In this plenary lecture the complexity of topotaxial reactions was discussed starting from simple crystallographic relations down to structural relations at the atomic scale. Every process involved in topotaxial transformation leaves some characteristic structural or chemical marker behind that is helpful for reconstructing the past sequence of transient processes. For example, exsolution and precipitation processes are a consequence of supersaturation of the existing solid solution. The excess solute is excreted finding the easiest possible structural relation with the parent crystal. To reconstruct the sequence of these unknown transient processes, detailed structural and chemical characterization of precipitate – matrix relations is of great help. In the lecture examples of such topotaxial processes were shown, including formation of sagenitic rutile and ilmenite-to-rutile transformation, both studied on natural mineral specimens from Brazil and Zambia.
B.04 Guest lecture
COBISS.SI-ID: 28588839The invited talk dealt with the phenomenon of twinning and related phase transformations in minerals that have always been an exciting topic for crystallographers. Based on crystal chemistry principles early scientists suggested that the atomic structure of the twin boundary must be related to an existing polymorphic modification of the parent phase. Normally, the twinning operation alone does not involve any change in chemistry, however twin sequences in polysomatic structures are known to accommodate elements that are typically not present in the parent phase. Based on the analogy with modular structures some researchers suggested that there is a high probability that local chemistry of macroscopic twins must encompass these impurity elements in same structural manner as in the polysomatic phases. The confirmation of this hypothesis was not possible until the development of modern electron microscopy that enabled a direct insight into the structure of twin boundaries at atomic scale. Despite a solid theoretical background it is surprising how little is done to prove these concepts experimentally. In this lecture experimental case studies were presented to illustrate the described concept of chemically-induced twinning in synthetic and natural minerals (mostly in the frame of basic research projects J1-4167 and J1-6742), including sphalerite, zincite and spinel.
B.04 Guest lecture
COBISS.SI-ID: 28819751The results of mineralogical and geochemical investigations in the frame of the project are applicable in numerous applicative projects related to investigations of drinking, thermal and mineral waters in Slovenia, investigations of energy raw materials (coal) and investigations related to technically and environmentally challenging projects such as the second block of the Krško nuclear power plant or storage of low and intermediate level radioactive waste. namely, zeolites and clays are most frequently represented in sediments and sedimentary rocks of Tertiary and Quaternary age. We presents the results of our research and our knowledge to interested public, teachers, primary and secondary school students and students of natural sciences. In May 2015 we guided a group of professors at the High School of Environment (Visoka šola za varstvo okolja) to Smrekovec, where we presented the mineralogical end petrological characteristic of rocks with the emphasis on zeolites of hydrothermal origin, among which the most widely represented minerals are laumontite, analcime and heulandite. Our monograph »Geopark Karavanke: secrets written in rocks« is especially dedicated to hikers who explore this geologically extremely rich territory. The monograph contains simplified descriptions of geological age, tectonic environment and processes, the origin of magma, sedimentary environment and formation of a stratovolcano at the bottom of the see in the seabed of the Smrekovec Oligocene basin. In this monograph we described also less widely known types of volcanic rocks such as peperites, hialoclastiotes, hialoclastitic breccias and autobreccias. These autoclastic rocks are related to the lava decomposition due to fast cooling in see water or de to mixing of lava and water-saturated silicoclastic and volcanoclastic sediment. We also collaborate in the high school educational process and in the frame of the Geohazard course we teach the masters students of Geology with threats represented by the volcanic activity.
F.27 Contribution to preserving/protecting natural and cultural heritage
COBISS.SI-ID: 2475861