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

The crystalline core of the Mala Fatra Mts. belongs to the basement of the Tatric Unit in the Western Carpathians. Two segments, the Luka an d Krivan, are distinguished in the Mala Fatra Mts., both with large gr anite plutons. This paper deals with the granitoid rocks of the Krivan segment. On the basis of their mineralogy and geochemistry: the hybri d and Magura granite types of Ivanov & Kamenicky (1957) were redefined as I- and S-type granitoids, respectively. The I-type granodiorites a nd tonalites have a characteristic mineral assemblage of plagioclase ( An(21-48)), Mg-biotite, epidote, interstitial K-feldspar, allanite, ho rnblende and zircons with <(I.T.)over bar> parameter above 350. They a re situated mainly on the southern slopes of the Krivan part of the Ma la Fatra Mts. The Al-in-hornblende barometer gives a pressure of 330 /- 60 MPa, the zircon and monazite saturation temperatures are between 745-810 degrees C and 750-810 degrees C, respectively. The water cont ent of the granitoid magma, estimated on the basis of biotite composit ion, was about 5 wt.% at 700 degrees C. This granite suite also contai ns mafic magmatic enclaves. The S-types granites are localized to the north of the I-type granitoids. They contain plagioclase (An(12-35)), Fe-biotite, K-feldspar and zircons with <(I.T.)over bar> parameter bel ow 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 degrees C or 720-790 degrees C). However, the biotite of the S-type granites suggest a lower water content of a bout 2-4 wt.% at 750 degrees C. It is noteworthy that according to inc reasing 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 pres sures of 300-400 MPa indicate the similar 12-15 km emplacement depth o f all the granitoid bodies in this area.