A novel nuclear forensic tool involving deposit type normalized rare earth element signatures

Abstract

Identifying the provenance of uranium‐rich materials is a critical objective of nuclear forensic analysis. Rare earth element (REE) distributions within uranium ores are well‐established forensic indicators, but quantifying and correlating trace element signatures for U ores to known deposits has thus far involved intricate statistical analyses. This study reports average chondrite normalized (CN)‐REE signatures for important U deposit types worldwide, which are then employed to evaluate U ore paragenesis using a simple linear regression analysis. This technique provides a straightforward method that can aid in determining the deposit type of U ores based on their REE abundances, and combined with other forensic indicators (e.g. radiogenic isotope signatures) can provide essential provenance information for nuclear materials.

Multivariate Analysis Based on Geochemical, Isotopic, and Mineralogical Compositions of Uranium-Rich Samples

“…The Australian sample is from Northern Territories, Australia. A mine location is not known for this sample, however, its CN-REE signature indicates that it is an unconformity-related deposit ( Figure S1; [11,12].…”

“…Since 1993, the International Atomic Energy Agency (IAEA) has reported 3497 incidents of nuclear and/or radioactive materials outside of regulatory control with 285 confirmed as "acts of trafficking or malicious use" [1]. The predominant source of nuclear fuel worldwide is uranium ore deposits, and therefore, these have been the subject of a growing number of mineralogical, chemical, and isotopic investigations [2][3][4][5][6][7][8][9][10][11][12]. These previous studies have determined and established various geochemical signatures as fingerprints for uranium ore deposits, which can then be used as a means of deciphering the origins of any unknown intercepted nuclear materials.…”

“…Uranium ore deposits are found globally with >800 locations identified [13]. These ore deposits are found in a wide variety of geological settings and span Earth's history from the Archean/early Proterozoic to recent times [5,12,13]. For the purpose of this study, we have adopted the IAEA [13] classification, which is based on the geological setting of the uranium deposit and takes into account either the host rock (e.g., intrusive type) or geological structure (e.g., Paleozoic unconformity).…”

“…For example, an elevated temperature of formation (>350 • C) allows for cations other than U 4+ to substitute more readily into the crystal structure of uraninite, U 4+ 1−x−y−z−u U 6+ x REE 3+ y M 2+ z 4− u )O 2+x−0.5y−z−2u the primary mineral of uranium ore (REE= rare earth elements, M 2+ represents divalent metals and indicates a vacant site; [14][15][16]). Thus, uraninite formed at higher temperatures typically contains higher abundances of Th 4+ , REEs 3+ , and Y 3+ [2,7,11,12,17]. To date, chondrite-normalized REE (CN-REE) patterns have proven to be the most effective forensic tool in terms of distinguishing between uraninite samples formed under different geologic conditions (e.g., [7,11,12]).…”

“…Thus, uraninite formed at higher temperatures typically contains higher abundances of Th 4+ , REEs 3+ , and Y 3+ [2,7,11,12,17]. To date, chondrite-normalized REE (CN-REE) patterns have proven to be the most effective forensic tool in terms of distinguishing between uraninite samples formed under different geologic conditions (e.g., [7,11,12]). Moreover, the concentration of Pb is linked to the age of the uraninite deposit as a result of the decay of 235 U and 238 U over geological time to 207 Pb and 206 Pb, respectively [15].…”