engleski

Garnet group minerals from the amphibolite facies metamorphic rocks of Krivaja-Konjuh ultramafic massif in Bosnia and Herzegovina

In Bosnia and Herzegovina’s ophiolite zone there are six different ophiolite complexes including Krivaja-Konjuh ultramafic massif. In the south-eastern parts of the massif, the basement is built of different varieties of amphibolites with subordinate occurrence of metamorphic rocks that don’t contain amphiboles. Locality NE of Vareš near the village of Vijaka is generally the best outcrop of amphibolite rocks. The results of petrologic studies indicate that the analyzed rocks can be divided into several groups like garnet-diopside amphibolite, garnet-diopside-hypersthene amphibolite, plagioclase-garnet rocks, garnet-pyroxene-plagioclase schist ; plagioclase-garnet-hornblende - diopside schist and porphyryblastic hornblende and garnet bearing schist. The garnets show wide variation in chemical composition with prevalance of almandine and pyrope component in all of analyzed samples. The differences in the composition profile through the garnets are attributed to changes in the metamorphic conditions during the growth of minerals. Abrupt changes in distribution of elements were observed in a thin zone on the very edge of the garnet grains which is interpreted as a result of the retrograde phase of metamorphism and rapid cooling.

minerals; chemical composition; garnet; metamorphic rocks; amphibolites; pyrope; almandine; grossular; andradite

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