Petrogenesis of kyanite-quartz segregations in mica schists of the Western Tatra Mountains (Slovakia)

Paulina Pyka,Aleksandra Gawęda,Magdalena Sikorska,Axel Müller,Krzysztof Szopa

doi:10.1515/mipo-2015-0007

Paulina Pyka, Aleksandra Gawęda + Show 3 more

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https://doi.org/10.1515/mipo-2015-0007

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Abstract

Abstract In the Tatra Mountains (Slovakia) metamorphic complex, kyanite-quartz segregations with biotite-rich selvage occur in mylonitized mica schists. In this paper, the problem of fluid flow and aluminium mobility during the uplift of the crystalline massif, and the position of the segregations in the history of Western Tatra metamorphic complex, is adressed. The reaction Alm + Rt ➔ Ilm + Ky + Qtz is considered to be the result of a pressure drop from above to below 9 kbar. Ti-in-biotite geothermometry shows the temperature range to be 579-639°C that is related to heating and decompression associated with granite intrusion. Major-element mass-balance calculations show that Al remained stable in the selvage + segregation system whereas other elements (e.g. Cr, HFSE) were mobilized. The kyanite-quartz segregations formed from local fluids generated during dehydration of the metapelitic rocks during uplift. The main mechanism was likely diffusion-driven mass-transfer into extension-related cracks.

Highlights

Kyanite, one of the polymorphic varieties of Al2SiO5, is an excellent marker of mediumto high-pressure metamorphism in metasedimentary rocks
In the Tatra Mountains (Slovakia) metamorphic complex, kyanite-quartz segregations with biotite-rich selvage occur in mylonitized mica schists
In the Tatra Mountains metamorphic complex, megacrystic kyanite-quartz segregations occur within the mylonitized mica-schists on the SW-slope of Baranèc Mt. in Slovakia (Pyka et al 2013a, b)

Summary

Introduction

One of the polymorphic varieties of Al2SiO5, is an excellent marker of mediumto high-pressure metamorphism in metasedimentary rocks. Specific vein- and lens-shaped segregations of Al2SiO5 polymorphs with quartz occur in many places in metapelitic rocks showing Barrowian metamorphism (Allaz et al 2005; Ague 2011). Their presence is usually interpreted as due to SiO2 and Al2O3 mobilization and crystallization from channelized fluid exsolved during metamorphism (Ague 2011). The aim of the current paper is to discuss the problem of fluid flow and aluminium mobility during the uplift of the crystalline massif and the position of the kyanite-quartz segregations in the history of the Western Tatra metamorphic complex

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