Dal Events

EES Ph.D. RESEARCH SEMINAR: Rifkhan Nayeem, Ph.D. Candidate

Thu, 06 Nov 2025 15:30:00 GMT

Ph.D. RESEARCH SEMINAR
DEPARTMENT OF EARTH AND
ENVIRONMENTAL SCIENCES
DALHOUSIE UNIVERSITY

Rifkhan Nayeem
Ph.D. Candidate

Department of Earth and Environmental Sciences
91̽��ƽ̨

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 91̽��ƽ̨, focusing on extracting rare earth elements (REE) from the tailings of diamond mines.

M.Sc. Thesis Defence: Pinar Gurun

Mon, 17 Nov 2025 16:00:00 GMT

M.Sc. Thesis Defence

Pinar Gurun
Department of Earth and Environmental Sciences, 91̽��ƽ̨

Title: Variations in Subduction Bending-Related Normal Faulting of the Incoming Juan De Fuca Plate Along the Cascadia Margin

Abstract: At most subduction zones, old and cold oceanic lithosphere undergoes pronounced plate bending that produces extensive normal faulting with large fault throws, which facilitates significant hydration of the incoming plate. The Cascadia subduction zone (SZ) presents a contrasting case: bend faulting is more limited, and the combination of a warm thermal regime, thick sediment cover, and young plate age restricts serpentinization of the mantle. Seismic studies indicate that most water in the incoming Juan de Fuca (JdF) plate is confined to the sediments and upper crust, with the lower crust and mantle remaining comparatively dry. Yet, other geophysical observations, including magnetotelluric, seismic tomography, surface heat flow, and seismic anisotropy, point to abundant fluids within the Cascadia subduction system, suggesting that despite its youth and warmth, the JdF plate is considerably more hydrated than previously inferred. However, the incoming JdF plate system displays along-strike variations in faulting and plate hydration at the trench. Current understanding of how these variations affect subduction zone processes, like intraslab earthquakes and slow slip events, even at a regional scale are not well understood due to the lack of modern seismic imaging. During June-July 2021, the Cascadia Seismic Imaging Experiment (CASIE21) acquired ~5347-line km of new marine multichannel seismic (MCS) reflection data covering much of the Cascadia margin, from Northern Vancouver Island to Northern California. The data were acquired using RIV Marcus G. Langseth with a 12-15 km streamer and a 6600 in3 tuned airgun array. Data processing was done by ION Geophysical to prestack depth migrated (PSDM) reflection images. To aid the interpretation of the seismic images, reflection events were identified and interpreted across sediments, crust, and uppermost mantle to characterize the extensional and/or transtensional deformation prior to subduction. This thesis discusses the obtained results and provides unique insights into the extensional/transtensional faults deforming the incoming oceanic JdF plate system with implications for plate hydration. A total of 1,157 faults were mapped, with five to six times more faults in the sedimentary section than in the igneous basement. Faults within the sedimentary section show strong along-margin variability. They are most dense offshore Vancouver Island, with steep apparent dips (typically >55°) and balanced trenchward-to ridgeward dip orientations. Within the oceanic crust and uppermost mantle, subduction bend related faults are most abundant offshore northern Oregon and exhibit steep true dips. Longer individual faults occur in regions where faulting is generally less frequent. A systematic comparison between sedimentary and crustal faulting across the margin reveals that profiles offshore Washington and northern Oregon exhibit the highest crust-to-sediment fault ratios, consistent with reactivation of ridge-parallelabyssal fabric and dense crustal faulting. Low ratios offshore Vancouver Island and southern Oregon coincide with more complex Nootka deformation zone, propagator wakes, or newly developed faults. Spatial analysis of extensional faulting in both sediments and oceanic crust reveals four distinct regions of inferred hydration along the margin, with the most significant hydration offshore central Oregon to southern

Washington, as supported by fault clustering and in alignment with previous seismic studies. Ultimately, the results shown in this thesis may be applicable to other young convergent margins and offer a new, margin-scale perspective on how subduction bend-related extensional faulting governs hydration processes in the incoming oceanic plate, with implications for fluid budgets, seismicity, and subduction zone dynamics at Cascadia margin.

Examining Committee

Dr. Beatrice Magnani, Southern Methodist University, External Examiner
Dr. Mladen Nedimovic, 91̽��ƽ̨, Supervisor
Dr. Alexandre Plourde, Geological Survey of Canada, Reader
Dr. Miao Zhang, 91̽��ƽ̨, Reader
Dr. Owen Sherwood, 91̽��ƽ̨, Chair

EES Honours Information Session (Fall 2025)

Wed, 19 Nov 2025 22:00:00 GMT

An Information Session will be held for all students in 2nd or 3rd year who are considering an Honours degree in Earth and Environmental Sciences on Wednesday, November 19th, 6:00 pm in the Milligan Room, 8th Floor Biology-Earth Sciences Wing, Life Sciences Centre.

All students who wish to pursue an Honours degree in Earth Sciences or Environmental Science are now required to attend an Honours Information Session. The session is recommended for students who intend to register for Honours degrees in 2026. Second year students considering an Honours, or who just want to know more about the process of doing an Honours degree, are also encouraged to attend.

Questions? Email tarah.wright@dal.ca

GAC 2025-2026 Howard Street Robinson Lecture Tour

Thu, 20 Nov 2025 15:30:00 GMT

Dr. Anthony (Willy) Williams-Jones

Title: Metals, Vapours and Volcanoes

EES PhD Candidate Lecture: Michael Powell, EES

Wed, 26 Nov 2025 17:30:00 GMT

Title: Experimental determination of high field strength element partition coefficients

EES Departmental Seminar: Denise Brushett, Department of Environment and Climate Change

Thu, 27 Nov 2025 15:30:00 GMT

Title: Municipal Flooding in Nova Scotia

EES Departmental Seminar: Owen Sherwood

Thu, 04 Dec 2025 15:30:00 GMT

Faculty Highlight Lecture
Dr. Owen Sherwood
Earth and Environmental Sciences
91̽��ƽ̨

Title: stable isotopes in unstable environments