Enklawy skał ultrazasadowych w bazalcie z Grodźca (Dolny Śląsk)

Abstract

INCLUSIONS OF ULTRABASIC ROCKS IN BASALT FROM GRODZIEC (LOWER SILESIA)

Summary

Ultrabasic inclusions, 2-5 cm in diameter, have been found to occur in a nephelinite plug of Grodziec (Złotoryja area, Lower Silesia). On the basis of microscope and chemical examinations, these rocks have been referred to olivinite. Their texture is coarse-grained, the size of the individual components considerably exceeding phenocrysts of the surrounding nephelinite. Contrast phenomena have been observed to appear at the boundary of the inclusions and nephelinite. Bronzite and chromite, which occur in these inclusions, prove their origin from ultrabasic substratum. This allows us to draw a conclusion that the peridotite-dunite massif, which occurs in the areas of Ząbkowice Śląskie (Szklary) and Świdnica - Wiry, stretches far to the west, to reach the regions of Złotoryja and Bolesławiec.