Mineralne, petrološke in geokemične lastnosti izbranih vrst naravnega kamna za oceno njihove radioaktivnosti

Kamnik, Špela (author), Zupančič, Nina (mentor)

Namen dela je bil poimenovati 69 vzorcev naravnega kamna glede na veljavne geološke klasifikacije, ki se prodajajo pod največkrat neustreznim tržnim imenom in z nepravilno kamnoseško klasifikacijo. Vzorcem, ki se na tržišču največkrat pojavljajo pod imenoma granit in marmor, sem določila 22 različnih imen. Vzorce kamnin sem razdelila v tri glavne skupine – magmatske, sedimentne in metamorfne. Največ vzorcev spada med magmatske kamnine, ki sem jih poimenovala kot kremenov granitoid, alkalno-glinenčev granit, alkalno-glinenčev sienit, sienogranit, monzogranit, pegmatit, grenodiorit, kremenov diorit, monzogabbro, gabbro, anortozit in riolit. V skupini sedimentnih kamnin sem določila apnenec, lehnjak in peščenjak. Vzorce metamorfnih kamnin sem klasificirala kot kvarcit, granulit, serpentinit, brečiziran serpentinit, migmatit, blestnik in gnajs. Z mikroskopskim pregledom v presevni polarizirani svetlobi, sem vzorcem določila mineralno sestavo. Kemijska sestava vzorcev je bila določena z rentgensko fluorescenčno analizo. Za potrebe magistrskega dela Igorja Osojnika so bile izvedene meritve specifične aktivnosti naravnih radionuklidov - 40K, 232Th in 238U. Pokazalo se je, da so najbolj radioaktivne granitoidne kamnine in metamorfne kamnine (migmatiti in granuliti), pri katerih je izvorna kamnina magmatska. Vse navedene kamnine imajo večji delež K-glinencev in/ali sljud, v nekaterih so z mikroskopijo potrjeni tudi akcesorni minerali (npr. cirkon). Enak rezultat sem dobila pri pregledu in primerjavi rezultatov rentgenske fluorescenčne analize in mineralne sestave kamnin, ki sta potrdili povezavo med vrsto kamnine in količino K2O, Th in U v njej. Najvišje vsebnosti dotičnih elementov so pri felzičnih magmatskih kamninah granitske skupine in metamorfnih kamninah (vzorci migmatitov in granulitov), ki so nastale z metamorfozo takšnih magmatskih kamnin. Najnižji deleži K2O, Th in U so v sedimentnih kamninah, prav tako so bile za te izmerjene najnižje specifične aktivnosti naravnih radionuklidov. Vzorčene sedimentne kamnine ne vsebujejo K-glinencev, sljud in akcesornih mineralov.

• Language: Slovenian
• Keywords: Geološka klasifikacija, K-glinenci, sljude, kalij, uran, torij
• Work type: Master's thesis/paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2020
• PID: 20.500.12556/RUL-116184
• COBISS.SI-ID: 16738819
• Publication date in RUL: 21.05.2020

Secondary language

• Language: English
• Title: Mineralogical, petrological and geochemical properties of selected types of natural stone to evaluate their radioactivity

Abstract

In context of my master's thesis I named 69 specimens of natural stone, according to valid geological classifications. Natural stone is sold under inappropriate market names with incorrect stonemasonry classification. Most common names for natural stone in the market are granite and marble, I classified the specimens at hand with 22 different names. Samples were divided into three main groups – magmatic, sedimentary and metamorphic. The largest portion of samples are magmatic rocks, which I named as quartz granitoide, alkali-feldspar granite, alkali-feldspar syenite, syenite-granite, monzogranite, pegmatite, granodiorite, quartz diorite, monzogabbro, gabbro, anorthosite and rhyolite. I identified limestone, travertine and sandstone in the group of sedimentary rocks. I classified the metamorphic rock samples as quartzite, granulite, serpentinite, brecciated serpentinite, migmatite, mica-schist and gneiss. I determined the mineral composition of the samples with microscopic research in transmitted polarized light. The chemical composition of the samples was determined with X-ray Fluorescence Spectrometry. Osojnik (2016) determined the specific activity of natural radionuclides - 40K, 232Th and 238U with high resolution gamma spectrometry. The most radioactive were granitoide rocks and metamorphic rocks (migmatites, granulites) of magmatic origin. These rocks have higher share of potassium feldspar and/or mica. In some specimens accessory minerals (e.g. zircon) were confirmed in microscopic research. The same result was obtained from comparing results of X-ray Fluorescence Spectrometry and the mineral composition of the specimens. The relation between the type of the rock and amount of potassium, thorium and uranium in it, does exist. The highest values of the elements in question are in felsic magmatic rocks of granite group and metamorphic rocks (migmatites and granulites) of magmatic origin. The lowest values of potassium, thorium and uranium are in the sedimentary rocks, and the lowest specific activities of natural radionuclides have been measured for these. Sampled sedimentary rocks do not contain potassium feldspar, mica and accessory minerals.

• Keywords: Geological classification, potassium feldspar, mica, potassium, uranium, thorium