Čík Š. & Petrík I., 2014: Margarite and pumpellyite (Al) from metamorphic rocks of the Malá Magura Mts.: P-T conditions of metamorphism and crystallization of associated granitoids. Acta Geologica Slovaca, 6, 2, 169–178. (in Slovak with English summary)

Výskyt margaritu a pumpellyitu (Al) v metamorfovaných horninách Malej Magury: Stanovenie P-T podmienok metamorfizmu a kryštalizácie asociujúcich granitoidov

Margarite and pumpellyite (Al) from metamorphic rocks of the Malá Magura Mts.: P-T conditions of metamorphism and crystallization of associated granitoids

Štefan Čík & Igor Petrík

Geologický ústav, Slovenská akadémia vied, Dúbravská 9, 840 05 Bratislava; geolcist@savba.sk, igor.petrik@savba.sk

Abstract

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. (Strážovské 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.

Key words: P-T conditions, margarite, pumpellyite-(Al), metamorphic rocks, migmatites, Strážovské Vrchy Mts, Western Carpathians, Slovakia

Manuscript received: 2013-10-09

Revised version accepted: 2014-04-29