Characterization of Impact Melt Rocks and Hydrothermal Mineralization at the Haughton Impact Structure, Devon Island, Canada: An Investigation of Impacts into Carbonate Targets
Impact cratering is a fundamental and ubiquitous geological process on all solid planetary bodies in our solar system. Impacts into carbonate-rich sedimentary target rocks on Earth are still poorly understood. The fate of carbonates during impact, in particular whether they undergo melting or decomp...
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| Format: | Text |
| Language: | English |
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Scholarship@Western
2020
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| Online Access: | https://ir.lib.uwo.ca/etd/6987 https://ir.lib.uwo.ca/context/etd/article/9370/viewcontent/PhD_Thesis_Cassandra_Marion_final.pdf https://ir.lib.uwo.ca/context/etd/article/9370/filename/0/type/additional/viewcontent/CMarion_PhDthesis_Microprobe_AppendixC.xlsx |
| Summary: | Impact cratering is a fundamental and ubiquitous geological process on all solid planetary bodies in our solar system. Impacts into carbonate-rich sedimentary target rocks on Earth are still poorly understood. The fate of carbonates during impact, in particular whether they undergo melting or decomposition, is actively debated. The dominant process is significant as decomposition would cause severe climatic effects due to release of large amounts of carbon dioxide into the atmosphere. At the root of the problem is the difficulty to distinguish and characterize the genesis of the variety of impactite carbonates produced. The Haughton impact structure in the Canadian High Arctic was formed in the Paleozoic Arctic Platform which overlies Precambrian metamorphic rocks. In order to better understand impactite formation and hydrothermal mineralization in impacts into calcareous targets, this study conducts a thorough investigation and characterization of the impactites and mineralization at the centre and around the central uplift periphery at Haughton. A variety of petrographic, geochemical and mineralogical techniques are applied to characterize the rocks, including microbeam analysis and cathodoluminescence. Recent shallow drill cores at the centre of structure reveal melt rocks unlike those previously identified at Haughton. The first, is a crystalline carbonate-sulfate-silicate melt rock classified based on a series of igneous textures. The second, is a silicate impact melt rock. Both cores are pervasively hydrothermally altered. Finally, we re-evaluate the hydrothermal mineralization at the centre and periphery within the cores and faulted target rocks. Overall this work confirms the presence of crystalline carbonate melt rocks at Haughton; presents detailed methodologies on how to distinguish between a wide range of carbonate and sulfate impactite products, hydrothermal replacement and diagenetic carbonate; presents an updated hydrothermal model and paragenesis for mineralization at the centre of the structure; ... |
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