Different models are discussed to interpret the presence of kyanite as a stable phase in contact aureoles especially in the andalusite-, sillimanitebearing aureoles. In such aureoles the polymorphic sequence kyanite → andalusite → sillimanite can be explained in terms of an essentially isobaric path during which kyanite initially crystallises from the breakdown of pyrophyllite or more likely mu...

The 18-km-diameter El’gygytgyn crater is located on the Chukotka peninsula, northeastern Russia. It represents the only currently known impact structure formed in siliceous volcanics, including tuffs. The impact melt rocks and target rocks provide an excellent opportunity to study shock metamorphism of volcanic rocks. The shockinduced changes observed in porphyritic volcanic rocks from El’gygyt...

The Scandinavian Caledonides comprise nappe stacks of far-travelled allochthons that record closure the Iapetus Ocean and subsequent continental collision Baltica Laurentia. Seve Nappe Complex (SNC) includes relics outermost Baltoscandian passive margin were subducted to mantle depths. earliest deep subduction events has been dated ca. 500–480 Ma. Evidence this event reported from northern expo...

Mineral assemblages that are diagnostic of ultrahigh-temperature (>900 °C) metamorphism generally restricted to Mg- and Al-rich rocks. However, in many metamorphic terrains such compositions do not occur, the rocks dominated by orthogneisses typically contain high-variance mineral particular pressure–temperature (P–T) conditions. Here we use whole-rock chemistry, thermodynamic phase equilibrium...