dc.contributor.author | Broom-Fendley, SL | |
dc.contributor.author | Wall, F | |
dc.contributor.author | Spiro, B | |
dc.contributor.author | Ullmann, CV | |
dc.date.accessioned | 2017-11-09T14:09:23Z | |
dc.date.issued | 2017-11-09 | |
dc.description.abstract | Carbonatites host some of the largest and highest grade rare earth element (REE) deposits but the composition and source of their REE-mineralising fluids remains enigmatic. Using C, O and 87Sr/86Sr isotope data together with major and trace element compositions for the REE-rich Kangankunde carbonatite (Malawi), we show that the commonly observed, dark brown, Fe-rich carbonatite that hosts REE minerals in many carbonatites is decoupled from the REE mineral assemblage. REE-rich ferroan dolomite carbonatites, containing 8–15 wt% REE2O3, comprise assemblages of monazite-(Ce), strontianite and baryte forming hexagonal pseudomorphs after probable burbankite. The 87Sr/86Sr values (0.70302–0.70307) affirm a carbonatitic origin for these pseudomorph-forming fluids. Carbon and oxygen isotope ratios of strontianite, representing the REE mineral assemblage, indicate equilibrium between these assemblages and a carbonatite-derived, deuteric fluid between 250 and 400 °C (δ18O + 3 to + 5‰VSMOW and δ13C − 3.5 to − 3.2‰VPDB). In contrast, dolomite in the same samples has similar δ13C values but much higher δ18O, corresponding to increasing degrees of exchange with low-temperature fluids (< 125 °C), causing exsolution of Fe oxides resulting in the dark colour of these rocks. REE-rich quartz rocks, which occur outside of the intrusion, have similar δ18O and 87Sr/86Sr to those of the main complex, indicating both are carbonatite-derived and, locally, REE mineralisation can extend up to 1.5 km away from the intrusion. Early, REE-poor apatite-bearing dolomite carbonatite (beforsite: δ18O + 7.7 to + 10.3‰ and δ13C −5.2 to −6.0‰; 87Sr/86Sr 0.70296–0.70298) is not directly linked with the REE mineralisation. | en_GB |
dc.description.sponsorship | This project was funded by the UK Natural Environment Research Council (NERC) SoS RARE project (NE/M011429/1) and by NIGL (NERC Isotope Geoscience Laboratory) Project number 20135. | en_GB |
dc.identifier.citation | Vol. 172, article 96 | en_GB |
dc.identifier.doi | 10.1007/s00410-017-1412-7 | |
dc.identifier.uri | http://hdl.handle.net/10871/30233 | |
dc.language.iso | en | en_GB |
dc.publisher | Springer Verlag | en_GB |
dc.rights | © The Author(s) 2017. Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. | en_GB |
dc.subject | Carbonatites | en_GB |
dc.subject | Rare earth elements | en_GB |
dc.subject | C and O isotopes | en_GB |
dc.subject | Sr isotopes | en_GB |
dc.subject | Chilwa Alkaline Province | en_GB |
dc.subject | Critical metals | en_GB |
dc.title | Deducing the source and composition of rare earth mineralising fluids in carbonatites: insights from isotopic (C, O, 87Sr/86Sr) data from Kangankunde, Malawi | en_GB |
dc.type | Article | en_GB |
dc.date.available | 2017-11-09T14:09:23Z | |
dc.identifier.issn | 0010-7999 | |
dc.description | This is the final version of the article. Available from Springer Verlag via the DOI in this record. | en_GB |
dc.identifier.journal | Contributions to Mineralogy and Petrology | en_GB |