Stanovenie P-T podmienok vzniku margaritu a pumpellyitu-(Al) v metamorfovaných horninách Malej Magury (Strážovské vrchy)

Margarite and pumpellyite-(Al) are relatively rare minerals in metamorphic and granitic rocks of the Western Carpathians. In this paper we present a description, interpretation and calculation of P-T conditions of margarite and pumpellyite-(Al) formation, recently found in migmatite and gneiss from the Tatric crystalline basement of Mala Magura Mts. (Stražovske vrchy Mts.). Using Thermocalc, with primary assemblage, the P-T conditions were calculated and yielded the following values: T = 668-782°C, P = 550-740 MPa. Peak metamorphic conditions for pseudosections (PERPLEX) gave intervals of T = 670-765°C, and P ~600-820 MPa. From the P-T reaction curves the conditions of low grade metamorphism were estimated for migmatite MM-1, the low grade metamorphism at T = 480°C and P = 460 MPa, and for the gneiss the low grade conditions in gneiss MMC-10 at about 300°C and P = 300 MPa. The data obtained for metamorphic conditions are interpreted as probable result of Variscan retrogression. The low T obtained for gneiss with pumpellyite is most probably due to an Alpine overprint.