Abstract
The Pan-African Lufilian belt (Zambia and Democratic Republic of Congo) is known for its world-class copper and cobalt deposits. In addition, the Lufilian Copperbelt hosts several uranium occurrences concentrated within deformed siliciclastic rocks of the basal Neoproterozoic Katanga Supergroup. We report LA-ICPMS and EMP analyses of the rare earth element (REE) and yttrium (Y) abundances (designated as the REY signatures) of uranium oxides from two uranium mineralizing events of the Lufilian belt previously dated at 652±8Ma and 530±6Ma by the U–Pb method on uraninite. Uranium oxides dated at ca. 650Ma from the External fold-and-thrust belt are characterized by (i) bell shape REE patterns centered on middle REE (MREE), (ii) positive europium (Eu) anomalies and (iii) relatively low Y contents. In contrast, uranium oxides dated at ca. 530Ma from the Domes region are characterized by (i) REE patterns but with a less pronounced light REE (LREE) fractionation, (ii) negative Eu anomalies and (iii) higher Y contents. Moreover, the External fold-and-thrust belt also contains uranium mineralization dated at ca. 530Ma having the same characteristics as the ca. 530Ma uranium oxides from the Domes region (a moderately fractionated REE pattern and a negative Eu anomaly).As REY signatures are known to reflect mineralizing processes, the distinct geochemical signatures of the two uranium oxide generations (ca. 650Ma and ca. 530Ma) provide meaningful information about the uranium cycle during the Pan-African orogeny. Compared to the REY signatures of the known worldwide uranium deposit types, the REY signature of uranium oxides dated at ca. 650Ma of the External fold-and-thrust belt is similar to the REE patterns from unconformity-related U deposits (Athabasca in Canada and Kombolgie in Australia). Uranium oxides of the Domes region and some of the External fold-and-thrust belt display similar characteristics to syn-metamorphic U deposit (Mistamisk in Canada). Accordingly, we propose that the two stages of uranium oxide crystallizations within the Lufilian belt, at ca. 650 and ca. 530Ma, occurred under distinct physico-chemical conditions. The first stage, at ca. 650Ma, may be related to late diagenesis hydrothermal processes, at the basement/cover interface, with the circulation of highly saline basinal brines linked to evaporites of the Roan Group. This Pan-African unconformity-related uranium deposit is the youngest of this type described to date. The second stage may be connected to metamorphic fluid circulations, at about 530Ma, during the Lufilian orogeny in the Domes region and also in the External fold-and-thrust belt.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.