EES Ph.D. RESEARCH SEMINAR: Rifkhan Nayeem, Ph.D. Candidate
Ph.D. RESEARCH SEMINAR
DEPARTMENT OF EARTH AND
ENVIRONMENTAL SCIENCES
DALHOUSIE UNIVERSITY
Rifkhan Nayeem
Ph.D. Candidate
Department of Earth and Environmental Sciences
Dalhousie University
Title: A Study of the Potential of Rare Earth Elements (REE) Extraction from Diamond Mine (Processed Kimberlite) Tailings
Abstract: Rare earth elements are crucial for the global transition to a green and modern economy. Their economic occurrence is rare, and their production is concentrated geographically. Consequently, they are classified as critical minerals in many jurisdictions, including Canada and require alternative sources to prevent potential disruption in the supply chain. Kimberlites, the main source of diamonds, can contain REE at levels comparable to some primary REE deposits, such as the REE clay deposits of South China. In this study, we investigated whether processed kimberlites (tailings) at diamond mine sites could be potential secondary sources of REE.
The first project examines the mineralogical and geochemical properties of kimberlite cores and tailings from two contrasting diamond mines: Snap Lake (Canada) and Voorspoed (South Africa). At Snap Lake, monazite (up to 62 wt% REE2O3), apatite (~1.5 wt% REE2O3), and anatase (~ 3000 ppm REE2O3) were identified as the principal REE host minerals in both kimberlite and tailings, whereas ancylite-(Ce) and allanite-(La) occurred exclusively in tailings, suggesting secondary formation. Monazite and anatase occur as intergrowths with cubic morphologies, interpreted as pseudomorphs after perovskite. This suggests replacement of perovskite by anatase during hydrothermal alteration by a CO₂-rich deuteric fluid, accompanied by monazite precipitation. In contrast, in the Voorspoed kimberlite and tailings, titanite, apatite, perovskite, and anatase are the principal phases hosting REE, with monazite being a subordinate phase. Bulk geochemical analyses reveal higher overall REE concentrations in Snap Lake tailings (mean = 690 ppm; n = 30) compared to Voorspoed (mean = 204 ppm; n = 10). In both deposits, tailings are consistently enriched in heavy rare earth elements (HREE) relative to their primary kimberlite equivalents. Additionally, tailings show higher concentrations of other critical elements, including Cu, Zn, Sc, and V, particularly at Snap Lake.
The second project involves an experimental investigation of perovskite dissolution. Although thermodynamic calculations suggest perovskite is unstable in hydrothermal environments, its breakdown kinetics are slow and remain unstudied under kimberlite conditions. The effects of temperature, pressure, CO₂ content, Ca2+ activity, REE content, and pH are poorly constrained due to limited experimental data and are primarily derived from studies on SYNROC, a material developed for radioactive waste immobilization. This study aims to address these knowledge gaps and improve understanding of perovskite behavior in kimberlitic systems.
The third project is focused on experimental investigation of REE release from primary host minerals during the enhanced carbonation used for CO₂ sequestration in kimberlite tailings. This experiment will test whether acid leaching of processed kimberlite used to enhance CO₂ sequestration also promotes REE release from perovskite, monazite and apatite. Experiments will be conducted with diluted HCl and H₂SO₄ solutions at ambient conditions.
Biography: Rifkhan received his B.Sc. (Hons) in Mineral Resources and Technology from Uva Wellassa University, Sri Lanka, in 2018 with a specialization in Mineral Processing Technology. His undergraduate thesis focused on engineering geology, where he proposed a cost-effective technique for road cut slope studies. In 2022, he obtained his Master of Philosophy (M.Phil.) in Earth Sciences from the University of Peradeniya, Sri Lanka, where his thesis focused on enhancing the value of low-quality gem minerals (Sapphire, ruby, and zircon) using various colour and clarity enhancement techniques (Heat treatment, nano diffusion, flux healing and enamel coating).
During his final year of his undergraduate degree, he completed his internship at the National Building Research Organization (NBRO), Sri Lanka, where he worked on landslide monitoring and geotechnical applications. Soon after completing his bachelor's degree, Rifkhan joined the Research Division of the Gem and Jewelry Research and Training Institute (GJRTI), Ministry of Industry and Entrepreneurship Development, Sri Lanka, as a full-time researcher, a position he held for four years. During this time, he also served as a part-time instructor in gemology for the Diploma in Gemology program at the institute’s Training Division. Following this, he worked as a colored stone gemologist at the Gemmological Laboratory of Colombo before beginning his doctoral studies.
In January 2023, Rifkhan began his Ph.D. in Earth and Environmental Sciences at Dalhousie University, focusing on extracting rare earth elements (REE) from the tailings of diamond mines.
Time
Location
Milligan Room, 8th Floor, Biology-Earth Sciences Wing Life Science Centre, Dalhousie University