DOI: 10.7939/82394
title: Supplementary tables related to the thesis: "Geochronology, mineral chemistry and geochemistry of the 1.1 Ga Kapuskasing ultramafic lamprophyres, Superior Craton, Canada", Fiona Clark, 2025

description: This file comprises supplementary tables for the thesis titled Geochronology, mineral chemistry and geochemistry of the 1.1 Ga Kapuskasing ultramafic lamprophyres, Superior Craton, Canada by Fiona Clark Ultramafic lamprophyres are rare, volatile-rich, mantle-derived magmas, providing crucial insights into deep mantle processes, lithospheric dynamics, and diamond exploration. Their occurrence along the Kapuskasing structural zone within the Superior craton offers a unique window into mantle dynamics and magmatic processes preceding the ~1.1 Ga Midcontinent Rift. This thesis employs integrated petrographic, geochemical, isotopic, and geochronological analyses to better classify these rocks, constrain their petrogenesis, and clarify their temporal and genetic relationship with regional tectonic events. The second chapter established robust classification criteria for the Kapuskasing ultramafic lamprophyres through detailed petrography and mineral chemistry using electron probe microanalysis. This study identified distinctive compositional trends in mica, spinel, olivine, ilmenite and clinopyroxene, enabling better discrimination of ultramafic lamprophyres, kimberlites, carbonate-rich olivine lamproites and olivine lamproites. The results highlight the challenges inherent in classifying ultramafic lamprophyres due to overlapping mineralogical characteristics with related rocks, advocating for an integrated petrographic, mineral chemical, and whole-rock geochemical approach for precise identification. Chapter three examines the petrogenetic history of the Kapuskasing ultramafic lamprophyres using comprehensive whole-rock geochemical analyses alongside Sr-Nd-Hf isotopic systems. The data indicate minimal lithospheric and crustal contamination during magma ascent, preserving key primary melt and source signatures. Geochemical modelling reveals that these magmas formed via low-degree partial melting (0.1-2%) of a mildly depleted, asthenospheric mantle source, closely resembling the PREvalent MAntle (PREMA) reservoir. The fourth chapter provides critical temporal constraints for the Kapuskasing ultramafic lamprophyre emplacement using precise in-situ U-Pb perovskite geochronology. New age data extend the known duration of alkaline magmatic activity in the Midcontinent Rift region to approximately 40 million years (~1160-1117 Ma). These findings challenge conventional plume-driven models for Midcontinent Rift initiation, instead suggesting a scenario driven by small-scale mantle convection processes initiated during earlier tectonic events such as the Shawinigan orogeny. This thesis significantly advances our understanding of ultramafic lamprophyre magmatism by refining classification schemes, elucidating complex petrogenetic processes and redefining the temporal framework of pre-rift magmatism associated with the Midcontinent Rift. By highlighting the nuanced interplay of regional tectonics and mantle dynamics, this work underscores the broader implications for interpreting mantle evolution, lithospheric stability, and diamond exploration potential.