New insights into mineralogy and geochemistry of allanite-bearing Mediterranean coastal sands from Northern Greece |
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| Institution: | 1. Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece;2. Department of Mineralogy, Petrology and Economic Geology, School of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece;3. Department of Geology and Geoenvironment, University of Athens. Panepistimioupolis, 15784 Zografou, Greece;4. Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany;5. Department of Geology, Rhodes University, Grahamstown, South Africa;6. Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, 3001 Leuven, Belgium;7. Departamento de Petrologia e Metalogenia, Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista - Julio de Mesquita Filho, 13506-900, Rio Claro, Brazil;8. Institute of Nuclear Physics, NCSR “Demokritos’’, Aghia Paraskevi 15310, Greece;9. Department of Earth Sciences, University of Perugia, Piazza Università, 06100 Perugia, Italy;1. Faculty of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran, Iran;2. School of Mining, Petroleum and Geophysics Engineering, Shahrood University of Technology, Shahrood, Iran;3. Department of Geological Engineering, Faculty of Engineering, Dokuz Eylul Universitesi, Bornova 35100, Izmir, Turkey;1. Área de Ciencias de la Tierra, Facultad de Ingeniería, Universidad Autónoma de San Luís de Potosí, Av. Dr. Manuel Nava No. 8, Zona Universitaria, San Luis Potosí, C.P., 78290, Mexico;2. Department of Energy Resources, University of Stavanger, 4036 Stavanger, Norway;3. Instituto de Geología, Universidad Autónoma de San Luis Potosí, Manuel Nava #5Zona Universitaria, San Luis Potosí, S.L.P., Mexico;4. Unidad Académica de Ciencias de la Tierra, Universidad Autónoma de Guerrero, Ex–Hacienda de San Juan Bautista, S/N, Taxco el Viejo, Guerrero, Mexico;5. Grupo de Geología Exógena y del Sedimentario, Valle de la Hiedra 113B, Fracc. Valle de Santiago, Soledad de Graciano Sánchez, San Luis Potosí, C.P. 78433, Mexico |
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| Abstract: | Allanite-bearing black coastal sands of Kavala (N. Greece) were studied using a combination of single-crystal XRD, EMPA, μ-XRF, bulk ICP-MS, LA-ICP-MS, μ-XANES and γ-ray spectrometry. The sands are rich in REE (ΣREE + Y: 4010 to 10,810 mg/kg), Th (236–1205 mg/kg) and other critical metals such as Nb, Ta and Co. The main REE- and Th-hosts are allanite and titanite. The allanite unit cell parameters were calculated whereas its formula was found to be (REE0.470Ca1.499Th0.031) (Ti0.031Fe+31.089Al1.880) (Si2.906Al0.094O12) (OH). The μ-XANES spectra showed that LREE are present in trivalent oxidation state. Analyses of the non-magnetic sand fractions showed higher LREE (12,470 mg/kg) due to accumulation of allanite. The materials showed elevated radioactivity ranging from 885 ± 13 to 3467 ± 20 Bq/kg. The obtained results provide new insights on the provenance of the sands, the abundance of REE, Th, and other immobile elements, and offer new clues for potential exploration and exploitation. |
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| Keywords: | Kavala Beach placer REE Thorium Allanite μ-XRF SR-XANES |
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