Vyskyt margaritu a pumpellyitu (Al) v metamorfovanych horninách Malej Magury: Stanovenie P-T podmienok metamorfizmu a kry?talizácie asociujúcich granitoidov

摘要

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 Malá Magura Mts. (Strá?ovské 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 suggest a possibility of Alpine overprint.