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Investigating Secular Trends in Metamorphism through the Construction and Application of a Relational Database (MetRec)

dc.contributor.advisorEglington, Bruce
dc.contributor.advisorPehrsson, Sally
dc.contributor.committeeMemberAnsdell, Kevin
dc.contributor.committeeMemberJohnston, Stephen
dc.creatorHone, Peter Roy
dc.creator.orcid0009-0003-3325-6002
dc.date.accessioned2023-10-04T23:22:18Z
dc.date.available2023-10-04T23:22:18Z
dc.date.copyright2023
dc.date.created2023-09
dc.date.issued2023-10-04
dc.date.submittedSeptember 2023
dc.date.updated2023-10-04T23:22:18Z
dc.description.abstractRecent studies of metamorphic trends have used dT/dP to compare records. dT/dP is calculated as the temperature estimate divided by the pressure estimate. This approximates a geothermal gradient for the sample (written as °C/GPa). Records are typically categorized by dT/dP into low, medium, and high samples. Previous studies, using a dataset of dT/dP, have looked at cycles of metamorphic trends, including a stark shift away from medium and high-pressure samples towards low pressure samples around 750 Ma. This study created a multi-table relational database, which combines previously published datasets with data from a literature review, with ~1000 records. This study has updated statistical methods, improved methods for categorizing records using facies classifications, and analyzed spatial association using mapping software and plate reconstruction models. The range of modern (<750 Ma) subduction related samples is also compared to modelled ranges of metamorphic records to establish the range of subduction-related material. It has been shown that subduction-related rocks younger than 750 Ma can span a broad range of dT/dP from less than ~175 °C/GPa to ~875 °C/GPa. This is far broader than previous authors have established (<440 °C/GPa) and records which overlap <750 Ma subduction-related records are far more numerous than previously noted. A comparison of the most common orogens sampled shows that the data is heavily skewed – 372 records from the database come from the Alpine-Himalayan complex, which accounts for 66% of blueschist samples in the database. This pulls the trends of modern data to match those of the Alps and Himalayas and has not previously been discussed in the literature. It is posited by this study that blueschists are much rarer than previously acknowledged and the prevalence of modern blueschist is due to the Alpine-Himalayan bias. There is little evidence for a bimodal distribution of dT/dP which has previously been used as a marker for modern metamorphism. The findings of this study show that metamorphic terranes, while being closely tied to supercontinent cyclicity, have remained relatively stable since the Archean and that all categories of dT/dP can be seen throughout time and back into the Archean.
dc.format.mimetypeapplication/pdf
dc.identifier.urihttps://hdl.handle.net/10388/15117
dc.language.isoen
dc.subjectPlate Tectonics metamorphism dT/dP
dc.titleInvestigating Secular Trends in Metamorphism through the Construction and Application of a Relational Database (MetRec)
dc.typeThesis
dc.type.materialtext
thesis.degree.departmentGeological Sciences
thesis.degree.disciplineGeology
thesis.degree.grantorUniversity of Saskatchewan
thesis.degree.levelMasters
thesis.degree.nameMaster of Science (M.Sc.)

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