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

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.