Uraniferous bitumen nodules in the Talvivaara Ni-Zn-Cu-Co deposit (Finland): influence of metamorphism on uranium mineralization in black shales

• Published in: Mineralium Deposita
• Main Authors: Lecomte, Andrei, Cathelineau, Michel, Deloule, Etienne, Brouand, Marc, Peiffert, Chantal, Loukola-Ruskeeniemi, Kirsti, Pohjolainen, Esa, Lahtinen, Hannu
• Other Authors: GeoRessources, Institut national des sciences de l'Univers (INSU - CNRS)-Centre de recherches sur la géologie des matières premières minérales et énergétiques (CREGU)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherches Pétrographiques et Géochimiques (CRPG), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Département Géosciences (AREVA-BU Mines), Groupe AREVA, Geol Survey Finland, FI-02151 Espoo, Finland, ANR-10-LABX-0021,RESSOURCES21,Strategic metal resources of the 21st century(2010)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Fennoscandian
• Online Access: https://hal.science/hal-01301693; https://doi.org/10.1007/s00126-013-0502-3

International audience In the central part of the Fennoscandian Shield, the Talvivaara Ni-Zn-Cu-Co deposit, hosted by Palaeoproterozoic metamorphosed black schists, contains low uranium concentrations ranging from 10 to 30 ppm. The Talvivaara black schists were deposited 2.0-1.9 Ga ago and underwent subsequent metamorphism during the 1.9-1.79 Ga Svecofennian orogeny. Anhedral uraninite crystals rimmed by bitumen constitute the main host of uranium. U-Pb secondary ion mass spectrometry dating indicates that uraninite crystals were formed between 1,878 +/- 17 and 1,871 +/- 43 Ma, during peak metamorphism. Rare earth element patterns and high Th content (average 6.38 wt%) in disseminated uraninite crystals indicate that U was concentrated during high temperature metamorphism (> 400 A degrees C). The formation of bitumen rims around uraninite may be explained by two distinct scenarios: (a) a transport of U coincident with the migration of hydrocarbons or (b) post-metamorphic formation of bitumen rims, through radiolytic polymerization of gaseous hydrocarbons at the contact with uraninite.