Mafické enklávy v diatexitických migmatitech svrateckého krystalinikaČlánek v PDF
Mafic enclaves from the diatexite migmatites in the Svratka crystalline complex
Metatexite and diatexite migmatites are widespread in the Svratka crystalline complex (SCC). Their geochemical character is close to melts that originated by a dehydration melting of micas. Petrological and geochemical (Rb, XFeO, W, Be, Sn) variations are result of fractional crystallization of the melt and variable degrees of melt-restite separation. Two distinct types mafic enclaves can be distinguished: (1) Biotite-rich enclaves with muscovite characterized by high content of REE, Y, Th, U, Zr, Hf, P and (2) Biotite to muscovite-biotite enclaves sometime with garnet or tourmaline characterized by low content of REE, Y, Th, U, Zr, Hf, P. Occurrence of the biotite-rich enclaves is in a good agreement with assumptions, that anatexis occurred principally through muscovite dehydratation melting locally accompanied by biotite dehydratation melting. The degree of melting during anatexis SCC based on the mineralogy and chemical composition of the metasedimentary rocks (especially Ti content in biotite). During exhumation SCC has been produced small amount of younger B-rich melt, which formed veinlets and small melt pockets in migmatites. These late stage partial melting is less effective then previous migmatitization and did not produce any significant restitic enclaves.
David Buriánek, Czech Geological Survey, Leitnerova 23, Brno, e-mail: email@example.com