Uranium and Thorium Resources of Estonia

Abstract

We provide a compilation of geology of uranium and thorium potential resources in the Ordovician black shale (graptolite argillite), Cambrian–Ordovician shelly phosphorite and in the secondary resources (tailings) of Estonia. Historical and new geological, XRF and ICP-MS geochemical data and ArcGIS modeling results of elemental distribution and tonnages are presented. The Estonian black shale contains 5.666 million tons of U, 16.533 Mt Zn, 12.762 Mt Mo, 47.754 Mt V and 0.213–0.254 Mt of Th. The Estonian phosphate resources, altogether about 3 billion metric tons of phosphate ore, contain about 147,000 to 175,000 tons of U. Rare earth element concentrations in the phosphorite ore average at 1200–1500 ppm of ΣREE. Thorium can also be a possible co-product. The mining waste dump at the Maardu contains at least 3650 tons of U and 730 tons of Th. The Sillamäe radioactive waste depository contains about 1200 tons of U and 800 tons of Th. Due to the neighboring geological positions, as well as environmental constraints and mining technologies, the black shale and phosphorite can be treated as a complex multi-resource, possibly at the continental scale, which needs to be extracted together.

Interpretation of the anomalous groundwater chemistry and 234U/238U activity ratio disequilibrium in the northern part of the baltic region

“…In the Upper Cambrian part of the O-Cm aquifer system, phosphorite is known as Obolus-sandstone (shelly phosphorite) of the Kallavere, Tsitre, Ülgase and Petseri Formations. The northernmost phosphorite deposits area is most enriched in U (~25-50 ppm) [36]. In the Lower Ordovician part of the O-Cm aquifer system, organic-rich marine metalliferous black shale, argillite rocks lie beneath most northern Estonia and western archipelagos.…”

“…These rocks are characterized by high concentrations of U (average 120 ppm). Thorium concentrations are analyzed in less than 100 drill cores, where the average varies between 13-17 ppm [35,36].…”

Main Precambrian and Paleozoic Mineral Resources of Estonia

“…Considering that future possible mining operations will have an annual production of 5Mt tons of ore, the estimated annual total REE amounts will be 720 tons at REE tot =1200ppm, or 900 tons at REE tot =1500 ppm. In addition, about 120 tons of uranium and 27 tons of thorium can be extracted each year [11].…”

“…GIS-based metal content calculations, which are based on data from more than 400 drill cores provide approximate total amounts for certain elements (Figure 1). For instance, the calculated tonnage of uranium is about 5.6656 Million tons (6.6796Mt as U 3 O 8 ), zinc tonnage is 16.5330Mt (20.5802Mt as ZnO), vanadium tonnage is 47.7538Mt, molybdenum about 12.7616Mt (19.1462Mt as MoO 3 ) and thorium tonnage in between 0.213-0.254Mt [11,12]. Western Estonia has the highest potential for these elements, especially for U and Mo production.…”

Assessment of 226Ra and U colloidal transport in a mining environment

“…Because of its decay to 222 Rn, a radioactive gas with a short half-life (3.8 d) which can cause health issues when inhaled depending on the concentration and the duration (WHO, 2009), 226 Ra is subject to dedicated monitoring in environments of high uranium concentration such as those of U mining (Landa, 2004;Liu et al, 2006), black shale mining (Phan et al, 2015;Soesoo et al, 2020) and the production areas of phosphate fertilizers (Michie, 1979;IAEA, 2013). Monitoring the mobility of U and 226 Ra is important in these environments, especially within the tailings storage facilities from U mining, which represent a worldwide volume of around 1 billion m 3 (the last available worldwide inventory calculated in 2004 gives a total volume of 908 million m 3 ) (IAEA, 2004).…”