Date of Award
5-16-2024
Publication Type
Thesis
Degree Name
M.Sc.
Department
Earth and Environmental Sciences
Supervisor
Ali Polat
Supervisor
Joel Gagnon
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Abstract
For the first time, this study presents field relationships, petrographic observations, mineral chemistry, whole rock major and trace element and Sr-Nd and Pb radiogenic isotope geochemistry data for kimberlite, carbonate-rich kimberlite and carbonatite dykes and sills with an estimated age of 1.1 Ga from Ripple Bay, Superior Region, Ontario. An extensive data set was utilized to constrain their petrogenesis and tectonic setting, which has very important implications for the long-standing debate on the co-genetic relationship of kimberlites and carbonatites. Ripple Bay kimberlites, carbonatites, and carbonate-rich kimberlites occur in the same dykes and sills that intrude the Archean Schreiber-Hemlo greenstone Belt. These rocks are divided into three distinct groups based on their carbonate content: 1) kimberlite (carbonate < 20%), 2) carbonate-rich kimberlite (carbonate >20%) and 3) carbonatites (carbonate >80%). Each group also displays a distinctive geochemical affinity. Trace element diagrams of Ripple Bay rocks show distinct negative anomalies of Rb, K, Sr, and Zr-Hf in kimberlites and carbonate-rich kimberlites, whereas carbonatites display negative anomalies in Rb, K, Nb-Ta, Pb, Hf-Zr, and Ti. The REE patterns of Ripple Bay rocks exhibit subparallel trends, with carbonatites displaying the most enriched REE patterns and carbonate-rich kimberlites showing the least enrichment. Ripple Bay rocks have very similar Sr and Nd isotope ratios and major and trace element composition, suggesting a common magma source and petrogenesis. Their geochemical compositions suggest a source that comprises mixtures of MORB-like depleted mantle and an enriched plume source. Ripple Bay rocks do not represent primary magmas because they evolved through fractional crystallization and exhibit crustal contamination. Their geochemistry suggest that the carbonate-rich kimberlites and carbonatites are related by fractional crystallization, whereas their relationship to the kimberlites involves different degrees of partial melting. Their location, geochemical characteristics, field relationships with neighboring rocks, and mineralogy supports their interpretation as 1.1 Ga formations associated with the Mid-continent rift system.
Recommended Citation
YILMAZ, Irmak, "Petrogenesis of 1.1 Ga carbonatite-kimberlite dykes and sills in the Schreiber greenstone belt, Ontario, Canada" (2024). Electronic Theses and Dissertations. 9473.
https://scholar.uwindsor.ca/etd/9473