| Abstract | The aim of this Master’s thesis is to analyse the mineralogical and chemical composition of pyroclastic rocks from the Bükkalja Volcanic Field and to determine which minerals host lithium and boron. A total of 12 samples were analysed from different Miocene pyroclastic units: Wind-Kalnik Unit, Eger Unit, Mango Unit, Demjén Unit, and Harsany Unit, with one sample from Kuchyna Tuff. Mineral composition was determined using polarisation microscopy and X-ray diffraction, chemical composition via X-ray fluorescence, lithium concentrations via atomic absorption spectrometry, and boron concentrations were determined using atomic emission spectrometry. Polarisation microscopy showed that samples consist of crystaloclasts, vitroclasts, and lithoclasts and mineralogical composition was further confirmed by the XRD analysis. Plagioclase, quartz, sanidine, biotite and hornblende are in the form of crystalloclasts. Lithoclasts are mostly andesitic to rhyolitic. Volcanic glass is abundant both as medium sieved glass shards and in the matrix as very fine to fine grained vitric particles. Clay minerals, mostly smectite, occur in the matrix. According to the XRF analysis, all of the analysed samples are rich in SiO2 component with concentrations ranging from 61 to 73 wt%. Most of the samples fall under the High-K Calc-Alkaline magmatic series, according to the SiO2/K2O ratio. AAS and AES were performed separately for magnetic and non-magnetic fractions, where biotite separated into the magnetic fraction and other minerals in the non-magnetic fraction. In the non-magnetic fraction, the lithium concentrations obtained were mostly below the detection limit and could only be measured in 3 samples. In these samples, the lithium concentrations ranged from 4,2 to 21,7 mg/kg, whereas the lithium concentrations in the non-magnetic, <125 magnetic μm, fraction were below the detection limit in 5 analysed samples. In the remaining non-magnetic fraction, lithium concentrations range from 1,8 to 20,1 mg/kg. Lithium concentrations in magnetic fractions ranged from 15,2 to 41,2 mg/kg. The boron concentrations in the non-magnetic fraction range from 835 to 4505 mg/kg, while the boron concentrations in the magnetic fractions range from 3044 to 26204 mg/kg. Magnetic fractions of all samples show an enrichment of boron and lithium compared to the non-magnetic fractions. It follows that lithium and boron may be present in the crystal structure of biotite and its alterations, such as chlorite. Additionally, boron could be found adsorbed to the clay minerals. |
| Abstract (croatian) | Cilj ovog diplomskog rada je mineraloška i kemijska analiza piroklastičnih stijena s vulkanskog polja Bükkalja, u svrhu utvrđivanja minerala nosioca litija i bora. Analizirano je 12 uzoraka koji pripadaju različitim miocenskim piroklastičnim jedinicama: Wind-Kalnik, Eger, Mangó, Demjén i Harsany te jedan uzorak Kuchyna tufa. Mineralni sastav određen je metodama polarizacijske mikroskopije i rendgenske difracije na prahu (XRD), kemijski sastav određen je rendgenskom fluorescencijom (XRF), kocentracije litija određene su atomskom apsorpcijskom spektrometrijom (AAS) i koncentracije bora određen su atomskom emisijskom spektrometrijom (AES). Polarizacijskom mikroskopijom utvrđeno je da se uzorci sastoje od kristaloklasta, vitroklasta i litoklasta te je mineralni sastav potvrđen rendgenskom difrakcijom. Plagioklas, kvarc, sanidin, biotit i hornblenda pojavljuju se kao kristaloklasti. Litoklasti su andezitnog do riolitnog sastava. Vulkansko staklo pojavljuje se u velikim količinama, kao vitroklasti i u matriksu. Minerali glina, većinski određeni kao smektit, pojavljuju se u matriksu. Prema rezultatima rendgenske fluorescencije svi analizirani uzorci pokazuju visok sadržaj SiO2 čije su koncentracije u rasponu od 61 do 73%. Prema omjeru SiO2/K2O većina uzoraka spada u visoko-kalijsku kalcijsko-alkalijsku magmatsku seriju. AAS i AES analize provedene su na uzorcima separiranima u magnetnu i nemagnetnu frakciju. Magnetna frakcija sastoji se većinski od biotita, a nemagnetna od ostalih prisutnih minerala. Koncentracije litija u nemagnetnoj frakciji su ispod granice detekcije u većini uzorka, dok se 3 uzorka u kojima su mjerljive kreću od 4,2 do 21,7 mg/kg. U nemagnetnoj, <125 μm frakciji koncentracija litija je u 5 uzoraka bila ispod granice detekcije, dok se koncentracije u uzorcima u kojima su mjerljive su u rasponu od 1,8 do 20,1 mg/kg. Koncentracije litija u magnetnoj frakciji su u rasponu od 15,2 do 41,2 mg/kg. Koncentracije bora u nemagnetnoj frakciji su u rasponu od 835 do 4505 mg/kg, a u magnetnoj od 3044 do 26240 mg/kg. Magnetne frakcije ovih uzoraka pokazuju obogaćenje litijem i borom u usporedbi s nemagnetnim frakcijama, iz čega slijedi da oba elements mogu biti prisutni u strukturi biotita i njegovim alteracijama, poput klorita, dok se bor još može pojaviti adsorbiran na minerale glina. |
