Western University Scholarship@Western Electronic Thesis and Dissertation Repository 4-15-2020 9:30 AM Impact-Generated Dykes and Shocked Carbonates from the Tunnunik and Haughton Impact Structures, Canadian High Arctic Jennifer D. Newman The University of Western Ontario Graduate Program in Geology A thesis submitted in partial fulfillment of the equirr ements for the degree in Doctor of Philosophy © Jennifer D. Newman 2020 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the Geology Commons Recommended Citation Newman, Jennifer D., "Impact-Generated Dykes and Shocked Carbonates from the Tunnunik and Haughton Impact Structures, Canadian High Arctic" (2020). Electronic Thesis and Dissertation Repository. 6950. https://ir.lib.uwo.ca/etd/6950 This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. Supervisor Osinski, Gordon R. The University of Western Ontario This dissertation/thesis is available at Scholarship@Western: https://ir.lib.uwo.ca/etd/6950 Abstract The Canadian High Arctic contains two impact structures created by hypervelocity impact events in carbonate-rich target rocks. The remote locations of the Tunnunik and Haughton impact structures means that there are aspects of these impact structures which have yet to be fully investigated. This study characterizes the range of impact-generated dykes exposed from both impact structures which include lithic breccias, impact melt-bearing breccias, and impact melt rocks. Breccias may include silicate impact glass fragments and evidence for carbonate melt. Impact melt rocks from the Haughton impact structure contain the rare terrestrial mineral moissanite. This is only the third reported occurrence of moissanite associated with an impact structure and the first to observe its presence in situ. Inclusions and variation of polytypes in moissanite provide information regarding high temperatures present during crater formation. The carbonate-rich rocks that form these impact structures contain well-developed shatter cones as evidence of shock metamorphism. As a shock classification system does not currently exist for carbonates, the effect of shock on the crystal structure of calcite and dolomite is examined using X-ray diffraction to better understand the extent of strain in both these minerals. Previous studies of shocked carbonates from terrestrial impact structures is limited and the goal here is to assign numerical values to indicate strain and thereby better quantify and compare shock in carbonates among impact structures. The parallel studies of impact-generated dykes and shock at the Tunnunik and Haughton impact structures allow for the comparison of two impact structures with similar diameters, 28-km for Tunnunik and 23-km for Haughton, in different states of preservation. The deeply eroded Tunnunik impact structure and well-preserved Haughton impact structure provide insights into complex crater formation in carbonate rich rocks that would otherwise not be available by only studying one site. Results from this pair of impact sites has expanded the knowledge of carbonate-rich impact structures and will help future investigations of other known carbonate-rich impact sites and ones yet to be discovered. ii Keywords Tunnunik impact structure, Haughton impact structure, impact cratering, impact breccia, impact melt rock, dyke, carbonate, shocked carbonate, dolomite, calcite, lattice strain, Arctic, X-ray diffraction, moissanite. iii Summary for Lay Audience Impact craters form when a large projectile, typically a fragment from an asteroid or comet, survives its transit through Earth’s atmosphere and strikes a solid rocky surface. The resulting crater may be tens of metres to several hundred kilometres in diameter, depending on the size and speed of the projectile. Examining the rocks affected and generated by impact events allow the impact process to be better understood. This study focuses on two remote impact sites in the Canadian High Arctic, the Tunnunik impact structure and Haughton impact structure, that formed in carbonate rocks consisting mainly of limestone and dolostone. Rocks affected by the shock created during the impact often display shatter cones near the centre of the impact structures which appear as small fractures or striation to the unaided eye. A technique called X-ray diffraction uses X-rays to investigate the crystal structure of calcite and dolomite, the primary minerals in the carbonate rocks that form the impact structures. Shock effects increase strain within the crystal structure of these minerals and the strain values derived from the X-ray diffraction analyses are compared among samples collected from different locations in each impact structure. The rocks generated by the impact event examined in this study include impact breccias and impact melt rocks found in impact-generated dykes. Breccias consist of fragments from one or more different types of carbonate rock and are held together by finer fragments that are too small to see without higher magnification. Breccias may also include small silicate glass fragments or melted carbonate clasts. Impact melt rocks consist of fine-grained recrystallized calcite, clasts from the limestone rocks adjacent to the dykes, and crystals of a rare mineral called moissanite. Moissanite is rare due to very specific conditions required for it to form and these conditions help identify temperatures reached in the impact melt rocks when they were generated. Comparing the results from the Tunnunik and Haughton impact structures has provided insights into their formation and expanded the knowledge of carbonate-rich impact structures. iv Co-Authorship Statement Chapter 1. Literature review of information relevant to this work was completed and written by Jennifer Newman. Comments and editing were provided by Dr. Gordon Osinski. Chapter 2. Sample analysis, data collection, and data processing were completed by Jennifer Newman. EPMA data collection was assisted by Marc Beauchamp. Chapter was written by Jennifer Newman. Comments and editing were provided by Dr. Gordon Osinski. Chapter 3. Sample analysis, data collection, and data processing were completed by Jennifer Newman. EPMA data collection was assisted by Marc Beauchamp. Chapter was written by Jennifer Newman. Comments and editing of were provided by Dr. Gordon Osinski. Chapter 4. Sample preparation, analysis, and data processing for all suite 1 samples were completed by Jennifer Newman. Powder X-ray diffraction data collection was assisted by Alexandra Rupert. Rietveld analyses for suite 2 samples began as a class project in Earth Sci 9516b: Advanced Mineralogy and Crystallography (2017). Dr. Roberta Flemming provided helpful and constructive discussions regarding sample processing and interpretation. I reprocessed all suite 2 samples, so that all samples were refined in a manner consistent with suite 1 samples. Ultimately all results presented in this chapter were processed and interpreted by Jennifer Newman. Chapter was written by Jennifer Newman. Comments and editing were provided by Dr. Gordon Osinski. Chapter 5. Sample preparation, analysis, and data processing were completed by Jennifer Newman. Powder X-ray diffraction data collection was assisted by Alexandra Rupert. Chapter was written by Jennifer Newman. Comments and editing were provided by Dr. Gordon Osinski. Chapter 6. Sample analysis and data processing were completed by Jennifer Newman. Data collection using the Raman spectrometer was assisted by Tianqi Xie. Chapter was written by Jennifer Newman. Comments and editing were provided by Dr. Gordon Osinski. Chapter 7. Summary of thesis was written by Jennifer Newman. Comments and edits were provided by Dr. Gordon Osinski. v Acknowledgements As I cast my leaving shadow on this five year mission, it could not have been achieved without the support and contribution of so many people. First, I would like to thank my supervisor Dr. Gordon ‘Oz’ Osinski for his guidance and the opportunity to work on an incredible project that included two amazing field seasons in the Arctic. I am grateful for field and research funding support from NSERC, the Canadian Space Agency, the Northern Scientific Training Program, and the OGS/QEII program from the Ontario government. The Polar Continental Shelf Program is thanked for logistical field support. When I started this journey, I did not have a sense of scope regarding the numerous aspects this project would cover, let alone the unexpected mineral discovery from Haughton found as I was nearing completion! The opportunity to participate in two CanMars Mars sample return analogue missions through my NSERC CREATE/CSA fellowship and the CanMoon 2019 Lunar sample return analogue mission while at Western were great experiences and I hope to put these experiences into practice. I am also grateful to Dr. Livio Tornabene for the opportunity to participate in planning MRO/HiRISE cycle 301 with Sarah Simpson and Alyssa Werynski, this was a valuable and amazing experience. My thesis committee is thanked for their suggestions, collaborations, and guidance during this endeavour. Racel Sopoco, Cassandra Marion, Taylor Haid, William Zylberman, Byung-Hun Choe, Gordon Osinski, Livio Tornabene, Jeremy Hansen, Rob Misener and the rest of the Tunnunik field team, thank you for your help