Miloš René

By Miloš René

Part of the book: Clay Minerals in Nature

By Miloš René

Thorium is a naturally occurring, slightly radioactive element. It is widely distributed in nature with an average concentration of 10.5 ppm Th in the upper earth’s crust. In general, thorium occurs in relatively small number in Th-enriched minerals: thorite, thorianite, monazite, bastnaesite, and thorogummite. However, the main world resources of thorium are coupled with monazite and bastnaesite. Monazite-enriched placer deposits occurring mainly in India, Brazil, Australia, and the USA form the recently available resources of thorium. Other commercially interested concentrations of thorium are coupled with bastnaesite mined from carbonatite deposits, especially from Bayan Obo deposit in China. Currently, the worldwide thorium resources by major deposit types are estimated to total about 6.2 million tons of Th. Issues associated with thorium’s natural radioactivity are a significant deterrent to its commercial use. The monazite concentrates are recently produced only in India, Brazil, Malaysia, Thailand, and Vietnam, with a total amount of about 7000 tons. Consequently, experimental nuclear reactors based on thorium fuel cycle are operated recently only in India. In the long term, consumption of thorium could increase substantially if its use as a nuclear fuel becomes commercialized.

Part of the book: Descriptive Inorganic Chemistry Researches of Metal Compounds

By Miloš René

The greisens evolved in the apical part of the Hub stock, formed by weakly greisenised topaz granites, are predominantly represented by Li-mica-topaz and topaz-Li-mica greisens. These greisens, relative to weakly greisenised topaz granites, are enriched in Ca, F, Fe, Li, Si, Sn and W and depleted in Al, K, Mg, Na, Ti, Y, Zr and ΣREE. Weakly greisenised topaz granites show convex tetrads in the normalised REE patterns. Compared to topaz granites, the greisens display lower ΣREE concentrations, partly higher negative Eu anomaly, high Y/Ho and low Zr/Hf ratios. Li-micas occurring in greisens are represented by zinnwaldite. Chemical composition of cassiterite is near to ideal SnO2 (>99 wt.% SnO2). The wolframite is represented by manganoan ferberite.

Part of the book: Contributions to Mineralization

By Miloš René

The Bohemian Massif hosts a significant quantity of uranium deposits bound by brittle shear zones developed in high-grade metamorphic rocks (Rožná, Okrouhlá Radouň, Zadní Chodov and Dyleň) and/or granites (Vítkov II and Lhota). According to the international atomic energy agency (IAEA) uranium deposits classification, these deposits are classified as metamorphic deposits. For shear zone-hosted uranium mineralisation, the no direct relationship between ore mineralisation and granite bodies is significant. Ore lenses and/or disseminated ore mineralisation form the shear zone-hosted uranium deposits. The host rocks of these deposits are transformed in aceites. Aceites are defined as low-temperature alkaline metasomatic rocks, which are closely associated with uranium mineralisation. Complex coffinite-uraninite or coffinite-uraninite-brannerite assemblages form the shear zone mineralisation with predominance coffinite about uraninite.

Part of the book: Uranium

By Miloš René

The Central European deposits were the first industrially mined uranium deposits in the world. Uranium minerals were noticed by miners in the Ore Mts. area (Saxony, Bohemia) for a long time prior the uranium discovery. The uranium mineral pitchblende was reported from this ore district as early as 1565. Pitchblende was firstly extracted for production of colouring agents used in the glassmaking industry. The German chemist Klaproth in 1789 detected uranium by analysing pitchblende. In 1896, A.H. Becquerel discovered the phenomenon of radioactivity. His student Marie Sklodowska-Curie recognized that pitchblende has higher radioactivity as pure uranium salts. Later, together with her husband P. Curie, they discovered two new elements: radium and polonium. Research by O. Hahn and its colleges led later to using of uranium as first nuclear weapons. The significant amount of uranium ores for producing of the Russian nuclear weapons and nuclear power plants in the former Eastern Bloc was mined in the East Germany (GDR) and Czechoslovakia. The total production of uranium ores in GDR from 1946 to 2012 was 219,626 t U. In Czechoslovakia, the total uranium production from 1945 to 2017 was 112,250 t U.

Part of the book: Uranium

By Miloš René

Allanite occurs as a relative rare REE mineral in selected granitic rocks of the Moldanubian batholith. This batholith represents one of the largest plutonic bodies in the European Variscan belt. Allanite was found in the Schlieren biotite granites and diorites 1 of the oldest Weinsberg suite, in biotite granodiorites of the youngest Freistadt suite and in dykes of microgranodiorites occurred in the eastern margin of the Klenov pluton. A majority of analyzed allanites are without any magmatic zoning, only allanite grains from the diorites 1 display complicated internal zoning with variable concentrations of Fe, Ca, Th, and REE. Analyzed allanites from the Schlieren granite, diorite 1, and the “margin” variety of the Freistadt granodiorite display ferriallanite-allanite substitution with low Feox = (Fe3+/(Fe3+ + Fe2+)) ratio (0.2–0.5). The analyzed allanites occurring in the microgranodiorites display slightly greater Feox = (Fe3+/(Fe3 + Fe2+)) ratios (0.45–0.6) and enrichment in Al (up to 2.2 apfu). All analyzed allanites are Mn-poor with its concentrations from 0.01 to 0.04 apfu. The Ce is a predominant rare earth element in all analyzed allanite grains; they are thus identified as allanite-(Ce). The highest concentrations of Ce were found in allanites from diorite 1 (0.31–0.41 apfu).

Part of the book: Rare Earth Elements and Their Minerals

By Miloš René

Titanite-rich granodiorites occurring in the Austrian Mühlviertel are intimately associated with the I/S-granites of the Mauthausen/Freistadt granite suite. These rocks form small irregular bodies in granites of this granitic suite of the Moldanubian batholith that are represented by usually fine-grained and dark granodiorites, which contain a large amount of titanite hell “spots” formed by aggregates of plagioclases and quartz. Titanite as a relative plentiful accessory mineral exists in the center of these “spots” as idiomorphic and sphenoidal grains. The composition of titanite ranges from 89 to 92 mol.% titanite end-member. According to its Al concentration, the analyzed titanites could be considered as low-Al titanites (Al = 0.05–0.08 atoms per formula unit). Titanite contains low concentrations of both (Al + Fe3+)–OH (2–9 mol.%) and (Al + Fe3+)–F (0–8 mol.%). Titanite together with Na-enriched plagioclase and quartz is originated during late-magmatic evolution of titanite-spots granodiorites.

Part of the book: Mineralogy

By Miloš René

Granitic rocks of the Moldanubian batholith are represented by four magmatic suites: I- to S-type Weinsberg biotite granites-granodiorites, S-type Eisgarn two-mica granites, S-type Melechov/Zvůle two mica, highly fractionated granites and I/S-type Freistadt biotite granites-granodiorites. The biotite granites of the Weinsberg suite are subaluminous to weakly peraluminous granites, enriched in Ba, Sr, and Zr. The two-mica granites of the Eisgarn suite are represented by a peraluminous, the low-Th Deštná granites, intermediate-Th Mrákotín, Číměř/Aalfang granites, and the high-Th Lipnice/Steinberg granites. The alkali feldspar and two-mica granites of the Melechov/Zvůle suite are highly fractionated, peraluminous granitic rocks, depleted especially in Ba, Zr, and Th. The granites to granodiorites of the Freistadt suite are subaluminous on Ba- and Sr-enriched granitic rocks.

Part of the book: Geochemistry

By Miloš René

The Central Bohemian magmatic complex belongs to the Central European Variscan belt. The granitic rocks of this plutonic complex are formed by several suites of granites, granodiorites, and tonalites, together with small bodies of gabbros, gabbro diorites, and diorites. The granodiorites of the Blatná suite are high-K, calc-alkaline to shoshonitic, and metaluminous to slightly peraluminous granitic rocks. Compared to the common I-type granites, granodiorites of the Blatná suite are enriched in Mg (1.0–3.4 wt.% MgO), Ba (838–2560 ppm), Sr. (257–506 ppm), and Zr (81–236 ppm). For granodiorites of the Blatná suite is assemblage of apatite, zircon, titanite, and allanite significant. Zircon contains low Hf concentrations (1.1–1.7 wt.% HfO2). The composition of titanite ranges from 83 to 92 mol.% titanite end-member. Allanite is relatively Al-poor and displays Feox. ratio 0.2–0.5.

Part of the book: Mineralogy

By Miloš René and Zdeněk Dolníček

Biotite granodiorites belonging to the redwitzite suite of western part of the Bohemian Massif occur as small bodies in metasediments of the Horní Slavkov crystalline unit and/or as inclusions in biotite granites of the Krušné Hory/Erzgebirge Mts. batholith. Biotite granodiorites contain plagioclase, K-feldspar, biotite, quartz, and accessory minerals (apatite, zircon). Some of these granodiorites were hydrothermally altered and during breakdown of biotite originated chlorite, titanite, ilmenite, and REE-fluorocarbonates. The anhedral grains and irregular aggregates of REE-fluorocarbonates appear homogenous in composition in back-scattered electron images. However, the detailed microprobe analyses of individual REE-fluorocarbonate grains show relatively high compositional variability on thin section scale, particularly with respect to their contents of Ca and Y. The REE-fluorocarbonates are represented by parisite, bastnäsite and relatively rare synchysite. REE-fluorocarbonates are more widespread in the Variscan granites of the Krušné Hory/Erzgebirge Mts. and Slavkovský les Mts. than previously considered. The occurrence of these REE-fluorocarbonates demonstrates that during later post-magmatic alterations, primary accessory minerals (allanite, monazite, xenotime, zircon) became unstable with remobilization of REE, Th, and U into newly formed secondary minerals (REE-fluorocarbonates and coffinite).

Part of the book: Recent Advances in Mineralogy