Crystallization of megacrysts by carbonatitic metasomatism : evidence from the Muskox kimberlite, Nunavut, Canada ...
Low-Cr and high-Cr clinopyroxene, garnet, olivine, and ilmenite megacrysts from the Muskox kimberlite (Nunavut, Canada) have been analyzed for major and trace elements, as well as Sr, Nd and Pb isotopes in an attempt to constrain the debated origin of the kimberlitic megacryst suite. Samples display...
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| Format: | Text |
| Language: | English |
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University of British Columbia
2020
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| Online Access: | https://dx.doi.org/10.14288/1.0395184 https://doi.library.ubc.ca/10.14288/1.0395184 |
| Summary: | Low-Cr and high-Cr clinopyroxene, garnet, olivine, and ilmenite megacrysts from the Muskox kimberlite (Nunavut, Canada) have been analyzed for major and trace elements, as well as Sr, Nd and Pb isotopes in an attempt to constrain the debated origin of the kimberlitic megacryst suite. Samples display compositional overlap with respective phases in websterite, while clinopyroxene Sr-Nd-Pb isotope systematics reveal similarities with both websteritic clinopyroxene and metasomatic clinopyroxene in peridotites from the same kimberlite, in addition to whole-rock isotope data for the Muskox and neighboring Jericho kimberlites. All studied lithologies may represent the products of mixing between EM1 mantle, locally restricted relic Proterozoic enriched mantle and HIMU carbonatitic fluid. Equilibrium melts calculated using clinopyroxene trace element data reaffirm a carbonatitic affinity of the metasomatic agent. Thermodynamic modeling using the Deep Earth Water model shows that megacryst mineral compositions cannot ... |
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