Karakterizacija dolomita psevdoziljske formacije v okolici Zagorja ob Savi

Možina, Cvetka (author), Jarc, Simona (mentor)

V zgornjem delu tako imenovane psevdoziljske formacije nastopa dolomit zgornjetriasne starosti. Vzorčevalno območje dolomita se nahaja ob cestnem odseku Sveta Planina – Klek v okolici Zagorja ob Savi. Vzorcem masivnega zgornjetriasnega dolomita smo določili mineralno in geokemično sestavo. Mineralno sestavo vzorcev smo določili z optično mikroskopijo, z vrstično elektronsko mikroskopijo v kombinaciji z energijsko disperzijsko spektroskopijo rentgenskih žarkov (SEM/EDS) in z metodo rentgenske difrakcije (XRD). Geokemično sestavo smo vzorcem določili s prenosnim rentgenskim fluorescenčnim analizatorjem (XRF). Mineralna sestava vseh desetih vzorcev dolomita je zelo podobna. Prevladuje dolomit, v večini vzorcev ga je nad 98 %, med akcesornimi minerali prevladujejo temni nepresevni minerali in sljude (muskovit). Prav tako smo pri analizi z optično mikroskopijo v vzorcih opazili kremen in glinence. Da v vseh vzorcih prevladuje dolomit, je potrdila tudi analiza z rentgensko difrakcijo (XRD). V dveh vzorcih je poleg dolomita pokazala še zelo majhno količino glinenih mineralov. Z analizo SEM/EDS smo v vzorcih preiskovali akcesorne minerale. V vseh vzorcih se pojavijo minerali apatitove skupine (najverjetneje fluorapatit). Železovi oksidi/hidroksidi so bili prisotni v skoraj vseh vzorcih, razen v enem. Pirit smo določili v skoraj vseh vzorcih, nismo ga zasledili le v dveh vzorcih. V nekaterih vzorcih smo zasledili še titanov oksid (najverjetneje rutil), sfalerit s povečano vsebnostjo kadmija, fluorit, sljude, kalcit, glinence in cirkon z manjšo vsebnostjo urana. Glinene minerale, halkopirit s povečano vsebnostjo arzena, kadmija in cinka, manganov oksid s povečano količino kobalta, niklja, bakra in cinka ter greenockit smo našli le v posameznih vzorcih. Geokemijska analiza vzorcev z metodo XRF je pokazala, da v obeh analiziranih vzorcih prevladujeta MgO (približno 20 %) in CaO (približno 30 %). V vzorcih so v zelo majhnih količinah (<1 %) prisotni še SiO₂, Fe₂O₃ in Sr, ostali oksidi in prvine so pod mejo detekcije.

• Language: Slovenian
• Keywords: Ključne besede: dolomit, SEM/EDS, geokemija, Zagorje ob Savi.
• Work type: Bachelor thesis/paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2018
• PID: 20.500.12556/RUL-99488
• COBISS.SI-ID: 1389918
• Publication date in RUL: 27.01.2018

Secondary language

• Language: English
• Title: Characterisation of Pseudozilian formation dolomite in the surroundings of Zagorje ob Savi

Abstract

In the upper part of the so called Pseudozilian formation Upper Triassic dolomite is also found. The sampling area of the dolomite is at the road section Sveta Planina hill - Klek in the in the surroundings of Zagorje ob Savi. We have determined mineral and geochemical composition of the samples of massive Upper Triassic dolomite. Mineral composition was determined by using optical microscopy, scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy (SEM/EDS) and with the method of X-ray diffraction (XRD). Geochemical composition of the samples was determined with a portable X-ray fluorescence analyser (XRF). The mineral composition of the ten samples is very similar. Dolomite prevails, in most samples the content is over 98 %, among accessory minerals there are mainly dark non-transparent minerals and mica (muscovite). Optical microscopy analysis of samples also showed the presence of quartz and feldspar. X-ray diffraction analysis confirmed that dolomite is predominant. In two samples there was a very small amount of clay minerals. SEM/EDS analysis was used to study accessory minerals. In all samples minerals of apatite group (most likely fluorapatite) were detected. Iron oxides/hydroxides were present in almost all the samples, except in one. Pyrite was found in almost all the samples, it wasn't found in only two of them. Some samples showed the presence of titanium oxide (most likely rutile), sphalerite with an increased content of cadmium, fluorite, mica, calcite, feldspar and zircon containing a small amount of uranium. Clay minerals, chalcopyrite with an increased content of arsenic, cadmium and zinc, manganese oxide with an increased content of cobalt, nickel, copper, zinc and greenockit were found only in some of the samples. Geochemical analysis of the samples with an XRF method showed that MgO (approximately 20 %) and CaO (approximately 30 %) are predominant in both analysed samples. The samples contain very small quantities (<1 %) of SiO₂, Fe₂O₃ and Sr, while other oxides and elements were under the detection limit.

• Keywords: KEY WORDS: dolomite, SEM/EDS, geochemistry, Zagorje ob Savi.