ZGORZEL SŁONECZNA W BAZALTOIDACH ŚLĄSKA I JEJ WPŁYW NA FIZYKOMECHANICZNE WŁAŚCIWOŚCI SKAŁ

Abstract

SUNBURN IN BASALTS OF SILESIA AND ITS INFLUENCE ON THE PHYSICAL AND MECHANICAL PROPERTIES OF ROCKS

Abstract. Sunburn is an untypical sort of basaltic disintegration. Its most characteristic symptoms are isometric, three-dimensional fair discolorations (so-called "spots") and a system of cracks - formation of these disjunctions leads to breaking up of the rock. Sunburn, contrary to weathering processes, develops in the whole volume of the rock. It occurs widely in basalts of Lower Silesia and Opole Silesia (recorded at 63% of all sites investigated). This process is often confused with tuffs, lava breccias, mineral incrustations, uneven fracture of rocks or so-called pseudo-sunburn phenomenon. The opinions about the negative influence of sunburn on physical and mechanical parameters of basalt predominate in the literature. The author's own investigations proved the very high parameters of small-grained grits made of the sunburned basalts (abrasion-resistance and frost-resistance) suiting the class I grits according to the Polish Standard. Macroscopic, microscopic and diffraction analyses are in conformity with the opinion of Ernst and Drescher-Kaden, that sunburn as a result of late-magmatic synchronous but unequal crystallisation of analcite and nepheline. However the atmospheric factors (temperature and humidity fluctuations) are important in manifesting the sunburn symptoms.