Abstract

The chemical composition of the meta-evaporitic series of Niccioleta is similar (evaporitic rocks excepted) to that of the common mica schist series. However, the sheet silicates have recorded the evaporitic nature of the sedimentation. Only the schist layers in the anhydrite rocks have relatively high Mg and B contents. Electron microprobe analysis proved that muscovites are more phengitic and more magnesian in the evaporitic rocks than in the schists. Small amounts of Mg-bearing chlorites and phlogopites are associated with the phengites (which contain micro-inclusions of tourmaline, rich in dravite). The sedimentary origin of the magnesian character is discussed, the magnesian aggradations of illites are the main factor; typical minerals of evaporite-bearing sediments, like smectites and corrensites do not appear in large quantities. The P-T conditions of regional metamorphism are postulated as 2-3 kbar and 400-450 degrees C.

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