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Minerals of radioactive metals
Published in Francis P. Gudyanga, Minerals in Africa, 2020
Thorium (Th) can be found in nature as a primordial element. Moazite, a chemically unre-active phosphate mineral, is the most important commercial source of thorium containing about 2.5%. Allanite can have 0.1–2% thorium and zirconia up to 0.4% thorium. Thorianite ThO2 is a rare mineral from which thorium can also be extracted. Thorite, thorium silicate, ThSiO4 has a high thorium content with the Th4+ and SiO44− ions often replaced with M3+ (M = Sc, Y, L) and phosphate PO34− ions, respectively. The minerals that contain significant quantities of thorium are often metamict [761] due to the element’s radioactivity [760].
Uranium Enrichment, Nuclear Fuels, and Fuel Cycles
Published in Robert E. Masterson, Nuclear Engineering Fundamentals, 2017
Thorium is found in small amounts in most rocks and soils and is about as common as the element lead. The average concentration of thorium in the Earth’s crust is about 12 parts per million (ppm). Thorium can be found in several common minerals including thorite (ThSiO4) and monazite (ThPO4). Monazite is a reddish–brown mineral containing the element phosphorous. It can usually be found in small isolated crystals. There are actually four different types of monazite, but only one of them contains thorium in significant quantities.
Mineralogy of various types of Th-U-REE mineralisation in the iron oxide – apatite deposits of the Bafq district, Central Iran
Published in Applied Earth Science, 2023
Khalegh Khoshnoodi, Samaneh Ziapour, Mohammad Yazdi, Michel Cuney
In the Bafq iron oxide-apatite deposits, five types of Th-U-REE mineralisation have been recognised: REE-P, Th-REE, Th only, U-REE and REE-U-Th mineralisations. REE-P mineralisation occurred essentially as apatite. The REEs are mainly as substitutions in apatite crystals and as small inclusion of monazite, xenotime and bastnasite within the apatite crystals. Apatite is the main host of the LREE. There are at least two generations of apatite in these deposits. The first generation includes large euhedral crystals intergrown with magnetite, and the second one occurs as subhedral to anhedral crystals in veins and veinlets as a later phase. The other types of mineralisation have occurred after the magnetite-apatite mineralisation. Th-REE and thorium mineralisation occurred as REE-bearing thorite and titanite, and Th-bearing minerals (thorite and huttonite). The U-REE mineralisation consists of uraninite and cleveite. REE-U-Th mineralisation is represented by davidite and allanite.
Behaviour of cerium(III) in the presence of components of soils and its humate complex
Published in Environmental Technology, 2021
Melania Jiménez-Reyes, Perla Tatiana Almazán-Sánchez, Marcos Solache-Ríos
The increasing agricultural use of rare-earth elements might cause environmental contamination. The distribution patterns of some lanthanide and actinides in Chinese soils were analyzed and increasing concentrations of radioactive and some rare-earth elements were found. The mineralogical composition of soils includes minerals-concentrators of radioactive and rare-earth elements, such as monazite, zircon, xenotime, thorite, and a thorium-cerium phase. The high content of these minerals in rocks determine the concentrations of U, Th, Ce, and La in the soils. According to the World Health Organization, the Chinese Guangdong province presents the highest rate of nasopharyngeal cancer in the world, possibly due to the high concentration of radionuclides in the environment [21]. Li et al. [17] studied the sorption-desorption of cerium (III) in soils from China and found that the adsorption was rapid and desorption was adjusted to the Elovich equation; however, they did not characterize the soil and therefore a mechanism was not reported. Desorption of Ce(III) from soils was studied by Wen et al. [22], they reported that desorption depends on the pH and the content of organic matter in the soils. Organic complexation affects the adsorption of cerium, as observed with MnO2 as adsorbent [23]. The redox reaction of cerium explains this behaviour; at pH above 8.2, Ce(III) readily oxidizes into Ce(IV), which is then preferentially adsorbed onto humic acids [24].
Sulfur in New Zealand geothermal systems: insights from stable isotope and trace element analyses of anhydrite from Rotokawa and Ngatamariki geothermal fields, Taupo Volcanic Zone
Published in New Zealand Journal of Geology and Geophysics, 2021
The analysed anhydrite from Rotokawa or Ngatamariki geothermal fields shows a wide range of rare earth element compositions and isotopic ratios. The analysed anhydrite occurs typically in veins, except for sample NM9-3206 from Ngatamariki. As a consequence, the chemistry of NM9-3206 anhydrite must in part reflect the trace element concentration of the plagioclase pseudomorph which it has replaced. Europium and Ba are enriched in this particular sample, in agreement with anhydrite being a replacement product of plagioclase. Similarly, the LREE depleted pattern of sample NM4-2208 reflects the depleted nature of the fluid (or the host silicified advanced argillic altered silicic tuff) in agreement with NM4 anhydrite being formed under the fossil magmatic-hydrothermal conditions (Chambefort et al. 2017). The LREE-depleted pattern is attributed to the co-crystallisation of LREE-bearing monazite, thorite and allanite in the Ngatamariki hydrothermal alteration halo (Chambefort et al. 2017), which supports the cogenetic origin of the anhydrite with the magmatic intrusion. In comparison, REE contents of magmatic-hydrothermal anhydrites are relatively enriched in REE reflecting the higher content in REE of the hydrothermal fluids.