The occurence of opaline matter in hydrothermally altered diabase, Debelo brdo, Povlen mountain area

Abstract

In this paper it is described the occurence of glassy opaline matter lining hydrothermal vent discovered in altered diabase. These diabase rocks represent tectonically emplaced extrusive igneous body within the volcanic-sedimentary ophiolitic assemblage so called diabase-chert formation. At the microscopic scale, an altered mass of diabase is composed of distinct domains of the wavy and reticular fibrous carbonates interlocking the interstitial patches of the amorphous to locally recrystalised opaline matter. It was observed that the opaline matter lined the altered mass as well, and that it occurs either in the form of boitroidal aggregates or as the alternating colorless and translucent milky white bands