PATRIK BENKO

Abstract: The crystalline core of the Mala Fatra Mts. belongs to the basement of the Tatric Unit in the Western Carpathians. Two segments, the Luka and Krivan, are distinguished in the Mala Fatra Mts., both with large granite plutons. This paper deals with the granitoid rocks of the Krivan segment. On the basis of their mineralogy and geochemistry the hybrid and Magura granite types of Ivanov & Kamenicky (1957) were redefined as I- and S-type granitoids, respectively. The I-type granodiorites and tonalites have a characteristic mineral assemblage of plagioclase (An21–48), Mg-biotite, epidote, interstitial K-feldspar, allanite, hornblende and zircons with I. T. parameter above 350. They are situated mainly on the southern slopes of the Krivan part of the Mala Fatra Mts. The Al-in-hornblende barometer gives a pressure of 330 ± 60 MPa, the zircon and monazite saturation temperatures are between 745–810 °C and 750–810 °C, respectively. The water content of the granitoid magma, estimated on the basis of biotite composition, was about 5 wt. % at 700 °C. This granite suite also contains mafic magmatic enclaves. The S-types granites are localized to the north of the I-type granitoids. They contain plagioclase (An12–35), Fe-biotite, K-feldspar and zircons with I. T. parameter below 300–350. In the absence of hornblende, we suppose the same pressure (330 MPa) for the emplacement of this granite suite. The zircon and monazite saturation temperatures are also within the same range as in the I-type granites (740–790 °C or 720–790 °C). However, the biotite of the S-type granites suggest a lower water content of about 2–4 wt. % at 750 °C. It is noteworthy that according to increasing body of data, the granitoid massifs in a 200 km long region in the present erosion cut between the Male Karpaty and Mala Fatra Mts. were emplaced at similar temperature and pressure conditions. The pressures of 300–400 MPa indicate the similar 12–15 km emplacement depth of all the granitoid bodies in this area.

Keywords: Mala Fatra granites, I- and S-type granites, petrology, biotite, zircon, monazite

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