Abstract
This paper considers petrogenetic processes related to the influence of fluid flows on rocks in regional deformation zones at different depth levels within the Earth’s crust. It was shown that silica mobility could be important for eclogites developing after (meta)gabbroids: in the absence of quartz, the main eclogitic minerals, garnet and omphacite, are stabilized to significantly lower pressures compared with the quartz-saturated system. Based on petrological data and the analysis of oxygen isotope distribution in coexisting minerals from the hypersthene-sillimanite Mg-Al-Si granulites of Palenyi Island (Por’ya Guba of the Lapland granulite belt), it was concluded that these rocks were formed at high temperature and pressure (approximately 900°C and 10 kbar) under the influence of an external fluid. The influence of the fluid flow had to be rather short and spatially nonuniform.
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