Tectogenesis of the metamorphosed series of the Kłodzko District: a tentative explanation

Abstract

The number of arguments indicate that meso- and epizonally metamorphosed rocks of the Kłodzko District were deposited in a span from Upper Proterozoic to Lower Devonian. Tectogenic and erogenic development of these series is believed to have taken place in Orcadian Phase of Early Hercynian movements. Tectogenic stage was characterized by tangential compression (F₁ folding, prograde metamorphism) and orogenic stage commenced under nearly confining pressure but went on in the field of vertical compression (microcline blastesis leading to the development of the Gierałtów, Śnieżnik, and Bystrzyca gneisses, development of F₂ folds in S₀ and S₁ planar structures, development of S₂ nearly horizontal axial schisto-sity. The Early Hercynian tectogene was greatly reconstructed in Bretonian or Sudetian Phase characterized by a couple of vertical forces effecting movements along physical discontinuities once produced in the erogenic stage (mostly S₂ surfaces). Dynamic transformations, diaftoresis, decollements, and local F₃ drag folds in S₂ planes, are the main features of this reconstruction. The rock series were piled up, which produced rapid increase of temperature. Once cataclased and mylonitised rocks were subjected to blastesis and metasomatic transformations producing polymetamorphic series (e.g. the Haniak gneisses). This process was accompanied by intense folding (development of F₄ folds). At greater depth partial melting gave rise to granitoid magma which intruded in the Upper Carboniferous (development of Kłodzko-Złoty Stok, Bielice, Kudowa, and Ścinawka granitoid massifs).