Inverse Modeling to Constrain Composition of CO2-Rich Parental Melt of Kimberlite: Model Development and Application to the Majuagaa Dyke, Southern West Greenland.
Abstract A model is developed to test the hypothesis that kimberlites can form by low-degree melting of asthenospheric mantle followed by entrainment and assimilation of lithospheric mantle. The developed model uses inversion calculations based upon rare earth and compatible trace elements. For kimb...
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Oxford University Press (OUP)
2022
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Online Access: | http://dx.doi.org/10.1093/petrology/egac127 https://academic.oup.com/petrology/advance-article-pdf/doi/10.1093/petrology/egac127/48517260/egac127.pdf https://academic.oup.com/petrology/article-pdf/64/2/egac127/49136301/egac127.pdf |
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croxfordunivpr:10.1093/petrology/egac127 2023-05-15T16:28:46+02:00 Inverse Modeling to Constrain Composition of CO2-Rich Parental Melt of Kimberlite: Model Development and Application to the Majuagaa Dyke, Southern West Greenland. Pilbeam, L H Rasmussen, T M Waight, T E Nielsen, T F D 2022 http://dx.doi.org/10.1093/petrology/egac127 https://academic.oup.com/petrology/advance-article-pdf/doi/10.1093/petrology/egac127/48517260/egac127.pdf https://academic.oup.com/petrology/article-pdf/64/2/egac127/49136301/egac127.pdf en eng Oxford University Press (OUP) https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model Journal of Petrology volume 64, issue 2 ISSN 0022-3530 1460-2415 Geochemistry and Petrology Geophysics journal-article 2022 croxfordunivpr https://doi.org/10.1093/petrology/egac127 2023-02-17T11:26:43Z Abstract A model is developed to test the hypothesis that kimberlites can form by low-degree melting of asthenospheric mantle followed by entrainment and assimilation of lithospheric mantle. The developed model uses inversion calculations based upon rare earth and compatible trace elements. For kimberlites (s.s.), an equation describing mass balance between a melt of unknown composition and a contaminant end-member of xenocrystic/assimilated material from the lithospheric mantle is inverted. This allows calculation of the mass fraction of xenocrystic minerals from the lithospheric mantle (olivine, orthopyroxene, clinopyroxene, garnet, ilmenite) entrained in the kimberlitic magma, as well as the source mineralogy and melt degree in the source region. The composition of the parental melt prior to interaction with the lithosphere is not assumed a priori but is calculated by the model. The CO2, H2O, K2O and P2O5 contents of the source are estimated assuming batch melting and the inversion models. The range and coupling of the model parameters are found using a non-linear most-squares inversion procedure, and the model space is visualised using a Self-Organising Map approach. Our earlier work supporting assimilation of xenocrystic opx is, however, not a precondition but provides a post-processing constraint, as well as the selection of a more likely set of solutions from the Self-Organising Map. The calculation is applied to a data set from the Majuagaa kimberlite dyke (southern West Greenland) including added whole rock analyses for CO2 and H2O. Major variations in whole rock compositions are related to flow differentiation of olivine macrocrysts. The textures of opx, cpx, gt and ilm megacrysts show evidence for reaction with the transporting melt and physical erosion in the kimberlitic mush. Using the bulk rocks in our inversion scheme results in a silico-carbonatite parental melt with major element concentrations consistent with experimental melts. The ol, opx, and cpx mass fractions in the source are not ... Article in Journal/Newspaper Greenland Oxford University Press (via Crossref) Greenland Journal of Petrology |
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Open Polar |
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Oxford University Press (via Crossref) |
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croxfordunivpr |
language |
English |
topic |
Geochemistry and Petrology Geophysics |
spellingShingle |
Geochemistry and Petrology Geophysics Pilbeam, L H Rasmussen, T M Waight, T E Nielsen, T F D Inverse Modeling to Constrain Composition of CO2-Rich Parental Melt of Kimberlite: Model Development and Application to the Majuagaa Dyke, Southern West Greenland. |
topic_facet |
Geochemistry and Petrology Geophysics |
description |
Abstract A model is developed to test the hypothesis that kimberlites can form by low-degree melting of asthenospheric mantle followed by entrainment and assimilation of lithospheric mantle. The developed model uses inversion calculations based upon rare earth and compatible trace elements. For kimberlites (s.s.), an equation describing mass balance between a melt of unknown composition and a contaminant end-member of xenocrystic/assimilated material from the lithospheric mantle is inverted. This allows calculation of the mass fraction of xenocrystic minerals from the lithospheric mantle (olivine, orthopyroxene, clinopyroxene, garnet, ilmenite) entrained in the kimberlitic magma, as well as the source mineralogy and melt degree in the source region. The composition of the parental melt prior to interaction with the lithosphere is not assumed a priori but is calculated by the model. The CO2, H2O, K2O and P2O5 contents of the source are estimated assuming batch melting and the inversion models. The range and coupling of the model parameters are found using a non-linear most-squares inversion procedure, and the model space is visualised using a Self-Organising Map approach. Our earlier work supporting assimilation of xenocrystic opx is, however, not a precondition but provides a post-processing constraint, as well as the selection of a more likely set of solutions from the Self-Organising Map. The calculation is applied to a data set from the Majuagaa kimberlite dyke (southern West Greenland) including added whole rock analyses for CO2 and H2O. Major variations in whole rock compositions are related to flow differentiation of olivine macrocrysts. The textures of opx, cpx, gt and ilm megacrysts show evidence for reaction with the transporting melt and physical erosion in the kimberlitic mush. Using the bulk rocks in our inversion scheme results in a silico-carbonatite parental melt with major element concentrations consistent with experimental melts. The ol, opx, and cpx mass fractions in the source are not ... |
format |
Article in Journal/Newspaper |
author |
Pilbeam, L H Rasmussen, T M Waight, T E Nielsen, T F D |
author_facet |
Pilbeam, L H Rasmussen, T M Waight, T E Nielsen, T F D |
author_sort |
Pilbeam, L H |
title |
Inverse Modeling to Constrain Composition of CO2-Rich Parental Melt of Kimberlite: Model Development and Application to the Majuagaa Dyke, Southern West Greenland. |
title_short |
Inverse Modeling to Constrain Composition of CO2-Rich Parental Melt of Kimberlite: Model Development and Application to the Majuagaa Dyke, Southern West Greenland. |
title_full |
Inverse Modeling to Constrain Composition of CO2-Rich Parental Melt of Kimberlite: Model Development and Application to the Majuagaa Dyke, Southern West Greenland. |
title_fullStr |
Inverse Modeling to Constrain Composition of CO2-Rich Parental Melt of Kimberlite: Model Development and Application to the Majuagaa Dyke, Southern West Greenland. |
title_full_unstemmed |
Inverse Modeling to Constrain Composition of CO2-Rich Parental Melt of Kimberlite: Model Development and Application to the Majuagaa Dyke, Southern West Greenland. |
title_sort |
inverse modeling to constrain composition of co2-rich parental melt of kimberlite: model development and application to the majuagaa dyke, southern west greenland. |
publisher |
Oxford University Press (OUP) |
publishDate |
2022 |
url |
http://dx.doi.org/10.1093/petrology/egac127 https://academic.oup.com/petrology/advance-article-pdf/doi/10.1093/petrology/egac127/48517260/egac127.pdf https://academic.oup.com/petrology/article-pdf/64/2/egac127/49136301/egac127.pdf |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland |
genre_facet |
Greenland |
op_source |
Journal of Petrology volume 64, issue 2 ISSN 0022-3530 1460-2415 |
op_rights |
https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model |
op_doi |
https://doi.org/10.1093/petrology/egac127 |
container_title |
Journal of Petrology |
_version_ |
1766018445750566912 |